Datopotamab Deruxtecan in Advanced or Metastatic HR+/HER2- and Triple-Negative Breast Cancer: Results From the Phase I TROPION-PanTumor01 Study

PURPOSE

Datopotamab deruxtecan (Dato-DXd) is an antibody-drug conjugate consisting of a humanized antitrophoblast cell-surface antigen 2 (TROP2) monoclonal antibody linked to a potent, exatecan-derived topoisomerase I inhibitor payload via a plasma-stable, selectively cleavable linker.

PATIENTS AND METHODS

TROPION-PanTumor01 (ClinicalTrials.gov identifier: NCT03401385) is a phase I, dose-escalation, and dose-expansion study evaluating Dato-DXd in patients with previously treated solid tumors. The primary study objective was to assess the safety and tolerability of Dato-DXd. Secondary objectives included evaluation of antitumor activity and pharmacokinetics. Results from patients with advanced/metastatic hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) breast cancer (BC) or triple-negative BC (TNBC) are reported.

RESULTS

At data cutoff (July 22, 2022), 85 patients (HR+/HER2- BC = 41, and TNBC = 44) had received Dato-DXd. The objective response rate by blinded independent central review was 26.8% (95% CI, 14.2 to 42.9) and 31.8% (95% CI, 18.6 to 47.6) for patients with HR+/HER2- BC and TNBC, respectively. The median duration of response was not evaluable in the HR+/HER2- BC cohort and 16.8 months in the TNBC cohort. The median progression-free survival in patients with HR+/HER2- BC and TNBC was 8.3 and 4.4 months, respectively. All-cause treatment-emergent adverse events (TEAEs; any grade, grade ≥3) were observed in 100% and 41.5% of patients with HR+/HER2- BC and 100% and 52.3% of patients with TNBC. Stomatitis was the most common TEAE (any grade, grade ≥3) in both HR+/HER2- BC (82.9%, 9.8%) and TNBC (72.7%, 11.4%) cohorts.

CONCLUSION

In patients with heavily pretreated advanced HR+/HER2- BC and TNBC, Dato-DXd demonstrated promising clinical activity and a manageable safety profile. Dato-DXd is currently being evaluated in phase III studies.

Comprehensive Analysis Identifies Variability in PI3K Pathway Alterations in Triple-Negative Breast Cancer Subtypes

PURPOSE

The PI3K pathway is frequently altered in triple-negative breast cancer (TNBC). Limited cell line and human data suggest that TNBC tumors characterized as mesenchymal (M) and luminal androgen receptor (LAR) subtypes have increased incidence of alterations in the PI3K pathway. The impact of PI3K pathway alterations across TNBC subtypes is poorly understood.

METHODS

Pretreatment tumor was evaluated from operable TNBC patients enrolled on a clinical trial of neoadjuvant therapy (NAT; A Robust TNBC Evaluation fraMework to Improve Survival [ClinicalTrials.gov identifier: NCT02276443]). Tumors were characterized into seven TNBC subtypes per Pietenpol criteria (basal-like 1, basal-like 2, immunomodulatory, M, mesenchymal stem-like, LAR, and unstable). Using whole-exome sequencing, RNA sequencing, and immunohistochemistry for PTEN, alterations were identified in 32 genes known to activate the PI3K pathway. Alterations in each subtype were associated with pathologic response to NAT.

RESULTS

In evaluated patients (N = 177), there was a significant difference in the incidence of PI3K pathway alterations across TNBC subtypes (P < .01). The highest incidence of alterations was seen in LAR (81%), BL2 (79%), and M (62%) subtypes. The odds ratio for pathologic complete response (pCR) in the presence of PIK3CA mutation, PTEN mutation, and/or PTEN loss was highest in the LAR subtype and lowest in the M subtype, but these findings did not reach statistical significance. Presence of PIK3CA mutation was associated with pCR in the LAR subtype (P = .02).

CONCLUSION

PI3K pathway alteration can affect response to NAT in TNBC, and targeted agents may improve outcomes, particularly in patients with M and LAR TNBC.

Lasofoxifene versus fulvestrant for ER+/HER2- metastatic breast cancer with an ESR1 mutation: results from the randomized, phase II ELAINE 1 trial

BACKGROUND

Acquired estrogen receptor alpha (ER/ESR1) mutations commonly cause endocrine resistance in ER+ metastatic breast cancer (mBC). Lasofoxifene, a novel selective ER modulator, stabilizes an antagonist conformation of wild-type and ESR1-mutated ER-ligand binding domains, and has antitumor activity in ESR1-mutated xenografts.

PATIENTS AND METHODS

In this open-label, randomized, phase II, multicenter, ELAINE 1 study (NCT03781063), we randomized women with ESR1-mutated, ER+/human epidermal growth factor receptor 2 negative (HER2-) mBC that had progressed on an aromatase inhibitor (AI) plus a cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) to oral lasofoxifene 5 mg daily or IM fulvestrant 500 mg (days 1, 15, and 29, and then every 4 weeks) until disease progression/toxicity. The primary endpoint was progression-free survival (PFS); secondary endpoints were safety/tolerability.

RESULTS

A total of 103 patients received lasofoxifene (n = 52) or fulvestrant (n = 51). The most current efficacy analysis showed that lasofoxifene did not significantly prolong median PFS compared with fulvestrant: 24.2 weeks (∼5.6 months) versus 16.2 weeks (∼3.7 months; P = 0.138); hazard ratio 0.699 (95% confidence interval 0.434-1.125). However, PFS and other clinical endpoints numerically favored lasofoxifene: clinical benefit rate (36.5% versus 21.6%; P = 0.117), objective response rate [13.2% (including a complete response in one lasofoxifene-treated patient) versus 2.9%; P = 0.124], and 6-month (53.4% versus 37.9%) and 12-month (30.7% versus 14.1%) PFS rates. Most common treatment-emergent adverse events with lasofoxifene were nausea, fatigue, arthralgia, and hot flushes. One death occurred in the fulvestrant arm. Circulating tumor DNA ESR1 mutant allele fraction (MAF) decreased from baseline to week 8 in 82.9% of evaluable lasofoxifene-treated versus 61.5% of fulvestrant-treated patients.

CONCLUSIONS

Lasofoxifene demonstrated encouraging antitumor activity versus fulvestrant and was well tolerated in patients with ESR1-mutated, endocrine-resistant mBC following progression on AI plus CDK4/6i. Consistent with target engagement, lasofoxifene reduced ESR1 MAF, and to a greater extent than fulvestrant. Lasofoxifene may be a promising targeted treatment for patients with ESR1-mutated mBC and warrants further investigation.

Open-label, phase II, multicenter study of lasofoxifene plus abemaciclib for treating women with metastatic ER+/HER2- breast cancer and an ESR1 mutation after disease progression on prior therapies: ELAINE 2

BACKGROUND

Acquired ESR1 mutations in estrogen receptor-positive (ER+) metastatic breast cancer (mBC) drive treatment resistance and tumor progression; new treatment strategies are needed. Lasofoxifene, a next-generation, oral, endocrine therapy and tissue-specific ER antagonist, provided preclinical antitumor activity, alone or combined with a cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) in ESR1-mutated mBC.

PATIENTS AND METHODS

In the open-label, phase II, ELAINE 2 trial (NCT04432454), women with ESR1-mutated, ER+/human epidermal growth factor receptor 2-negative (HER2-) mBC who progressed on prior therapies (including CDK4/6i) received lasofoxifene 5 mg/day and abemaciclib 150 mg b.i.d until disease progression/toxicity. The primary endpoint was safety/tolerability. Secondary endpoints included progression-free survival (PFS), clinical benefit rate (CBR), and objective response rate (ORR).

RESULTS

Twenty-nine women (median age 60 years) participated; all but one were previously treated with a CDK4/6i (median duration 2 years). The lasofoxifene-abemaciclib combination was well tolerated with primarily grade 1/2 treatment-emergent adverse events (TEAEs), most commonly diarrhea, nausea, fatigue, and vomiting. One patient (with no prior CDK4/6i) discontinued treatment due to grade 2 diarrhea. No deaths occurred during the study. Median PFS was 56.0 weeks [95% confidence interval (CI) 31.9 weeks-not estimable; ∼13 months]; PFS rates at 6, 12, and 18 months were 76.1%, 56.1%, and 38.8%, respectively. CBR at 24 weeks was 65.5% (95% CI 47.3% to 80.1%). In 18 patients with measurable lesions, ORR was 55.6% (95% CI 33.7% to 75.4%). ESR1-mutant circulating tumor DNA (ctDNA) allele fraction decreased from baseline to week 4 in 21/26 (80.8%) patients.

CONCLUSIONS

Lasofoxifene plus abemaciclib had an acceptable safety profile, was well tolerated, and exhibited meaningful antitumor activity in women with ESR1-mutated, ER+/HER2- mBC after disease progression on prior CDK4/6i. Observed decreases in ESR1-mutant ctDNA with lasofoxifene concordant with clinical response suggest target engagement. If the ELAINE 2 findings are confirmed in the initiated, phase III, ELAINE 3 trial, these data could be practice-changing and help address a critical unmet need.

Efficacy of futibatinib, an irreversible fibroblast growth factor receptor inhibitor, in FGFR-altered breast cancer

Several alterations in fibroblast growth factor receptor (FGFR) genes have been found in breast cancer; however, they have not been well characterized as therapeutic targets. Futibatinib (TAS-120; Taiho) is a novel, selective, pan-FGFR inhibitor that inhibits FGFR1-4 at nanomolar concentrations. We sought to determine futibatinib's efficacy in breast cancer models. Nine breast cancer patient-derived xenografts (PDXs) with various FGFR1-4 alterations and expression levels were treated with futibatinib. Antitumor efficacy was evaluated by change in tumor volume and time to tumor doubling. Alterations indicating sensitization to futibatinib in vivo were further characterized in vitro. FGFR gene expression between patient tumors and matching PDXs was significantly correlated; however, overall PDXs had higher FGFR3-4 expression. Futibatinib inhibited tumor growth in 3 of 9 PDXs, with tumor stabilization in an FGFR2-amplified model and prolonged regression (> 110 days) in an FGFR2 Y375C mutant/amplified model. FGFR2 overexpression and, to a greater extent, FGFR2 Y375C expression in MCF10A cells enhanced cell growth and sensitivity to futibatinib. Per institutional and public databases, FGFR2 mutations and amplifications had a population frequency of 1.1%-2.6% and 1.5%-2.5%, respectively, in breast cancer patients. FGFR2 alterations in breast cancer may represent infrequent but highly promising targets for futibatinib.

Abemaciclib Is Effective in Palbociclib-Resistant Hormone Receptor-Positive Metastatic Breast Cancers

Cyclin-dependent kinases 4/6 inhibitor (CDK4/6i) plus endocrine therapy (ET) is standard of care for patients with hormone receptor (HR)-positive, HER2-negative metastatic breast cancer (MBC). However, resistance to CDK4/6is plus ET remains a clinical problem with limited therapeutic options following disease progression. Different CDK4/6is might have distinct mechanisms of resistance, and therefore using them sequentially or targeting their differentially altered pathways could delay disease progression. To understand pathways leading to resistance to the CDK4/6is palbociclib and abemaciclib, we generated multiple in vitro models of palbociclib-resistant (PR) and abemaciclib-resistant (AR) cell lines as well as in vivo patient-derived xenografts (PDX) and ex vivo PDX-derived organoids (PDxO) from patients who progressed on CDK4/6i. PR and AR breast cancer cells exhibited distinct transcriptomic and proteomic profiles that sensitized them to different classes of inhibitors; PR cells upregulated G2-M pathways and responded to abemaciclib, while AR cells upregulated mediators of the oxidative phosphorylation pathway (OXPHOS) and responded to OXPHOS inhibitors. PDX and organoid models derived from patients with PR breast cancer remained responsive to abemaciclib. Resistance to palbociclib while maintaining sensitivity to abemaciclib was associated with pathway-specific transcriptional activity but was not associated with any individual genetic alterations. Finally, data from a cohort of 52 patients indicated that patients with HR-positive/HER2-negative MBC who progressed on palbociclib-containing regimens can exhibit a meaningful overall clinical benefit from abemaciclib-based therapy when administered after palbociclib. These findings provide the rationale for clinical trials evaluating the benefit of abemaciclib treatment following progression on a prior CDK4/6i.

SIGNIFICANCE

Palbociclib-resistant breast cancers respond to abemaciclib and express pathway-specific signatures of sensitivity, providing a biomarker-driven therapeutic option for patients with metastatic breast cancer following disease progression on cyclin-dependent kinases 4/6 inhibitors.

Epigenetically upregulating TROP2 and SLFN11 enhances therapeutic efficacy of TROP2 antibody drug conjugate sacitizumab govitecan

TROP2 antibody drug conjugates (ADCs) are under active development. We seek to determine whether we can enhance activity of TROP2 ADCs by increasing TROP2 expression. In metaplastic breast cancers (MpBC), there is limited expression of TROP2, and downregulating transcription factor ZEB1 upregulates E-cad and TROP2, thus sensitizing cancers to TROP2 ADC sacituzumab govitecan (SG). Demethylating agent decitabine decreases DNA methyltransferase expression and TROP2 promoter methylation and subsequently increases TROP2 expression. Decitabine treatment as well as overexpression of TROP2 significantly enhance SG antitumor activity. Decitabine also increases SLFN11, a biomarker of topoisomerase 1 inhibitor (TOP1) sensitivity and is synergistic with SG which has a TOP1 payload, in TROP2-expressing SLFN11-low BC cells. In conclusion, TROP2 and SLFN11 expression can be epigenetically modulated and the combination of demethylating agent decitabine with TROP2 ADCs may represent a novel therapeutic approach for tumors with low TROP2 or SLFN11 expression.

PTEN in triple-negative breast carcinoma: protein expression and genomic alteration in pretreatment and posttreatment specimens

Background

Recent advances have been made in targeting the phosphoinositide 3-kinase pathway in breast cancer. Phosphatase and tensin homolog (PTEN) is a key component of that pathway.

Objective

To understand the changes in PTEN expression over the course of the disease in patients with triple-negative breast cancer (TNBC) and whether PTEN copy number variation (CNV) by next-generation sequencing (NGS) can serve as an alternative to immunohistochemistry (IHC) to identify PTEN loss.

Methods

We compared PTEN expression by IHC between pretreatment tumors and residual tumors in the breast and lymph nodes after neoadjuvant chemotherapy in 96 patients enrolled in a TNBC clinical trial. A correlative analysis between PTEN protein expression and PTEN CNV by NGS was also performed.

Results

With a stringent cutoff for PTEN IHC scoring, PTEN expression was discordant between pretreatment and posttreatment primary tumors in 5% of patients (n = 96) and between posttreatment primary tumors and lymph node metastases in 9% (n = 33). A less stringent cutoff yielded similar discordance rates. Intratumoral heterogeneity for PTEN loss was observed in 7% of the patients. Among pretreatment tumors, PTEN copy numbers by whole exome sequencing (n = 72) were significantly higher in the PTEN-positive tumors by IHC compared with the IHC PTEN-loss tumors (p < 0.0001). However, PTEN-positive and PTEN-loss tumors by IHC overlapped in copy numbers: 14 of 60 PTEN-positive samples showed decreased copy numbers in the range of those of the PTEN-loss tumors.

Conclusion

Testing various specimens by IHC may generate different PTEN results in a small proportion of patients with TNBC; therefore, the decision of testing one versus multiple specimens in a clinical trial should be defined in the patient inclusion criteria. Although a distinct cutoff by which CNV differentiated PTEN-positive tumors from those with PTEN loss was not identified, higher copy number of PTEN may confer positive PTEN, whereas lower copy number of PTEN would necessitate additional testing by IHC to assess PTEN loss.

Trial registration

NCT02276443.

Predictive Roles of Baseline Stromal Tumor-Infiltrating Lymphocytes and Ki-67 in Pathologic Complete Response in an Early-Stage Triple-Negative Breast Cancer Prospective Trial

High stromal tumor-infiltrating lymphocytes (sTILs) are associated with improved pathologic complete response (pCR) in triple-negative breast cancer (TNBC). We hypothesize that integrating high sTILs and additional clinicopathologic features associated with pCR could enhance our ability to predict the group of patients on whom treatment de-escalation strategies could be tested. In this prospective early-stage TNBC neoadjuvant chemotherapy study, pretreatment biopsies from 408 patients were evaluated for their clinical and demographic features, as well as biomarkers including sTILs, Ki-67, PD-L1 and androgen receptor. Multivariate logistic regression models were developed to generate a computed response score to predict pCR. The pCR rate for the entire cohort was 41%. Recursive partitioning analysis identified ≥20% as the optimal cutoff for sTILs to denote 35% (143/408) of patients as having high sTILs, with a pCR rate of 59%, and 65% (265/408) of patients as having low sTILs, with a pCR rate of 31%. High Ki-67 (cutoff > 35%) was identified as the only predictor of pCR in addition to sTILs in the training set. This finding was verified in the testing set, where the highest computed response score encompassing both high sTILa and high Ki-67 predicted a pCR rate of 65%. Integrating Ki67 and sTIL may refine the selection of early stage TNBC patients for neoadjuvant clinical trials evaluating de-escalation strategies.

Operational Metrics for the ELAINE 2 Study Combining a Traditional Approach With a Just-in-TIME Model

PURPOSE

There are numerous barriers to enrollment in oncology biomarker-driven studies.

METHODS

The ELAINE 2 study (ClinicalTrials.gov identifier: NCT04432454) is an open-label phase 2 study of lasofoxifene combined with abemaciclib in patients with advanced or metastatic estrogen receptor-positive/human epidermal growth factor receptor 2-negative breast cancer with an ESR1 mutation. ELAINE 2 opened clinical sites by using a Traditional approach, which activated a site before patient identification, and the Tempus TIME Trial network, which opened a site only after identifying an eligible patient. This manuscript presents the operational metrics comparing the Traditional and TIME Trial site data.

RESULTS

The study enrolled patients over 34 weeks and 16 sites (six Traditional and 10 TIME Trial) participated. Duration for full clinical trial agreement execution for Traditional sites and TIME Trial sites averaged 200.5 (range, 142-257) and 7.6 days (range, 2-14), respectively. Institutional review board approval time for Traditional sites and TIME Trial sites was 27.5 (range, 12-71) and 3.0 days (range, 1-12), respectively. Duration from study activation to first consent was 33.3 (range, 18-58) and 8.8 days (range, 1-35) for Traditional and TIME Trial sites, respectively. The first patient on study was at a TIME Trial site 115 days before a Traditional site and the first seven patients enrolled were at TIME Trial sites. Traditional sites consented 23 and enrolled 16 patients, while TIME Trial sites consented 16 and enrolled 13. The trial enrolled 29 patients in 8.5 months with the anticipated enrollment duration being 12-18 months.

CONCLUSION

The TIME Trial network opened earlier and enrolled the first study patients. These results demonstrate that the Just-in-TIME model, along with a Traditional model, can improve enrollment in biomarker-driven studies.

A phase II study of neoadjuvant atezolizumab and nab-paclitaxel in patients with anthracycline-resistant early-stage triple-negative breast cancer

PURPOSE

Neoadjuvant anti-PD-(L)1 therapy improves the pathological complete response (pCR) rate in unselected triple-negative breast cancer (TNBC). Given the potential for long-term morbidity from immune-related adverse events (irAEs), optimizing the risk-benefit ratio for these agents in the curative neoadjuvant setting is important. Suboptimal clinical response to initial neoadjuvant therapy (NAT) is associated with low rates of pCR (2-5%) and may define a patient selection strategy for neoadjuvant immune checkpoint blockade. We conducted a single-arm phase II study of atezolizumab and nab-paclitaxel as the second phase of NAT in patients with doxorubicin and cyclophosphamide (AC)-resistant TNBC (NCT02530489).

METHODS

Patients with stage I-III, AC-resistant TNBC, defined as disease progression or a < 80% reduction in tumor volume after 4 cycles of AC, were eligible. Patients received atezolizumab (1200 mg IV, Q3weeks × 4) and nab-paclitaxel (100 mg/m² IV,Q1 week × 12) as the second phase of NAT before undergoing surgery followed by adjuvant atezolizumab (1200 mg IV, Q3 weeks, × 4). A two-stage Gehan-type design was employed to detect an improvement in pCR/residual cancer burden class I (RCB-I) rate from 5 to 20%.

RESULTS

From 2/15/2016 through 1/29/2021, 37 patients with AC-resistant TNBC were enrolled. The pCR/RCB-I rate was 46%. No new safety signals were observed. Seven patients (19%) discontinued atezolizumab due to irAEs.

CONCLUSION

This study met its primary endpoint, demonstrating a promising signal of activity in this high-risk population (pCR/RCB-I = 46% vs 5% in historical controls), suggesting that a response-adapted approach to the utilization of neoadjuvant immunotherapy should be considered for further evaluation in a randomized clinical trial.

Phase 1b study of combined selinexor and eribulin for the treatment of advanced solid tumors and triple-negative breast cancer

BACKGROUND

Selinexor (KPT-330) is a potent inhibitor of exportin 1 (XPO1), in turn inhibiting tumor growth. Selinexor enhances the antitumor efficacy of eribulin in triple-negative breast cancer (TNBC) in vitro and in vivo. Given the unmet medical need in TNBC and sarcoma, the authors explored the safety and efficacy of this combination.

METHODS

The authors conducted a phase 1b trial of combined selinexor and eribulin using a 3 + 3 dose-escalation design in patients who had advanced solid tumors and in those who had TNBC in a dose-expansion cohort.

RESULTS

Patients with TNBC (N = 19), sarcoma (N = 9), and other cancers (N = 3) were enrolled in the dose-escalation cohort (N = 10) and in the dose-expansion cohort (N = 21). The median number lines of prior therapy received was four (range, from one to seven prior lines). The most common treatment-related adverse events for selinexor were nausea (77%), leukopenia (77%), anemia (68%), neutropenia (68%), and fatigue (48%). One dose-limiting toxicity occurred at the first dose level with prolonged grade 3 neutropenia. The recommended phase 2 dose was 80 mg of selinexor orally once per week and 1 mg/m² eribulin on days 1 and 8 intravenously every 3 weeks. The objective response rate (ORR) was 10% in three patients. In the dose-escalation cohort, the ORR was 10%, whereas six patients with had stable disease. In the TNBC dose-expansion cohort (n = 18), ORR was 11%, and there were two confirmed partial responses with durations of 10.8 and 19.1 months (ongoing).

CONCLUSIONS

Selinexor and eribulin had an acceptable toxicity profile and modest overall efficacy with durable responses in select patients.

PLAIN LANGUAGE SUMMARY

Effective therapies for advanced, triple-negative breast cancer and sarcoma represent an unmet need. Exportin 1 is associated with the transport of cancer-related proteins. Preclinical studies have demonstrated tumor growth inhibition and enhanced tumor sensitivity in patients who receive selinexor combined with eribulin. In this phase 1b study, the authors evaluated the safety profile and clinical activity of the combination of selinexor, a potent oral inhibitor of exportin 1, and eribulin in patients with advanced cancers enriched for triple-negative breast cancer or sarcoma. The combination was well tolerated; most adverse events were mild or moderate, reversible, and managed with dose modifications or growth factor support. The combination of selinexor and eribulin produced an antitumor response, particularly in some patients with triple-negative breast cancer. This work lays the foundation for prospective investigations of the role of selinexor and eribulin in the treatment of triple-negative breast cancer.

Abstract P3-02-03: A phase Ib trial of bintrafusp alfa and eribulin in patients with metastatic triple negative breast cancer (TNBC)

Background: Metastatic TNBC is an aggressive breast cancer subtype with poor prognosis and limited systemic therapy options. While pembrolizumab in combination with chemotherapy is approved for PD-L1 positive TNBC, limited immunotherapy options exist for patients with progressive and/or PD-L1 negative disease. TGFβ released by cancer cells and stromal fibroblasts attenuates the intrinsic antitumor potential of immune cells within the tumor microenvironment mediating resistance to immunotherapy. Consequently, inhibition of TGFβ signaling could potentially enhance antitumor responses to anti-PD-L1/PD-1 therapies. Bintrafusp alfa is a bifunctional fusion protein composed of the extracellular domain of TGF-β receptor II (a TGF-β “trap”) fused to a human IgG1 monoclonal antibody blocking programmed cell death ligand 1. Preclinical studies have shown that eribulin downregulates TGFβ by phosphorylation of Smad proteins. Therefore, combining eribulin with bintrafusp alfa may have a synergistic effect. This study evaluated the combination of bintrafusp alfa with eribulin in patients with metastatic TNBC. Methods: This is a phase 1b, open label, single center study evaluating bintrafusp alfa in combination with eribulin in patients with metastatic TNBC who had relapsed/progressed on prior therapies. Patients with ER/PR ≤10% with measurable disease were enrolled. Patients who received prior anti-PD-1/PD-L1 therapies in the metastatic setting were excluded. Patients received bintrafusp alfa 1200 mg intravenously every 2 weeks in combination with eribulin (1.4 mg/m2 (dose level 1), 1.1 mg/m2, or 0.7 mg/m2) on days 1, 8, 22, 29 on every 6-week cycle. Primary objectives were to determine the recommended phase II dose (RP2D) as well as to evaluate the safety and tolerability of eribulin in combination with the fixed dose of bintrafusp alfa. Secondary objective was to determine the overall response rate (ORR) according to RECIST 1.1. Bayesian optimal interval (BOIN) design was employed to identify the RP2D. Toxicities assessed using CTCAE v4.03. Tumor assessments were performed every 6 weeks. Results: A total of 25 patients were enrolled on the study. Twenty-one patients were evaluable (3 screen failures, 1 received only one dose of study treatment). Median age 59 (range 27-85). Median number of prior therapies 2 (range 0-8). The most common reason for protocol discontinuation was disease progression (n = 15, 71%). Four patients experienced dose limiting toxicities (DLTs); 3 with decreased neutrophil count and 1 with increased aspartate aminotransferase. Five patients (24%) experienced grade 4 toxicities (increased aspartate aminotransferase, hypokalemia, hypophosphatemia, neutropenia). Nine patients (43%) experienced grade 3 toxicities. Three patients (14%) discontinued study due to toxicity. Total of 2 deaths were observed, none related to treatment. Most common toxicities (any grade) include anemia (n = 13 patients), elevated aspartate aminotransferase (11), neutropenia (n = 10), elevated aminotransferase (9), headache (n = 9), hypokalemia (n = 8), hyperglycemia (n = 8), leukopenia (n = 8), and fatigue (n = 8). RP2D was eribulin 1.1 mg/m2 with bintrafusp alfa 1200 mg. Six patients had PR (28.6%), 2 had SD (9.5%) and 12 had PD (57.1%) as the best response. One patient withdrew before response evaluation. Median PFS was 1.7 months (95% CI: (1.2, 5.9) and median OS was 11.1 months (95%CI: (5.2, 15.7). Conclusions: The combination of bintrafusp alfa with eribulin has manageable safety profile with meaningful clinical activity in patients with TNBC. Further studies evaluating TGF inhibitors in breast cancer are warranted.

Citation Format: Senthil Damodaran, Diane Liu, Jill Schwartz, Vicente Valero, David Ramirez, Sadia Saleem, Naoto T. Ueno, Nuhad K. Ibrahim, Meghan S. Karuturi, Rashmi K. Murthy, Stacy Moulder, Jennifer K. Litton. A phase Ib trial of bintrafusp alfa and eribulin in patients with metastatic triple negative breast cancer (TNBC) [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-02-03.

Abstract OT1-11-01: Phase II study of talazoparib, a PARP inhibitor, in somatic BRCA1/2 mutant metastatic breast cancer identified by cell-free DNA or tumor tissue genotyping

Background: PARP inhibitors are currently approved for the treatment of germline BRCA1/2 mutant metastatic breast cancer (MBC), which accounts for 5-10% of breast cancer. We hypothesize that a PARP inhibitor may also have efficacy in somatic BRCA1/2 mutant MBC, expanding the potential clinical applicability of PARP inhibitors. We previously demonstrated that somatic BRCA1/2 mutations can be identified by both cell-free DNA and tumor tissue genotyping in a subset of patients with MBC who are not germline BRCA1/2 carriers. Furthermore, a PARP inhibitor was demonstrated to induce cell growth inhibition in a circulating tumor cell culture model generated from a patient with pathogenic somatic BRCA1 mutant MBC (Vidula, Dubash, CCR, 2020). In this trial, we are evaluating the efficacy of a PARP inhibitor in somatic BRCA1/2 mutant MBC. Trial Design: This phase II investigator-initiated clinical trial is enrolling 30 patients with somatic BRCA1/2 mutant MBC identified via cell-free DNA or tumor tissue genotyping. Patients are treated with talazoparib, a PARP inhibitor, until disease progression. At baseline and every 3 months, patients undergo CT chest, abdomen, and pelvis, and a bone scan for disease assessment. Patients undergo blood collection at baseline for the Cancer Risk B (CR-B) assay, a novel flow variant assay to assess double-strand break repair mutations in circulating blood cells (Syeda, 2017) and monthly blood collection for cell-free DNA analysis to evaluate changes in the genomic environment. Eligibility Criteria: Patients with MBC with a pathogenic somatic BRCA1/2 mutation identified by cell-free DNA or tumor tissue genotyping are eligible. Both patients with triple-negative breast cancer (≥ 1 prior chemotherapy) or hormone receptor positive/HER2- MBC (≥ 1 prior hormone therapy) are eligible. Patients should not be known germline BRCA1/2 carriers. There is no limit on prior therapies including receipt of a prior platinum (in the absence of disease progression on prior platinum). A prior PARP inhibitor is not allowed. Adequate performance status and organ function are needed. Specific Aims: Primary aim is progression-free survival (PFS) assessed by RECIST 1.1. Secondary aims include objective response rate and toxicity assessed by NCI CTCAE v 5.0. Exploratory aims include assessing impact of BRCA1/2 reversion mutations in cell-free DNA, studying serial changes in BRCA1/2 mutant allelic frequency in cell-free DNA, comparing pre- and post-treatment cell-free DNA results to identify changes in the genomic environment, assessing the CR-B assay positivity rate, and correlating these biomarker analyses with patient response. Statistical Methods: This study uses a two-stage design with 80% power to demonstrate that talazoparib is associated with “success” (PFS &gt; 12 weeks) in 53% patients (4% alpha). Accrual: This study (NCT03990896) is open at Massachusetts General Hospital, MD Anderson, University of California San Francisco, and Emory, with pending activation at Northwestern, Cornell, and Vanderbilt. Five patients are enrolled as of 7/2022. Funding: This study is supported by a Pfizer ASPIRE award and Conquer Cancer Foundation of ASCO–Breast Cancer Research Foundation- Career Development Award. Contact information: Neelima Vidula, MD, Massachusetts General Hospital, nvidula@mgh.harvard.edu

Citation Format: Neelima Vidula, Senthil Damodaran, Erica L. Blouch, Nora Horick, Nathan Royce Ruffle-Deignan, Manali Bhave, Ami N. Shah, Leticia Varella, Vandana Abramson, Joseph Sparano, Leif Ellisen, Ishraq Alim, Harry Ostrer, Hope Rugo, Aditya Bardia. Phase II study of talazoparib, a PARP inhibitor, in somatic BRCA1/2 mutant metastatic breast cancer identified by cell-free DNA or tumor tissue genotyping [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT1-11-01.

Abstract HER2-01: HER2-01 Clinical and Molecular Characteristics of HER2-low/zero Early Stage Triple-Negative Breast Cancer

Background: In the metastatic setting, low HER2 expression is associated with clinical benefit from trastuzumab deruxtecan, a HER2-targeting antibody drug conjugates. However, little is known about the biological significance of low HER2 expression in patients with early stage triple-negative breast cancer (TNBC) receiving neoadjuvant therapy (NAT). Methods: Out of 595 patients with stage I-III TNBC enrolled on the prospective ARTEMIS trial (NCT02276443) from 2015-2021, we identified 367 patients with available HER2 immunohistochemistry (IHC) results on pre-NAT tumor tissue (HER2-zero: n=218; HER2-low [IHC 1+, 2+]: n=149). All patients were treated with anthracycline-based NAT. In cases where sufficient pre-NAT tumor tissue were available, additional IHC and/or RNAseq were performed. Differential gene expression (DGE) and pathway analysis were performed using DEseq2. Gene set enrichment analysis (GSEA) was performed using the Hallmark gene sets. Deconvolution analyses were performed using CIBERSORT. We controlled for multiple hypothesis using a false discovery rate (FDR) threshold with the Benjamini-Hochberg method, accepting as significant genes with at least a 2-fold change and &lt; 5% FDR. Results: Table 1 summarizes baseline clinicopathological features of the 367 patients. Compared to HER2-zero tumors, HER2-low tumors were less likely of metaplastic histology (p=0.001), associated with lower Ki67 (p=0.017) and were more likely to be androgen receptor (AR)-positive (p=0.01). There were no significant differences in tumor-infiltrating lymphocytes (TILs) infiltration and PD-L1 expression between HER2-zero and HER2-low tumors. Among the 226 patients with sufficient pre-NAT tissue for RNAseq, DGE analyses demonstrated upregulation of genes involved in fatty acid metabolism (ACSM1) and steroid hormone metabolism (DHRS2, UGT2B28) in HER2-low tumors compared with HER2-zero tumors. Deconvolution analyses revealed no significant differences between predicted proportions of immune cell subpopulations between HER2-low and HER2-zero tumors. Although rates of pCR were not significantly different between patients with HER2-zero (46%) and HER2-low tumors (40%) (p=0.34), non-pCR in patients with HER2-low tumors was associated with increased expression of EREG, which encodes an EGFR ligand, while non-pCR in patients with HER2-zero tumors was associated with downregulation in genes involved in immune response pathways. GSEA further identified the Hallmark allograft rejection (FDR q=0.001), interferon gamma response (FDR q=0.002), and interferon alpha response pathways (FDR q=0.007) as the 3 most significantly downregulated pathways in HER2-zero tumors from patients experiencing a non-pCR relative to HER2-zero tumors from patients experiencing a pCR. Conclusion: In early stage TNBC, low HER2 expression is associated with increased AR expression and upregulation of genes associated with fatty acid and steroid hormone metabolism. Gene expression analyses suggest that drivers of resistance to NAT differ between HER2-low and HER2-zero tumors. Biological differences between HER2-zero and HER2-low tumors exist and may influence future personalized treatment for patients with early stage TNBC.

Citation Format: Clinton Yam, Ziyi Li, Anil Korkut, Wencai Ma, Elisabeth Kong, Holly A. Hill, Hussein Abbas, Sausan Abouharb, Beatriz Adrada, Banu K. Arun, Carlos H. Barcenas, Ajit Bisen, Daniel Booser, Aman Buzdar, Rosalind Candelaria, Junjie Chen, Alyson Clayborn, Senthil Damodaran, Qingqing Ding, Haven Garber, Gabriel N. Hortobagyi, Kelly K. Hunt, Nuhad K. Ibrahim, Adaeze Iheme, Meghan S. Karuturi, Kimberly Koenig, Rachel M. Layman, Jangsoon Lee, Jennifer K. Litton, Melissa Mitchell, Giancarlo Moscol, Jason Mouabbi, Rashmi K. Murthy, Oluchi Oke, Paula Pohlmann, David Ramirez, Elizabeth Ravenberg, Sadia Saleem, Mediget Teshome, Vicente Valero, Jason White, Madison Williams, Wendy Woodward, Chasity Yajima, Naoto T. Ueno, Ken Chen, Gaiane Rauch, Lei Huo, Debu Tripathy. HER2-01 Clinical and Molecular Characteristics of HER2-low/zero Early Stage Triple-Negative Breast Cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr HER2-01.

Abstract P5-05-02: Estrogen receptor 1 (ESR1) mutations in circulating tumor DNA (ctDNA) from patients with ER+/HER2- metastatic breast cancer (mBC) treated with lasofoxifene plus abemaciclib in the ELAINE 2 study

Introduction: Use of long-term endocrine therapy (ET) for ER+ breast cancer often leads to acquired ESR1 mutations (mutESR1), causing endocrine resistance, tumor progression, and poor prognosis. An unmet clinical need exists for treating ER+ mBC patients with mutESR1, particularly after progression on CDK4/6 inhibitors (CDK4/6i). ELAINE 2 is an open-label, phase 2, multicenter trial evaluating safety and efficacy of lasofoxifene (LAS [selective estrogen receptor modulator]) plus abemaciclib (Abema [CDK4/6i], provided by Eli Lilly) in patients with ER+/HER2- and mutESR1 mBC who progressed after prior ET. Preliminary data with LAS plus Abema showed median progression-free survival of 55.7 wks, objective response rate of 50%, and 24-wk clinical benefit (CB) rate of 69%, with an acceptable safety and tolerability profile. Here, we report ESR1 ctDNA mutant allele frequency (MAF) and correlations of ESR1 MAF changes with CB.

Methods: ELAINE 2 patients with detectable ctDNA mutESR1 at baseline (BL) were analyzed. Oral LAS 5 mg/day and Abema 150 mg BID were taken until disease progression, death, unacceptable toxicity, or withdrawal from the study. ctDNA was assessed by the Sysmex-Inostics SafeSeq assay—which detects mutESR1 at low allele fractions—at BL, every 4 wks, and end of treatment. MAF changes from BL to wk 4 were characterized as decreased (decrease in ESR1 MAF or none detected [ND]), increased (increase in MAF), or equivocal (in polyclonal patients [&gt;1 mutESR1] with some MAF increasing and decreasing trends). Correlations of MAF change at 4 wks with CB at 24 wks were explored.

Results: 29 patients (median of 2 prior metastatic therapies: 97% CDK4/6i, 79% fulvestrant, 48% chemotherapy) had BL mutESR1 of Y537S (66%), D538G (45%), Y537N (28%), and other less frequently detected mutations; 14 (48.3%) patients were polyclonal. 26 of 29 patients had evaluable BL and wk-4 ctDNA results: 21 patients had decreased MAF (81% [54% with ND]), 3 (12%) had increased, and 2 (8%) had equivocal ESR1 MAF changes (Table). CB at 24 wks was seen in 17 patients with a decrease, 2 with an increase, and 1 with equivocal MAF change. A sensitivity of 89.5% and specificity of 20% were calculated for predicting CB based on direction of ESR1 MAF change. The positive predictive value (PPV) for CB with decreased MAF was 81% and the negative predictive value (NPV) for an increased MAF was 33%. Of the 14 (54%) patients with ND ESR1 MAF, 13 had CB resulting in 87% sensitivity, 50% specificity, 93% PPV, and 33% NPV.

Conclusion: In ELAINE 2, 81% of patients had decrease/cleared (ND) mutESR1 after 4 wks of LAS plus Abema, which correlated with clinical benefit. All mutESR1 detected appear targeted with this therapy. High sensitivity and favorable PPV were observed in patients with decreased MAF, and even more so in those with ND MAF; however, increased MAF was less specific and not as predictive of treatment failure. Our results indicate that ESR1 liquid biopsy evaluation may be an adequate non-invasive surrogate marker for monitoring patients on treatment. Further study in a larger population of women with endocrine-resistant mBC and acquired mutESR1 is warranted to explore this potential for monitoring treatment response or resistance to this novel LAS-Abema combination.

Table. Change from baseline to week 4 in ESR1 MAF and clinical benefit at 24 weeks. CI, confidence interval; MAF, mutant allele fraction; ND, none detected; NPV, negative predictive value; PPV, positive predictive value. *Sensitivity and specificity analyses do not include equivocal results.

Citation Format: Senthil Damodaran, Halle Moore, Ciara C. O’Sullivan, Paul V. Plourde, Gary Riordan, Hillary S. Sloane, Debu Tripathy, Dominic Carroll, David J Portman. Estrogen receptor 1 (ESR1) mutations in circulating tumor DNA (ctDNA) from patients with ER+/HER2- metastatic breast cancer (mBC) treated with lasofoxifene plus abemaciclib in the ELAINE 2 study [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-05-02.

Abstract PD13-08: PD13-08 Phase 1 TROPION-PanTumor01 Study Evaluating Datopotamab Deruxtecan (Dato-DXd) in Unresectable or Metastatic Hormone Receptor–Positive/HER2–Negative Breast Cancer (BC)

Background: Datopotamab deruxtecan (Dato-DXd) is an antibody-drug conjugate (ADC) consisting of a humanized anti-TROP2 IgG1 monoclonal antibody covalently linked to a highly potent topoisomerase I (Topo I) inhibitor payload via a stable, tumor-selective, tetrapeptide-based cleavable linker. Dato-DXd demonstrated compelling single-agent antitumor activity in heavily pretreated patients (pts) with metastatic triple-negative BC (Krop, SABCS 2021). This is the first report of results from the TROPION-PanTumor01 study in pts with unresectable or metastatic hormone receptor–positive (HR+)/human epidermal growth factor receptor 2–negative (HER2−; including HER2-low and HER2-zero) BC.

Methods: TROPION-PanTumor01 (NCT03401385) is a phase 1, multicenter, open-label, 2-part dose-escalation/expansion study evaluating Dato-DXd in previously treated pts with solid tumors. Based on previous clinical findings and exposure-response results from pts with NSCLC, Dato-DXd 6 mg/kg IV Q3W is being evaluated in pts with unresectable or metastatic HR+/HER2− BC that progressed on standard therapies. The primary objectives were safety and tolerability. Tumor responses, including ORR (complete response [CR] + partial response [PR]) and DCR (CR + PR + stable disease [SD]), were assessed per RECIST version 1.1 by blinded independent central review.

Results: As of the April 29, 2022, data cutoff, 41 pts had received Dato-DXd (median follow-up, 10.9 mo [range, 7-13]); 9 pts were ongoing. The primary cause of treatment discontinuation was disease progression (63%; progressive disease [PD] or clinical progression). Median age was 57 y (range, 33-75); 54% had de novo metastatic disease. Pts were heavily pretreated (Table) with a median of 5 (range, 3-10) prior regimens in the advanced setting; 95% had prior CDK4/6i (adjuvant/metastatic). Median time from initial treatment for metastatic disease to the first dose of Dato-DXd was 42.7 mo (range, 10.2-131.1). Treatment-emergent adverse events (TEAEs; all cause) were observed in 98% (any grade) and 41% (grade ≥3) of pts. Most common TEAEs (any grade, grade ≥3) were stomatitis (80%, 10%), nausea (56%, 0%), fatigue (46%, 2%), and alopecia (37%, 0%). Serious TEAEs were observed in 6 pts (15%); 1 pt died due to dyspnea, which was not considered to be treatment related. Dose reductions occurred in 5 pts due to stomatitis (n=3), fatigue (n=2), keratitis (n=1), and decreased appetite (n=1) (&gt;1 AE per pt); 14 pts had treatment delayed due to stomatitis (n=8), retinopathy (n=1), dysphagia (n=1), fatigue (n=1), malaise (n=1), COVID-19 (n=1), cellulitis (n=1), urinary tract infection (n=1), decreased lymphocyte count (n=1), and nasal congestion (n=1; &gt;1 AE per pt). Three pts discontinued treatment due to keratitis (n=1) and pneumonitis (n=2); 1 case of pneumonitis was adjudicated as grade 2 drug-related interstitial lung disease. The ORR was 29% (11 confirmed PRs; 1 pending confirmation), the DCR was 85% (35/41), and the clinical benefit rate (CR + PR + SD ≥6 mo) was 41% (17/41).

Conclusions: Dato-DXd demonstrated a manageable safety profile and encouraging antitumor activity, with high disease control in heavily pretreated pts, the majority having received prior CDK4/6i. Based on these findings, the TROPION-Breast01 (NCT05104866) randomized phase 3 study comparing 2L+ Dato-DXd vs investigator’s choice chemotherapy is currently enrolling pts with HR+/HER2− BC.

Prior Therapies in the Adjuvant or Metastatic Setting

Citation Format: Funda Meric-Bernstam, Ian Krop, Dejan Juric, Takahiro Kogawa, Erika Hamilton, Alexander I. Spira, Toru Mukohara, Takuya Tsunoda, Senthil Damodaran, Jonathan Greenberg, Wen Gu, Fumiaki Kobayashi, Hong Zebger-Gong, Yui Kawasaki, Rie Wong, Aditya Bardia. PD13-08 Phase 1 TROPION-PanTumor01 Study Evaluating Datopotamab Deruxtecan (Dato-DXd) in Unresectable or Metastatic Hormone Receptor–Positive/HER2–Negative Breast Cancer (BC) [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD13-08.

Application of Artificial Intelligence to Plasma Metabolomics Profiles to Predict Response to Neoadjuvant Chemotherapy in Triple-Negative Breast Cancer

There is a need to identify biomarkers predictive of response to neoadjuvant chemotherapy (NACT) in triple-negative breast cancer (TNBC). We previously obtained evidence that a polyamine signature in the blood is associated with TNBC development and progression. In this study, we evaluated whether plasma polyamines and other metabolites may identify TNBC patients who are less likely to respond to NACT. Pre-treatment plasma levels of acetylated polyamines were elevated in TNBC patients that had moderate to extensive tumor burden (RCB-II/III) following NACT compared to those that achieved a complete pathological response (pCR/RCB-0) or had minimal residual disease (RCB-I). We further applied artificial intelligence to comprehensive metabolic profiles to identify additional metabolites associated with treatment response. Using a deep learning model (DLM), a metabolite panel consisting of two polyamines as well as nine additional metabolites was developed for improved prediction of RCB-II/III. The DLM has potential clinical value for identifying TNBC patients who are unlikely to respond to NACT and who may benefit from other treatment modalities.

Abstract 1210: Resolving clonal substructure from single cell genomic data in primary and metastatic tumors using CopyKit

Advances in single cell copy number sequencing technologies have enabled the generation of data on hundreds to thousands of cells in parallel. Despite the rapid development in these technologies, there is a significant bottleneck for the analysis of the resulting large-scale datasets. Here we present CopyKit, a comprehensive and user-friendly toolkit for the analysis of single cell copy number data. CopyKit provides a suite of tools for pre-processing, QC, copy number inference, and subclone clustering to delineate the clonal diversity of tumors. We performed single cell copy number sequencing of 2977 cells from two breast tumor liver metastasis. CopyKit identified 4 and 12 subclonal populations, including amplification of PDGFRA, KRAS, and MYC as well as losses of PTEN, FOXO1, RB1, and BRCA1, many of which were spatially segregated in the tumor mass of the two tumors. Additionally, we applied CopyKit to study metastatic dissemination from a primary ER+ breast tumor with two matched metastatic sites and two colorectal carcinomas with matched liver metastatic tissues. This analysis demonstrated that the breast metastatic tumors selected for subclones that were lacking ERBB2 amplification in the primary site. Furthermore, the liver metastasis had deletions of chromosomes 18, 19, and 20p and a focal gain of FGFR1, while the pleural effusion acquired two additional focal gains on chromosome 8, including MYC. The colorectal metastatic tumors diverged from the primary tumor with copy number events affecting important cancer genes such as gain of SOX4, MYC, CDK8 and deletions of FHIT, CHEK1, and CHEK2. Collectively, this study shows that CopyKit provides a comprehensive set of tools for resolving clonal substructure from single cell copy number data for diverse applications in cancer biology.

Citation Format: Darlan Conterno Minussi, Junke Wang, Aislyn Schalck, Yun Yan, Hua-Jun Wu, Cheng Peng, Min Hu, Emi Sei, Mary Edgerton, Hui Chen, Alejandro Contreras, David Hui, Senthil Damodaran, Scott Kopetz, Bora Lim, Nicholas Navin. Resolving clonal substructure from single cell genomic data in primary and metastatic tumors using CopyKit [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1210.

Abstract 1791: Epigenetically upregulating TROP2 enhances therapeutic efficacy of TROP2 ADC sacitizumab govitecan

Purpose: TROP2 is overexpressed in many tumor types and is being actively pursued as a target. Sacituzumab govitecan (SG), a humanized anti-TROP2 antibody conjugated with SN-38, was approved for treatment of metastatic triple negative breast cancer, with the greatest efficacy in patients with medium or high TROP2 levels. We sought to enhance efficacy of TROP2-targeted therapies by pharmacological regulation of TROP2 expression.

Methods: TROP2 levels were assessed by immunohistochemistry (IHC) in two sets of breast tumors: a set of surgical samples and a tissue microarray. TROP2 mRNA expression was assessed in surgical samples and breast cancer patient-derived xenografts (PDXs) with RNAseq and assessed in the TCGA. In cell lines, expression of TROP2, E-cadherin (E-cad), and Schlafen family member 11 (SLFN11) were assessed by immunoblotting and qPCR following drug treatment or cell line manipulation. Epithelial-mesenchymal transition was evaluated by cell migration, cell invasion, and anchorage-independent growth assays. Antitumor efficacy of drug combination was assessed by cell survival, cell colony formation, and apoptosis assays.

Results: By IHC, TROP2 was expressed in only 40% of metaplastic breast cancers (MpBC), but nearly all non-MpBC tumors. TCGA database evaluation further showed higher TROP2 levels in non-MpBC tumors than metaplastic tumors. In breast cancer surgical specimens, breast cancer PDXs, and the TCGA, there was a strong correlation between TROP2 and E-cad expression. In vitro, we demonstrated that downregulating transcriptional factor zinc finger E-box binding homeobox 1 (ZEB1) led to mesenchymal-epithelial transition with upregulation of both E-cad and TROP2 expression in breast cancer cells, leading to increased sensitivity to SG treatment. Screening of epigenetic modulators identified DNA methyltransferase inhibitor decitabine as an enhancer of TROP2 and E-cad expression in PDX cell lines of metaplastic cancer origin and mesenchymal subtype breast cancer cell lines. Decitabine increased TROP2 expression by decreasing TROP2 promoter methylation. Decitabine was significantly synergistic with SG, and enhanced apoptosis. Similarly, overexpression of TROP2 (by plasmid) in cell lines enhanced activity of SG. Furthermore, decitabine increased expression of SLFN11, a putative biomarker of SN38 sensitivity, and was synergistic with SG in TROP2 expressing, SLFN11 low breast cancer cell lines.

Conclusion: TROP2 is expressed in most breast cancers, but is expressed less frequently in MpBC, an aggressive subtype unresponsive to traditional therapies. Epigenetic modulator decitabine upregulates TROP2 and SLFN11 expression and enhances antitumor efficacy of SG. Combinatorial treatment of TROP2 ADCs with epigenetic modulators of TROP2 represent a novel therapeutic strategy for tumors with low TROP2 or SLFN11 expression.

Citation Format: Ming Zhao, Timothy P. DiPeri, Gabriela Raso, Yasmeen Q. Rizvi, Xiaofeng Zheng, Kurt Evans, Argun Akcakanat, Fei Yang, Debu Tripathy, Ecaterina Ileana Dumbrava, Senthil Damodaran, Funda Meric-Bernstam. Epigenetically upregulating TROP2 enhances therapeutic efficacy of TROP2 ADC sacitizumab govitecan [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1791.

Abstract 1798: Mechanisms of acquired resistance to palbociclib reveals pathways of response to abemaciclib

Background: CDK4/6 inhibitors (CDK4/6i) plus endocrine therapy (ET) delay progression and improve survival in patients with hormone receptor positive (HR+), HER2 negative metastatic breast cancer (MBC). However, most patients develop resistance to CDK4/6i leading to disease progression, thus new therapies to overcome resistance are needed. CDK4/6i [palbociclib (palbo), ribociclib (ribo), and abemaciclib (abema)] have the same nominal targets but vary in their target specificity and are pharmacologically distinct. Clinical benefit was observed in patients treated with abema after progression on a prior CDK4/6i suggesting that palbo/ribo refractory tumors retain abema sensitivity. We hypothesize that mechanisms driving acquired resistance to palbo and abema are distinct, and palbo-resistant models may be responsive to abema.

Models: 1) MCF-7 and T47D palbo and abema resistant cells, 2) patient derived xenografts (PDX) established from patients who progressed on ET alone (ET-resistant) or palbo + ET (palbo-resistant), 3) organoids derived from the palbo-resistant PDX, and 4) a HR+/HER2- MBC patient cohort who received abema after progression on palbo therapy.

Results: RNA-sequencing and proteomic analysis revealed that palbo and abema resistant cells exhibit more than 30 differentially altered pathways. EMT, IL6/STAT3, and CSC pathways were upregulated only in palbo-resistant cells, but not in abema-resistant cells. Palbo-resistant cells also showed upregulation of G2M/Mitotic spindle and downregulation of ER pathways, whereas abema-resistant cells displayed downregulation of G2M/Mitotic spindle and upregulation of ER pathways. Mechanistic analysis revealed that palbo-resistant cells are responsive to abema with a delay in doubling time and a reduction of the proliferation marker pHH3. Further, cells accumulated in the G2M-phase with concomitant high phospho-(Y15)-CDK1 and cyclin B levels. Organoid cultures generated from palbo-resistant PDX were sensitive to abema. Likewise, abema significantly delayed the tumor growth of palbo-resistant PDX, correlating in vivo with ex vivo treatments. Moreover, we assessed response to abema after progression on palbo in the ET-resistant PDX model (CDK4/6 sensitive) demonstrating a continued survival benefit from abema treatment compared to palbo. Clinical outcome analyses of a MBC patient cohort treated with abema following prior CDK4/6i showed a median progression free survival (PFS) of 6.3 months in those treated sequentially vs a PFS of 4.0 months in non-sequential treated patients.

Conclusion: Differential mechanism underlying palbo and abema acquired resistance can be exploited to overcome CDK4/6i resistance. These results provide rationale for clinical trials evaluating the benefit of abema treatment following progression on a prior CDK4/6i.

Citation Format: Juliana Navarro-Yepes, Nicole M. Kettner, Tuyen Bui, Akshara S. Raghavendra, Xiayu Rao, Jing Wang, Aysegul Sahin, Senthil Damodaran, Debasish Tripathy, Kelly K. Hunt, Khandan Keyomarsi. Mechanisms of acquired resistance to palbociclib reveals pathways of response to abemaciclib [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1798.

Abstract 1768: Anti-tumor activity and biomarker analysis for datopotamab deruxtecan in breast cancer PDX models

Background: Trophoblast cell surface antigen (TROP2), is expressed on many tumors including breast cancer, thus TROP2 antibody drug conjugates are being pursued as a therapeutic strategy. Datopotamab deruxtecan (Dato-DXd) is composed of a humanized anti-TROP2 IgG1 monoclonal antibody attached to a highly potent topoisomerase I inhibitor payload (an exatecan derivative DXd) via a stable tetrapeptide-based cleavable linker. Dato-DXd has shown promise in the treatment of TROP2 expressing lung and breast cancers. However, the role of TROP2 as a predictor of therapeutic sensitivity is yet to be elucidated. We sought to determine efficacy of Dato-DXd in breast cancer patient-derived xenografts (PDXs) as well as explore biomarkers of response and combinations with PARP inhibitors.

Methods: Membrane expression of TROP2 was assessed in 31 breast cancer PDXs and matching patient tumors by immunohistochemistry (IHC). Schlafen family member 11 (SLFN11) nuclear expression was also assessed by IHC. The antitumor efficacy of two doses (1 and 10 mg/kg, q3wk, IV) of Dato-DXd and the isotype control-DXd (IgG-DXd) were tested against 9 breast cancer PDXs derived from residual tumors after neoadjuvant chemotherapy. The PDXs represented a range of TROP2 expression levels, including 3 TROP2 negative/low PDXs. The antitumor activity of Dato-DXd in combination with PARP inhibition (olaparib) was assessed in 3 PDXs with intermediate Dato-DXd activity. Tumor volumes were measured twice weekly; antitumor activity was assessed by treatment-to-control ratio (T/C) and event-free survival (EFS-2). T/C ratio was calculated as (Vt,21/Vt,0)/(Vc,21/Vc,0), where t = treatment, c = control (no treatment or IgG-DXd), and V = tumor volume (mm3). Stable disease (SD) and response (R) were based on day 21 (-30- to 20% and &lt;-30%, respectively). An event was defined as tumor doubling.

Results: TROP2 H-score in PDXs correlated with TROP2 expression in matched patients (r= 0.7264, p&lt;0.0001), however expression was lower in PDXs (p= 0.04). Dato-DXd caused R/SD in 2 of 9 models at 1 mg/kg, and in 4 of 9 models at 10 mg/kg. All models that regressed with Dato-DXd expressed TROP2. TROP2 expression was associated with higher antitumor activity compared to IgG-DXd based on T/C ratio (r= -0.7448, p= 0.0213) and EFS-2 (r= 0.9318, p= 0.0068) at 10 mg/kg but not at 1 mg/kg. Three models with low TROP2 expression had &gt;50% SLFN11 positivity in the nucleus by IHC; 2 of 3 had doubling of EFS-2 both by Dato-DXd and IgG-DXd. The combination of Dato-DXd and olaparib had improved activity over single agents in 2 of 3 models. Additional comparative predictive and pharmacodynamic biomarker studies will be presented.

Conclusion: Dato-DXd is a promising therapy for breast cancer patients including those resistant to standard chemotherapy. Additional biomarkers may better integrate DXd sensitivity into patient selection.

Citation Format: Erkan Yuca, Kurt Evans, Argun Akcakanat, Gabriela Raso, Yasmeen Q. Rizvi, Fei Yang, Lauren Byers, Senthil Damodaran, Okajima Daisuke, Funda Meric-Bernstam. Anti-tumor activity and biomarker analysis for datopotamab deruxtecan in breast cancer PDX models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1768.

Open-label, phase 2, multicenter study of lasofoxifene (LAS) combined with abemaciclib (Abema) for treating pre- and postmenopausal women with locally advanced or metastatic ER+/HER2− breast cancer and an ESR1 mutation after progression on prior therapies

1022

Background: Resistance to endocrine therapy can develop when treating estrogen receptor positive (ER+), metastatic breast cancer (mBC). Treatment with aromatase inhibitors can lead to acquired mutations in the estrogen receptor 1 ( ESR1), which can constitutively activate the ER, leading to endocrine resistance and worse disease prognosis. Treatment options for mBC patients with an ESR1 mutation are limited. Further, data suggest that patients could derive clinical benefit from Abema after progression on prior cyclin-dependent kinase 4/6 inhibitor (CDK4/6i). LAS, a third-generation selective estrogen receptor modulator, as monotherapy or combined with a CDK4/6i, was shown to have superior efficacy over fulvestrant (FVT) in preclinical breast cancer models expressing ESR1 mutations. Based on these results, a phase 2 clinical trial of LAS combined with Abema was initiated in mBC patients with ESR1 mutations. Methods: ELAINE 2 is an open-label, phase 2, multicenter trial evaluating the safety and efficacy of LAS combined with the CDK4/6i, Abema. Study participants were pre- and postmenopausal women with ER+/HER2- mBC with acquired ESR1 mutation (identified by ctDNA testing), whose disease had progressed on one or two lines of hormonal therapy for metastatic disease with or without a CDK4/6i (including Abema). Patients took oral LAS 5 mg/day and Abema 150 mg BID. Treatment continued until evidence of disease progression, death, unacceptable toxicity, or withdrawal from the study. The primary endpoint was safety, and secondary endpoints were progression free survival (PFS), objective response rate (ORR), and clinical benefit rate (CBR). Results: 29 patients were enrolled at 16 US sites (Oct 2020 to June 2021). Mean age was 58.3 y (35-79 y); 86% were Caucasian. Most had progressed with at least 2 previous hormonal treatments (80%). All except 1 patient received a prior CDK4/6i and 72% had received prior FVT; 48% had chemotherapy in the metastatic setting. Four patients discontinued the trial due to adverse events (AEs, n = 2), consent withdrawal (n = 1), or investigator withdrawal (n = 1). No deaths occurred during the study and few Grade 3/4 AEs were observed. Most common AEs were diarrhea, nausea, and leukopenia. Five patients had an Abema dose reduction from 150 mg to 100 mg BID. To date, 11 patients have progressed and 14 continue treatment. The censored median PFS was 13.9 mos (95% CI, 8.0‒NE), the ORR 33.3% (95% CI, 16.3‒56.3) with 6 confirmed partial responses, and the CBR 62.1% (95% CI, 44.0‒77.3). Conclusions: LAS combined with Abema in the ELAINE 2 trial was well tolerated and demonstrated robust and meaningful efficacy in women with ER+/HER2- mBC and an ESR1 mutation who had progressed on previous CDK4/6i therapies. Clinical trial information: NCT04432454.

Phase Ib study of selinexor and eribulin combination in advanced solid tumors and triple-negative breast cancer

3108

Background: Selinexor (KPT-330) is potent inhibitor of Exportin-1. In vitro, Selinexor was found to be synergistic with eribulin in triple negative breast cancer (TNBC) cell lines and enhanced antitumor activity of eribulin in TNBC patient-derived xenografts (PMID 28810913). Methods: We conducted a phase Ib trial in combination of selinexor and eribulin using 3 + 3 design in dose escalation for patients with advanced solid tumors and in TNBC in dose expansion cohort. Eribulin could be discontinued after combination for 6 cycles at physician discretion. Primary objectives: Safety, Recommended Phase 2 Dose (RP2D). Secondary Objectives: Objective Response Rate (ORR), Duration of Response (DOR), Disease Control Rate (DCR), Overall Survival (OS) and Progression Free Survival (PFS). Results: 31 patients, TNBC (n = 19), sarcoma (n = 8), others (n = 4) enrolled in dose escalation (n = 10) and dose expansion phases (n = 21). Median prior therapies:4 (1–6). Study initiated selinexor at 60mg twice weekly and eribulin 1.4mg/m2 on Day1, Day8 every 3 weeks which led to 1 Dose Limiting Toxicity (DLT) and hence, selinexor 80mg once weekly and eribulin 1mg/m2 was elected as RP2D due to efficacy and tolerability. As of 01/15/2022, of 29 patients (94%) who have discontinued treatment, 24 (77%) were due to progressive disease, 3 (10%) withdrew consent and 2 (6%) due to toxicities (G1 pneumonitis; G3 neutropenia) while 2 (6%) remain on trial. All 31 patients had at least one treatment emergent adverse event (TEAE) while most prevalent TEAEs (all grades) were leukopenia (77%), nausea (71%), anemia and neutropenia (68%) and fatigue (48%). The most common G3/4 TEAE were leukopenia (26%) and neutropenia (29%). 2 DLTs occurred; 1 in first dose level (DL); 1 in second DL dosed at selinexor 80 mg once weekly due to G3 neutropenia. ORR for all was 10% while DCR (SD+PR+CR) > 6 months seen in 3 (15%) TNBC and 2 (20%) sarcoma patients. The median OS and PFS for all were 12.3 (7.3, 27.3) months and 2.3 (1.6, 4.1) months. In dose escalation cohort, ORR was 10% where one patient (3%) with vaginal SCC had confirmed PR (-44%) for 2.1 months. Five patients (62.5%) with sarcoma had stable disease (SD). One patient with high grade sarcoma has SD for 68 months and remains on selinexor after 4 months of eribulin and selinexor. In TNBC dose expansion (n = 19), ORR was 10.5% with 2 confirmed PRs and median duration of response (DOR) of 10.8 months. One patient who has remained on treatment for 18 months, and after receiving 8 months of eribulin and selinexor, remains on selinexor with 100% target regression and an indeterminate brain lesion. Conclusions: Selinexor with eribulin is safe with manageable toxicity profile and modest overall clinical efficacy. Durable responses and disease control were observed with metastatic TNBC. Further study is needed to examine the determinants of response to this combination. Clinical trial information: NCT02419495.

Operational metrics for the ELAINE II study combining a traditional approach with a just-in-time model

1504

Background: Trial recruitment that requires specific actionable mutations based on next-generation sequencing (NGS) is challenging. Barriers can include competing studies, physician study awareness, site proximity, mutation incidence, among other concerns. Methods: This study (NCT04432454) opened clinical sites using two methods during the COVID-19 pandemic. The “Traditional” approach included site selection, IRB and contract approval, and trial activation prior to a patient being identified for enrollment. The second approach used the Tempus “TIME” Trials network that would only open a site after identifying a patient with a mutation of interest and eligible for the trial. Results: The first patient enrolled was on 10/12/20 and the last patient was on 6/24/21. A total of 16 sites (6 Traditional and 10 TIME) participated. All Traditional sites, and none of the TIME sites, were affiliated with major academic institutions. Duration for full CTA execution for Traditional sites averaged 200.5 days (range 142 to 257) and for TIME sites averaged 7.6 days (range 2 to 14). IRB approval time average for Traditional sites was 27.5 days (range 12 to 71) and TIME sites was 3.0 days (range 1 to 12 days). Days from site selection to activation letter for Traditional sites was on average 250.0 days (range 187 to 281) and for TIME sites was 131.6 days (range 22 to 248). Time from study activation to first consent was 33.3 days (range 18 to 58) for Traditional sites and 8.8 days (range 1 to 35) for TIME sites. The first patient on-study was at a TIME site 115 days prior to a Traditional site and the first 7 patients enrolled were at TIME sites. Traditional sites consented 23 and enrolled 16 patients while the TIME sites consented 16 and enrolled 13. The trial enrolled all 29 patients in 8 months with the anticipated enrollment duration being 12 to 18 months. Conclusions: Although the Traditional and TIME programs had different operational models, they both contributed a significant number of patients and reduced the projected enrollment timeline. TIME sites enrolled the initial patients. These results demonstrate that the “Just-in-Time model,” in conjunction with a Traditional model, can reduce projected overall time to enrollment in biomarker-driven studies. [Table: see text]

Phase II Study of Copanlisib in Patients With Tumors With PIK3CA Mutations: Results From the NCI-MATCH ECOG-ACRIN Trial (EAY131) Subprotocol Z1F

PURPOSE

Activating mutations in PIK3CA are observed across multiple tumor types. The NCI-MATCH (EAY131) is a tumor-agnostic platform trial that enrolls patients to targeted therapies on the basis of matching genomic alterations. Arm Z1F evaluated copanlisib, an α and δ isoform-specific phosphoinositide 3-kinase (PI3K) inhibitor, in patients with PIK3CA mutations (with or without PTEN loss).

PATIENTS AND METHODS

Patients received copanlisib (60 mg intravenous) once weekly on days 1, 8, and 15 in 28-day cycles until progression or toxicity. Patients with KRAS mutations, human epidermal growth factor receptor 2-positive breast cancers, and lymphomas were excluded. The primary end point was centrally assessed objective response rate (ORR); secondary end points included progression-free survival, 6-month progression-free survival, and overall survival.

RESULTS

Thirty-five patients were enrolled, and 25 patients were included in the primary efficacy analysis as prespecified in the Protocol. Multiple histologies were enrolled, with gynecologic (n = 6) and gastrointestinal (n = 6) being the most common. Sixty-eight percent of patients had ≥ 3 lines of prior therapy. The ORR was 16% (4 of 25, 90% CI, 6 to 33) with P = .0341 against a null rate of 5%. The most common reason for protocol discontinuation was disease progression (n = 17, 68%). Grade 3/4 toxicities observed were consistent with reported toxicities for PI3K pathway inhibition. Sixteen patients (53%) had grade 3 toxicities, and one patient (3%) had grade 4 toxicity (CTCAE v5.0). Most common toxicities include hyperglycemia (n = 19), fatigue (n = 12), diarrhea (n = 11), hypertension (n = 10), and nausea (n = 10).

CONCLUSION

The study met its primary end point with an ORR of 16% (P = .0341) with copanlisib showing clinical activity in select tumors with PIK3CA mutation in the refractory setting.

Biomarkers for Adjuvant Endocrine and Chemotherapy in Early-Stage Breast Cancer: ASCO Guideline Update

PURPOSE

To update recommendations on appropriate use of breast cancer biomarker assay results to guide adjuvant endocrine and chemotherapy decisions in early-stage breast cancer.

METHODS

An updated literature search identified randomized clinical trials and prospective-retrospective studies published from January 2016 to October 2021. Outcomes of interest included overall survival and disease-free or recurrence-free survival. Expert Panel members used informal consensus to develop evidence-based recommendations.

RESULTS

The search identified 24 studies informing the evidence base.

RECOMMENDATIONS

Clinicians may use Oncotype DX, MammaPrint, Breast Cancer Index (BCI), and EndoPredict to guide adjuvant endocrine and chemotherapy in patients who are postmenopausal or age > 50 years with early-stage estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-negative (ER+ and HER2-) breast cancer that is node-negative or with 1-3 positive nodes. Prosigna and BCI may be used in postmenopausal patients with node-negative ER+ and HER2- breast cancer. In premenopausal patients, clinicians may use Oncotype in patients with node-negative ER+ and HER2- breast cancer. Current data suggest that premenopausal patients with 1-3 positive nodes benefit from chemotherapy regardless of genomic assay result. There are no data on use of genomic tests to guide adjuvant chemotherapy in patients with ≥ 4 positive nodes. Ki67 combined with other parameters or immunohistochemistry 4 score may be used in postmenopausal patients without access to genomic tests to guide adjuvant therapy decisions. BCI may be offered to patients with 0-3 positive nodes who received 5 years of endocrine therapy without evidence of recurrence to guide decisions about extended endocrine therapy. None of the assays are recommended for treatment guidance in individuals with HER2-positive or triple-negative breast cancer. Treatment decisions should also consider disease stage, comorbidities, and patient preferences.Additional information is available at www.asco.org/breast-cancer-guidelines.

Abstract P1-19-01: Palbociclib plus endocrine therapy significantly enhances overall survival of HR+/HER2- metastatic breast cancer patients compared to endocrine therapy alone - A large institutional study

PURPOSE: Cyclin-dependent kinase 4/6 inhibitor (CDKi) therapy combined with endocrinetherapy is considered standard of care for patients with advanced hormone receptor (HR)-positive, HER2-negative breast cancer (BC). The Breast Medical Oncology Database at MDAnderson Cancer Center (MDACC) was analyzed to assess effectiveness of CDKi+palbociclib. PATIENTS AND METHODS: From a total of 5402 advanced HR+ HER2- BC patients referred toMDACC between 1997 and 2020, we identified eligible patients who received palbociclib incombination with first- (n=778) and second-line (n=410) endocrine therapy. We furtheridentified “control” patients who received endocrine therapy alone in the first- (n=2452) andsecond-line (n=1183) setting. We conducted a propensity score matching analysis to balancethe baseline demographic and clinical characteristics between the palbociclib treated andcontrol cohorts to assess the effect of palbociclib treatment on progression-free survival (PFS)and overall survival (OS). Stratified log-rank test was used to assess the effect of palbociclib inthe matched cohorts. RESULTS: For the propensity-matched cohort in the first-line setting (n=708), the palbociclibgroup had significantly longer median PFS (17.4 vs. 11.1 months; p&lt;0.0001) compared tocontrols. Median OS (44.3 vs. 40.2 months; p =1) did not show any survival benefit in the firstline setting. However, in the second-line setting, with 380 propensity-matched cohort, thepalbociclib group had significantly longer PFS (10 vs 5 months, p&lt;0.0001) as well as OS (33 vs 24months; p &lt; 0.022), compared to controls.2. CONCLUSION: In this single center analysis, of a large cohort of metastatic HR+ HER2- BCpatients, palbociclib in combination with endocrine therapy was associated with improved PFSin both first- and second-line settings and OS in the second-line setting compared withendocrine therapy alone cohort.3

Citation Format: Akshara Singareeka Raghavendra, Min Jin Ha, Nicole M. Kettner, Senthil Damodaran, Rachel Layman, Kelly K Hunt, Yu Shen, Debu Tripathy, Khandan Keyomarsi. Palbociclib plus endocrine therapy significantly enhances overall survival of HR+/HER2- metastatic breast cancer patients compared to endocrine therapy alone - A large institutional study [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-19-01.

Abstract P1-18-35: Futibatinib in combination with fulvestrant in patients with metastatic breast cancer (MBC) harboring high-level FGFR1 amplification: Preliminary data from a phase 2 study

Background: FGFR gene amplifications are found in 18% of breast cancers (BCs), with FGFR1 amplifications occurring in ≈10% of cases, predominantly in hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2−) MBCs. FGFR1 amplifications are associated with resistance to endocrine therapy, and in preclinical experiments, FGFR pathway inhibition has been shown to overcome resistance to hormone therapy in BC harboring FGFR1 amplifications. Futibatinib, a highly selective, irreversible FGFR1-4 inhibitor, has shown preclinical activity in BC xenograft models harboring FGFR1/2 amplifications. In a phase 1 study, futibatinib showed promising clinical activity and tolerability across tumor types, including MBC, harboring various FGFR aberrations. A multicohort phase 2 trial (FOENIX-MBC2; NCT04024436) was designed to evaluate futibatinib alone (cohorts 1-3) or in combination with fulvestrant (cohort 4) in patients with MBC harboring FGFR2 or FGFR1 amplifications, respectively. Here, we report preliminary safety data from cohort 4 of FOENIX-MBC2, including data from a safety lead-in. Methods: Cohort 4 of FOENIX-MBC2 enrolled adult patients with HR+ HER2− MBC harboring high levels of FGFR1 amplification (FGFR1:CEN8 ratio ≥5 or FGFR1 copy number ≥10 signals per cell), Eastern Cooperative Oncology Group performance status 0-1, and adequate organ function. Patients were fulvestrant naive and had previously received 1-2 endocrine-containing therapies, ≤1 chemotherapy regimen, and a CDK4/6 inhibitor (if eligible). Cohort 4 began with a safety lead-in to assess dose-limiting toxicities (DLTs) during the first treatment cycle. Patients received oral futibatinib 20 mg once daily continuously, and intramuscular fulvestrant 500 mg was administered on days 1 and 15 of cycle 1 and day 1 of every subsequent 28-day cycle. Patients were treated until disease progression, unacceptable toxicity, or another discontinuation criterion was met. Results: As of data cutoff (March 31, 2021), cohort 4 had enrolled 8 female patients with HR+ HER2− MBC harboring high-level FGFR1 amplification. The median age was 55.5 years (range: 31-62 years), and all patients had received ≥2 prior therapies for advanced/metastatic BC. The median duration of treatment was 8.0 weeks (range: 3.0-32.7 weeks); 3 of 8 patients (38%) were continuing treatment at time of data cutoff. All patients experienced treatment-related adverse events (TRAEs; grade ≥3: 25%). The most common TRAE was hyperphosphatemia (88%), followed by constipation (62%), transaminase elevation (50%), dry mouth (38%), and alopecia (38%). Among these TRAEs, grade ≥3 events were only reported for hyperphosphatemia (12%), and no serious adverse events were reported. In this cohort, TRAEs led to dose reductions in 4 patients, dosing interruptions in 3 patients, and treatment discontinuation in 1 patient; no patients died due to TRAEs. DLTs were evaluated in 5 patients following 1 treatment cycle (1 patient was enrolled after data cutoff, and 4 of 9 patients were not evaluable for DLTs); DLTs were not experienced by any of the 5 evaluable patients. Conclusions: Based on these preliminary safety results, the combination of futibatinib and fulvestrant appears to be safe and tolerable in patients with HR+ HER− MBC harboring high-level FGFR1 amplification. The safety profile was consistent with the individual profiles of both drugs, and the treatment combination did not appear to result in synergistic toxicity. As no DLTs were observed in 5 evaluable patients, the recommended futibatinib dose in combination with fulvestrant is 20 mg once daily. Efficacy will be evaluated in the complete 28-patient post-lead-in cohort, in which enrollment is ongoing.

Citation Format: Senthil Damodaran, Nisha Unni, Karthik V. Giridhar, Brooke Daniel, Sacha Howell, Luis Costa, Marta Ferreira, Masashi Shimura, Gareth Tomlinson, Maciej Gil, Nicholas Turner. Futibatinib in combination with fulvestrant in patients with metastatic breast cancer (MBC) harboring high-level FGFR1 amplification: Preliminary data from a phase 2 study [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-18-35.

Abstract PD11-06: Radiomics model based on magnetic resonance image compilation (MagIC) as early predictor of pathologic complete response to neoadjuvant systemic therapy in triple-negative breast cancer

Background and Purpose: There is currently lack of recognized imaging criteria for prediction of treatment response to NAST in breast cancer patients. And early identification of treatment response to neoadjuvant systemic therapy (NAST) in Triple Negative Breast Cancer (TNBC) patients is important for appropriate treatment selection and response monitoring. A novel MRI sequence, Magnetic Resonance Image Compilation (MagIC) is capable of simultaneous quantitation of several tissue water properties including longitudinal (T1), transverse (T2) relaxation times, and proton density (PD). In this study we evaluated the ability of a radiomic model extracted from a novel MagIC sequence acquired early during NAST to predict pathologic complete response to NAST in TNBC. Materials and Methods: This IRB approved prospective ARTEMIS trial (NCT02276443) included 184 women (122 training dataset, 62 testing dataset) diagnosed with stage I-III TNBC. All patients were scanned with MagIC on a 3T MRI scanner at baseline (184 patients), and after 4 cycles (156 Patients) of NAST. T1, T2 and PD maps were generated from the source images using SyMRI (SyntheticMR, Linkoping, Sweden). Histopathology at surgery was used to determine pathologic complete response (pCR) which was defined as absence of the invasive cancer in the breast and axillary lymph nodes. 3D contouring of the tumors was performed using an in-house toolbox. 310 (10 first-order, 300 GLCM) textural features were extracted from each map, with total of 930 features/patient. Radiomic features were compared between pCR and non-pCR using Wilcoxon Rank Sum test and Fisher’s exact test. To build a multivariate, predictive model, logistic regression with elastic net regularization was performed for texture feature selection. The tuning parameter was optimized using 5-fold cross-validation based on the average area under curve (AUC) of each fold of a cross-validation using training data. Then the testing data were used to compare model’s performance by AUC. Results: Univariate analysis found 23 PD, 17 T1 and 10 T2 radiomic features at C4 time point to be able to predict pCR status with AUC &gt;70% in both training and testing cohort. The top performing radiomic features were Entropy, Variance, Homogeneity and Energy (Tables1-2). Multivariate radiomics models from C4-PD, and C4-T1 maps showed best performance during both cross validation and independent testing. The radiomic signature of C4-T1 map that included 27features had best performance, with an AUC of 0.77, 0.70 (95% CI: 0.571-0.868) in training and testing cohort respectively. C4-PD map radiomic signature that included 6features was able to predict the pCR status with AUC of 0.73, 0.72 (95% CI: 0.571-0.868) in training and testing cohort respectively. Conclusion: Our data found that MagIC-based radiomics signature could potentially predict pathologic complete response in TNBC early during NAST. This data shows the potential application of MagIC radiomic model for improvement of response assessment in TNBC.

Table 1.Best performing radiomic features from PD map after 4 cycles of NAST in TNBC patients.FeatureTraining CohortTraining CohortTraining CohortTesting CohortTesting CohortTesting CohortNAUC95% CINAUC95% CIP-valuePD-mapAngular Variance of Sum entropy1060.73820.6437-0.8328500.73240.5895-0.8752&lt;0.001Range of Sum entropy1060.73930.6446-0.834500.72120.5753-0.867&lt;0.001Angular Variance of Sum entropy1060.75960.6662-0.853500.70190.5538-0.8501&lt;0.001Average of Sum entropy1060.73470.6367-0.8327500.70990.5613-0.8585&lt;0.001Angular Variance of Sum variance1060.70160.602-0.8011500.70190.5543-0.8495&lt;0.001Range of Sum variance1060.70050.6001-0.8009500.700.5499-0.8476&lt;0.001

Table 2.Best performing radiomic features from T1-T2 maps after 4 cycles of NAST in TNBC patients.FeatureTraining CohortTraining CohortTraining CohortTesting CohortTesting CohortTesting CohortNAUC95% CINAUC95% CIP-valueT1-mapAngular Variance of Sum entropy1060.76530.6762-0.8544500.70510.5524-0.8579&lt;0.001Range of Sum entropy1060.76530.6759-0.8547500.70350.5503-0.8567&lt;0.001Average of Entropy1060.75250.6568-0.8482500.71630.572-0.8607&lt;0.001Average of Sum entropy1060.750.6552-0.8448500.70190.555-0.8488&lt;0.001Angular Variance of Energy1060.7450.6493-0.8407500.73080.59-0.8715&lt;0.001Range of Energy1060.74290.6466-0.8392500.72920.5885-0.8699&lt;0.001Average of Energy1060.74110.6438-0.8384500.7260.5852-0.8667&lt;0.001Average of Entropy1060.73360.635-0.8322500.74040.602-0.8787&lt;0.001Average of Maximum probability1060.70760.6054-0.8098500.71630.5704-0.8623&lt;0.001Range of Maximum probability1060.70550.6018-0.8092500.75640.6195-0.8933&lt;0.001T2-mapAngular Variance of Energy1060.74820.6531-0.8433500.70990.5644-0.8555&lt;0.001Range of Energy1060.7450.6495-0.8405500.70350.5569-0.8501&lt;0.001Average of Entropy1060.74070.6416-0.8399500.72920.585-0.8733&lt;0.001Average of Sum entropy1060.73860.6405-0.8367500.72440.5797-0.869&lt;0.001Average of Energy1060.73180.6309-0.8327500.72120.5743-0.86&lt;0.001Angular Variance of Sum entropy1060.7290.631-0.827500.72760.5857-0.8695&lt;0.001Range of Sum entropy1060.72760.6295-0.8257500.72280.5796-0.8659&lt;0.001Average of Information measure of correlation 11060.71580.6147-0.8169500.70990.5638-0.8561&lt;0.001Average of Entropy1060.700.5903-0.8028500.74360.6014-0.8858&lt;0.001

Citation Format: Nabil Elshafeey, Ken-Pin Hwang, Beatriz Elena Adrada, Rosalind Pitpitan Candelaria, Medine Boge, Rania M Mahmoud, Huiqin Chen, Jia Sun, Wei Yang, Aikaterini Kotrotsou, Benjamin C Musall, Jong Bum Son, Gary J Whitman, Jessica Leung, Huong Le-Petross, Lumarie Santiago, Deanna Lynn Lane, Marion Elizabeth Scoggins, David Allen Spak, Mary Saber Guirguis, Miral Mahesh Patel, Frances Perez, Abeer H Abdelhafez, Jason B White, Lei Huo, Elizabeth Ravenberg, Wei Peng, Alastair Thompson, Senthil Damodaran, Debu Tripathy, Stacey L Moulder, Clinton Yam, Mark David Pagel, Jingfei Ma, Gaiane Margishvili Rauch. Radiomics model based on magnetic resonance image compilation (MagIC) as early predictor of pathologic complete response to neoadjuvant systemic therapy in triple-negative breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD11-06.

Abstract OT2-24-03: Phase II study of a PARP inhibitor in metastatic breast cancer with somaticBRCA1/2mutations identified by cell-free DNA: Genotyping based clinical trial

Background: Two PARP inhibitors are approved for germline BRCA1/2 mutant metastatic breast cancer (MBC), based on clinical trials demonstrating an improvement in patient outcomes and quality of life. However, germline BRCA1/2 mutations are identified in 5-10% of breast cancer, limiting their potential applicability. Our prior work demonstrated that somatic BRCA1/2 mutations can be detected in cell-free DNA (cfDNA) in a proportion of patients with MBC who are not germline BRCA1/2 carriers, and that a PARP inhibitor caused growth inhibition in a circulating tumor cell line generated from a patient with MBC and a pathogenic somatic BRCA1 mutation (Vidula, Dubash, CCR, 2020). Thus, we hypothesize that a PARP inhibitor may have efficacy in somatic BRCA1/2 mutant MBC identified by cfDNA. Trial Design: This phase II investigator initiated open label clinical trial is enrolling 30 patients who have pathogenic somatic BRCA1/2 mutations found in cfDNA. Patients must not be known germline BRCA1/2 carriers. Patients receive treatment with the PARP inhibitor, talazoparib, until disease progression. Serial imaging (CT chest, abdomen, pelvis, and bone scan) occurs every 3 months, and cfDNA is collected monthly to evaluate changes in the genomic environment. Patients will also have blood collected at baseline for the Cancer Risk B assay (CR-B), a novel flow variant assay to assess double strand break repair mutations in circulating blood cells (Syeda, Genetics, 2017). Eligibility criteria: Patients with MBC (TNBC with ≥ 1 prior chemotherapy or HR+/HER2- with ≥ 1 prior hormone therapy or ineligible for hormone therapy) with a somatic BRCA1/2 mutation identified in cfDNA (established pathogenic variant) are being enrolled. Patients should not be known germline BRCA1/2 carriers (genetic testing is not required but can be obtained per physician discretion) and may not have previously received a PARP inhibitor. There is no limit on the number of prior therapies, and a prior platinum chemotherapy is allowed in the absence of disease progression on the platinum. Patients must have adequate performance status and organ function. Specific Aims: The primary endpoint is progression-free survival (PFS) using RECIST 1.1. Secondary endpoints include objective response rate and toxicity (NCI CTCAE v 5.0). Exploratory objectives include evaluating serial changes in BRCA1/2 mutant allelic frequency in cfDNA, evaluating the impact of BRCA1/2 reversion mutations, comparing pre- and post-treatment cfDNA results to identify markers of resistance, evaluating the CR-B assay positivity rate, and ultimately correlating these analyses with treatment response. Statistical Methods: A two-stage design with 80% power to demonstrate that talazoparib is associated with “success” (PFS &gt; 12 weeks) in ≥53% patients (4% alpha) is being used. Accrual: This study (NCT03990896) is currently open at Massachusetts General Hospital, where 4 patients are completing screening for enrollment. This study will be activated soon at the University of California San Francisco, MD Anderson, Mayo Clinic Rochester and Jacksonville, Northwestern, and Emory (7 academic centers). Funding: Support for this study is provided by a Pfizer ASPIRE award and Conquer Cancer Foundation of ASCO–Breast Cancer Research Foundation- Career Development Award. Contact information: Neelima Vidula, MD, Massachusetts General Hospital, nvidula@mgh.harvard.edu

Citation Format: Neelima Vidula, Erica Blouch, Erin Basile, Nathan Royce Ruffle-Deignan, Nora Horick, Senthil Damodaran, Alvaro Moreno Aspitia, Manali Bhave, Ami Shah, Minetta C. Liu, Joseph Sparano, Harry Ostrer, Hope Rugo, Leif W. Ellisen, Aditya Bardia. Phase II study of a PARP inhibitor in metastatic breast cancer with somaticBRCA1/2mutations identified by cell-free DNA: Genotyping based clinical trial [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr OT2-24-03.

Abstract GS1-05: Datopotamab deruxtecan in advanced/metastatic HER2- breast cancer: Results from the phase 1 TROPION-PanTumor01 study

Background: Datopotamab deruxtecan (Dato-DXd) is an antibody-drug conjugate consisting of a humanized anti-TROP2 IgG1 monoclonal antibody conjugated to a potent topoisomerase I inhibitor payload via a stable tetrapeptide-based cleavable linker. Preliminary results from the phase 1 TROPION-PanTumor01 study demonstrate that Dato-DXd has encouraging antitumor activity and a manageable safety profile in patients with non-small cell lung cancer (NSCLC) (Meric-Bernstam, ASCO 2021) and those with triple-negative breast cancer (TNBC) (Bardia, ESMO BC 2021). Updated results from the TNBC cohort are presented here. Methods: TROPION-PanTumor01 (NCT03401385) is a phase 1, multi-center, open-label, 2-part study evaluating Dato-DXd in previously treated patients with solid tumors. Based on the dose-escalation results in patients with NSCLC, Dato-DXd 6 mg/kg intravenously every 3 weeks is being evaluated in patients with advanced/metastatic TNBC and HR+/HER2− breast cancer who relapsed/progressed on standard therapies. Two patients with TNBC received Dato-DXd 8 mg/kg prior to selection of 6 mg/kg for dose expansion. Safety and efficacy were assessed, including objective response rate (ORR) per RECIST version 1.1 by blinded independent central review (BICR). Results: As of the April 6, 2021, data cutoff, 43 patients with TNBC had received ≥1 dose of Dato-DXd, with 27 patients (63%) continuing and 16 patients (37%) discontinuing treatment all due to disease progression. The median age was 53 years (range, 32-82 years). Forty-one patients (95%) had received ≥2 prior lines of therapy; 19 patients (44%) had received prior immunotherapy and 7 (16%) had received prior sacituzumab govitecan. The median duration of treatment was 2.8 months (range, 0.7-6.9 months). The median follow-up was 3.9 months (range, 0.3-9.2 months). Among 38 patients evaluable for response, the ORR by BICR was 39% (15 partial responses [PR]), with 12 confirmed and 3 pending confirmation. The disease control rate was 84% (32/38). The median time to response was 1.35 months (1.2-3.2 months) for the 12 confirmed PRs. All-cause treatment-emergent adverse events (TEAEs; any grade, grade ≥3) were observed in 95% and 35% of patients, respectively; 2 events were grade 4 and 0 grade 5. The most common TEAEs (any grade [≥30%], grade ≥3) included nausea (58%, 0%), stomatitis (53%, 9%), alopecia (35%, N/A), vomiting (35%, 2%), and fatigue (33%, 7%). One patient had grade 3 decreased neutrophil count; no cases of grade ≥3 diarrhea were observed. No cases of treatment-related interstitial lung disease as adjudicated by an independent committee were reported. Serious TEAEs were observed in 5 patients (12%); no TEAEs were associated with death. Dose reductions occurred in 9 patients due to stomatitis, fatigue, mucosal inflammation, dry eye, retinal exudates, and blurred vision (multiple counts per TEAE). Three patients had dose interruptions due to stomatitis, mucosal inflammation, bronchitis, and musculoskeletal chest pain. No patients discontinued treatment due to adverse events. Conclusions: Preliminary results showed that Dato-DXd demonstrates promising antitumor activity with a manageable safety profile in patients with previously treated advanced/metastatic TNBC; confirmatory studies in patients with breast cancer are warranted.

Citation Format: Ian Krop, Dejan Juric, Toshio Shimizu, Anthony Tolcher, Alexander Spira, Toru Mukohara, Aaron E. Lisberg, Takahiro Kogawa, Kyriakos P. Papadopoulos, Erika Hamilton, Senthil Damodaran, Jonathan Greenberg, Wen Gu, Fumiaki Kobayashi, Ferdinand Guevara, Takahiro Jikoh, Yui Kawasaki, Funda Meric-Bernstam, Aditya Bardia. Datopotamab deruxtecan in advanced/metastatic HER2- breast cancer: Results from the phase 1 TROPION-PanTumor01 study [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr GS1-05.

Palbociclib plus endocrine therapy significantly enhances overall survival of HR+/HER2- metastatic breast cancer patients compared to endocrine therapy alone in the second-line setting-a large institutional study

Cyclin-dependent-kinase-4/6 inhibitor (CDKi) plus endocrine therapy (ET) is standard of care for patients with advanced hormone receptor (HR)-positive, HER2-negative breast cancer (BC). The Breast Medical Oncology database at MD Anderson Cancer Center (MDACC) was analyzed to assess effectiveness of the CDKi palbociclib plus ET compared to ET alone. From a total of 5402 advanced HR+ HER2- BC patients referred to MDACC between 1997 and 2020, we identified eligible patients who received palbociclib in combination with first- (n=778) and second-line (n=410) ET. We further identified "control" patients who received ET alone in the first- (n=2452) and second-line (n=1183) settings. Propensity score matching analysis was conducted to balance baseline demographic and clinical characteristics between palbociclib and control cohorts to assess the effect of palbociclib treatment on progression-free survival (PFS) and overall survival (OS). For propensity-matched-cohort in the first-line setting (n=708), palbociclib group had significantly longer median PFS (17.4 vs. 11.1 months; p<0.0001) compared to controls. Median OS (44.3 vs. 40.2 months) did not show a statistically significant benefit in the first line setting. However, in the second-line setting, with 380 propensity-matched-cohort, the palbociclib group had significantly longer PFS (10 vs 5 months, p<0.0001) as well as OS (33 vs 24 months; p < 0.022), compared to controls. We conclude that in this single center analysis of a large cohort of metastatic HR+ HER2- BC patients, palbociclib in combination with ET was associated with improved PFS in both first- and second-line settings and OS in the second-line setting compared with ET alone cohort.

Remission of T2DM by digital twin technology with reduction of cardiovascular risk: interim results of randomised controlled clinical trial

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): TWIN HEALTH INC

Background

 Twin Precision Treatment (TPT) is a novel intervention designed to improve glycemia and reverse T2D using a Whole-Body Digital Twin (WBDT) platform powered by Artificial Intelligence and the Internet of Things. Technology enabled precision nutrition, a combination of macro, micro and biota nutrients, along with Continuous Glucose Monitoring (CGM) have been demonstrated to be a key for reversal of diabetes. WBDT platform captures 174 health markers and 3000 daily data points through a panel of blood tests and connected devices that measure weight, physical activity, sleep and BP. CGM is used initially and then the algorithm predicts personalized glucose responses from multiple inputs. Nutritional, physical activity and sleep counseling is through an app or phone to provide individualized meal plans that balance 87 macro, micro and probiotic nutrients to reduce glucotoxicity and lipotoxicity. Program physicians titrate medications and monitor metabolic outcomes. 

Purpose

 To assess the initial change, in glycemic, extra glycemic, cardiovascular parameters for patients who completed 3 months longitudinal follow up.

Methods

 We performed an interim analysis [n = 173, 139 TWIN Intervention arm (T), 34 Control group (C)] of ongoing randomized controlled trial of TPT across India

Results

 The mean age (years) in the T was 43.04 (±8.6, 95% CI 41.57 to 44.52) which was significantly less as compared to the C 51.4 (±9.6, 95% CI 48.3 to 54.5); p &lt; 0.0001. The mean duration of diabetes (years) in the T was 3.5 (±2.6) which was comparable to the C 4.3 (±2.6); p = 0.12 ns. In the T there were 113 male (84.3%) and 21 female (15.6%) as compared to C, 15 male (38.4%) and 24 female (61.5%); p &lt; 0.0001. The difference of change for HbA1c (%), small dense LDL-C sdLDL (mg/dL), TG/HDL Ratio, HOMA 2IR (%), Visceral Adiposity Index (VAI), Systolic BP (mmHg), BMI (kg/m2), Framingham Risk Score (%), in T when compared to C, were significant. The mean reduction HbA1c, sdLDL, HOMA 2IR, VAI, SBP, BMI, FRS in T was -3.2 % (8.8 to 5.6), -14.1 mg/dL, (52.6 to 38.5), -0.9 % (1.9 to 1), -2.3 (4.6 to 2.3), -10.3mmHg (128.4 to 118.1), -2.9 kg/m2 (27.1 to 24.2), -7.9% (16 to 8.1), respectively. (figure) At baseline in T, mean daily intake of medication was 1.7 which reduced significantly (p &lt; 0.0001) to 0.05. 96 patients in T were able to stop anti-diabetic medications

Discussion

 The initial results are an early indicator for the translation of the scientific rationale for the technological intervention, through digital twin technology, powered by Internet of Things and Artificial Intelligence, as a modality to enable reversal of diabetes. TPT appears to have potential to mitigate the cardiovascular risk as assessed by Framingham Risk Score and modulate the non glycemic parameters, including BMI and SBP. However, larger, long-term studies would yield precise insights for the durability of the significant change that has been observed in this study Abstract Figure. Comparison for the Change in the Glycemi

Estrogen Receptor: A Paradigm for Targeted Therapy

Nearly two-thirds of breast cancers overexpress estrogen receptors, and endocrine therapy is considered the backbone of systemic therapy both in early and advanced settings. While this is now widely recognized in clinical practice, this is the culmination of outstanding contribution of many investigators and patients. Indubitably, estrogen receptor targeting has had the most impact among targeted therapies and has significantly affected patient survival. In this commentary, we revisit a landmark article published in Cancer Research in 1977 by Knight and colleagues, which laid the groundwork for the use of estrogen receptors in prognostication and adjuvant treatment selection, as well as some of the key breakthroughs in estrogen receptor biology that span more than a century.See related article by Knight and colleagues, Cancer Res 1977;37:4669-71.

Immune Phenotype and Response to Neoadjuvant Therapy in Triple-Negative Breast Cancer

PURPOSE

Increasing tumor-infiltrating lymphocytes (TIL) is associated with higher rates of pathologic complete response (pCR) to neoadjuvant therapy (NAT) in patients with triple-negative breast cancer (TNBC). However, the presence of TILs does not consistently predict pCR, therefore, the current study was undertaken to more fully characterize the immune cell response and its association with pCR.

EXPERIMENTAL DESIGN

We obtained pretreatment core-needle biopsies from 105 patients with stage I-III TNBC enrolled in ARTEMIS (NCT02276443) who received NAT from Oct 22, 2015 through July 24, 2018. The tumor-immune microenvironment was comprehensively profiled by performing T-cell receptor (TCR) sequencing, programmed death-ligand 1 (PD-L1) IHC, multiplex immunofluorescence, and RNA sequencing on pretreatment tumor samples. The primary endpoint was pathologic response to NAT.

RESULTS

The pCR rate was 40% (42/105). Higher TCR clonality (median = 0.2 vs. 0.1, P = 0.03), PD-L1 positivity (OR: 2.91, P = 0.020), higher CD3⁺:CD68⁺ ratio (median = 14.70 vs. 8.20, P = 0.0128), and closer spatial proximity of T cells to tumor cells (median = 19.26 vs. 21.94 μm, P = 0.0169) were associated with pCR. In a multivariable model, closer spatial proximity of T cells to tumor cells and PD-L1 expression enhanced prediction of pCR when considered in conjunction with clinical stage.

CONCLUSIONS

In patients receiving NAT for TNBC, deep immune profiling through detailed phenotypic characterization and spatial analysis can improve prediction of pCR in patients receiving NAT for TNBC when considered with traditional clinical parameters.

Genomic, Transcriptomic, and Proteomic Profiling of Metastatic Breast Cancer

PURPOSE

Metastatic breast cancer (MBC) is not curable and there is a growing interest in personalized therapy options. Here we report molecular profiling of MBC focusing on molecular evolution in actionable alterations.

EXPERIMENTAL DESIGN

Sixty-two patients with MBC were included. An analysis of DNA, RNA, and functional proteomics was done, and matched primary and metastatic tumors were compared when feasible.

RESULTS

Targeted exome sequencing of 41 tumors identified common alterations in TP53 (21; 51%) and PIK3CA (20; 49%), as well as alterations in several emerging biomarkers such as NF1 mutations/deletions (6; 15%), PTEN mutations (4; 10%), and ARID1A mutations/deletions (6; 15%). Among 27 hormone receptor-positive patients, we identified MDM2 amplifications (3; 11%), FGFR1 amplifications (5; 19%), ATM mutations (2; 7%), and ESR1 mutations (4; 15%). In 10 patients with matched primary and metastatic tumors that underwent targeted exome sequencing, discordances in actionable alterations were common, including NF1 loss in 3 patients, loss of PIK3CA mutation in 1 patient, and acquired ESR1 mutations in 3 patients. RNA sequencing in matched samples confirmed loss of NF1 expression with genomic NF1 loss. Among 33 patients with matched primary and metastatic samples that underwent RNA profiling, 14 actionable genes were differentially expressed, including antibody-drug conjugate targets LIV-1 and B7-H3.

CONCLUSIONS

Molecular profiling in MBC reveals multiple common as well as less frequent but potentially actionable alterations. Genomic and transcriptional profiling demonstrates intertumoral heterogeneity and potential evolution of actionable targets with tumor progression. Further work is needed to optimize testing and integrated analysis for treatment selection.

Phase II multicenter study of talazoparib for somatic BRCA1/2 mutant metastatic breast cancer

TPS1110

Background: PARP inhibitors are approved for the treatment of HER2 negative metastatic breast cancer (MBC) with germline BRCA1/2 mutations, based on phase III studies demonstrating an improvement in progression-free survival (PFS) compared to chemotherapy in this population and better patient reported outcomes (Robson, NEJM, 2017; Litton, NEJM, 2018). However, germline BRCA1/2 mutations account for only 5-10% of breast cancer, limiting the current clinical applicability of PARP inhibitors. Somatic BRCA1/2 mutations are detectable in circulating cell-free DNA (cfDNA) in ̃13.5% of patients with MBC; in pre-clinical models, pathogenic somatic BRCA1/2 mutations have been shown to respond to PARP inhibition (Vidula, CCR, 2020). The purpose of this study is to evaluate the efficacy of talazoparib, a PARP inhibitor, in patients with MBC who have somatic BRCA1/2 mutations detectable in cfDNA, in the absence of a germline BRCA1/2 mutation, which we hypothesize will be effective in this setting. This study may help expand the population of patients with MBC who benefit from PARP inhibitors. Methods: This is an investigator initiated multicenter, single arm, phase II clinical trial studying the efficacy of talazoparib in 30 patients with MBC who have pathogenic somatic BRCA1/2 mutations detected in cfDNA. Patients with MBC who are found to have pathogenic somatic BRCA1/2 mutations detected in cfDNA in the absence of a germline BRCA1/2 mutation are eligible. Patients may have triple negative (with ≥ 1 prior chemotherapy), or hormone receptor positive/HER2 negative breast cancer (with ≥ 1 prior hormone therapy). Patients may have received any number of prior lines of chemotherapy, including a prior platinum (in the absence of progression). They must have adequate organ function and ECOG performance status ≤2, and should not have previously received a PARP inhibitor. Patients are treated with talazoparib 1 mg daily until disease progression or intolerability, with serial imaging using CT chest/abdomen/pelvis and bone scan performed at baseline and every 12 weeks, and cfDNA collection every 4 weeks. Primary endpoint is PFS by RECIST 1.1. Patients are being enrolled in a two-stage design with 80% power to demonstrate that the treatment is associated with “success” (PFS > 12 weeks) in ≥53% patients (4% alpha). Secondary endpoints include objective response rate and safety (NCI CTCAE v 5.0). Exploratory analyses include studying serial changes in cfDNA BRCA1/2 mutant allelic frequency and comparing pre-and post-treatment cfDNA for the emergence of BRCA1/2 reversion and resistance mutations. This study is activated and open at Massachusetts General Hospital, where 2 patients are completing screening. It is also opening soon at 6 other academic centers (NCT03990896). Grant support includes a Pfizer ASPIRE award and 2020 Conquer Cancer Foundation of ASCO – Breast Cancer Research Foundation – Career Development Award. Clinical trial information: NCT03990896 .

The impact of gut microbial composition on response to neoadjuvant chemotherapy (NACT) in early-stage triple negative breast cancer (TNBC)

590

Background: The impact of gut microbiome on tumor biology, progression and response to immunotherapy has been shown across cancer types. However, there is little known about the impact of gut microbial composition on response to chemotherapy. We have previously shown that the gut microbiome remains unaltered during NACT in a cohort of 32 patients. Here we investigate the association between gut microbiome and response to NACT in a larger cohort of early-stage TNBC. Methods: Longitudinal fecal samples were collected from 85 patients with newly-diagnosed, early-stage TNBC patients enrolled in the ARTEMIS trial (NCT02276443). Patients all received standard NACT with adriamycin/cyclophosphamide (AC); volumetric change was assessed using ultrasound and patients with < 70% volumetric reduction (VR) after 4 cycles of AC were recommended to receive targeted therapy in addition to standard NACT to improve response rates. We performed 16S sequencing on bacterial genomic DNA extracted from 85 pre-AC fecal samples using the 2x250 bp paired-end read protocol. Quality-filtered sequences were clustered into Operational Taxonomic Units and classified using Mothur method with the Silva database version 138. For differential taxa-based univariate analysis, abundant microbiome taxa at species, genus, family, class, and order levels were analyzed using DESeq2 after logit transformation. Alpha-diversity indices within group categories were calculated using phyloseq. Microbial alpha diversity (within-sample diversity) was measured by Simpson's reciprocal index. β-diversity was measured using weighted UniFrac distances between the groups. The association between microbiota abundance and pathologic complete response (pCR) or residual disease (RD) was assessed using DESeq2 analysis. Results: Pre-AC fecal samples from 85 patients were available for analysis. Amongst them, there were 46 patients with pCR and 39 patients with RD. There was no significant difference in alpha diversity (p = 0.8) or beta-diversity (p = 0.7) between the pCR and RD groups. However, relative to patients with RD, the gut microbiome in patients with pCR was enriched for the Bifidobacterium longum species (p = 0.03). The gut microbiome in patients with RD was enriched for Lachnospiraceae (p = 0.03) at the genus level and the Bacteroides thetaiotaomicron species (p = 0.02). Conclusions: We have demonstrated significant differences in the gut microbial composition in patients with pCR as compared to patients with RD. Further investigation in larger studies is needed to support therapeutic exploration of gut microbiome modulation in TNBC patients receiving chemotherapy such as probiotic supplementation or fecal microbiota transplant.

Phase I safety and efficacy study of autophagy inhibition with hydroxychloroquine to augment the antiproliferative and biological effects of preoperative palbociclib plus letrozole for estrogen receptor-positive, HER2-negative metastatic breast cancer (MBC)

1067

Background: Endocrine therapy with a CDK4/6 inhibitor is standard of care for patients (pts) with estrogen-receptor-positive (ER+), HER2-negative MBC, yet resistance ultimately develops. We have shown that low doses of palbociclib activates autophagy, which reverses initial G1 cell cycle arrest. High concentrations of palbociclib induce senescence, but these are off target effects of the drug. The autophagy inhibitor hydroxychloroquine (HCQ) induces senescence at a lower (i.e. on-target) continuous dosing of palbociclib, in in vitro and in vivo models. This strategy is being tested in a phase I/II trial (NCT03774472). Results from the phase I portion are reported here. Methods: The phase I part of this study uses a dose escalation 3+3 design testing HCQ, 400, 600 and 800 mg daily (6 pts at 800 mg) with continuously dosed palbociclib at 75 mg and letrozole 2.5 mg daily. Dose limiting toxicity (DLT) includes any study drug-related grade ≥ 3 nonhematological (lab) toxicity. Responding pts may continue on therapy beyond 8 weeks for up to 52 weeks. Primary objective is to determine safety, tolerability and the recommended phase 2 dose (RP2D) of HCQ. Secondary objectives are overall tumor response and time to progression. Eligible pts are ≥18 years of age, postmenopausal (ovarian suppression allowed) with ER+/HER2-negative MBC, ECOG performance status score of ≤1 and with adequate renal, hepatic, and hematologic function. Response is assessed per RECIST v1.1. Results: Between 9/24/18 and 12/15/20, 14 pts were evaluable for safety. Median age was 41 with Asian (1, 7.1%), Black (2, 14.3%) White (11, 78.6%) patients enrolled. No DLTs were observed. One pt progressed during the DLT period and 2 withdrew consent (one during the DLT period); two pts were replaced for DLT assessment. Reasons for coming off study were grade 3 skin toxicity (1), per protocol at 8 weeks (non-measurable or pt/physician preference, 9), and (2) full duration treatment at 50 and 52 weeks. Adverse events (AEs) of grade ≥3 were hematologic (29), metabolism/nutrition (2), musculoskeletal/ connective tissue (1), and skin/subcutaneous tissue (3), with no serious AEs reported. The percent of palbociclib doses held per pt due to neutrophil level ranged from 0-37.5% with no apparent relation to HCQ dose. Best response was partial (2) stable (11); and progression (1). For measurable disease, tumor decreases of 11%, 12%, 21%, 26%, 30%, 55% and increase in 1 pt by 55% were seen. Conclusions: This phase I study showed acceptable safety and no HCQ dose-toxicity relationship. The RP2D of HCQ is 800 mg/day with continuous dosing palbociclib at 75 mg/day and letrozole at 2.5 mg/day. The phase 2 trial will proceed in the neoadjuvant setting, with Ki67 proliferative index response as the primary endpoint. Clinical trial information: NCT03774472 .

Neoadjuvant atezolizumab (atezo) and nab-paclitaxel (nab-p) in patients (pts) with triple-negative breast cancer (TNBC) with suboptimal clinical response to doxorubicin and cyclophosphamide (AC)

592

Background: Neoadjuvant anti-PD-(L)1 therapy confers an improvement in pathological complete response (pCR) rate in unselected TNBC. However, given the potential for long-term morbidity from immune related adverse events (irAE), it is important to optimize the risk-benefit ratio for the use of these novel agents in the curative neoadjuvant setting. Suboptimal clinical response to neoadjuvant therapy (NAT) by sonography is associated with low rates of pCR rate (2-5%, GeparTrio and Aberdeen trials). Here, we report the results of a single arm phase II study of atezo and nab-p as the second phase of NAT in pts with TNBC with suboptimal clinical response to AC (NCT02530489). Methods: Pts with stage I-III TNBC showing suboptimal response to 4 cycles of doxorubicin and cyclophosphamide (AC), defined as disease progression or a <80% reduction in tumor volume by sonography, were eligible. Pts received atezo (1200mg IV, Q3 weeks x 4), and nab-p (100mg/m2 IV, Q1 week, x 12) as the second phase of NAT before undergoing surgery followed by adjuvant atezo (1200mg IV, Q3 weeks, x 4 cycles). This single arm, two-stage Gehan-type study was designed to detect an improvement in pCR from 5% to 20% in order to deem the regimen worthy of further study in a large, randomized, phase II/III trial; success was defined as pCR in 8 out of 37 pts enrolled. In a subset of pts, sufficient baseline tumor tissue was available for stromal TIL assessment (n=29). Results: 34 pts were enrolled from 2/2016-12/2020. Among the 33 pts who have completed NAT, the pCR rate was 30% (10/33, 95% CI: 16-49%) and the pCR/RCB-I rate was 42% (14/33, 95% CI: 25-61%). Clinicopathological characteristics are described in the table below. Treatment-related adverse events (all grades) occurring in ≥ 20% of pts include fatigue (73%), anemia (55%), peripheral sensory neuropathy (55%), neutropenia (48%), rash (42%), ALT elevation (39%), AST elevation (33%), nausea (30%), anorexia (24%), diarrhea (21%), myalgia (21%). Discontinuation of atezo due to irAEs occurred in 4 pts (12%, nephritis [n=2]; adrenal insufficiency [n=1]; hepatitis [n=1]); 2 of these pts had pCR. Conclusions: This study met its primary endpoint, demonstrating a promising signal of activity in this high risk pt population (pCR=30% vs 5% in historical controls). The 12% discontinuation rate due to irAEs confirms that further evaluation of a strategy administering immunotherapy only to pts with high risk disease not responding to AC warrants further investigation. Exploratory genomic and immunological correlative studies are ongoing. Clinical trial information: NCT02530489. [Table: see text]

Abstract OT-34-01: Phase Ib/II trial of copanlisib in combination with trastuzumab and pertuzumab after induction treatment of HER2 positive metastatic breast cancer with PIK3CA mutation or PTEN mutation

Background:The PI3K/Akt/mTOR pathway is a critical regulator of cell growth, survival, and metabolism in cancer. Its activation plays an important role in resistance to chemotherapy and HER2 targeted therapy. PIK3CA activating mutations and PTEN loss were reported in 30% and 16% of BOLERO-1 and 32% and 12% of BOLERO-3 patients, respectively. Exploratory analyses suggested that the addition of everolimus to trastuzumab and chemotherapy improved progression free survival (PFS) in patients with PIK3CA mutations and PTEN loss. In the phase III CLEOPATRA trial, while the combination of pertuzumab (P) plus trastuzumab (H) plus docetaxel (T) as compared with trastuzumab (H) plus docetaxel (T), significantly prolonged PFS (18.5 vs 12.4 months) for first-line treatment for HER2-positive (+ve) metastatic breast cancer (MBC), longer median PFS was observed in patients with wildtype versus mutated PIK3CA in both the control (13.8 v 8.6 months) and pertuzumab groups (21.8 v 12.5 months). Copanlisib is a highly selective, class 1 pan-PI3K inhibitor with predominant activity against both the δ and α isoforms. It is currently FDA approved for the treatment of adults with relapsed follicular lymphoma. This study hypothesizes that the addition of copanlisib to dual HER2 targeted therapy after first line induction treatment will improve clinical outcomes in HER2 positive MBC patients with PIK3CA or PTEN genomic alterations. Trial Design: This is a randomized, two- arm, open label, phase-2 study to evaluate the clinical activity of copanlisib added to HP maintenance after induction with THP in HER2 +ve MBC patients with PIK3CA mutations or PTEN loss. A safety run-in cohort (phase 1B) will be performed. Copanlisib will be administered weekly on D1, D8 of a 21-day cycle. Eligibility criteriaHER2 +ve MBC based on ASCO-CAP criteria (HER2 status based on metastatic tissue)• Activating mutations in PIK3CA, or PTEN loss• ECOG performance status ≤1• Normal organ and marrow function• Within 8 weeks of completion of first-line induction therapy with THP (Phase-2). Any prior treatment provided eligible to receive THP induction (Phase-1B) Specific aimsTo assess the benefit of adding copanlisib to HP in HER2+ve MBC patients with PIK3CA mutations or PTEN loss after induction treatment (Phase-2)• To determine safety and recommended phase 2 dose (RP2D) of copanlisib, HP combination in HER2 MBC patients (Phase-1B)• To correlate PFS and OS with the triplet combination with the number of induction cycles, hormone receptor status, and PTEN loss by IHC• To identify potential predictive and prognostic biomarkers for copanlisib activity Statistical methodsThe primary objective of the phase-1B portion is to determine the RP2D for the combination of copanlisib, trastuzumab, and pertuzumab. Phase 1 portion will use a 3+3 dose de-escalation design. The primary objective of the phase 2 portion is to determine a difference in PFS with the addition of copanlisib to HP maintenance after induction. Projected median PFS in control group is 8 months and 16 months in the experimental arm. We aim to detect a HR of 0.50 with power of 0.90 with 1-sided alpha of 0.1. With a sample size of 82, 12 months post-accrual follow-up, and accrual rate of 5 patients per month, the study duration is 30 months. To have 82 evaluable patients with a 15% drop-out rate, we would need to enroll 96 patients. A Wieand rule futility interim analysis will be conducted when half of the total of 54 required PFS events are observed.

Citation Format: Senthil Damodaran, Rashmi K Murthy, Maliha Nusrat, Babita Saigal, Samantha C Trager, Debu Tripathy, Funda Meric-Bernstam. Phase Ib/II trial of copanlisib in combination with trastuzumab and pertuzumab after induction treatment of HER2 positive metastatic breast cancer with PIK3CA mutation or PTEN mutation [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr OT-34-01.

Abstract OT-09-01: An open-label, multicenter study evaluating the safety of lasofoxifene in combination with abemaciclib for the treatment of pre and postmenopausal women with locally advanced or metastatic ER+/HER2− breast cancer and have an ESR1 mutation

Endocrine therapy is the established treatment for metastatic breast cancer (MBC) in patients that express estrogen receptor (ER) and/or progesterone receptor (PR). Agents targeting the ER pathway such as aromatase inhibitors (AIs) and fulvestrant with or without additional biologic agents are effective, but not curative. Over the last several years, clinical studies have shown that adding a CDK 4/6 inhibitor (CDKi) to endocrine treatment (either AIs or fulvestrant) significantly increases time to progression for MBC patients. Unfortunately, resistance due to a number of causes eventually develops. Secondary mutations in estrogen receptor (ESR1), most frequently seen after AI treatment produce constitutive activation of ER and are associated with a worse disease prognosis. Treatment options for MBC patients with an ESR1 mutation are limited and currently there are no approved therapies. Additionally, limited data exist to justify whether cyclin dependent kinase 4/6 inhibitors (CDK4/6i) should be continued, substituted for another CDK4/6i or discontinued all together. Lasofoxifene is a third generation SERM previously investigated for the treatment of osteoporosis and vulvo-vaginal atrophy (VVA). Clinical data have shown a significant reduction in the incidence of ER+ breast cancer in postmenopausal women with osteoporosis treated with lasofoxifene. These results supported further studies which showed significant in vitro and in vivo efficacy in pre-clinical breast cancer models. Moreover, a significant benefit was seen in pre-clinical models with lasofoxifene either as monotherapy or in combination with a CDK4/6i over fulvestrant (with or without a CDK4/6i) in breast cancer cells expressing ESR1 mutations. The multicenter phase 2 (ELAINE 1) study is currently enrolling patients evaluating the activity of lasofoxifene monotherapy compared to fulvestrant. Also, studies have shown that abemaciclib has meaningful clinical activity in patients previously exposed to other CDK4/6i (palbociclib/ribociclib) and chemotherapy. The pre-clinical and clinical study results also provide a strong rationale to pursue a phase 2 clinical trial in BC patients with ESR1 mutations in combination with a CDK4/6i.The ongoing study (ElAINE 2) is an open-label, multi-center study evaluating the safety of the combination of lasofoxifene and CDK4/6i abemaciclib. Inclusion criteria include pre- and postmenopausal women with ER+ ESR1mutation-bearing advanced breast cancer who have progressed on prior hormonal treatment and a CDK4/6i (including abemaciclib); 24 patients with measurable or evaluable disease (i.e. bone only) will be recruited. The primary endpoint will be the safety of the combination. Secondary endpoints will include progression free survival (PFS), objective response rate (ORR), clinical benefit rate (CBR), duration of response (DoR) and time to response (TTR), with exploratory serial circulating tumor DNA landscape analysis. The study started in 2Q2020 and will complete recruitment in 1 year. Ten centers in the US will be participating. Recruitment status will be provided at the time of presentation.

Citation Format: Senthil Damodaran, Paul V Plourde, Debu Tripathy, Simon N Jenkins, David J Portman. An open-label, multicenter study evaluating the safety of lasofoxifene in combination with abemaciclib for the treatment of pre and postmenopausal women with locally advanced or metastatic ER+/HER2− breast cancer and have an ESR1 mutation [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr OT-09-01.

Abstract PS4-05: Prospective evaluation of the gut microbiome and response to neoadjuvant therapy (NAT) in early-stage triple negative breast cancer (TNBC)

Introduction: Emerging data suggest that the gut microbial composition influences responses to chemotherapy and immunotherapy. However, similar data in patients with TNBC receiving NAT remains limited. Thus, we investigated the association between the gut microbial composition in patients with newly-diagnosed, early-stage TNBC and response to NAT in a cohort of patients enrolled in the ARTEMIS trial (NCT02276443). Methods: We performed 16S sequencing on bacterial genomic DNA extracted from pre-NAT fecal samples using the 2x250 bp paired-end read protocol. Quality-filtered sequences were clustered into Operational Taxonomic Units and classified using Mothur method with the Silva database version 128. Associations between abundance and pathologic response to NAT were assessed using the Mann Whitney U Test. A cohort of 32 patients had longitudinal samples collected. Mann-Whitney U Test and Fishers exact were used to compare clinical variables as appropriate between the pCR and non-pCR groups. Results: There was no significant difference in age, race or stage between the pCR and non-pCR groups (Table 1). As expected, the pCR group was enriched for high TIL (p=0.026). There was no difference in alpha-diversity of the gut microbiome between patients with NAT-sensitive (pCR) and NAT-resistant disease (non-pCR) (p=0.5). Relative to patients with NAT-sensitive disease (pCR), the gut microbiome in patients with NAT-resistant disease was enriched for Fusobacterium (p=0.009), Intestinimonas (p=0.01) and Lachnospiraceae (p=0.003) at the genus level; the median abundances between pCR and non-pCR are provided in Table 1. Longitudinal samples collected during NAT demonstrated no substantial impact of NAT on the gut microbiome.

Conclusions: Taken together, these data suggest that response to NAT may be influenced by the gut microbial composition, which remains unaltered during NAT. Research efforts to modulate the gut microbiome should be further explored as a potential therapeutic strategy in TNBC.

Table 1: Median Microbial Abundance and Clinicopathological Variables (N=43)pCR (n=18)Non-pCR (n=25)p- valueMicrobial AbundanceFusobacterium1 x 10-61.02 x 10-50.009Intestinimonas6.4 x 10-54.8 x 10-40.01Lachnospiraceae6.2 x 10-31.0 x 10-20.003Age median, interquartile range (n=44)45 (38-59)53 (46-58)0.61n (%)Race/EthnicityWhite, non-Hispanic11 (61.1)14 (56.0)0.53White, Hispanic4 (22.2)3 (12.0)Black2 (11.1)7 (28.0)Asian1 (5.6)1 (4.0)T categoryT15 (27.8)4 (16.0)0.15T213 (72.2)17 (68.0)T304 (16.0)T400Nodal statusNegative12 (66.7)14 (56.0)0.54Positive6 (33.3)11 (44.0)StageI3 (16.7)3 (12.0)0.91II11 (61.1)15 (60.0)III4 (22.2)7 (28.0)TIL&lt;20%7 (38.9)19 (76.0)0.026&gt;20%11 (61.1)6 (24.0)

Citation Format: Nour Abuhadra, Chia-Chi Chang, Clinton Yam, Ryan Sun, Lei Huo, Jason White, Elizabeth E Ravenberg, Jennifer Litton, Bora Lim, Naoto T Ueno, Banu Arun, Debu Tripathy, Senthil Damodaran, Rashmi Murthy, Vicente Valero, Gabriel Hortobagyi, Nuhad Ibrahim, Alastair Thompson, Elizabeth Mittendorf, Stacy Moulder, Robert Jenq. Prospective evaluation of the gut microbiome and response to neoadjuvant therapy (NAT) in early-stage triple negative breast cancer (TNBC) [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS4-05.

Functional Tumor Volume by Fast Dynamic Contrast-Enhanced MRI for Predicting Neoadjuvant Systemic Therapy Response in Triple-Negative Breast Cancer

BACKGROUND

Dynamic contrast-enhanced (DCE) MRI is useful for diagnosis and assessment of treatment response in breast cancer. Fast DCE MRI offers a higher sampling rate of contrast enhancement curves in comparison to conventional DCE MRI, potentially characterizing tumor perfusion kinetics more accurately for measurement of functional tumor volume (FTV) as a predictor of treatment response.

PURPOSE

To investigate FTV by fast DCE MRI as a predictor of neoadjuvant systemic therapy (NAST) response in triple-negative breast cancer (TNBC).

STUDY TYPE

Prospective.

POPULATION/SUBJECTS

Sixty patients with biopsy-confirmed TNBC between December 2016 and September 2020.

FIELD STRENGTH/SEQUENCE

A 3.0 T/3D fast spoiled gradient echo-based DCE MRI ASSESSMENT: Patients underwent MRI at baseline and after four cycles (C4) of NAST, followed by definitive surgery. DCE subtraction images were analyzed in consensus by two breast radiologists with 5 (A.H.A.) and 2 (H.S.M.) years of experience. Tumor volumes (TV) were measured on early and late subtractions. Tumors were segmented on 1 and 2.5-minute early phases subtractions and FTV was determined using optimized signal enhancement thresholds. Interpolated enhancement curves from segmented voxels were used to determine optimal early phase timing.

STATISTICAL TESTS

Tumor volumes were compared between patients who had a pathologic complete response (pCR) and those who did not using the area under the receiver operating curve (AUC) and Mann-Whitney U test.

RESULTS

About 26 of 60 patients (43%) had pCR. FTV at 1 minute after injection at C4 provided the best discrimination between pCR and non-pCR, with AUC (95% confidence interval [CI]) = 0.85 (0.74,0.95) (P < 0.05). The 1-minute timing was optimal for FTV measurements at C4 and for the change between C4 and baseline. TV from the early phase at C4 also yielded a good AUC (95%CI) of 0.82 (0.71,0.93) (P < 0.05).

DATA CONCLUSION

FTV and TV measured at 1 minute after injection can predict response to NAST in TNBC.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY: 4.

A phase II study of Mirvetuximab Soravtansine in triple-negative breast cancer

Folate receptor alpha (FRα) has been reported to be expressed in up to 80% of triple-negative breast cancers (TNBC) with limited expression in normal tissues, making it a promising therapeutic target. Mirvetuximab soravtansine (mirvetuximab-s) is an antibody drug conjugate which has shown promise in the treatment of FRα-positive solid tumors in early phase clinical trials. Herein, are the results of the first prospective phase II trial evaluating mirvetuximab-s in metastatic TNBC. Patients with advanced, FRα-positive TNBC were enrolled on this study. Mirvetuximab-s was administered at a dose of 6.0 mg/kg every 3 weeks. 96 patients with advanced TNBC consented for screening. FRα staining was performed on tumor tissue obtained from 80 patients. The rate of FRα positivity by immunohistochemistry was 10.0% (8/80). Two patients were treated on study, with best overall responses of stable disease in one and progressive disease in the other. Adverse events were consistent with earlier studies. The study was terminated early due to the low rate of FRα positivity in the screened patient population and lack of disease response in the two patients treated. The observed rate of FRα positivity was considerably lower than previously reported and none of the patients had a partial or complete response. Treatment with mirvetuximab-s should only be further explored in TNBC if an alternate biomarker strategy is developed for patient selection on the basis of additional preclinical data.

Clinical implications of breast cancer tumor genomic testing

One of the important applications of genetic testing is genetic testing of the tumor to identify non-inherited somatic mutations. The advent of high-throughput genomic and proteomic techniques has enabled characterization of genomic alterations and accelerated development of novel matching therapies for cancer. Consequently, mutational status has increasingly defined treatment selection for patients with solid tumors. The effectiveness of targeted therapy depends on matching with the right target; targets that are differentially expressed in tumor cells and provide growth and survival advantage. Currently, multiple targeted therapies have been approved by the Food and Drug Administration (FDA) for treatment of solid tumors including breast, lung, and melanoma, while many others are being evaluated in clinical trials. In addition to identifying actionable genomic alterations of interest, tumor genome sequencing also has the potential to detect germline mutations that has clinical implications for both the patient and their family. While targeted therapies have transformed our approach to cancer care in solid tumor patients within the past decade, lack of sustained responses and emergence of acquired resistance limit their clinical activity. In this article, we discuss tumor genome sequencing in breast cancers and their clinical implication.

Prognostic impact of high stromal tumor-infiltrating lymphocytes (sTIL) in the absence of pathologic complete response (pCR) to neoadjuvant therapy (NAT) in early stage triple negative breast cancer (TNBC)

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Background: Pathologic complete response is an excellent surrogate for disease-free survival (DFS) and overall survival (OS) in TNBC. High sTIL is associated with improved pCR rates in TNBC. Recent data suggest that high sTIL is also associated with improved outcomes in patients who received no chemotherapy for early stage TNBC (Park, Annals of Oncology, 2019). Thus, we hypothesized that high sTIL may have prognostic impact in patients who do not achieve pCR to NAT. Methods: Pretreatment core biopsies from 182 patients with early-stage TNBC enrolled on the ARTEMIS trial (NCT02276443) were evaluated for sTIL by H&E. Patients were stratified according to sTIL (low < 30%, and high > 30%) and pCR (patients with pCR vs. no pCR). The primary outcome measure was DFS, defined from the date of diagnosis to the first local recurrence, distant metastases or death. Cox proportional hazards regression model was used. During follow-up 33 events for DFS were observed. Results: Among subjects who achieve pCR, DFS was excellent regardless of sTIL status and significantly better than those without pCR (p < 0.05). However, patients with high sTIL and no pCR demonstrated significantly worse DFS compared to all subjects having pCR (HR 0.18, 95% CI 0.04-0.76, p = 0.02). Additionally, we did not find a significant difference between high and low sTIL patients who did not achieve pCR. Conclusions: In early TNBC receiving NAT, for patients failing to achieve pCR, high sTIL was not associated with improved DFS; outcomes were comparable to those with low sTIL without pCR. Thus, high sTIL at baseline does not appear to confer an intrinsic prognostic benefit in the absence of pCR.