Event-free survival by residual cancer burden with pembrolizumab in early-stage TNBC: exploratory analysis from KEYNOTE-522

BACKGROUND

KEYNOTE-522 demonstrated statistically significant improvements in pathological complete response (pCR) with neoadjuvant pembrolizumab plus chemotherapy and event-free survival (EFS) with neoadjuvant pembrolizumab plus chemotherapy followed by adjuvant pembrolizumab in patients with high-risk, early-stage triple-negative breast cancer (TNBC). Prior studies have shown the prognostic value of the residual cancer burden (RCB) index to quantify the extent of residual disease after neoadjuvant chemotherapy. In this preplanned exploratory analysis, we assessed RCB distribution and EFS within RCB categories by treatment group.

PATIENTS AND METHODS

A total of 1174 patients with stage T1c/N1-2 or T2-4/N0-2 TNBC were randomized 2 : 1 to pembrolizumab 200 mg or placebo every 3 weeks given with four cycles of paclitaxel + carboplatin, followed by four cycles of doxorubicin or epirubicin + cyclophosphamide. After surgery, patients received pembrolizumab or placebo for nine cycles or until recurrence or unacceptable toxicity. Primary endpoints are pCR and EFS. RCB is a prespecified exploratory endpoint. The association between EFS and RCB was assessed using a Cox regression model.

RESULTS

Pembrolizumab shifted patients into lower RCB categories across the entire spectrum compared with placebo. There were more patients in the pembrolizumab group with RCB-0 (pCR), and fewer patients in the pembrolizumab group with RCB-1, RCB-2, and RCB-3. The corresponding hazard ratios (95% confidence intervals) for EFS were 0.70 (0.38-1.31), 0.92 (0.39-2.20), 0.52 (0.32-0.82), and 1.24 (0.69-2.23). The most common first EFS events were distant recurrences, with fewer in the pembrolizumab group across all RCB categories. Among patients with RCB-0/1, more than half [21/38 (55.3%)] of all events were central nervous system recurrences, with 13/22 (59.1%) in the pembrolizumab group and 8/16 (50.0%) in the placebo group.

CONCLUSIONS

Addition of pembrolizumab to chemotherapy resulted in fewer EFS events in the RCB-0, RCB-1, and RCB-2 categories, with the greatest benefit in RCB-2. These findings demonstrate that pembrolizumab not only increased pCR rates, but also improved EFS among most patients who do not have a pCR.

Impact of dose reductions on adjuvant abemaciclib efficacy for patients with high-risk early breast cancer: analyses from the monarchE study

In monarchE, adjuvant abemaciclib significantly improved invasive disease-free survival (IDFS) and distant relapse-free survival (DRFS), with sustained benefit beyond the 2-year treatment period. Abemaciclib dose reductions were allowed to proactively manage adverse events. Exploratory analyses to investigate the impact of dose reductions on efficacy were conducted. Across the three patient subgroups as defined by relative dose intensity (≤66%, 66-93%, ≥93%), the estimated 4-year IDFS rates were generally consistent (87.1%, 86.4%, and 83.7%, respectively). In the time-dependent Cox proportional hazard model, the effect of abemaciclib was consistent at the full dose compared to being reduced to a lower dose (IDFS hazard ratio: 0.905; 95% confidence interval: 0.727, 1.125; DRFS hazard ratio: 0.942; 95% confidence interval: 0.742, 1.195). These analyses showed that the efficacy of adjuvant abemaciclib was not compromised by protocol mandated dose reductions for patients with node positive, hormone receptor positive, human epidermal growth factor 2-negative, high-risk early breast cancer.

Clinical effectiveness and safety of olaparib in BRCA-mutated, HER2-negative metastatic breast cancer in a real-world setting: final analysis of LUCY

PURPOSE

The interim analysis of the phase IIIb LUCY trial demonstrated the clinical effectiveness of olaparib in patients with germline BRCA-mutated (gBRCAm), human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer (mBC), with median progression-free survival (PFS) of 8.11 months, which was similar to that in the olaparib arm of the phase III OlympiAD trial (7.03 months). This prespecified analysis provides final overall survival (OS) and safety data.

METHODS

The open-label, single-arm LUCY trial of olaparib (300 mg, twice daily) enrolled adults with gBRCAm or somatic BRCA-mutated (sBRCAm), HER2-negative mBC. Patients had previously received a taxane or anthracycline for neoadjuvant/adjuvant or metastatic disease and up to two lines of chemotherapy for mBC.

RESULTS

Of 563 patients screened, 256 (gBRCAm, n = 253; sBRCAm, n = 3) were enrolled. In the gBRCAm cohort, median investigator-assessed PFS (primary endpoint) was 8.18 months and median OS was 24.94 months. Olaparib was clinically effective in all prespecified subgroups: hormone receptor status, previous chemotherapy for mBC, previous platinum-based chemotherapy (including by line of therapy), and previous cyclin-dependent kinase 4/6 inhibitor use. The most frequent treatment-emergent adverse events (TEAEs) were nausea (55.3%) and anemia (39.2%). Few patients (6.3%) discontinued olaparib owing to a TEAE. No deaths associated with AEs occurred during the study treatment or 30-day follow-up.

CONCLUSION

The LUCY patient population reflects a real-world population in line with the licensed indication of olaparib in mBC. These findings support the clinical effectiveness and safety of olaparib in patients with gBRCAm, HER2-negative mBC.

CLINICAL TRIAL REGISTRATION

Clinical trials registration number: NCT03286842.

Adjuvant Abemaciclib Plus Endocrine Therapy for Hormone Receptor-Positive, Human Epidermal Growth Factor Receptor 2-Negative, High-Risk Early Breast Cancer: Results From a Preplanned monarchE Overall Survival Interim Analysis, Including 5-Year Efficacy Outcomes

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical trial updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported.Two years of adjuvant abemaciclib combined with endocrine therapy (ET) resulted in a significant improvement in invasive disease-free survival (IDFS) and distant relapse-free survival (DRFS) that persisted beyond the 2-year treatment period in patients with hormone receptor-positive, human epidermal growth factor receptor 2-negative, node-positive, high-risk early breast cancer (EBC). Here, we report 5-year efficacy results from a prespecified overall survival (OS) interim analysis. In the intent-to-treat population, with a median follow-up of 54 months, the benefit of abemaciclib was sustained with hazard ratios of 0.680 (95% CI, 0.599 to 0.772) for IDFS and 0.675 (95% CI, 0.588 to 0.774) for DRFS. This persistence of abemaciclib benefit translated to continuous separation of the curves with a deepening in 5-year absolute improvement in IDFS and DRFS rates of 7.6% and 6.7%, respectively, compared with rates of 6% and 5.3% at 4 years and 4.8% and 4.1% at 3 years. With fewer deaths in the abemaciclib plus ET arm compared with the ET-alone arm (208 v 234), statistical significance was not reached for OS. No new safety signals were observed. In conclusion, abemaciclib plus ET continued to reduce the risk of developing invasive and distant disease recurrence beyond the completion of treatment. The increasing absolute improvement at 5 years is consistent with a carryover effect and further supports the use of abemaciclib in patients with high-risk EBC.

First-Line Ipatasertib, Atezolizumab, and Taxane Triplet for Metastatic Triple-Negative Breast Cancer: Clinical and Biomarker Results

PURPOSE

To evaluate a triplet regimen combining immune checkpoint blockade, AKT pathway inhibition, and (nab-) paclitaxel as first-line therapy for locally advanced/metastatic triple-negative breast cancer (mTNBC).

PATIENTS AND METHODS

The single-arm CO40151 phase Ib study (NCT03800836), the single-arm signal-seeking cohort of IPATunity130 (NCT03337724), and the randomized phase III IPATunity170 trial (NCT04177108) enrolled patients with previously untreated mTNBC. Triplet therapy comprised intravenous atezolizumab 840 mg (days 1 and 15), oral ipatasertib 400 mg/day (days 1-21), and intravenous paclitaxel 80 mg/m2 (or nab-paclitaxel 100 mg/m2; days 1, 8, and 15) every 28 days. Exploratory translational research aimed to elucidate mechanisms and molecular markers of sensitivity and resistance.

RESULTS

Among 317 patients treated with the triplet, efficacy ranged across studies as follows: median progression-free survival (PFS) 5.4 to 7.4 months, objective response rate 44% to 63%, median duration of response 5.6 to 11.1 months, and median overall survival 15.7 to 28.3 months. The safety profile was consistent with the known toxicities of each agent. Grade ≥3 adverse events were more frequent with the triplet than with doublets or single-agent paclitaxel. Patients with PFS >10 months were characterized by NF1, CCND3, and PIK3CA alterations and increased immune pathway activity. PFS <5 months was associated with CDKN2A/CDKN2B/MTAP alterations and lower predicted phosphorylated AKT-S473 levels.

CONCLUSIONS

In patients with mTNBC receiving an ipatasertib/atezolizumab/taxane triplet regimen, molecular characteristics may identify those with particularly favorable or unfavorable outcomes, potentially guiding future research efforts.

Intrinsic Subtype and Overall Survival of Patients with Advanced HR+/HER2- Breast Cancer Treated with Ribociclib and ET: Correlative Analysis of MONALEESA-2, -3, -7

PURPOSE

The MONALEESA-2, -3, -7 trials demonstrated statistically significant and clinically meaningful progression-free survival and overall survival (OS) benefits with ribociclib plus endocrine therapy (ET) versus ET alone in hormone receptor-positive, HER2-negative (HR+/HER2-) advanced breast cancer (ABC). Understanding the association of intrinsic subtypes with survival outcomes could potentially guide treatment decisions. Here, we evaluated the association of intrinsic subtypes with OS in MONALEESA-2, -3, -7.

EXPERIMENTAL DESIGN

Tumor samples from MONALEESA-2, -3, -7 underwent PAM50-based subtyping. The relationship between subtypes and OS was assessed using univariable and multivariable Cox proportional hazards models. Multivariable models were adjusted for clinical prognostic factors.

RESULTS

Overall, 990 tumors (among 2,066 patients) from ribociclib (n = 580) and placebo (n = 410) arms were profiled. Subtype distribution was luminal A, 54.5%; luminal B, 28.0%; HER2-enriched (HER2E) 14.6%; and basal-like, 2.8%; and was consistent across treatment arms. The luminal A subtype had the best OS outcomes in both arms, while basal-like had the worst. Patients with HER2E (HR, 0.60; P = 0.018), luminal B (HR, 0.69; P = 0.023), and luminal A (HR, 0.75; P = 0.021) subtypes derived OS benefit with ribociclib. Patients with basal-like subtype did not derive benefit from ribociclib (HR, 1.92; P = 0.137); however, patient numbers were small (n = 28).

CONCLUSIONS

The prognostic value of intrinsic subtypes for OS was confirmed in this pooled analysis of the MONALEESA trials (largest dataset in HR+/HER2- ABC). While basal-like subtype did not benefit, a consistent OS benefit was observed with ribociclib added to ET across luminal and HER2E subtypes.

Association between event-free survival and overall survival in early-stage triple-negative breast cancer

Aim: This study evaluated event-free survival (EFS) as a surrogate outcome for overall survival (OS) in neoadjuvant therapy for early-stage triple-negative breast cancer (eTNBC). Methods: Meta-regression analyses based on a targeted literature review were used to evaluate the individual- and trial-level associations between EFS and OS. Results: In the individual-level analyses, 3-year EFS was a significant predictor of 5-year OS (p < 0.01; coefficient of determinations [R2]: 0.82 [95% CI: 0.68-0.91]). Additionally, there was a statistically significant association between the treatment effect on EFS and OS at the trial level (p < 0.001; R2: 0.64 [95% CI: 0.45-0.82]). Conclusion: This study demonstrates significant associations between EFS and OS and suggests that EFS is a valid surrogate for OS following neoadjuvant therapy for eTNBC.

Assessment of inspiration and technical quality in anteroposterior thoracic radiographs using machine learning

INTRODUCTION

Chest radiographs are the most performed radiographic procedure, but suboptimal technical factors can impact clinical interpretation. A deep learning model was developed to assess technical and inspiratory adequacy of anteroposterior chest radiographs.

METHODS

Adult anteroposterior chest radiographs (n = 2375) were assessed for technical adequacy, and if otherwise technically adequate, for adequacy of inspiration. Images were labelled by an experienced radiologist with one of three ground truth labels: inadequate technique (n = 605, 25.5 %), adequate inspiration (n = 900, 37.9 %), and inadequate inspiration (n = 870, 36.6 %). A convolutional neural network was then iteratively trained to predict these labels and evaluated using recall, precision, F1 and micro-F1, and Gradient-weighted Class Activation Mapping analysis on a hold-out test set. Impact of kyphosis on model accuracy was assessed.

RESULTS

The model performed best for radiographs with adequate technique, and worst for images with inadequate technique. Recall was highest (89 %) for radiographs with both adequate technique and inspiration, with recall of 81 % for images with adequate technique and inadequate inspiration, and 60 % for images with inadequate technique, although precision was highest (85 %) for this category. Per-class F1 was 80 %, 81 % and 70 % for adequate inspiration, inadequate inspiration, and inadequate technique respectively. Weighted F1 and Micro F1 scores were 78 %. Presence or absence of kyphosis had no significant impact on model accuracy in images with adequate technique.

CONCLUSION

This study explores the promising performance of a machine learning algorithm for assessment of inspiratory adequacy and overall technical adequacy for anteroposterior chest radiograph acquisition.

IMPLICATIONS FOR PRACTICE

With further refinement, machine learning can contribute to education and quality improvement in radiology departments.

Patritumab Deruxtecan (HER3-DXd), a Human Epidermal Growth Factor Receptor 3-Directed Antibody-Drug Conjugate, in Patients With Previously Treated Human Epidermal Growth Factor Receptor 3-Expressing Metastatic Breast Cancer: A Multicenter, Phase I/II Trial

PURPOSE

Human epidermal growth factor receptor 3 (HER3) is broadly expressed in breast cancer; high expression is associated with an adverse prognosis. Patritumab deruxtecan (HER3-DXd) is an investigational HER3-targeted antibody-drug conjugate that is being evaluated as a novel treatment in HER3-expressing advanced breast cancer in the U31402-A-J101 study.

METHODS

Adults with disease progression on previous therapies were eligible. Patients in the dose-escalation, dose-finding, and dose-expansion parts received HER3-DXd 1.6-8.0 mg/kg intravenously once every 3 weeks or one of two alternative dosing regimens. In the dose-escalation part, the primary objectives were to determine the maximum tolerated dose and recommended dose for expansion (RDE). The safety and efficacy of the RDE were assessed during dose expansion.

RESULTS

One hundred eighty-two enrolled patients received ≥1 dose of HER3-DXd. Patients had a median of five previous therapies for advanced disease. Efficacy results are reported across clinical subtypes: hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-negative) breast cancer (n = 113; objective response rate [ORR], 30.1%; median progression-free survival [mPFS], 7.4 months), triple-negative breast cancer (n = 53; ORR, 22.6%; mPFS, 5.5 months), and HER2-positive breast cancer (n = 14; ORR, 42.9%; mPFS, 11.0 months). Objective responses were observed in cancers with HER3-high and HER3-low membrane expression. Dose-limiting toxicities observed during dose selection were decreased platelet count and elevated aminotransferases. In dose expansion, GI and hematologic toxicities were the most common treatment-emergent adverse events (TEAEs) observed. Grade ≥3 TEAEs were observed in 71.4% of patients, and 9.9% discontinued treatment because of TEAEs. Three grade 3 and one grade 5 treatment-related interstitial lung disease events occurred.

CONCLUSION

HER3-DXd demonstrated a manageable safety profile and durable efficacy in heavily pretreated patients across clinical subtypes. These data warrant further evaluation of HER3-DXd in patients with HER3-expressing metastatic breast cancer.

Neoadjuvant immunotherapy and chemotherapy regimens for the treatment of high-risk, early-stage triple-negative breast cancer: a systematic review and network meta-analysis

BACKGROUND

Patients with triple-negative breast cancer (TNBC) are generally younger and more likely to experience disease recurrence and have the shortest survival among all breast cancer patients. Recently, neoadjuvant delivery of the programmed cell death protein-1 inhibitor pembrolizumab plus chemotherapy followed by adjuvant pembrolizumab was approved for patients with high-risk, early-stage TNBC, but this treatment regimen has not been evaluated in head-to-head trials with other neoadjuvant treatment regimens. Therefore, the objective of this study was to estimate the relative efficacy of neoadjuvant pembrolizumab + chemotherapy followed by adjuvant pembrolizumab versus other neoadjuvant treatments for early-stage TNBC through a systematic review and network meta-analysis (NMA).

METHODS

EMBASE, MEDLINE, Cochrane Central Register of Controlled Trials, conference abstracts, and clinical trial registries were searched for randomized controlled trials evaluating neoadjuvant treatments for early-stage TNBC. NMA was performed to estimate relative treatment effects among evaluated interventions.

RESULTS

Five trials met the inclusion criteria and were included in the NMA. The relative efficacy of neoadjuvant pembrolizumab + chemotherapy followed by adjuvant pembrolizumab was favorable to paclitaxel followed by anthracycline + cyclophosphamide in terms of pathologic complete response (pCR), event-free survival (EFS), and overall survival; paclitaxel + carboplatin followed by anthracycline + cyclophosphamide in terms of pCR and EFS; paclitaxel + bevacizumab followed by anthracycline + cyclophosphamide + bevacizumab in terms of pCR; and paclitaxel + carboplatin + veliparib followed by anthracycline + cyclophosphamide in terms of EFS.

CONCLUSIONS

Neoadjuvant pembrolizumab + chemotherapy followed by adjuvant pembrolizumab confers benefits in response and survival outcomes versus alternative neoadjuvant treatments for early-stage TNBC.

Pilot clinical trial and phenotypic analysis in chemotherapy-pretreated, metastatic triple-negative breast cancer patients treated with oral TAK-228 and TAK-117 (PIKTOR) to increase DNA damage repair deficiency followed by cisplatin and nab paclitaxel

BACKGROUND

A subset of triple-negative breast cancers (TNBCs) have homologous recombination deficiency with upregulation of compensatory DNA repair pathways. PIKTOR, a combination of TAK-228 (TORC1/2 inhibitor) and TAK-117 (PI3Kα inhibitor), is hypothesized to increase genomic instability and increase DNA damage repair (DDR) deficiency, leading to increased sensitivity to DNA-damaging chemotherapy and to immune checkpoint blockade inhibitors.

METHODS

10 metastatic TNBC patients received 4 mg TAK-228 and 200 mg TAK-117 (PIKTOR) orally each day for 3 days followed by 4 days off, weekly, until disease progression (PD), followed by intravenous cisplatin 75 mg/m2 plus nab paclitaxel 220 mg/m2 every 3 weeks for up to 6 cycles. Patients received subsequent treatment with pembrolizumab and/or chemotherapy. Primary endpoints were objective response rate with cisplatin/nab paclitaxel and safety. Biopsies of a metastatic lesion were collected prior to and at PD on PIKTOR. Whole exome and RNA-sequencing and reverse phase protein arrays (RPPA) were used to phenotype tumors pre- and post-PIKTOR for alterations in DDR, proliferation, and immune response.

RESULTS

With cisplatin/nab paclitaxel (cis/nab pac) therapy post PIKTOR, 3 patients had clinical benefit (1 partial response (PR) and 2 stable disease (SD) ≥ 6 months) and continued to have durable benefit in progression-free survival with pembrolizumab post-cis/nab pac for 1.2, 2, and 3.6 years. Their post-PIKTOR metastatic tissue displayed decreased mismatch repair (MMR), increased tumor mutation burden, and significantly lower levels of 53BP1, DAG Lipase β, GCN2, AKT Ser473, and PKCzeta Thr410/403 compared to pre-PIKTOR tumor tissue.

CONCLUSIONS

Priming patients' chemotherapy-pretreated metastatic TNBC with PIKTOR led to very prolonged response/disease control with subsequent cis/nab pac, followed by pembrolizumab, in 3 of 10 treated patients. Our multi-omics approach revealed a higher number of genomic alterations, reductions in MMR, and alterations in immune and stress response pathways post-PIKTOR in patients who had durable responses.

TRIAL REGISTRATION

This clinical trial was registered on June 21, 2017, at ClinicalTrials.gov using identifier NCT03193853.

Dose escalation and expansion cohorts in patients with advanced breast cancer in a Phase I study of the CDK7-inhibitor samuraciclib

Samuraciclib is a selective oral CDK7-inhibitor. A multi-modular, open-label Phase I study to evaluate safety and tolerability of samuraciclib in patients with advanced malignancies was designed (ClinicalTrials.gov: NCT03363893). Here we report results from dose escalation and 2 expansion cohorts: Module 1A dose escalation with paired biopsy cohort in advanced solid tumor patients, Module 1B-1 triple negative breast cancer (TNBC) monotherapy expansion, and Module 2A fulvestrant combination in HR+/HER2- breast cancer patients post-CDK4/6-inhibitor. Core study primary endpoints are safety and tolerability, and secondary endpoints are pharmacokinetics (PK), pharmacodynamic (PD) activity, and anti-tumor activity. Common adverse events are low grade nausea, vomiting, and diarrhea. Maximum tolerated dose is 360 mg once daily. PK demonstrates dose proportionality (120 mg-480 mg), a half-life of approximately 75 hours, and no fulvestrant interaction. In dose escalation, one partial response (PR) is identified with disease control rate of 53% (19/36) and reduction of phosphorylated RNA polymerase II, a substrate of CDK7, in circulating lymphocytes and tumor tissue. In TNBC expansion, one PR (duration 337 days) and clinical benefit rate at 24 weeks (CBR) of 20.0% (4/20) is achieved. In combination with fulvestrant, 3 patients achieve PR with CBR 36.0% (9/25); in patients without detectable TP53-mutation CBR is 47.4% (9/19). In this study, samuraciclib exhibits tolerable safety and PK is supportive of once-daily oral administration. Clinical activity in TNBC and HR+/HER2-breast cancer post-CDK4/6-inhibitor settings warrants further evaluation.

Investigating potential immune mechanisms of trilaciclib administered prior to chemotherapy in patients with metastatic triple-negative breast cancer

PURPOSE

In a phase II trial in patients with metastatic triple-negative breast cancer (mTNBC; NCT02978716), administering trilaciclib prior to gemcitabine plus carboplatin (GCb) enhanced T-cell activation and improved overall survival versus GCb alone. The survival benefit was more pronounced in patients with higher immune-related gene expression. We assessed immune cell subsets and used molecular profiling to further elucidate effects on antitumor immunity.

METHODS

Patients with mTNBC and ≤ 2 prior chemotherapy regimens for locally recurrent TNBC or mTNBC were randomized 1:1:1 to GCb on days 1 and 8, trilaciclib prior to GCb on days 1 and 8, or trilaciclib alone on days 1 and 8, and prior to GCb on days 2 and 9. Gene expression, immune cell populations, and Tumor Inflammation Signature (TIS) scores were assessed in baseline tumor samples, with flow cytometric analysis and intracellular and surface cytokine staining used to assess immune cell populations and function.

RESULTS

After two cycles, the trilaciclib plus GCb group (n = 68) had fewer total T cells and significantly fewer CD8+ T cells and myeloid-derived suppressor cells compared with baseline, with enhanced T-cell effector function versus GCb alone. No significant differences were observed in patients who received GCb alone (n = 34). Of 58 patients in the trilaciclib plus GCb group with antitumor response data, 27 had an objective response. RNA sequencing revealed a trend toward higher baseline TIS scores among responders versus non‑responders.

CONCLUSION

The results suggest that administering trilaciclib prior to GCb may modulate the composition and response of immune cell subsets to TNBC.

A Gene Panel Associated With Abemaciclib Utility in ESR1-Mutated Breast Cancer After Prior Cyclin-Dependent Kinase 4/6-Inhibitor Progression

PURPOSE

For patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer (MBC), first-line treatment is endocrine therapy (ET) plus cyclin-dependent kinase 4/6 inhibition (CDK4/6i). After disease progression, which often comes with ESR1 resistance mutations (ESR1-MUT), which therapies to use next and for which patients are open questions. An active area of exploration is treatment with further CDK4/6i, particularly abemaciclib, which has distinct pharmacokinetic and pharmacodynamic properties compared with the other approved CDK4/6 inhibitors, palbociclib and ribociclib. We investigated a gene panel to prognosticate abemaciclib susceptibility in patients with ESR1-MUT MBC after palbociclib progression.

METHODS

We examined a multicenter retrospective cohort of patients with ESR1-MUT MBC who received abemaciclib after disease progression on ET plus palbociclib. We generated a panel of CDK4/6i resistance genes and compared abemaciclib progression-free survival (PFS) in patients without versus with mutations in this panel (CDKi-R[-] v CDKi-R[+]). We studied how ESR1-MUT and CDKi-R mutations affect abemaciclib sensitivity of immortalized breast cancer cells and patient-derived circulating tumor cell lines in culture.

RESULTS

In ESR1-MUT MBC with disease progression on ET plus palbociclib, the median PFS was 7.0 months for CDKi-R(-) (n = 17) versus 3.5 months for CDKi-R(+) (n = 11), with a hazard ratio of 2.8 (P = .03). In vitro, CDKi-R alterations but not ESR1-MUT induced abemaciclib resistance in immortalized breast cancer cells and were associated with resistance in circulating tumor cells.

CONCLUSION

For ESR1-MUT MBC with resistance to ET and palbociclib, PFS on abemaciclib is longer for patients with CDKi-R(-) than CDKi-R(+). Although a small and retrospective data set, this is the first demonstration of a genomic panel associated with abemaciclib sensitivity in the postpalbociclib setting. Future directions include testing and improving this panel in additional data sets, to guide therapy selection for patients with HR+/HER2- MBC.

Cost-Effectiveness of Neoadjuvant Pembrolizumab Plus Chemotherapy Followed by Adjuvant Single-Agent Pembrolizumab for High-Risk Early-Stage Triple-Negative Breast Cancer in the United States

INTRODUCTION

The randomized phase III KEYNOTE-522 trial demonstrated that addition of pembrolizumab to neoadjuvant chemotherapy provided a significant improvement in event-free survival and a favorable trend in overall survival for high-risk early-stage triple-negative breast cancer (eTNBC). This analysis evaluated the cost-effectiveness of pembrolizumab in combination with chemotherapy as neoadjuvant treatment and continued as a single-agent adjuvant treatment after surgery vs. neoadjuvant chemotherapy for patients with high-risk eTNBC in the USA.

METHODS

The analysis was conducted from a US third-party public healthcare payer perspective. A multistate transition model was developed using efficacy and safety data from the KEYNOTE-522 trial. The model included four mutually exclusive health states: event-free, locoregional recurrence, distant metastasis, and death to simulate patients' lifetime disease course. Quality-adjusted life years (QALYs) were calculated on the basis of EuroQoL-5 Dimensions utility data collected in KEYNOTE-522. Costs for drug acquisition/administration, adverse events, disease management, and subsequent therapies were reported (2021 US dollars). Costs and outcomes were discounted at 3% annually. A series of sensitivity analyses were performed to test the robustness of the main results.

RESULTS

In the base case scenario, pembrolizumab plus chemotherapy followed by pembrolizumab resulted in expected gains of 3.37 life years (LYs) and 2.90 QALYs, and an incremental cost of $79,046 versus chemotherapy. The incremental cost per QALY gained was $27,285, which is lower than all commonly cited US willingness-to-pay thresholds. Sensitivity analyses showed the results were robust over plausible values of key model inputs and assumptions.

CONCLUSIONS

Compared with neoadjuvant chemotherapy, pembrolizumab in combination with chemotherapy as neoadjuvant treatment and continued as a single-agent adjuvant treatment after surgery is considered a cost-effective option for high-risk eTNBC in the USA.

Risk of Recurrence in Patients with HER2+ Early-Stage Breast Cancer: Literature Analysis of Patient and Disease Characteristics

Human epidermal growth factor receptor 2 (HER2) overexpression occurs in 15% to 20% of patients with early-stage breast cancers (EBCs). Without HER2-targeted therapy, 30% to 50% of patients relapse within 10 years, many developing incurable metastatic disease. This literature review was designed to identify and validate patient- and disease-related factors associated with recurrence in patients with HER2+ EBC. Peer-reviewed primary research articles and congress abstracts were identified by searching MEDLINE. Articles published in English from 2019 to 2022 were included to identify contemporary treatment options. Results were analyzed for the relationship between risk factors and surrogates of HER2+ EBC recurrence to determine how identified risk factors affected HER2+ EBC recurrence. Sixty-one articles and 65 abstracts that assessed age at diagnosis, body mass index (BMI), tumor size at diagnosis, hormone receptor (HR) status, pathologic complete response (pCR) status, and biomarkers were analyzed. We confirmed the results of previously published reviews reporting residual cancer burden >0, non-pCR, and fewer tumor-infiltrating lymphocytes (TILs) as risk factors of recurrence. HR status remained an important risk factor for recurrence, with HER2+/HR+ disease more likely to recur. Two or more positive lymph nodes, higher BMI, larger primary tumor size, and low Ki67 were more commonly associated with HER2+ EBC recurrence. The identification of patient and disease factors frequently associated with HER2+ EBC recurrence in the literature provides insight into potential recurrence risk factors. Further investigation into the risk factors identified in this review could lead to improved treatments for patients at high risk for HER2+ EBC recurrence.

Abemaciclib plus endocrine therapy for hormone receptor-positive, HER2-negative, node-positive, high-risk early breast cancer (monarchE): results from a preplanned interim analysis of a randomised, open-label, phase 3 trial

BACKGROUND

Adjuvant abemaciclib plus endocrine therapy previously showed a significant improvement in invasive disease-free survival and distant relapse-free survival in hormone receptor-positive, human epidermal growth factor receptor 2 (HER2; also known as ERBB2)-negative, node-positive, high-risk, early breast cancer. Here, we report updated results from an interim analysis to assess overall survival as well as invasive disease-free survival and distant relapse-free survival with additional follow-up.

METHODS

In monarchE, an open-label, randomised, phase 3 trial, adult patients (aged ≥18 years) who had hormone receptor-positive, HER2-negative, node-positive, early breast cancer at a high risk of recurrence with an Eastern Cooperative Oncology Group performance status of 0 or 1 were recruited from 603 sites including hospitals and academic and community centres in 38 countries. Patients were randomly assigned (1:1) by means of an interactive web-based response system (block size of 4), stratified by previous chemotherapy, menopausal status, and region, to receive standard-of-care endocrine therapy of physician's choice for up to 10 years with or without abemaciclib 150 mg orally twice a day for 2 years (treatment period). All therapies were administered in an open-label manner without masking. High-risk disease was defined as either four or more positive axillary lymph nodes, or between one and three positive axillary lymph nodes and either grade 3 disease or tumour size of 5 cm or larger (cohort 1). A smaller group of patients were enrolled with between one and three positive axillary lymph nodes and Ki-67 of at least 20% as an additional risk feature (cohort 2). This was a prespecified overall survival interim analysis planned to occur 2 years after the primary outcome analysis for invasive disease-free survival. Efficacy was assessed in the intention-to-treat population. Safety was assessed in all treated patients. The study is registered with ClinicalTrials.gov, NCT03155997, and is ongoing.

FINDINGS

Between July 17, 2017, and Aug 12, 2019, 5637 patients were randomly assigned (5601 [99·4%] were women and 36 [0·6%] were men). 2808 were assigned to receive abemaciclib plus endocrine therapy and 2829 were assigned to receive endocrine therapy alone. At a median follow-up of 42 months (IQR 37-47), median invasive disease-free survival was not reached in either group and the invasive disease-free survival benefit previously reported was sustained: HR 0·664 (95% CI 0·578-0·762, nominal p<0·0001). At 4 years, the absolute difference in invasive disease-free survival between the groups was 6·4% (85·8% [95% CI 84·2-87·3] in the abemaciclib plus endocrine therapy group vs 79·4% [77·5-81·1] in the endocrine therapy alone group). 157 (5·6%) of 2808 patients in the abemaciclib plus endocrine therapy group died compared with 173 (6·1%) of 2829 patients in the endocrine therapy alone group (HR 0·929, 95% CI 0·748-1·153; p=0·50). The most common grade 3-4 adverse events were neutropenia (in 548 [19·6%] of 2791 patients receiving abemaciclib plus endocrine therapy vs 24 [0·9%] of 2800 patients in the endocrine therapy alone group), leukopenia (318 [11·4%] vs 11 [0·4%]), and diarrhoea (218 [7·8%] vs six [0·2%]). Serious adverse events occurred in 433 (15·5%) of 2791 patients receiving abemaciclib plus endocrine therapy versus 256 (9·1%) of 2800 receiving endocrine therapy. There were two treatment-related deaths in the abemaciclib plus endocrine therapy group (diarrhoea and pneumonitis) and none in the endocrine therapy alone group.

INTERPRETATION

Adjuvant abemaciclib reduces the risk of recurrence. The benefit is sustained beyond the completion of treatment with an absolute increase at 4 years, further supporting the use of abemaciclib in patients with high-risk hormone receptor-positive, HER2-negative early breast cancer. Further follow-up is needed to establish whether overall survival can be improved with abemaciclib plus endocrine therapy in these patients.

FUNDING

Eli Lilly.

Q-TWiST analysis of pembrolizumab combined with chemotherapy as first-line treatment of metastatic triple-negative breast cancer that expresses PD-L1

OBJECTIVE

In the KEYNOTE-355 (KN355) trial, pembrolizumab in combination with chemotherapy demonstrated superior efficacy and manageable safety compared with chemotherapy alone in patients with previously untreated locally recurrent inoperable and metastatic triple-negative breast cancer (mTNBC) with PD-L1 positive (Combined Positive Score [CPS]≥ 10) tumours. This study aimed to evaluate the clinical benefits and risks of pembrolizumab measured by quality-adjusted survival in the trial population.

METHODS

The study used data from the final analysis of KN355. The Quality-adjusted Time Without Symptoms of disease progression or Toxicity of treatment (Q-TWiST) analysis was used to compare treatments of pembrolizumab plus chemotherapy versus chemotherapy alone. Patients' survival time was partitioned into three health states - toxicity before disease progression (TOX), time without symptoms or toxicity before disease progression (TWiST), and relapse (REL). Utilities for these health states were estimated using EuroQol-5 Dimensions, 3 Levels (EQ-5D-3L) data collected in KN355. Q-TWiST was derived as the utility-weighted sum of the mean health state durations.

RESULTS

Patients randomised to pembrolizumab plus chemotherapy had 3.7 months greater Q-TWiST (relative gain of 18%; P = 0.003) compared to those randomised to chemotherapy at the median follow-up of 44 months, and 4.3 months greater Q-TWiST (relative gain of 20%; P = 0.004) at the maximum follow-up of 52 months. The Q-TWiST gain increased with longer follow-up time.

CONCLUSIONS

Pembrolizumab plus chemotherapy was associated with statistically significant and clinically important improvement in Q-TWiST compared to chemotherapy in previously untreated PD-L1-positive mTNBC.

Discordance in management of adverse events associated with oral therapies in hormone receptor–positive breast cancer among health care providers and experts: Findings from an online decision support tool

382

Background: Oral targeted therapies (OTTs) inhibiting CDK4/6, PI3K, and mTOR have established roles across multiple lines of therapy in patients with advanced hormone receptor–positive, HER2-negative breast cancer (HR+ BC). Abemaciclib, a CDK4/6 inhibitor (i), now also is approved in the adjuvant setting for eligible patients with early-stage HR+ BC. These OTTs are associated with various adverse events (AEs), such as cytopenias, diarrhea, hepatotoxicity, and rash. Optimal AE management is critical to promote patient adherence and achieve the best possible outcomes. Here we report an analysis of healthcare professional (HCP) management of AEs associated with OTTs in HR+ BC using an online decision support tool. Methods: The online tool was developed with 5 BC experts providing recommendations on the management of AEs associated with OTTs. Within the online tool, HCPs were prompted to input relevant patient case details through a series of predefined questions, including which OTT and type of AE the patient is experiencing, along with their management approach. Participants were then shown an expert recommendation based on the specific characteristics of that case and were asked if their management plan changed based on that recommendation. Results: Between September 2021 and April 2022, 557 cases were entered by 390 participants. Among 291 cases of patients currently receiving oral therapy, CDK4/6i therapy was most commonly selected (82%), followed by PI3Ki (11%) and mTORi (8%) therapy. The most common AE reported for CDK4/6i, PI3Ki, and mTORi therapy were cytopenias (56%), hyperglycemia (64%), and stomatitis (57%), respectively. With CDK4/6i, HCPs were discordant with expert recommendations for management of AEs reported in 44%, 39%, and 35% of entered cases with ribociclib, abemaciclib, and palbociclib, respectively. The greatest variance between HCP and expert recommendations were with management of VTE, hepatotoxicity, QT prolongation, and rash (Table). Among HCPs with discordant results from the experts, 50% changed their AE management plan after viewing the expert recommendation. Conclusions: These data suggest that HCPs may be challenged to optimally manage AEs related to OTTs in patients with HR+ BC. Use of an online tool may enhance HCP management of these AEs for patients with HR+ BC. A detailed analysis of the tool, including HCP planned management vs expert recommendations, will be presented.[Table: see text]

Trilaciclib prior to gemcitabine plus carboplatin for metastatic triple-negative breast cancer: phase III PRESERVE 2

Triple-negative breast cancer (TNBC) is an aggressive malignancy for which cytotoxic chemotherapy remains the backbone of treatment. Trilaciclib is an intravenous cyclin-dependent kinase 4/6 inhibitor that induces transient cell cycle arrest of hematopoietic stem and progenitor cells and immune cells during chemotherapy exposure, protecting them from chemotherapy-induced damage and enhancing immune activity. Administration of trilaciclib prior to gemcitabine plus carboplatin (GCb) significantly improved overall survival (OS) compared with GCb alone in an open-label phase II trial in patients with metastatic TNBC, potentially through protection and direct activation of immune function. The randomized, double-blind, placebo-controlled, phase III PRESERVE 2 trial will evaluate the efficacy and safety of trilaciclib administered prior to GCb in patients with locally advanced unresectable or metastatic TNBC. Clinical Trial Registration: NCT04799249 (ClinicalTrials.gov).

Cost-effectiveness of pembrolizumab plus chemotherapy as first-line treatment in PD-L1-positive metastatic triple-negative breast cancer

Objective: This study evaluated the cost-effectiveness of pembrolizumab/chemotherapy combinations for previously untreated metastatic triple-negative breast cancer patients in the USA with PD-L1 combined positive score ≥10. Methods: A partitioned-survival model was developed to project health outcomes and direct medical costs over a 20-year time horizon. Efficacy and safety data were from randomized clinical trials. Comparative effectiveness of indirect comparators was assessed using network meta-analyses. A series of sensitivity analyses were performed to test the robustness of the results. Results: Pembrolizumab/chemotherapy resulted in total quality-adjusted life-year (QALY) gains of 0.70 years and incremental cost-effectiveness ratio of US$182,732/QALY compared with chemotherapy alone. The incremental cost-effectiveness ratio for pembrolizumab/nab-paclitaxel versus atezolizumab/nab-paclitaxel was US$44,157/QALY. Sensitivity analyses showed the results were robust over plausible values of model inputs. Conclusion: Pembrolizumab/chemotherapy is cost effective compared with chemotherapy as well as atezolizumab/nab-paclitaxel as first-line treatment for PD-L1-positive metastatic triple-negative breast cancer from a US payer perspective.

Phase I Trial of a Novel Anti-HER2 Antibody-Drug Conjugate, ARX788, for the Treatment of HER2-Positive Metastatic Breast Cancer

PURPOSE

ARX788 is a novel antibody-drug conjugate (ADC) comprised of an anti-HER2 mAb and a potent tubulin inhibitor payload AS269 that is site-specifically conjugated to the antibody via a nonnatural amino acid incorporated into the antibody. Herein, we present the results of a phase I study of the safety, pharmacokinetics, and antitumor activity of ARX788 in patients with HER2-positive metastatic breast cancer (MBC).

PATIENTS AND METHODS

Patients with HER2-positive MBC received ARX788 at doses of 0.33, 0.66, 0.88, 1.1, 1.3, or 1.5 mg/kg every 3 weeks, or 0.88, 1.1, or 1.3 mg/kg every 4 weeks. The dose-limiting toxicity (DLT) was assessed for 84 days for pulmonary toxicity and at a duration of one cycle (21 or 28 days) for other toxicities.

RESULTS

In total, 69 patients were enrolled. No DLT or drug-related deaths occurred. Most patients (67/69; 97.1%) experienced at least one treatment-related adverse event (TRAE). Common (≥ 30%) TRAEs included an increase in aspartate aminotransferase, an increase in alanine aminotransferase, corneal epitheliopathy, alopecia, hypokalemia, interstitial lung disease (ILD)/pneumonitis, and an increase in aldosterone. While 34.8% of participants experienced ILD/pneumonitis, only 2 had a severity of grade 3. At 1.5 mg/kg every 3 weeks, the recommended phase II dose, the objective response rate was 65.5% [19/29, 95% confidence interval (CI), 45.7-82.1], the disease control rate was 100% (95% CI, 81.2-100), and the median progression-free survival was 17.02 months (95% CI, 10.09-not reached).

CONCLUSIONS

ARX788 demonstrated a manageable safety profile with promising preliminary signs of activity in patients with HER2-positive MBC who progressed on prior anti-HER2 therapies.

Defining transcriptomic profiles of early-stage mucinous breast cancers: A FLEX sub study

3134

Background: Mucinous breast cancer (MuBC) is a rare subtype of invasive ductal carcinoma (IDC) that accounts for less than 2% of all breast cancers and is associated with a favorable prognosis. Since MuBCs are rare in clinical trials, current treatment guidelines are extrapolated from IDC-no special type (IDC-NST). To provide better understanding of MuBCs and factors contributing to their clinical behavior, we examined the transcriptomic profiles of MuBCs in our FLEX study. Methods: The prospective, observational FLEX Study (NCT03053193) includes stage I-III breast cancer patients who receive MammaPrint (MP)/BluePrint (BP) testing and consent to full transcriptome and clinical data collection. For this study, histologically confirmed MuBCs (n = 102) in the FLEX database were included. All patients examined were ER+/HER2- by immunohistochemistry and Luminal by BP. MuBC was compared with IDC matched for Age, MP, and BP index (n = 97). Differential gene expression analyses (DGEA) were performed with R package ‘limma’ and differentially expressed genes (DEGs) were considered significant if they had an adjusted p < 0.05 and fold change ≥ 2. Results: DGEA comparing MuBC (n = 102) with IDC (n = 97) revealed 60 DEGs, regardless of the genomic risk, of which 42 genes were upregulated and 18 were downregulated in MuBC relative to IDC. Genes associated with MuBC, such as MUC2, TFF1, CARTPT were among the upregulated genes. Of the 102 MuBC patients, 56 were Luminal A (MP Low Risk-LR) and 46 were Luminal B (MP High Risk-HR) by MammaPrint and BluePrint. Comparison of LR MuBC with LR IDC revealed 111 DEGs. Functional enrichment showed upregulation of pathways involved in estrogen response (early & late) and androgen response and a downregulation of the epithelial to mesenchymal transition (EMT) and E2F pathways in LR MuBC compared to LR IDC. DGEA between HR MuBC and HR IDC revealed only 22 DEGs with immune pathways being downregulated in HR MuBC. DGEA comparing LR MuBC with HR MuBC resulted in 63 DEGs, indicating LR and HR MuBC are biologically distinct types. Interestingly in LR MuBC, the tumor suppressor marker SCUBE2 is upregulated. Over expression of SCUBE2 is associated with better prognosis. Conclusions: Although MuBCs are often expected to have low clinical risk, MP revealed that half of the MuBCs examined in this study were MP High Risk (Luminal B). MP low risk MuBC is biologically different from MP low risk IDC, and downregulation of E2F and EMT pathways might lead to favorable prognoses in MP low risk MuBC. MP high risk MuBC showed limited DEGs compared to high-risk IDCs indicating these tumor types are highly genomically similar and likely to benefit from chemotherapy. The downregulation of immune pathways in MP high risk MuBC may lead to immune surveillance escape resulting in metastasis and further investigation is needed. Clinical trial information: NCT03053193.

Phase 1b/2 study of ladiratuzumab vedotin (LV) in combination with pembrolizumab for first-line treatment of triple-negative breast cancer (SGNLVA-002, trial in progress)

TPS1127

Background: Patients with metastatic triple-negative breast cancer (mTNBC) have a poor prognosis. Treatment combinations of anti-programmed death ligand 1 (anti–PD-L1) agents with chemotherapy have shown promise in mTNBC. LV is an investigational antibody–drug conjugate directed to LIV-1, a protein highly expressed on breast cancer cells, via a humanized IgG1 monoclonal antibody conjugated to monomethyl auristatin E (MMAE) by a protease-cleavable linker. LIV-1–mediated delivery of MMAE disrupts microtubules and induces cell cycle arrest and apoptosis. LV has also been shown to drive immunogenic cell death (ICD) to elicit an immune response. LV + pembrolizumab may result in synergistic activity through LV-induced ICD, creating a microenvironment favorable for enhanced anti–PD-L1 activity. Preliminary results show LV delivered once every 3 weeks (Q3W) + pembrolizumab was tolerable with encouraging antitumor activity in patients with mTNBC (Han 2019). Additionally, interim results of weekly LV monotherapy at doses up to 1.5 mg/kg were clinically active and generally well tolerated (Tsai 2021). Based on pharmacokinetic and pharmacodynamic modeling and simulation analysis, an intermittent LV + pembrolizumab dosing regimen is being evaluated to further enhance efficacy and improve the tolerability profile. Due to an unmet medical need for patients with mTNBC who are PD-L1 low or negative, Part D will focus on this patient population. Methods: SGNLVA-002 (NCT03310957) is an ongoing global single-arm, open-label phase 1b/2 study of LV + pembrolizumab as 1L therapy for patients with unresectable locally advanced/mTNBC. Part D is currently enrolling ̃40 patients. Eligible patients must have advanced disease with no prior cytotoxic/anti–PD-L1 treatment, PD-L1 combined positive score < 10, measurable disease per RECIST v1.1 and an ECOG score ≤1. Patients with Grade ≥2 pre-existing neuropathy or active central nervous system metastases are not permitted. Patients will receive LV at 1.5 mg/kg on Days 1 and 8 plus pembrolizumab 200 mg on Day 1 Q3W. The primary objectives are to evaluate the safety/tolerability and objective response rate of LV + pembrolizumab. Secondary objectives include duration of response, disease control rate, progression-free survival, and overall survival. Safety and efficacy endpoints will be summarized with descriptive statistics. Global enrollment is ongoing in the US, EU, and Asia. Clinical trial information: NCT03310957.

Clinical outcomes with alpelisib (ALP) plus fulvestrant (FUL) after prior treatment (tx) with FUL in patients (pts) with advanced breast cancer (ABC): A real-world (RW) analysis

1055

Background: ALP (α-selective PI3K inhibitor and degrader) + FUL was FDA approved and reflected in the NCCN guidelines in 2019 for pts with hormone receptor–positive/human epidermal growth factor receptor 2–negative (HR+/HER2−) ABC with PIK3CA mutations following progression on or after endocrine-based therapy (ET). The Phase III SOLAR-1 trial excluded prior FUL, and data on ALP + FUL after FUL are limited. As cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) + ET (including FUL) is the standard in the first line (1L) or second line (2L) for pts with HR+/HER2− ABC, more data on ALP + FUL post-FUL are needed. Here we report patterns and clinical outcomes on RW use of ALP + FUL in pts with HR+/HER2– ABC with prior FUL exposure. Methods: This retrospective study used de-identified electronic health record data from the ConcertAI Patient360 Breast Cancer data product sourced from US oncology centers. Adults with HR+/HER2− ABC treated with ALP + FUL (index tx) who received prior FUL (monotherapy or in combination) in the metastatic setting were included; pts with a PIK3CA negative test on or prior to the index were excluded. Pts were followed until date of death or last activity. RW progression-free survival (rwPFS), defined as first documented progression/death from ALP + FUL start date, was assessed. Results: This analysis included 157 pts (median age, 63 y [57-71 y]) who received ALP + FUL from 2019 to 2021, with 11.5% pts in 1L, 17.8% in 2L, 26.8% in third line (3L), and 43.9% in fourth line and beyond (4L+). Prior FUL tx included CDK4/6i + FUL (74.5%), FUL alone (33.8%), and non-CDK4/6i + FUL (21.0%). In pts who received ALP + FUL in 1L (n = 18), prior FUL exposure was in the same line without documented progression. In the metastatic setting, 28.0% of pts received > 1 FUL-containing regimen and/or 72.0% received prior chemotherapy (CT). At the median duration of follow-up (8.7 mo [4.1-12.5 mo]), the median rwPFS was 5.7 mo (4.0-7.3 mo) in the overall population. The median rwPFS was also analyzed by line of therapy (Table). In pts with CDK4/6i + FUL as immediate prior therapy (n = 39), the median rwPFS was 6.2 mo (3.0-9.1 mo); 79.5% of these pts received ALP in ≤ 3L. At the time of analysis, 107 pts (68.2%) had discontinued ALP + FUL; the median time to discontinuation was 4.7 mo (3.7-6.1 mo). Following discontinuation of ALP + FUL, CT was the most common subsequent therapy (33.8%). Conclusions: This analysis on RW data from early years of ALP access in the US shows clinical benefit of ALP + FUL in pts with HR+/HER2− ABC with PIK3CA mutation even when exposed to prior FUL, confirming the oncogenic dependence of the tumor on the PIK3CA mutation. [Table: see text]

Quality of life (QOL) with ribociclib (RIB) plus aromatase inhibitor (AI) versus abemaciclib (ABE) plus AI as first-line (1L) treatment (tx) of hormone receptor-positive/human epidermal growth factor receptor–negative (HR+/HER2−) advanced breast cancer (ABC), assessed via matching-adjusted indirect comparison (MAIC)

1015

Background: The combination of a cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) + endocrine therapy is the recommended 1L tx for HR+/HER2− ABC. A statistically significant overall survival (OS) benefit with RIB + AI was recently reported for MONALEESA-2 (ML-2); final OS results for the MONARCH 3 (MON-3) trial of ABE + AI are pending. QoL is an important end point that affects tx decisions. Understanding the impact of CDK4/6i on QoL is of increasing importance given use in earlier tx lines for ABC and an emerging role in treating early breast cancer, where QoL considerations may be more relevant. MAIC analysis allows for comparative effectiveness in the absence of head-to-head trial data. In this analysis, patient (pt)-reported QoL for the Phase III ML-2 (RIB + AI) and MON-3 (ABE + AI) trials were compared using MAIC with a focus on individual domains; the PALOMA-2 trial could not be considered for this analysis because of the different pt-reported outcome measures evaluated in the trial compared to ML-2 and MON-3. Methods: An anchored MAIC of QoL with RIB + AI vs ABE + AI was performed using data from EORTC QLQ-C30 and BR-23 questionnaires, individual participant data from ML-2 (data cutoff: 6/10/2021), and published data from MON-3 (data cutoff: 11/3/2017). All available QoL data were used in this analysis; the median follow-up for ML-2 was 79.7 months, and the median duration of follow-up at which QoL data were reported for MON-3 was 26.73 months. Inclusion and exclusion criteria were generally similar. Pts in both arms of ML-2 were weighted to match baseline characteristics in the corresponding arms of MON-3. Cox proportional hazards model was used to generate hazard ratios (HRs); anchored HRs were calculated using the Bucher method. Time to sustained deterioration (TTSD) was calculated as the time from randomization to a ≥ 10-point deterioration with no later improvement above this threshold. Results: 205 and 149 pts from the ML-2 arms of RIB/PBO were matched to 328 and 165 pts from the ABE/PBO arms of MON-3. After weighting, pt characteristics were well balanced. TTSD significantly favored RIB vs ABE in appetite loss (HR, 0.46; 95% CI, 0.27-0.81), diarrhea (HR, 0.42; 95% CI, 0.23-0.79), and fatigue (HR, 0.63; 95% CI, 0.41-0.96) as measured by QLQ-C30 and arm symptoms (HR, 0.49; 95% CI, 0.30-0.79) as assessed by BR-23. TTSD did not significantly favor ABE vs RIB in any functional or symptom scale of the QLQ-C30 or BR-23. Conclusions: This MAIC suggests that RIB + AI is associated with better symptom-related QoL vs ABE + AI for postmenopausal pts with HR+/HER2− ABC in the 1L setting. QoL differences between CDK4/6i and their associated adverse event profiles may impact clinical decisions in HR+/HER2− ABC.

Event-free survival by residual cancer burden after neoadjuvant pembrolizumab + chemotherapy versus placebo + chemotherapy for early TNBC: Exploratory analysis from KEYNOTE-522

503

Background: KEYNOTE-522 (NCT03036488) tested the benefit from adding pembrolizumab (pembro) to chemotherapy (chemo) in patients (pts) with early TNBC. The primary results showed statistically significant and clinically meaningful improvements in pCR and EFS with pembro.Prior studies have shown the prognostic value of the residual cancer burden (RCB) method to quantify the extent of residual disease after neoadjuvant chemo. In this exploratory analysis, we assessed EFS by RCB in KEYNOTE-522. Methods: 1174 pts with previously untreated, nonmetastatic, stage T1c/N1-2 or T2-4/N0-2 TNBC were randomized 2:1 to pembro 200 mg Q3W or placebo (pbo) given with 4 cycles of paclitaxel + carboplatin, then 4 cycles of doxorubicin or epirubicin + cyclophosphamide. After definitive surgery, pts received pembro or pbo for 9 cycles or until recurrence or unacceptable toxicity. Dual primary endpoints are pCR and EFS. RCB was assessed by the local pathologist at the time of surgery. The association between RCB categories (RCB-0, -1, -2, -3, corresponding to increasingly larger residual cancer) and EFS was assessed based on a Cox regression model with treatment as a covariate. Results: Median follow-up was 39.1 months at data cutoff (23 MAR 2021). Pembro shifted RCB to lower categories across the entire spectrum (Table). The HRs (95% CI) for EFS were 0.70 (0.38 - 1.31) for RCB-0 (equivalent to pCR), 0.92 (0.39 - 2.20) for RCB-1, 0.52 (0.32 - 0.82) for RCB-2, and 1.24 (0.69 - 2.23) for RCB-3. The most common EFS event in both arms was distant recurrence, which occurred in fewer pts in the pembro arm in all RCB categories. Conclusions: Increased RCB score was associated with worse EFS. Pts with residual disease had lower RCB values in the pembro arm, including fewer pts with RCB-3. Pembro + chemo prolonged EFS vs chemo alone in the RCB-0, -1, and -2 categories; the small sample size limits interpretation in the RCB-3 category. The small subset of pts with extensive residual disease (RCB-3) in both arms, 5.1% and 6.7%, respectively, had a poor prognosis. These results highlight the importance of neoadjuvant treatment with pembro for improving survival in pts with early TNBC, and identified a subset of pts for whom additional therapies will be needed. Clinical trial information: NCT03036488. [Table: see text]

Phase 3 ENABLAR-2 study to evaluate enobosarm and abemaciclib combination compared to estrogen-blocking agent for the second-line treatment of AR+, ER+, HER2- metastatic breast cancer in patients who previously received palbociclib and estrogen-blocking agent combination therapy

TPS1121

Background: Targeting the androgen receptor (AR) may be the next important endocrine therapy for advanced breast cancer. The AR has been demonstrated to be a tumor suppressor when activated. Enobosarm is an oral selective AR targeting agonist that activates the AR in breast cancer. Preclinical studies in CDK4/6 inhibitor resistant PDX models demonstrated combinatorial synergistic activity of enobosarm plus CDK 4/6 inhibitors. An open-label, Phase 2 study, was conducted in 136 women with heavily pretreated ER+ HER2- metastatic breast cancer that were randomized to oral daily enobosarm at a dose of 9 or 18 mg. The efficacy evaluable (EE) group were patients that were AR positive (> 10% AR nuclear staining). In the EE population with measurable disease at baseline, 10 patients had received prior endocrine therapy + a CDK 4/6 inhibitor. Subsequent treatment with enobosarm resulted in a clinical benefit rate of 50% and the best overall response rate (ORR) was 30% (2CRs and 1 PR). Of the 10 patients, 7 had AR nuclear staining ≥40%. None of the patients with AR nuclear staining < 40% responded to enobosarm. Although a small subset of the study, it appears that enobosarm has activity in patients who had ≥40% AR staining and who had progressed on standard endocrine therapy with a CDK 4/6 inhibitor. Overall, treatment with enobosarm was well tolerated with significant positive effects on quality-of-life measurements. Methods: The ENABLAR-2 trial is an ongoing Phase 3, randomized, open-label, efficacy and safety study in patients with AR+ ER+ HER2- MBC with AR nuclear staining of ≥40%, who have progressed after one line of systemic therapy comprising estrogen blocking agent and palbociclib. The planned sample size is 186 patients randomized 1:1 to enobosarm + abemaciclib OR fulvestrant if the first line of therapy for MBC was a non-steroidal AI plus palbociclib, until disease progression, toxicity, or loss of clinical benefit. If first line therapy for metastatic breast cancer was fulvestrant plus palbociclib, then the patient will be randomized 1:1 to either enobosarm + abemaciclib OR an AI. Randomization will be stratified by AR% nuclear staining, ≥60% versus < 60%, as well as by estrogen blocking agent such that each cohort will have the same number of subjects previously receiving fulvestrant + palbociclib in first line therapy. The key objectives are to determine the safety and efficacy of enobosarm and abemaciclib combination versus an alternative estrogen blocking agent with the primary endpoint of PFS. Secondary endpoints include ORR, duration of response, overall survival, change from baseline in Short Physical Performance Battery (SPPB), change in EORTC Quality of Life Questionnaire (EORTC-QLQ) and change in body composition as measured by DEXA. Clinical trial information: NCT05065411.

Clinical implications for patients with discordant oncotype and MammaPrint results

560

Background: Genomic tests provide critical information regarding risk of recurrence and inform treatment plans by identifying those patients who may safely forgo chemotherapy (CT) or shorten endocrine therapy (ET) duration. The IMPACT trial demonstrated that the 70 -gene risk of recurrence assay MammaPrint (MP) and 80-gene subtyping assay BluePrint (BP) inform treatment planning and increase physician confidence. However, not all genomic tests yield the same results. To examine consistency among genomic tests, we analyzed therapy implications for patients who received results from both MP/BP and Recurrence Score (RS). Methods: Using the FLEX cohort (NCT03053193), we examined 723 patients who received both MP/BP, and RS genomic assays. We assessed the potential clinical impact by examining the standardized reports of RS and MP/BP results. MP classified tumors as either ultralow, low, or high risk and BP further classified them as luminal, basal, or HER2. RS classified tumors as low (RS0-10), intermediate (RS11-25), or high (RS26-100). Clinical impact was defined as discordant genomic resulting in different treatment recommendations. Undertreatment indicates patients who may not have received CT based on RS but may have based on MP/BP and overtreatment those patients who would have received CT based on RS, but not based on MP/BP. ET duration too long is indicative of those patients that are ultralow risk by MP, regardless of RS classification, as those patients may have safely reduced the duration of their ET. Although outcomes are not available, treatment impacts are presuming a patient received both tests, but the treating physician opted to guide therapy according to the RS results rather than MP/BP. Results: We observed discordant results with a clinical impact in 49% (354) of patients, with 34% (244) who may be undertreated, 2% (11) potentially overtreated, and 14% (99) who may not be given the option to decrease ET to two years based on ultralow MP genomic risk. Of 114 concordant High-Risk tumors, 14% (16) were genomically Basal, and likely to require more aggressive CT than typically used in ER+ cancers. The table below summarizes the results. Conclusions: More than half of the patients in this cohort were at potential risk for undertreatment or overtreatment. The risk to patients is far more significant in the event of undertreatment, as this may result in incurable metastatic recurrence. Discordance between RS and MP/BP most often results in potential undertreatment if RS is used for treatment decision-making. Clinical trial information: NCT03053193.

Targeting HER2-positive metastatic breast cancer with ARX788, a novel anti-HER2 antibody-drug conjugate in patients whose disease is resistant or refractory to T-DM1, and/or T-DXd, and/or tucatinib-containing regimens

TPS1112

Background: The overexpression and/or amplification of human epidermal growth factor receptor 2 (HER2) occurs in approximately 20% of breast cancers (BC) and is a major driver of tumor development and progression. This HER2 subtype confers aggressive tumor behavior and the HER2 receptor remains a valuable target for antibodies, bi-specifics, and antibody drug conjugates (ADC). With advances in targeted therapy, patients with HER2-positive breast cancer (HER2+ BC) may experience an improved prognosis, including survival. Novel HER2-targeted therapies are being investigated to overcome drug resistance and to help mitigate adverse events (e.g., cardiotoxicity). ARX788 is a next-generation ADC using a technology platform whereby a HER2 specific monoclonal antibody is conjugated with Amberstatin269 (AS269), a potent cytotoxic tubulin inhibitor. Site-specificity, high homogeneity, and stable covalent conjugation of ARX788 leads to its slow release and prolonged peak of serum pAF-AS269, which may contribute to the lower systemic toxicity and increased targeted delivery of payload to tumor cells at a lower effective dose compared to other HER2 ADCs. Clinical activity has been seen in Phase I HER2 breast and pan-tumor studies. Methods: Trial Design: ACE-Breast-03 (NCT04829604) is a global, phase 2 study designed to assess anticancer activity and safety of ARX788 in patients with metastatic HER2 positive breast cancer. Patients whose disease is resistant or refractory to T-DM1, and/or T-DXd, and/or tucatinib-containing regimens are eligible. Patients must have adequate organ function. Any brain metastases must be radiographically stable without steroid dependence. Efficacy will be assessed using Response Evaluation Criteria in Solid Tumors (RECIST) v1.1 by imaging every 6 weeks on study. Endpoints include objective response rate (ORR), disease control rate (DCR), progression-free survival (PFS), overall survival (OS), best overall response (BOR), duration of response (DOR), and time to response (TTR). The safety and tolerability profile will be evaluated. Blood samples will be collected at specified time points to determine serum concentrations of ARX788, total antibody, and metabolite pAF-AS269. Potential predictive and/or prognostic biomarkers at baseline and on-treatment will be analyzed for exploratory purposes. Descriptive statistics will be used to evaluate anticancer activity, safety, and tolerability. The study is currently recruiting patients. Please contact breast03trialinquiry@ambrx.com for additional information. Clinical trial information: NCT04829604.

EPIK-B4: A phase 2, randomized study of metformin (MET) extended release (XR) +/- dapagliflozin (DAPA) to prevent hyperglycemia (HG) in patients (pts) with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-), PIK3CA-mutated (mut) advanced breast cancer (ABC) treated with alpelisib (ALP) and fulvestrant (FUL)

TPS1107

Background: ALP (α-selective PI3K inhibitor and degrader) is approved with FUL for pts with PIK3CA-mut HR+, HER2− ABC. HG is a known on-target effect of PI3K inhibition, manageable with oral anti-HG agents such as MET and dose interruptions/modifications of ALP and reversible upon discontinuation of ALP. Although HG management guidelines were refined throughout the SOLAR-1 and BYLieve studies evaluating ALP + FUL/letrozole, there remains a need for optimized strategies beyond initial MET therapy that offers earlier and more sustained improvement of HG, particularly for pts at an increased risk for severe HG. In preclinical models, the addition of a SGLT2 inhibitor to ALP (+/− MET) reduced HG while maintaining ALP efficacy. The aim of this study is to evaluate the safety and efficacy of prophylactic MET XR +/− the SGLT2 inhibitor DAPA in reducing severe HG in pts with PIK3CA-mut HR+, HER2− ABC on ALP + FUL with an increased risk for severe HG (grade ≥ 3) on ALP. Methods: EPIK-B4 is a Phase II, randomized (1:1), open-label, active-controlled study assessing the efficacy and safety of MET XR +/− DAPA (starting at Cycle 1 Day 1 [C1D1]) with ALP (300 mg orally [PO], once daily [QD], starting at C1D8) + FUL (500 mg intramuscularly on C1D1, C1D15, and D1 of subsequent cycles) in pts (N ≈ 132) with HR+, HER2–, PIK3CA-mut ABC after progression on/after endocrine-based treatment (Tx). MET XR is administered PO starting at 500 mg QD (titrated up to 2 g QD) and MET XR + DAPA starting at 500 mg and 5 mg QD (titrated up to 2 g and 10 mg QD), respectively. Eligible pts include adult men or postmenopausal women with confirmed HR+, HER2–, PIK3CA-mut ABC and ≥ 1 risk factor for severe HG (diabetes [fasting plasma glucose (FPG) ≥ 126 mg/dL and/or HbA1c ≥ 6.5%], prediabetes [FPG ≥ 100 to < 126 mg/dL and/or HbA1c 5.7% to < 6.5%], obesity [BMI ≥ 30], age ≥ 75 years); prior endocrine-based Tx (eg, FUL or oral SERD) was permitted. Randomization is stratified by baseline diabetes status. Key exclusion criteria include > 1 line of Tx in the metastatic setting; prior chemotherapy (metastatic setting) or PI3K, mTOR, or AKT inhibitor; type I or II diabetes requiring Tx; or antecedent of pancreatitis or severe cutaneous reaction. The primary endpoint is the occurrence of severe HG (grade ≥ 3 [glucose > 250 mg/dL] based on laboratory assessments) over the first 8 weeks of ALP + FUL. Secondary endpoints include progression-free survival, overall response and clinical benefit rates with confirmed response, safety, and tolerability. A biomarker analysis is planned as an exploratory objective. Recruitment is ongoing with enrollment planned in 56 sites across 8 countries; completion of primary data collection is anticipated in 2023. Clinical trial information: NCT04899349; EUDRACT#2021-001908-15.

Sacituzumab govitecan (SG) versus treatment of physician’s choice (TPC) in patients (pts) with previously treated, metastatic triple-negative breast cancer (mTNBC): Final results from the phase 3 ASCENT study

1071

Background: Treatment goals for pts with metastatic breast cancer include extended survival and improved quality of life (QoL). SG is an antibody-drug conjugate composed of an anti–Trop-2 antibody coupled to the cytotoxic SN-38 payload via a proprietary, hydrolyzable linker. SG received FDA approval for pts with mTNBC who received ≥2 prior chemotherapies (at least 1 in the metastatic setting). In the pivotal phase 3 ASCENT study (NCT02574455), SG demonstrated a significant survival benefit over single-agent chemotherapy TPC in the primary analysis population of pts with second line or greater (2L+) mTNBC without known brain metastases at baseline (Bardia A et al. NEJM 2021) and QoL (Loibl S. et al. ESMO 2021). With additional follow up, we present the final data on efficacy, including overall survival (OS), safety, and QoL. Methods: Pts with mTNBC refractory or relapsing after ≥2 prior chemotherapies with at least 1 in the metastatic setting were randomized 1:1 to receive SG (10 mg/kg IV on days 1 and 8, every 21 days) or TPC (capecitabine, eribulin, vinorelbine, or gemcitabine) until disease progression or unacceptable toxicity. Primary endpoint was progression-free survival (PFS) per RECIST 1.1 by independent review in pts without known brain metastases at baseline. Key secondary endpoints included OS, safety, and health-related QoL. Safety was analyzed in pts who received ≥1 dose of study drug. Results: Of 529 pts enrolled, 468 did not have known brain metastases at baseline (median age: 54 y [range, 27-82]; median prior lines: 4 [range, 2-17]). As of Feb 25, 2021 (final database lock), SG (n = 235) vs TPC (n = 233) significantly improved median PFS (5.6 vs 1.7 mo; HR: 0.39; P< 0.0001) and median OS (12.1 vs 6.7 mo; HR: 0.48; P< 0.0001). The OS rate at 24 months was 22.4% (95% CI, 16.8-28.5) in the SG arm and 5.2% (95% CI, 2.5-9.4) in the TPC arm. In the safety population (n = 482), key treatment-related grade ≥3 adverse events with SG (n = 258) vs TPC (n = 224) were diarrhea (11% vs 0.4%), neutropenia (52% vs 33%), anemia (8% vs 5%), and febrile neutropenia (6% vs 2%). There was no grade ≥3 neuropathy and 1 case of grade 3 interstitial lung disease reported with SG. No patient experienced a treatment-related death with SG, and there was 1 treatment-related death with TPC due to neutropenic sepsis. Treatment discontinuations due to AEs were ≤3% in both arms. SG arm showed clinically meaningful and statistically significant improvements than the TPC arm in scores for all five primary focus health-related QoL domains. Conclusions: The analysis based on the final database lock of ASCENT confirms the superior survival outcomes of SG over single-agent chemotherapy, with a manageable safety profile and improvement in QoL for pts with mTNBC in the 2L+ setting. These findings reinforce SG as an effective treatment option for this pt population. Clinical trial information: NCT02574455.

The Breast Cancer Index Registry Study: Initial analysis of the first 1,000 patients

e12513

Background: The Breast Cancer Index (BCI) is a gene expression-based biomarker that reports two results: BCI Predictive [BCI (H/I)], which predicts benefit from extended endocrine therapy (EET), and BCI Prognostic, which combines the Molecular Grade Index (MGI) with BCI (H/I) to provide individualized risk of both late (5-10 years) and overall (0-10 years) distant recurrence. The NCCN clinical practice guideline recommends use of BCI for prediction of benefit from EET in early stage, hormone receptor positive (HR+) breast cancer patients. Methods: The BCI Registry study was designed to prospectively evaluate the long-term clinical outcome, medication adherence and quality of life in HR+ early-stage breast cancer patients receiving BCI testing as part of routine clinical care. The BCI registry will enroll approximately 3,000 patients after completion of 4-7 years of primary adjuvant endocrine therapy. Patients will be followed for disease recurrence for at least 10 years from diagnosis. Patients extending endocrine therapy will be assessed annually for medication adherence. To evaluate the impact of BCI results on EET decision making, both the physician and patient will complete Decision Impact Questionnaires. Clinicopathological data are collected within the ClinCapture electronic data capture system. The BCI Registry Study is registered on ClinicalTrials.gov under NCT04875351. Results: The BCI Registry Study completed enrollment of the first 1,000 patients in January 2022. Clinical data were available for 942 patients (76.8% T1; 51.3% grade II; 75.4% N0). BCI test results were reported for 842 patients. 315 patients (37.4%) were classified as BCI (H/I)-High and 527 patients (62.6%) as BCI (H/I)-Low. Further, in node-negative (N0) patients, BCI classified 314 N0 patients (47.9%) with high risk for late distant recurrence and 342 patients (52.1%) with low risk. In node-positive (N1) patients, BCI classified 138 patients (74.2%) as high risk for late distant recurrence and 48 patients (25.8%) as low risk. The associated clinicopathological factors are shown in the table. Conclusions: The analysis of the first 1,000 BCI Registry patients confirms the expected distribution of clinicopathological factors. BCI by H/I status and prognostic risk groups are consistent with previous clinical validation studies. Clinical trial information: NCT04875351. [Table: see text]

Phase 1 pilot study with dose expansion of chemotherapy in combination with CD40 agonist and Flt3 ligand in metastatic triple-negative breast cancer

TPS1126

Background: Only a subset of patients with metastatic triple-negative breast cancer demonstrate response to currently approved PD-1 immune checkpoint blockade, and few have durable responses. Antigen presentation defects may be a reason for this low response because deficiency of antigen-presenting DC1 dendritic cells is associated with poor anti-tumor immunity. CD40 agonists are a class of agents that activate antigen presenting cells including dendritic cells and B cells and also repolarize macrophages. Flt3 ligand is a growth factor that increases dendritic cells. In line with this, we recently demonstrated in pre-clinical models that the combination of liposomal-doxorubicin chemotherapy, a CD40 agonist, and a Flt3 ligand improves outcomes of breast cancer compared to alternate combinations. Methods: This is a single arm phase I pilot study of liposomal-doxorubicin, CDX-1140 (CD40 agonist), and CDX-301 (Flt3 ligand) combination therapy in patients with metastatic or unresectable locally advanced metastatic triple-negative breast cancer. Patients will be randomized to 3 lead-in arms (triplet therapy, doublet immunotherapy only, liposomal-doxorubicin only) prior to receiving full triplet therapy with fresh tissue biopsies before and after the lead-in treatment. CDX-301 will be discontinued after 2 cycles; liposomal-doxorubicin and CDX-1140 will be continued until disease progression or clinically limiting toxicities. Primary endpoint is determination of a recommended phase 2 dose based on treatment-related adverse events including dose-limiting toxicities. Secondary endpoints include anti-tumor immune response after triplet therapy, after immunotherapy alone, and after liposomal-doxorubicin alone; median progression-free survival, overall response rate, duration of response, and clinical benefit rate. Key eligibility criteria are unresectable stage III or stage IV triple-negative breast cancer (ER ≤10%, PR ≤10%, HER2/neu negative), 1st to 3rd line metastatic treatment setting (1st line patients need to be PD-L1 negative by 22C3 assay), measurable disease by RECIST 1.1 criteria, consent for pre-treatment and on-treatment biopsies of amenable soft tissue tumor lesions, no prior treatment with an anti-CD40 antibody or a Flt3 ligand, no anthracycline treatment in the metastatic setting, no prior progression while on anthracycline-based therapy or within 6 months of completing neoadjuvant chemotherapy, and no history of non-infectious pneumonitis or current pneumonitis. This trial will enroll up to 45 patients across multiple sites. Clinical trial information: NCT05029999.

Clinical and biomarker results of neoadjuvant phase II study of pembrolizumab and carboplatin plus docetaxel in triple-negative breast cancer (TNBC) (NeoPACT)

513

Background: Addition of pembrolizumab to anthracycline-taxane-platinum chemotherapy improves pathologic complete response (pCR) and event free survival (EFS) in TNBC. Aim of this study was to assess the efficacy of the anthracycline free neoadjuvant regimen of pembrolizumab plus carboplatin plus docetaxel (Cb+D) in TNBC. Methods: In this multicenter study, eligible patients with stage I-III TNBC received carboplatin (AUC 6) + docetaxel (75 mg/m2) + pembrolizumab (200 mg) every 21 days x 6 cycles. The primary endpoint was pCR (no evidence of invasive tumor in breast and axilla). Secondary endpoints were residual cancer burden (RCB), EFS, toxicity, and immune response biomarkers. RNA isolated from pretreatment tumor tissue was subjected to next generation sequencing. Samples were classified as DNA Damage Immune Response (DDIR) signature and DetermaIO signature positive/negative using predefined cutoffs. Evaluation of stromal tumor infiltrating lymphocytes (sTILs) was performed using standard criteria. Results: 117 patients were enrolled from September 2018 to January 2022. 18% were African American, 39% had node positive disease, 88% had stage II/III disease and 15% had ER/PR 1-10%. Pathologic response information is available for 105 patients. pCR and RCB 0+1 rates were 60% (95% CI 51%-70%) and 71% (95% CI 62%-80%), respectively. Treatment related adverse events led to discontinuation of any trial drug in 12% of patients. Immune adverse events were observed in 28% of patients (Grade ≥3=6%). 47% of patients had sTILs ≥30%, 48% were DetermaIO positive, and 61% DDIR positive. The table describes the impact of these biomarkers on pCR and RCB. The areas under the prediction curve (AUC) for pCR were 0.660, 0.709, and 0.719 for DDIR, sTILs, and DetermaIO respectively. At a median follow up of 21 months, 2-year EFS is 88% in all patients; 98% in pCR group and 82% in no pCR group. Conclusions: Neoadjuvant pembrolizumab plus Cb+D regimen yields pCR of 60% and 2-year EFS of 88% in the absence of adjuvant pembrolizumab. The regimen was well tolerated, and no new toxicity signals were noted. Immune enrichment identified by sTILs or DetermaIO signature was associated with high pCR rates approaching or exceeding 80%. PD-L1 and additional biomarker analyses are ongoing. Clinical trial information: NCT03639948. [Table: see text]

Impact of steroid premedication on atezolizumab (atezo)-induced immune cell activation: A comparative analysis of IMpassion130 and IMpassion131 peripheral blood mononuclear cells (PBMCs)

1083

Background: The immune checkpoint inhibitor (ICI) atezo showed disparate outcomes as first-line therapy for metastatic TNBC when combined with nab-paclitaxel (nPac) in IMpassion130 [Schmid 2018] vs solvent-based paclitaxel (Pac) in IMpassion131 [Miles 2021]. A key difference between the trials was use of steroid premedication for Pac in IMpassion131 but not for nPac in IMpassion130. In patients (pts) receiving ICIs, prior steroid exposure has been linked to worse outcome [Drakaki 2020]. Further, IMpassion130 and IMpassion131 subgroup analyses suggested reduced atezo treatment effect in taxane-pretreated pts. This post hoc biomarker study explored the impact of: 1) steroids on systemic immune cell activation with atezo+taxane; 2) prior taxane exposure on atezo-induced immune cell activation. Methods: PBMCs collected at baseline and at day 1, cycle 2 (wk 4) were selected from matched pts (RECIST responders, PD-L1+, no liver metastases) from IMpassion130 and IMpassion131. Single-cell RNAseq was performed and the transcriptomic profile of immune cells was analyzed using GSEA pathway analyses, cell proportion and TCR clonality. Results: CITEseq from 695,851 single cells was generated from 39 IMpassion130 PBMC pairs (29 atezo+nPac; 10 placebo [Pla]+nPac) and 35 IMpassion131 pairs (26 atezo+Pac; 9 Pla+Pac). At wk 4, atezo+nPac resulted in increased IFNα and IFNγ responses across multiple cell types (CD4+ and CD8+ T cells, B cells, NK cells and monocytes) and proliferation in NK cells, but reduced TNF signaling across multiple cell types. In contrast, 4 wks of Pla+nPac increased TNF signaling but decreased IFNα and IFNγ responses. In the presence of steroids, 4 wks of atezo+Pac also increased IFNα and IFNγ responses mainly in NK cells and monocytes, but not T cells, and reduced proliferative pathways across B and T cells and TNF signaling. Pla+Pac increased TNF signaling only in NK cells, but reduced proliferative signatures across cell types. The only on-treatment change differing significantly between atezo+nPac vs atezo+Pac was the increase in proliferation pathways in NK, T and B cells with atezo+nPac. There were no significant changes in proportions of cell subsets or TCR clonality. PBMCs from taxane-pretreated pts had higher RNA-based metabolic profile (OxPhos, DNA repair and IFNα). Taxane-naive but not taxane-pretreated immune cells had increased IFNγ and IFNα response after atezo+taxane. Conclusions: Our results suggest that atezo+taxane promotes IFNα and IFNγ responses and that steroid co-administration reduces proliferation pathways across immune cells. Prior taxane exposure was associated with an increased metabolic status, possibly rendering immune cells less sensitive to atezo-induced activation. The immune context of taxane-naive TNBC may result in more potent immune activation with atezo. Clinical trial information: NCT02425891 and NCT03125902.

Whole transcriptome analysis of tumors with discordant oncotype and MammaPrint results in the FLEX trial

556

Background: Genomic tests, such as MammaPrint (MP) and Oncotype DX Breast Recurrence Score (RS), assess risk of recurrence in patients with early breast cancer (EBC). Using both assays may yield discordant results which leads to uncertainty in treatment recommendations. The assays differ in technology and genes analyzed. RS relies on RT-PCR to query 16 cancer-related genes and 5 controls. MP uses a microarray to query 70 cancer-related genes and 465 normalization controls. Here we explore the genetic basis for discordance by using the FLEX whole transcriptome database to examine differentially expressed genes among patients who received discordant RS and MP results. Methods: Patients with EBC enrolled in the FLEX study (NCT03053193) undergo standard of care MP and BluePrint (BP) tests, and consent to clinically annotated whole transcriptome data collection. MP stratifies risk of recurrence as Low risk and High. RS classifies patients as Low Risk (RS 0-10), Intermediate (RS 11-25), and High Risk (RS 26-100). Due to low representation of BP Basal and BP HER2-type tumors in this data set, we only examined BP Luminal-type tumors (N = 705). We used full genome transcriptomes to compare gene expression among discordant cases. Gene expression data were quantile normalized and analyzed using R package ‘limma’. Genes were considered differentially expressed at a fold change of at least 1.7 and an adjusted p-value of lower than 0.05. To keep the analysis as unbiased as possible, comparisons between RS categories only included tumors within the same MP score range and similarly comparisons of MP categories only contained tumors within the same RS score range. Results: The comparisons between discordant cases, their numbers and the amount of differentially expressed genes (DEGs) are shown below. Sample sizes are shown in parentheses. Of the 49 DEGs found in the RS Intermediate group, several are associated with increased proliferation or increased metastatic potential. SCUBE2 and MMP9 were among the 49 genes and are among the 70-genes assayed by MP. Conclusions: The comparisons highlight the genomic diversity of the RS Intermediate (RS11-25) group, as seen with the high number of DEGs. MP separates cases into more genomically distinct categories, as reflected by fewer DEGs. Clinical trial information: NCT03053193. [Table: see text]

FLEX, the 30,000 breast cancer transcriptome project: A platform for early breast cancer research using full-genome arrays paired with clinical data

TPS612

Background: The ongoing, multi-center FLEX trial (NCT03053193) began in the United States in 2017, with the ultimate goal of 30,000 patients enrolled. The primary objective is to create a large-scale collaborative registry of early-stage breast cancer patients that links comprehensive clinical and full genome expression data to reveal new prognostic and/or predictive gene signatures. A key secondary objective of the trial is to enable investigator-initiated studies to explore early-stage breast cancer at a relatively low cost to the investigator. Methods: The prospective FLEX trial enrolls patients aged ≥ 18 years with histologically proven stage I-III breast cancer, with negative or 1-3 positive lymph nodes. Eligible patients have received MammaPrint, with or without BluePrint testing as standard of care, and consent to clinically annotated full transcriptome data collection. The FLEX base study protocol permits investigators to submit their own concept proposal, and upon review and approval by the Research and Scientific Review Committees, investigators interrogate clinical and genomic data from the FLEX database. The 10-year enrollment goal is a minimum of 30,000 patients. Since April 2017, 9,170 patients have been enrolled at over 109 sites in the United States. To date, 38 investigator-initiated substudies have been approved and are in progress, and 28 abstracts have been published in the US scientific congresses. To ensure inclusion of diverse populations, patients from local communities and 11 National Cancer Institute-designated Comprehensive Cancer Centers were included. Our diverse data set is helping meet the needs of historically under-represented patients with breast cancer. Of the self-reported ethnicities within the FLEX database, 65% are White or Caucasian, 8% Black or African American, 4% Latin American, and 2% Asian. There are 5 ongoing FLEX sub studies investigating racial disparities. The molecular profiling and differential gene expression analysis in early-stage breast cancer patients of African American, Asian, Hispanic ancestries helps to provide critical insights that correlate tumor biology with treatment outcomes. FLEX is expanding globally with sites anticipated in multiple European countries. The FLEX trial continues to expedite the discovery and development of novel genomic profiles, bringing precision oncology into the clinic to improve breast cancer management. Clinical trial information: NCT03053193.

Comprehensive whole-exome and transcriptome profiling to identify actionable alterations associated with response to PARP inhibitors in breast cancer

1096

Background: The use of targeted therapies identified using genetic and genomic approaches is now routine in breast cancer (BC). In this clinical lab experience study the frequency of actionable somatic alterations in DNA repair pathway genes associated with the use of PARP inhibitors (PARPi) is described. Methods: BC samples were sequenced with the Oncomap ExTra assay, which uses whole-exome DNA sequencing with germline subtraction to detect somatic single base substitutions, indels, and copy number alterations, and RNA sequencing to detect gene fusions. Clinically actionable alterations were defined as associated with FDA approved drugs or clinical trial enrollment. Here, the focus is on 49 repair genes associated with PARPi response: ARID1A, ATM, ATR, ATRX, BAP1, BARD1, BLM, BRCA1/2, BRIP1, CDK12, CHEK1/2, EPCAM, ERCC1/2/3/4/5, FANCA/C/D2/E/F/G/I/L/M, MLH1, MRE11A, MSH2/6, MUTYH, NBN, PALB2, PMS2, PPP2R2A, PTEN, RAD21/50/51/51B/51C/51D/52/54L, XRCC1/2/3. Results: Of 1103 BCs, 246 (22.3%) had mutations in repair genes; 69 (6.3%) were in BRCA1/2. Repair gene mutations were less common in HER2+ cancers (n=27, 14.3%) compared to HR+ HER2- (n=156, 23.9%) or TN cancers (n=49, 26.1%) (p<0.01). Across subtypes, the top four most commonly mutated of the repair genes were PTEN (27.2%), ARID1A (22.8%), BRCA2 (14.2%), and BRCA1 (14.2%); 33 cancers (13.4%) had mutations in multiple (≥2) repair genes. For the 69 cancers with BRCA1/2 mutations, 11 (15.9%) carried other repair gene mutations (9 of 35 BRCA1; 3 of 35 BRCA2). RNA sequencing found 19 fusions in repair genes in 17 patients (1.5%); CDK12 was involved in 13 (68.4%), and RAD51C in 3 (15.8%). Fusion incidence was more frequent in HER2+ cancers (p<0.01) (Table). Conclusions: PARPi therapy is FDA approved for HER2- germline BRCA1/2 mutated BC patients. Recent evidence suggests somatic BRCA1/2 mutations predict PARPi benefit (Tung, NM. J Clin Oncol 2020). In addition to BRCA1/2 alterations, our study also highlights the importance of alterations in other DNA repair genes associated with response to PARPi. Trials are ongoing to determine if these genes predict for PARPi benefit.[Table: see text]

Economic and Humanistic Burden of Triple-Negative Breast Cancer: A Systematic Literature Review

BACKGROUND

Triple-negative breast cancer (TNBC) accounts for 10-20% of all breast cancers (BCs). It is more commonly diagnosed in younger women and often has a less favorable prognosis compared with other BC subtypes.

OBJECTIVE

The objective of this study was to provide a literature-based extensive overview of the economic and humanistic burden of TNBC to assist medical decisions for healthcare payers, providers, and patients.

METHODS

A systematic literature review was performed using multiple databases, including EMBASE, MEDLINE, Econlit, the Cochrane Central Register of Controlled Trials, and the Cochrane Database of Systematic Reviews, from database inception to 16 May 2021. In addition, a targeted search was performed in the Northern Light Life Sciences Conference Abstracts database from 2016 through June 2021. The bibliographies of included articles were reviewed to identify other potentially relevant publications. Quality assessment of the included studies was conducted.

RESULTS

The review identified 19 studies assessing the economic burden and 10 studies assessing the humanistic burden of TNBC. Studies varied widely in study design, settings, patient populations, and time horizons. The estimates of mean per-patient annual direct medical costs ranged from around $20,000 to over $100,000 in stage I-III TNBC and from $100,000 to $300,000 in stage IV TNBC. Healthcare costs and resource utilization increased significantly with disease recurrence, progression, and increased cancer stage or line of therapy. Compared with the costs of systemic anticancer therapy, cancer management costs comprised a larger portion of total direct costs. The estimates of indirect costs due to productivity loss ranged from $207 to $1573 per patient per month (all costs presented above were adjusted to 2021 US dollars). Cancer recurrence led to significantly reduced productivity and greater rates of leaving the workforce. A rapid deterioration of health utility associated with disease progression was observed in TNBC patients. Treatment with pembrolizumab or talazoparib showed significantly greater improvements in health-related quality of life (HRQoL) compared with chemotherapy, as measured by EORTC QLQ-C30, QLQ-BR23, and FACT-B.

CONCLUSION

TNBC is associated with a substantial economic burden on healthcare systems and societies and considerably reduced productivity and HRQoL for patients. This study synthesized the published literature on the economic and humanistic burden of TNBC and highlighted the need for continued research due to the rapidly changing landscape of TNBC care.

Adjuvant Abemaciclib Combined with Endocrine Therapy for High Risk Early Breast Cancer: Safety and Patient-Reported Outcomes From the monarchE Study

BACKGROUND

In monarchE, abemaciclib plus endocrine therapy (ET) as adjuvant treatment of hormone receptor-positive, human epidermal growth factor 2-negative, high risk, early breast cancer demonstrated a clinically meaningful improvement in invasive disease-free survival versus ET alone. Detailed safety analyses conducted at a median follow-up of 27 months and key patient-reported outcomes (PRO) are presented.

PATIENTS AND METHODS

The safety population included all patients who received at least one dose of study treatment (n=5591). Safety analyses included incidence, management, and outcomes of common and clinically relevant adverse events (AEs). Patient-reported health-related quality-of-life, ET symptoms, fatigue, and side effect burden were assessed.

RESULTS

The addition of abemaciclib to ET resulted in higher incidence of Grade≥3 AEs (49.7% vs 16.3% with ET alone), predominantly laboratory cytopenias (e.g., neutropenia [19.6%]) without clinical complications. Abemaciclib-treated patients experienced more serious adverse events (SAEs; 13.3% vs 7.8%). Discontinuation of abemaciclib and/or ET due to AEs occurred in 18.5% of patients, mainly due to Grade1/2 AEs (66.8%). AEs were managed with comedications (e.g., antidiarrheals), abemaciclib dose holds (61.7%), and/or dose reductions (43.4%). Diarrhea was generally low grade (Grade1/2: 77%); Grade2/3 events were highest in the first month (20.5%), most short-lived (≤7 days) and did not recur. Venous thromboembolic events (VTE) were higher with abemaciclib+ET (2.5%) vs ET (0.6%); in the abemaciclib arm, increased VTE risk was observed with tamoxifen vs AIs (4.3% vs 1.8%). PROs were similar between arms, including being 'bothered by side effects of treatment', except for diarrhea. At ≥3 months, most patients reporting diarrhea reported "a little bit" or "somewhat".

CONCLUSION

In patients with high risk EBC, adjuvant abemaciclib+ET has an acceptable safety profile and tolerability is supported by PRO findings. Most AEs were reversible and manageable with comedications and/or dose modifications, consistent with the known abemaciclib toxicity profile.

Effects of capecitabine as part of neo-/adjuvant chemotherapy - A meta-analysis of individual breast cancer patient data from 13 randomised trials including 15,993 patients

BACKGROUND

Despite the large number of patients with early breast cancer (EBC) who have been treated with capecitabine in randomised trials, no individual patient data meta-analysis has been conducted. The primary objective was to examine the effect of capecitabine on disease-free survival (DFS), and the secondary objectives were to analyse distant DFS (DDFS), overall survival (OS), pathological complete response (for neoadjuvant studies) and the interaction between capecitabine-related toxicity and treatment effect.

METHODS

www.

CLINICALTRIALS

gov and www.pubmed.ncbi.nlm.nih.gov were searched using the following criteria: use of capecitabine for EBC as adjuvant or neoadjuvant therapy; multicentre randomised trial with >100 patients; recruitment completed, and outcomes available. Required data were available for 13 trials.

RESULTS

Individual data from 15,993 patients were collected. Cox regression analyses of all included patients revealed that the addition of capecitabine did not alter DFS significantly compared with treatment without capecitabine (hazard ratio [HR] 0.952; 95% CI 0.895-1.012; P value = 0.115). There was also no effect on DFS in the subset of studies where capecitabine was given instead of another drug (HR 1.035; 95% CI 0.945-1.134; P = 0.455). However, capecitabine administered in addition to the standard systemic treatment improved DFS (HR 0.888; 95% CI 0.817-0.965; P = 0.005). An OS improvement was observed in the entire cohort (HR 0.892; 95% CI 0.824-0.965, P = 0.005) and in the subset of capecitabine addition (HR 0.837; 95% CI 0.751, 0.933, P = 0.001). Subgroup analyses revealed that triple-negative breast cancer (TNBC) patients benefitted from treatment with capecitabine overall and in addition to other systemic treatments in terms of DFS and OS.

CONCLUSION

Capecitabine was able to improve DFS and OS in patients with TNBC and in all patients with EBC when administered in addition to systemic treatment.

Overall Survival with Ribociclib plus Letrozole in Advanced Breast Cancer

BACKGROUND

In a previous analysis of this phase 3 trial, first-line ribociclib plus letrozole resulted in significantly longer progression-free survival than letrozole alone among postmenopausal patients with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer. Whether overall survival would also be longer with ribociclib was not known.

METHODS

Here we report the results of the protocol-specified final analysis of overall survival, a key secondary end point. Patients were randomly assigned in a 1:1 ratio to receive either ribociclib or placebo in combination with letrozole. Overall survival was assessed with the use of a stratified log-rank test and summarized with the use of Kaplan-Meier methods after 400 deaths had occurred. A hierarchical testing strategy was used for the analysis of progression-free survival and overall survival to ensure the validity of the findings.

RESULTS

After a median follow-up of 6.6 years, 181 deaths had occurred among 334 patients (54.2%) in the ribociclib group and 219 among 334 (65.6%) in the placebo group. Ribociclib plus letrozole showed a significant overall survival benefit as compared with placebo plus letrozole. Median overall survival was 63.9 months (95% confidence interval [CI], 52.4 to 71.0) with ribociclib plus letrozole and 51.4 months (95% CI, 47.2 to 59.7) with placebo plus letrozole (hazard ratio for death, 0.76; 95% CI, 0.63 to 0.93; two-sided P = 0.008). No new safety signals were observed.

CONCLUSIONS

First-line therapy with ribociclib plus letrozole showed a significant overall survival benefit as compared with placebo plus letrozole in patients with HR-positive, HER2-negative advanced breast cancer. Median overall survival was more than 12 months longer with ribociclib than with placebo. (Funded by Novartis; MONALEESA-2 ClinicalTrials.gov number, NCT01958021.).