Evolution of HER2 expression between pre-treatment biopsy and residual disease after neoadjuvant therapy for breast cancer

INTRODUCTION

We have previously found that HER2 expression is dynamic, and can change from the primary breast tumor to matched recurrences. With this work, we aimed to assess the dynamics of HER2 during neoadjuvant treatment.(NAT).

METHODS

We reviewed HER2 expression in pre- and post-treatment samples from consecutive patients with early-stage breast cancer that received NAT and underwent surgery at Dana-Farber Brigham Cancer Center between 01/2016-08/2022. The primary outcome was evolution of HER2 expression from pre- to post-NAT specimens in patients with residual disease.

RESULTS

Among 1613 patients receiving NAT, 1080 had residual disease at surgery. A total of 319 patients (29.5%) experienced a change in HER2 expression (HER2 0 vs. HER2-low vs. HER2-positive) from the pre-treatment sample to residual disease, with roughly equal distribution between decreased (50.5%) and increased HER2 expression (49.5%). Similar rates of change in HER2 expression were observed with anthracycline-based (31.8%) or taxane/platinum-based regimens (32.4%). Patients with HER2-0 or HER2-low tumors at diagnosis were likelier to experience a change in HER2 expression post-NAT compared to HER2-positive (32.3% vs. 21.3%, p < 0.001). Changes in HER2 expression post-NAT were prognostic among patients with HER2-positive tumors at diagnosis (3-year recurrence-free survival for change vs. no change: 71.6% vs. 89.6%, p = 0.006) but not among those with HER2-negative tumors at diagnosis (3-year recurrence-free survival for change vs. no change: 79.3% vs. 81.1%, p = 0.31).

CONCLUSIONS

Nearly 30% of patients with early-stage breast cancer showed a change in HER2 expression after NAT. Changes in HER2 expression post-NAT were only prognostic in the setting of HER2-positive tumors becoming HER2-negative at surgery.

Response-guided neoadjuvant sacituzumab govitecan for localized triple-negative breast cancer: results from the NeoSTAR trial

BACKGROUND

Sacituzumab govitecan (SG), a novel antibody-drug conjugate (ADC) targeting TROP2, is approved for pre-treated metastatic triple-negative breast cancer (mTNBC). We conducted an investigator-initiated clinical trial evaluating neoadjuvant (NA) SG (NCT04230109), and report primary results.

PATIENTS AND METHODS

Participants with early-stage TNBC received NA SG for four cycles. The primary objective was to assess pathological complete response (pCR) rate in breast and lymph nodes (ypT0/isN0) to SG. Secondary objectives included overall response rate (ORR), safety, event-free survival (EFS), and predictive biomarkers. A response-guided approach was utilized, and subsequent systemic therapy decisions were at the discretion of the treating physician.

RESULTS

From July 2020 to August 2021, 50 participants were enrolled (median age = 48.5 years; 13 clinical stage I disease, 26 stage II, 11 stage III). Forty-nine (98%) completed four cycles of SG. Overall, the pCR rate with SG alone was 30% [n = 15, 95% confidence interval (CI) 18% to 45%]. The ORR per RECIST V1.1 after SG alone was 64% (n = 32/50, 95% CI 77% to 98%). Higher Ki-67 and tumor-infiltrating lymphocytes (TILs) were predictive of pCR to SG (P = 0.007 for Ki-67 and 0.002 for TILs), while baseline TROP2 expression was not (P = 0.440). Common adverse events were nausea (82%), fatigue (76%), alopecia (76%), neutropenia (44%), and rash (48%). With a median follow-up time of 18.9 months (95% CI 16.3-21.9 months), the 2-year EFS for all participants was 95%. Among participants with a pCR with SG (n = 15), the 2-year EFS was 100%.

CONCLUSIONS

In the first NA trial with an ADC in localized TNBC, SG demonstrated single-agent efficacy and feasibility of response-guided escalation/de-escalation. Further research on optimal duration of SG as well as NA combination strategies, including immunotherapy, are needed.

Comprehensive genomic characterization of HER2-low and HER2-0 breast cancer

The molecular underpinnings of HER2-low and HER2-0 (IHC 0) breast tumors remain poorly defined. Using genomic findings from 1039 patients with HER2-negative metastatic breast cancer undergoing next-generation sequencing from 7/2013-12/2020, we compare results between HER2-low (n = 487, 47%) and HER2-0 tumors (n = 552, 53%). A significantly higher number of ERBB2 alleles (median copy count: 2.05) are observed among HER2-low tumors compared to HER2-0 (median copy count: 1.79; P = 2.36e-6), with HER2-0 tumors harboring a higher rate of ERBB2 hemideletions (31.1% vs. 14.5%). No other genomic alteration reaches significance after accounting for multiple hypothesis testing, and no significant differences in tumor mutational burden are observed between HER2-low and HER2-0 tumors (median: 7.26 mutations/megabase vs. 7.60 mutations/megabase, p = 0.24). Here, we show that the genomic landscape of HER2-low and HER2-0 tumors does not differ significantly, apart from a higher ERBB2 copy count among HER2-low tumors, and a higher rate of ERBB2 hemideletions in HER2-0 tumors.

Combination Therapies to Improve the Efficacy of Immunotherapy in Triple-negative Breast Cancer

Immune checkpoint inhibition combined with chemotherapy is currently approved as first-line treatment for patients with advanced PD-L1-positive triple-negative breast cancer (TNBC). However, a significant proportion of metastatic TNBC is PD-L1-negative and, in this population, chemotherapy alone largely remains the standard-of-care and novel therapeutic strategies are needed to improve clinical outcomes. Here, we describe a triple combination of anti-PD-L1 immune checkpoint blockade, epigenetic modulation thorough bromodomain and extra-terminal (BET) bromodomain inhibition (BBDI), and chemotherapy with paclitaxel that effectively inhibits both primary and metastatic tumor growth in two different syngeneic murine models of TNBC. Detailed cellular and molecular profiling of tumors from single and combination treatment arms revealed increased T- and B-cell infiltration and macrophage reprogramming from MHCIIlow to a MHCIIhigh phenotype in mice treated with triple combination. Triple combination also had a major impact on gene expression and chromatin profiles shifting cells to a more immunogenic and senescent state. Our results provide strong preclinical evidence to justify clinical testing of BBDI, paclitaxel, and immune checkpoint blockade combination.

Clinical outcomes of de novo metastatic HER2-positive inflammatory breast cancer

Inflammatory breast cancer (IBC) is a rare, aggressive form of breast cancer that presents as de novo metastatic disease in 20-30% of cases, with one-third of cases demonstrating HER2-positivity. There has been limited investigation into locoregional therapy utilization following HER2-directed systemic therapy for these patients, and their locoregional progression or recurrence (LRPR) and survival outcomes. Patients with de novo HER2-positive metastatic IBC (mIBC) were identified from an IRB-approved IBC registry at Dana-Farber Cancer Institute. Clinical, pathology, and treatment data were abstracted. Rates of LRPR, progression-free survival (PFS), overall survival (OS), and pathologic complete response (pCR) were determined. Seventy-eight patients diagnosed between 1998 and 2019 were identified. First-line systemic therapy comprised chemotherapy for most patients (97.4%) and HER2-directed therapy for all patients (trastuzumab [47.4%]; trastuzumab+pertuzumab [51.3%]; or trastuzumab emtansine [1.3%]). At a median follow-up of 2.7 years, the median PFS was 1.0 year, and the median OS was 4.6 years. The 1- and 2-year cumulative incidence of LRPR was 20.7% and 29.0%, respectively. Mastectomy was performed after systemic therapy in 41/78 patients (52.6%); 10 had a pCR (24.4%) and all were alive at last follow-up (1.3-8.9 years after surgery). Among 56 patients who were alive and LRPR-free at one year, 10 developed LRPR (surgery group = 1; no-surgery group = 9). In conclusion, patients with de novo HER2-positive mIBC who undergo surgery have favorable outcomes. More than half of patients received systemic and local therapy with good locoregional control and prolonged survival, suggesting a potential role for local therapy.

Adjuvant Olaparib for Germline BRCA Carriers With HER2-Negative Early Breast Cancer: Evidence and Controversies

In the OlympiA study, 1 year of adjuvant olaparib significantly extended invasive disease-free survival and overall survival. The benefit was consistent across subgroups, and this regimen is now recommended after chemotherapy for germline BRCA1/2 mutation (gBRCA1/2m) carriers with high-risk, HER2-negative early breast cancer. However, the integration of olaparib in the landscape of agents currently available in the post(neo)adjuvant setting-ie, pembrolizumab, abemaciclib, and capecitabine-is challenging, as there are no data suggesting how to select, sequence, and/or combine these therapeutic approaches. Furthermore, it is unclear how to best identify additional patients who could benefit from adjuvant olaparib beyond the original OlympiA criteria. Since it is unlikely that new clinical trials will answer these questions, recommendations for clinical practice can be made through indirect evidence. In this article, we review available data that could help guide treatment decisions for gBRCA1/2m carriers with high-risk, early-stage breast cancer.

PD-1 blockade and CDK4/6 inhibition augment nonoverlapping features of T cell activation in cancer

We performed single-cell RNA-sequencing and T cell receptor clonotype tracking of breast and ovarian cancer patients treated with the CDK4/6 inhibitor ribociclib and PD-1 blockade. We highlight evidence of two orthogonal treatment-associated phenomena: expansion of T cell effector populations and promotion of T cell memory formation. Augmentation of the antitumor memory pool by ribociclib boosts the efficacy of subsequent PD-1 blockade in mouse models of melanoma and breast cancer, pointing toward sequential therapy as a potentially safe and synergistic strategy in patients.

Abstract PD7-07: Somatic alterations in primary tumors of patients (pts) with metastatic breast cancer (MBC) may predict likelihood of brain metastasis

Background: Despite advances in treatment options, outcomes remain poor for many pts with breast cancer brain metastases (BCBMs). Identifying genomic predictors of brain metastasis from primary tumors could lead to better stratification of pts at risk and drive the development of preventative strategies. The objective of this study was to describe the landscape of genomic alterations in primary tumors from pts with MBC who subsequently did or did not develop BCBMs.

Methods: We performed a case control study to identify somatic alterations in primary tumors associated with a higher incidence of brain metastases. We reviewed outcomes for 2562 unique MBC patients from a single institution who underwent targeted next-generation DNA sequencing of &gt; 280 cancer-related genes (OncoPanel) from their tumor between July 1, 2013 and December 31, 2020. Pts were included in this analysis if they had at least 2 years of follow-up from date of metastatic diagnosis and OncoPanel testing on a primary breast tumor. We compared single nucleotide variants (oncogenic or likely oncogenic), copy number variation (amplification and deep deletions) and tumor mutation burden in the primary tumors of pts in this cohort. Copy number variation was corrected for Panel version and tumor purity. Wilcoxon rank sum test and Fisher exact test was used to compare genomic differences between groups. False discovery rate was used to correct for multiple hypothesis testing and q &lt; 0.1 was considered significant

Results: A total of 369 pts were included in the final analytic cohort. Of these, 115 were diagnosed with brain mets (cases, BM group) and 224 were not (controls, nBM group). The BM group was enriched for patients with HER2-positive breast cancer (33 vs 12.5%), consistent with previous work. In the whole cohort, the most common and clinically significant somatic alterations (oncogenic single nucleotide variants or copy number high amplification or two copy deletion) are shown in Table 1. When adjusting for subtype there were no significantly enriched SNVs in BM vs nBM group. When adjusting for subtype, FGFR1 amplification was significantly enriched in hormone receptor positive HER2 negative (HR+ HER2-) patients with BM (log2 odds ratio 1.22, q &lt; 0.1). Tumor mutation burden was not significantly different in primary tumors between the BM and nBM groups (median TMB 7.3 vs 6.1, Wilcoxon p = 0.08).

Pathway analysis combining all subtypes revealed that RTK_RAS pathway (log2 odds ratio 1.64, q value &lt; 0.1) and TP53 pathway (log2 odds ratio 1.15, q value &lt; 0.1) gene sets were significantly enriched in the BM group. When controlling for subtype, pathway analysis revealed that RTK_RAS pathway gene set was significantly enriched in HR+ HER2- BM group (log2 odds ratio 1.36 q &lt; 0.1).

Conclusions: In this case control series of patients with metastatic breast cancer with or without brain metastases, we found that primary tumors that are enriched for somatic alterations in the RTK_RAS and TP53 pathway may be associated with higher risk of developing brain metastases. Further validation in larger cohorts is warranted.

Table 1. Frequency of somatic alterations in primary tumor by brain metastasis outcome.

Citation Format: Sheheryar Kabraji, Yvonne Y. Li, Melissa E. Hughes, Hersh V. Gupta, Lauren Buckley, Janet L. Files, Ayesha Mohammed-Abreu, Anne-Marie Feeney, Greg Kirkner, Ashka Patel, Ana C. Garrido-Castro, Romualdo Barroso-Sousa, Brittany Bychkovsky, Matthew Meyerson, Sara Tolaney, Deborah A. Dillon, Bruce Johnson, Eric Winer, Andrew Cherniack, Nancy U. Lin. Somatic alterations in primary tumors of patients (pts) with metastatic breast cancer (MBC) may predict likelihood of brain metastasis [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD7-07.

Abstract OT3-15-01: TBCRC-053: P-RAD: A Randomized Study of Preoperative Chemotherapy, Pembrolizumab and No, Low or High Dose RADiation in Node-Positive, HER2-Negative Breast Cancer

Background: The introduction of immune checkpoint inhibitors (ICI) to standard neoadjuvant chemotherapy regimens has been shown to significantly improve outcomes in patients with triple negative breast cancer and is being investigated for high-risk hormone receptor-positive (HR+)/human epidermal growth factor-2 negative (HER2-) breast cancer. Preclinical evidence suggests radiation therapy (RT) can stimulate intra-tumoral T cell infiltration and enhance the expression and immune detection of tumor-specific neoantigens. This phase II pilot randomized study (NCT04443348) aims to evaluate the safety and efficacy of two different doses of preoperative primary tumor RT boost when combined with neoadjuvant pembrolizumab, then followed by standard neoadjuvant chemotherapy. Dual co-primary endpoints include determining the pathologic complete response (pCR) rate in the non-irradiated and pathologically confirmed metastatic axillary lymph node(s) in each treatment arm and quantifying tumor-infiltrating T lymphocytes in on-treatment (C1D14) tumor biopsies. We hypothesize that high-dose RT will increase the proportion of tumors with high T cell infiltration (i.e., top quartile) from 25% to 55%. Secondary endpoints include measuring residual cancer burden, evaluating tolerability of the regimen, and assessing quality of life. Exploratory endpoints include evaluation of treatment-associated changes in the tumor immune microenvironment, circulating immune cell analyses, and circulating tumor DNA kinetics. Methods: The study plans to enroll 128 participants with either triple negative (n=80) or high-risk HR=/HER2- (n=48) breast cancer who will be randomized to receive no, low (9 Gy), or high (24 Gy) dose of preoperative RT boost, after which 24 participants of either breast cancer subtype will be enrolled to an exploratory high dose proton therapy boost cohort. The eligibility criteria include patients who have biopsy-proven, axillary lymph node-positive breast cancer that is either triple negative (defined as ER&lt; 10%, PR&lt; 10%, and HER2-negative) or high-risk HR+/HER2- (grade III or having a high-risk genomic assay score). Study treatment is given in 6-week cycles, with 400 mg Pembrolizumab given on day 1 of each cycle. For those participants randomized to receive a preoperative RT boost, treatment is delivered in 3 fractions (3 × 3 Gy or 3 × 8 Gy) over consecutive business days, where one of the fractions is given on the same day as C1D1 Pembrolizumab. Standard neoadjuvant chemotherapy begins on C1D15 with paclitaxel (plus carboplatin for triple negative) administered weekly for 12 weeks, and then starting on C3D15, dose-dense doxorubicin/cyclophosphamide is administered every 2 weeks for 8 weeks. Following neoadjuvant treatment, participants will receive standard breast surgery (including removal of the pathologically confirmed metastatic lymph node) followed by adjuvant pembrolizumab, radiation therapy, and standard-of-care systemic therapy as clinically indicated. Tissue samples from the primary tumor and biopsy-proven lymph node are taken at baseline, C1D14, and at the time of surgery. There are eleven blood collection timepoints throughout the neoadjuvant and adjuvant settings. Participants will be followed for 2 years after surgery to assess safety and durability of responses. Results: This study has accrued 12 participants to date, including 10 with triple negative breast cancer and 2 with high-risk HR+/HER2- breast cancer. Formal results for this study are forthcoming, as the trial is actively accruing at 6 institutions, with plans to open at 3 more within the year. For persons with a specific interest in this trial, please contact Joseph Connolly, Multi-Center Coordinator, at jconnolly28@mgh.harvard.edu.

Citation Format: Joseph J. Connolly, Laura M. Spring, Alphonse G. Taghian, Michele Gadd, Laura Warren, Ana C. Garrido-Castro, Tari King, Elizabeth A. Mittendorf, Jose P. Leone, Dana L. Casey, Lisa Carey, Tiffany A. Traina, Yara Abdou, Atif Khan, George Plitas, Jean Wright, Cesar Augusto Santa-Maria, Lisa Jacobs, Rachel Blitzblau, E Shelley Hwang, Carey Anders, Ian Krop, Antonio C. Wolff, Alastair M. Thompson, Elyssa Denault, Gaorav Gupta, Alice Ho. TBCRC-053: P-RAD: A Randomized Study of Preoperative Chemotherapy, Pembrolizumab and No, Low or High Dose RADiation in Node-Positive, HER2-Negative Breast Cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT3-15-01.

Abstract HER2-10: HER2-10 Dynamics of HER2-low expression in triple-negative breast cancer

Background: With the development of novel antibody drug conjugates (ADC), it is increasingly important to understand the changes that occur in cell-surface targets over time from early-stage to metastatic breast cancer. Discordance in HER2 expression per immunohistochemistry (IHC) has been reported between primary and metastatic tumors in patients (pts) with HER2-negative breast cancer defined per ASCO/CAP guidelines, with both gain and loss of expression described. Representation of HR-negative (TNBC) tumors has been limited in these studies, and HER2 status at multiple time points in TNBC has not been described. Here we report changes in HER2 IHC in patients diagnosed with TNBC, using a collection of matched tumor samples over time. Methods: Pts were identified from two sources: 1) an institutional database including all consecutive pts who underwent surgery for stage I-III breast cancer at Dana-Farber/Brigham Cancer Center between 2015-2018, and 2) a prospective research biopsy protocol for pts with known or suspected metastatic breast cancer. Pts were included in the present analysis if they received neoadjuvant chemotherapy (NAC) for stage I-III TNBC (eTNBC), or if they were diagnosed with any stage TNBC and ultimately developed metastatic TNBC (mTNBC). Clinical pathology records were reviewed for HER2 IHC results of samples collected at: initial diagnosis (DX); residual disease (RD) post-NAC, if applicable; and at recurrence (M). HER2 IHC was classified as HER2-0 if HER2 IHC 0, and HER2-low if 1+ or 2+ (and ISH non-amplified). For matched comparisons, if IHC was performed in more than one DX sample (e.g., breast, node), only the breast was considered; if more than one M sample, only the first M biopsy with available IHC was considered. Results: Among 110 pts in this cohort, 101 were initially diagnosed with eTNBC (79 received NAC; 22 underwent surgery as first intervention) and 9 with de novo mTNBC. Median age was 48.7 years (range 19.8-71.6). Among all pts, a total of 292 samples (136 DX, 53 RD, 103 M) had available HER2 IHC scores. When restricting to one sample per time point, HER2-low prevalence was 49/102 (48.0%) in DX breast tumors, 21/53 (39.6%) in RD, and 13/58 (22.4%) in first M samples (with all remaining samples HER2-0, except one HER2 3+ sample). In eTNBC pts, HER2 IHC scores were available for 50 paired DX and RD, and 48 paired DX and M samples. Among 50 pts with paired DX and RD, HER2 IHC was discordant in 56% (28/50) (Table 1). Of the 21 HER2-0 DX tumors, 23.8% (5/21) became HER2-low at RD. Of the 29 HER2-low DX tumors, 51.7% (15/29) became HER2-0 at RD. Among 48 eTNBC pts who recurred and had paired DX and M samples, HER2 IHC was discordant in 50% (24/48) (Table 1). Change from HER2-0 to low was 12.5% (3/24), and from HER2-low to HER2-0 was 66.7% (16/24). Among 9 de novo mTNBC pts, 5 had HER2 IHC available in paired DX breast and M prior to starting therapy; 3 were concordant (IHC 0, n=2; IHC 1+, n=1), one had IHC 0 in DX breast and IHC 2+ in M (liver), one had IHC 1+ in DX breast and IHC 0 in M (node). Conclusions: HER2 IHC classification was discordant in about half of the TNBC cases we examined, with more frequent rates of conversion from HER2-low to HER2-0 in both paired DX/RD post-NAC, and paired DX/M samples. Additional analyses will be presented exploring HER2 IHC changes among multiple metastases per patient. Genomic and molecular analysis, including whole exome sequencing, RNA sequencing, and methylation profiling, are underway in these samples to further elucidate HER2 evolutionary dynamics.

Citation Format: Ana C. Garrido-Castro, Lan D. Ngo, Edward T. Richardson, Allison Frangieh, Ayesha Mohammed-Abreu, Melissa E. Hughes, Jorge Gomez Tejada Zanudo, John Navarro, Paolo Tarantino, Elizabeth A. Mittendorf, Sara Tolaney, Tari King, Eric Winer, Nancy U. Lin, Nikhil Wagle. HER2-10 Dynamics of HER2-low expression in triple-negative breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr HER2-10.

Abstract HER2-05: HER2-05 Comprehensive genomic characterization of HER2-low breast cancer

Background: About half of all breast cancers exhibit low HER2 expression. Despite lack of ERBB2 amplification, HER2-low tumors respond to trastuzumab deruxtecan (T-DXd), leading to the NCCN recommendation of T-DXd both for patients with HER2+ and HER2-low metastatic breast cancer (MBC). It remains however unclear if HER2-low represents a distinct molecular entity, as compared to HER2-0 MBC. Here, we compare the genomic landscape of HER2-low versus HER2-0 breast cancers in a large, single institution cohort. Methods: We identified consecutive patients with MBC seen at Dana-Farber Cancer Institute between 07/2013 and 12/2020. Patients were included if they had HER2-negative MBC per ASCO/CAP Guidelines and had undergone next generation sequencing (NGS) testing with a targeted, tumor-only platform (OncoPanel). Based on the HER2 status of the specimen tested by NGS, patients were divided into 2 groups: (i) HER2-low if immunohistochemistry (IHC) 1+ or 2+ non-amplified, or (ii) HER2-0 if IHC 0. Mutations of interest detected on NGS were classified as oncogenic using the OncoKB tool and additional annotation. Genomic profiles of HER2-low and HER2-0 tumors were compared using Chi-Square and Kruskal-Wallis tests. To determine genomic event enrichment between the two HER2 groups, logistic regression models were used, accounting for background rate and estrogen receptor (ER) expression. ERBB2 copy counts were calculated for tumors with recorded histology-estimated purities and copy-number segmentation using a simple model of allelic gain/loss. Results: Among 1847 patients with HER2-negative MBC, 1043 underwent NGS testing on a HER2-low (n=489, 47%) or HER2-0 sample (n=554, 53%). Most samples were metastatic (71%, n=743) while 29% (n=300) were from primary tumors. 73% had ductal histology, 13% were lobular and 14% had mixed or other histology. ER expression was enriched among HER2-low vs. HER2-0 tumors (76% vs. 60%; p&lt; 0.001). Focusing on the most commonly occurring genetic mutations, no major differences were observed in HER2-low vs. HER2-0 tumors, after correcting for ER status (Table 1). Among all mutational events, any mutation in MPL, CYLD, and MAP3K and oncogenic mutations in TP53 and NF1 were more common in HER2-0, while any mutation in MTOR, RAD21, DNMT3A, and PDGFRA were enriched in HER2-low patients, when controlling for ER status and background mutational rate (p&lt; 0.05). However, no mutation reached significance after accounting for multiple hypothesis testing. Similarly, no deep deletion or high amplification CNV events reached significance for either group. Analysis of tumor mutational burden in HER2-low vs. HER-0 tumors revealed no significant differences (median: 7.26 muts/Mb vs. 7.60 muts/Mb, p=1.00), including when accounting for ER status. Finally, among tumors with sufficient tumor purity for ERBB2 copy count analysis (n=374 and 419 for HER2-low and HER2-0, respectively), HER2-low tumors had a significantly higher number of ERBB2 alleles as compared to HER2-0 (&lt; 2 copies, 15.0% vs. 30.9%, 2 copies 67.4% vs. 60.5%, and &gt;2 copies, 17.6% vs. 8.6%; p&lt; 0.001 by Kruskal-Wallis). Conclusions: To our knowledge, this is the largest comprehensive genomic analysis of HER2-low MBC to date. In our cohort of patients with HER2-negative MBC, the genomic landscape of HER2-low and HER2-0 tumors did not differ significantly, apart from a higher number of ERBB2 alleles. These data further support the notion that HER2-low, as currently defined, is not a distinct molecular subtype of breast cancer.

Citation Format: Paolo Tarantino, Hersh V. Gupta, Melissa E. Hughes, Janet L. Files, Sarah Strauss, Gregory Kirkner, Anne-Marie Feeney, Yvonne Y. Li, Ana C. Garrido-Castro, Romualdo Barroso-Sousa, Brittany Bychkovsky, Laura MacConaill, Neal Lindeman, Bruce Johnson, Matthew Meyerson, Sheheryar Kabraji, Rinath Jeselsohn, Xintao Qiu, Rong Li, Henry W. Long, Eric Winer, Deborah A. Dillon, Giuseppe Curigliano, Andrew Cherniack, Sara Tolaney, Nancy U. Lin. HER2-05 Comprehensive genomic characterization of HER2-low breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr HER2-05.

Abstract P5-14-06: Tumor Genomic Landscape in Older Women with Metastatic Breast Cancer (MBC)

Background. Patients (pts) who develop MBC at older ages are underrepresented in clinical trials, are less likely to be included in comprehensive biomarker characterization studies, and experience worse breast cancer-specific survival than their younger counterparts. Elucidating genomic underpinnings of MBC and possible therapeutic targets for older breast cancer patients are critical priorities. Methods. We identified pts age &gt;70 years at MBC diagnosis and a younger cohort (ages 50-69; age &lt; 50), who were treated for MBC at a single center and who had their metastatic (or if not available, the primary) tumor, assessed by a targeted, tumor-only next generation sequencing (NGS) platform (OncoPanel) between 2013-2020. The NGS panel included mutations, copy number variation, tumor mutational burden (TMB), and hypermutation (HM) status, with mutations classified as oncogenic using the OncoKB tool and additional annotation. Copy number events were selected as being “oncogenic” if a high amplification was called for an oncogene or a deep deletion for a tumor suppressor. We compared findings for older (age &gt;70) vs. younger (age &lt; 50 and ages 50-69) MBC pts using Chi-Square and Kruskal-Wallis tests. To determine genomic event enrichment, logistic regression (LR) models were used, controlling for age (continuous), background rate, and tumor subtype (those with unknown subtype [n=27] were excluded from models). False discovery rate (FDR) was used to correct for multiple hypothesis testing. Results. The final analytic cohort included 2,380 pts. The median age at MBC diagnosis was 54.1 years overall (range 18.5- 91.9) and 73.6 years for those age &gt;70. A total of 137 metastatic and 76 primary tumors were sequenced in pts age &gt;70; in those age &lt; 70, 1383 metastatic and 784 primary tumors were sequenced (for age &lt; 50 [n=857] and 50-69 [n=1310]). Older pts were more likely to present with HR+/HER2- tumors (70.9% v. 62.4% v. 52.4%), and less likely to present with HER2+ (9.4% v. 14.4% v. 22.8%) or triple-negative breast cancer (TNBC) (18.8% v. 21.9% vs. 24.0%) at MBC diagnosis (listed &gt;70, 50-69, &lt; 50; P=1e-7). Older pts had higher average TMB vs. younger pts (9.57 in pts &gt; 70, 8.56 in ages 50-69, 7.34 in ages &lt; 50; P=3.5e-5). This was due to older pts having a higher incidence of hypermutation status as defined as TMB &gt;10: 26.3% in age &gt;70, 23.2% in ages 50-69, 16.8% in age &lt; 50. Using q=0.1 as the threshold of significance, the presence of CDH1, PIK3CA, MAP3K1, TET2, and AKT oncogenic mutations were also enriched in older pts, while the presence of oncogenic GATA3, BRCA2, and TP53 mutations, as well as any mutation in BRCA1 were enriched in younger pts (too few oncogenic BRCA1 mutations were present for accurate modeling). The frequency of oncogenic PIK3CA mutations in HR+/HER2- tumors was highest in the oldest pts (44.4% in pts age &gt;70 v. 31.6% in age 50-69 v. 26.7% in age &lt; 50). Of pts who had oncogenic BRCA1/2 mutations identified on tumor-only NGS testing and underwent clinical germline testing (n=7 v. 60 v. 67, oldest to youngest), older pts had the lowest incidence of germline BRCA pathogenic variants (14.3% vs. 47.2.% vs. 67.2%; p=0.01); most BRCA mutations identified on NGS testing in older patients were considered likely somatic. When assessing enrichment in copy number events, ERBB2, RAD21, and BRIP1 amplifications were all significantly less frequent in older pts (q&lt; 0.1), even when accounting for tumor subtype. Conclusions. In a large cohort of pts with MBC, the mutational and copy number landscape for older pts differs from that in younger pts, even after controlling for tumor subtype. Key actionable findings include a higher proportion of high TMB and PIK3CA-mutated tumors, emphasizing the importance of genomic profile testing in this pt population and further exploration of efficacy and tolerability of relevant therapies in those age &gt;70 years.

Citation Format: Hersh V. Gupta, Rachel Freedman, Melissa E. Hughes, Yvonne Y. Li, Gregory Kirkner, Janet L. Files, Sarah Strauss, Ana C. Garrido-Castro, Lauren Buckley, Romualdo Barroso-Sousa, Brittany Bychkovsky, Sara Tolaney, Laura MacConaill, Neal Lindeman, Bruce Johnson, Matthew Meyerson, Eric Winer, Deborah A. Dillon, Andrew Cherniack, Nancy U. Lin. Tumor Genomic Landscape in Older Women with Metastatic Breast Cancer (MBC) [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-14-06.

Abstract P4-08-11: AKT and EZH2 inhibitors kill TNBCs by hijacking mechanisms of involution

Triple negative breast cancer (TNBC) is the most aggressive breast cancer subtype and has the highest rate of recurrence. The predominant standard of care for advanced TNBC is systemic chemotherapy with or without immunotherapy, however responses are typically short-lived. Thus, there is an urgent need to develop more effective treatments. PI3K pathway components represent plausible therapeutic targets, as approximately 40% of TNBCs have PIK3CA/AKT1/PTEN alterations. However, unlike hormone receptor-positive tumors, it is still unclear if or how PI3K pathway inhibitors will be effective in triple-negative disease. Here we identify a promising AKT inhibitor-based therapeutic combination for TNBC. Specifically, we show that AKT inhibitors potently synergize with agents that suppress the histone methyltransferase, EZH2, and promote robust tumor regression in multiple TNBC models in vivo. AKT and EZH2 inhibitors exert these effects by first cooperatively driving basal-like TNBC cells into a more differentiated, luminal-like state, which cannot be effectively induced by either agent alone. More importantly, once differentiated, these agents kill TNBCs by hijacking signals that normally drive mammary gland involution. Together these findings identify a promising therapeutic strategy for this highly aggressive tumor type and illustrate how deregulated epigenetic enzymes can insulate tumors from oncogenic vulnerabilities. These studies also reveal how developmental tissue-specific cell death pathways may be co-opted for therapeutic benefit.

Citation Format: Amy Schade, Naiara Perurena, Marina Watanabe, Carrie L. Rodriguez, Patrick Loi, Natalie Pilla, Rachel A. Davis, Kaia Mattioli, Dongxi Xiang, Jason J. Zoeller, Zhe Li, Ana C. Garrido-Castro, Sara Tolaney, Karen Cichowski. AKT and EZH2 inhibitors kill TNBCs by hijacking mechanisms of involution [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-08-11.

Multiomics in primary and metastatic breast tumors from the AURORA US network finds microenvironment and epigenetic drivers of metastasis

The AURORA US Metastasis Project was established with the goal to identify molecular features associated with metastasis. We assayed 55 females with metastatic breast cancer (51 primary cancers and 102 metastases) by RNA sequencing, tumor/germline DNA exome and low-pass whole-genome sequencing and global DNA methylation microarrays. Expression subtype changes were observed in ~30% of samples and were coincident with DNA clonality shifts, especially involving HER2. Downregulation of estrogen receptor (ER)-mediated cell-cell adhesion genes through DNA methylation mechanisms was observed in metastases. Microenvironment differences varied according to tumor subtype; the ER+/luminal subtype had lower fibroblast and endothelial content, while triple-negative breast cancer/basal metastases showed a decrease in B and T cells. In 17% of metastases, DNA hypermethylation and/or focal deletions were identified near HLA-A and were associated with reduced expression and lower immune cell infiltrates, especially in brain and liver metastases. These findings could have implications for treating individuals with metastatic breast cancer with immune- and HER2-targeting therapies.

Abstract P2-14-18: A randomized phase II trial of carboplatin with or without nivolumab in metastatic triple-negative breast cancer

Background: Platinum agents induce DNA crosslinking and cause accumulation of genotoxic stress, which leads to immune activation via IFN-γ signaling, making the combination with nivolumab (PD-1 antibody) an attractive strategy to enhance the benefit of either agent alone in metastatic triple-negative breast cancer (mTNBC). Methods: In this phase II open-label, investigator-initiated, multicenter trial, patients with unresectable locally advanced or mTNBC treated with 0-1 prior lines of chemotherapy in the metastatic setting were randomized 1:1 to carboplatin (AUC 6) with or without nivolumab (360 mg) IV every 3 weeks. Stratification factors included: germline BRCA (gBRCA) status, prior neo/adjuvant platinum, and number of prior lines of metastatic therapy. After approval of PD-L1 inhibition for mTNBC, the study was amended to include first-line mTNBC only and PD-L1 status was added as a stratification factor. Patients randomized to carboplatin alone were allowed to crossover at progression to receive nivolumab (+ nab-paclitaxel post-amendment). The primary objective was to compare progression-free survival (PFS) per RECIST 1.1 criteria of carboplatin with or without nivolumab in first-line mTNBC in the intent-to-treat (ITT) population. Key secondary objectives were objective response rate (ORR), overall survival (OS), clinical benefit rate, and duration and time to objective response. PD-L1 status was confirmed centrally using the SP142 Ventana assay (positive, ≥1% IC). Paired research biopsies at baseline, on-treatment and at progression were performed, if safely accessible. The trial closed to accrual prior to reaching target accrual due to approval of PD-1 inhibition in combination with platinum-based chemotherapy for PD-L1+ mTNBC. Results: Between 1/30/2018 and 12/9/2020, 78 patients enrolled. Three patients did not receive protocol treatment, and the safety analysis was conducted among the 75 that received any treatment; 37 received carboplatin + nivolumab (Arm A), 38 received carboplatin alone (Arm B). Median age was 59.1 yrs (range: 25.4-75.8). Four patients (5.3%) had a known gBRCA1/2 mutation. Sixty-two (82.7%) patients received 0 prior lines (ITT population) and 13 (17.3%) 1 prior line of metastatic therapy. Sixty-seven patients (89.3%) experienced any grade ≥2 treatment-related adverse event (AE). The most frequent AE were platelet count decrease (n=40; 53.3%), anemia (n=36; 48.0%), neutrophil count decrease (n=33; 44.0%) and fatigue (n=24; 32.0%). Grade 3/4 AE were observed in 46 (61.3%) patients, and there was one grade 5 AE (COVID19 pneumonia). Any grade ≥2 immune-related AE (irAE) were observed in 25 of the 37 (67.6%) patients treated with carboplatin + nivolumab. Grade 3/4 irAE were observed in 11 (29.7%) patients. In the ITT population (32 on Arm A; 30 on Arm B), median PFS was 4.2 months with carboplatin + nivolumab, and 5.5 months with carboplatin (stratified HR 0.98, 95% CI [0.51 - 1.88]; p=0.95). ORR was 25% vs. 23.3%, respectively. At a median follow-up of 23.5 months, median OS was 17.5 months vs. 10.7 months (stratified HR 0.63, 95% CI [0.32 - 1.24]; p=0.18). In patients with PD-L1+ mTNBC (13 on Arm A; 11 on Arm B), median PFS was 8.3 months and 4.7 months, respectively (stratified HR 0.63, 95% CI [0.21 - 1.89]; p=0.41). ORR was 23.1% vs. 27.3%, respectively. Median OS was 17.5 months vs. 9.6 months (stratified HR 0.59, 95% CI [0.20 - 1.75]; p=0.34). Conclusions: Addition of nivolumab to carboplatin in patients with previously untreated mTNBC, unselected by PD-L1 status, did not significantly improve PFS. A trend toward improved PFS and OS was observed in patients with PD-L1+ mTNBC. Tissue, blood and intestinal microbiome biomarker analyses are planned; bulk tumor and single-cell sequencing, and TCR sequencing in peripheral blood are ongoing. Clinical trial information: NCT03414684.

Citation Format: Ana C Garrido-Castro, Noah Graham, Kevin Bi, Jihye Park, Jingxin Fu, Tanya Keenan, Edward Thomas Richardson, Ricardo Pastorello, Paulina Lange, Victoria Attaya, Robert Wesolowski, Natalie Sinclair, Zarah Lucas, Steve Lo, Nadine Tung, Meredith Faggen, Peter A Kaufman, Caroline C Block, Fred Briccetti, Madhavi Toke, Wendy Chen, Kai Wucherpfennig, Sascha Marx, Ye Tian, Judith Agudo, Jennifer L Guerriero, Stuart Schnitt, Nancy U Lin, Eric P Winer, Elizabeth A Mittendorf, Nabihah Tayob, Eliezer Van Allen, Sara M Tolaney. A randomized phase II trial of carboplatin with or without nivolumab in metastatic triple-negative breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-14-18.

Understanding resistance to immune checkpoint inhibitors in advanced breast cancer

INTRODUCTION

The addition of immune checkpoint inhibitors (ICIs) to frontline chemotherapy has improved survival for patients with advanced triple-negative breast cancer (TNBC) expressing programmed death-ligand 1 (PD-L1). Nonetheless, most patients develop resistance, with outcomes remaining poor for this population. Moreover, unsatisfactory activity has been observed with ICIs in PD-L1-negative TNBC and in other breast cancer (BC) subtypes, warranting a deeper understanding of resistance to ICIs in BC.

AREAS COVERED

We discuss the immune landscape of distinct BC subtypes, review the clinical activity of immunotherapy in BC, and highlight strategies under development to overcome resistance to ICIs.

EXPERT OPINION

Activity and resistance to ICIs in BC are strongly related to the intrinsic immunophenotype of the tumor tissue. Several promising biomarkers reflecting the immunological state of BC are emerging, with only PD-L1 expression currently adopted into clinical practice. However, limitations make of PD-L1 a sub-optimal biomarker for patient selection, which require efforts to integrate this marker with other immunological features. Concomitantly, a wide variety of drug combinations designed to overcome immune-resistance are being evaluated, with some encouraging signals observed in early-phase trials. Combination strategies tailored to patient and tumor immunophenotype may allow to overcome resistance and fully exploit the potential of ICIs.

Dermal Lymphatic Invasion, Survival, and Time to Recurrence or Progression in Inflammatory Breast Cancer

OBJECTIVES

Dermal lymphatic invasion (DLI) with tumor emboli is a common pathologic characteristic of inflammatory breast cancer (IBC), although its presence is not required for diagnosis. We examined whether documented DLI on skin biopsy was associated with survival and time to recurrence or progression in IBC.

MATERIALS AND METHODS

A total of 340 women enrolled in the IBC Registry at Dana-Farber Cancer Institute between 1997 and 2019 were included in this study. Kaplan-Meier curves and multivariable Cox proportional hazards models were used to estimate hazard ratios and 95% confidence intervals for associations of DLI and overall survival, time to locoregional recurrence/progression, and distant metastasis by stage at presentation.

RESULTS

DLI was detected in 215 (63.2%) of IBC cases overall. At disease presentation, IBC with DLI had a higher prevalence of de novo metastases (37.7% vs. 26.4%), breast skin ulceration (6.1% vs. 2.4%), and lymphovascular invasion within the breast parenchyma (52.9% vs. 25.5%) and a lower prevalence of palpable breast mass (48.2% vs. 70.6%) than IBC without DLI. Over a median follow-up of 2.0 years, 147 deaths occurred. DLI was not associated with survival or recurrence in multivariable models (all P ≥0.10). For example, among women with stage III disease, hazard ratios (95% confidence intervals) for DLI presence was 1.29 (0.77-2.15) for overall survival, 1.29 (0.56-3.00) for locoregional recurrence, and 1.71 (0.97-3.02) for distant metastasis.

CONCLUSION

Although the extent of tumor emboli in dermal lymphatics may be associated with biological features of IBC, DLI was not an independent prognostic marker of clinical outcomes in this study.

Abstract PS10-34: Clinical outcomes in de novo metastatic HER2-positive inflammatory breast cancer

Background: Advances in HER2-directed therapy have significantly improved survival in HER2+ metastatic breast cancer. Approximately 30% of de novo metastatic inflammatory breast cancer (mIBC) is HER2+, though there has been limited IBC representation in clinical trials evaluating the role of HER2-directed agents as first-line metastatic therapy. Elevated rates of locoregional progression or recurrence (LRPR) with systemic therapy alone also raise the question of whether trimodality therapy (TMT) may improve outcomes in IBC patients (pts) with limited metastatic disease, particularly in the setting of increasingly effective anti-HER2 therapy. Methods: Pts diagnosed with de novo HER2+ mIBC were identified from an IRB-approved IBC registry at Dana-Farber Cancer Institute. Clinical, pathology and treatment data were manually abstracted by chart review. Progression-free survival (PFS) was defined as time from IBC diagnosis to LRPR, distant progression/relapse or death (in the absence of event, censored at date of last follow-up). Overall survival (OS) was defined as time from IBC diagnosis to death from any cause or censored at date last known alive. For pts who underwent surgery of the primary tumor, pathologic complete response (pCR) was defined as no residual invasive carcinoma in the breast and axilla and survival was estimated from date of surgery. Median PFS and OS were estimated by Kaplan-Meier method; cumulative incidence of CNS metastasis and LRPR were estimated with death as competing risk. Results: 78 pts diagnosed between 1998-2019 with de novo HER2+ mIBC (41 hormone receptor (HR)-positive; 37 HR-negative) were identified. Median age at diagnosis was 53 years (yr; range: 24-91). Sites of metastatic disease at presentation included bone only (n=12), lymph node/contralateral chest wall only (n=17), bone and lymph node (n=5), visceral (n=40) and CNS with extracranial disease (n=4). As initial HER2-directed therapy, 37 pts received trastuzumab (H), 40 H plus pertuzumab and 1 T-DM1. At a median follow-up of 2.7 yr in the overall cohort, median PFS was 1.0 yr (IQR: 0.5-2.8 yr; 60 events) and median OS was 4.6 yr (IQR: 2.9-8.7 yr; 39 deaths). 34 pts had CNS metastasis with a cumulative incidence of 20% and 28% at 1 and 2 yr, respectively. LRPR developed in 26 pts, of which 16 occurred within 12 months (mo) of diagnosis. Cumulative incidence of LRPR at 1 and 2 yr was 21% and 29%, respectively. In 41 pts (53%), mastectomy was performed after receipt of systemic therapy. Median time from IBC diagnosis to surgery was 7.5 mo (IQR: 6.0-9.9 mo). Radiation was administered in 33 pts, 3 pre- and 30 post-mastectomy. Median OS from surgery was 5.2 yr (IQR: 3.1-8.4 yr). 9/41 pts (22%) achieved pCR; all pCR pts were alive at 1.3-8.9 yr since surgery. To investigate the value of therapy for locoregional control, a landmark analysis was performed in the subset of pts alive and LRPR free at 12 mo from diagnosis (n=56). 27 had surgery within 12 mo from diagnosis and 29 did not. LRPR occurred in 10/56; 9 were among pts who did not undergo surgery. Cumulative LRPR incidence at 1 and 2 yr since the 12 mo landmark was 21% and 29%, respectively, in pts who did not undergo surgery, and 0% at both time points in pts who had surgery (1 LRPR at 8 yr). Conclusion: Long-term outcomes in de novo HER2+ mIBC are overall similar to those reported in metastatic HER2+ non-IBC. More than half of pts underwent systemic and local therapy with good locoregional control and prolonged survival, suggesting a potential role for aggressive local therapy in this mIBC subset with favorable prognosis and effective systemic therapy. The high incidence of early CNS involvement in de novo HER2+ mIBC prompted us to explore this group in detail (Warren SABCS 2020 abstract). Larger studies are needed to better understand the effectiveness of TMT in HER2+ mIBC, highlighting the importance of collaborative research efforts in this rare subset.

Citation Format: Ana C. Garrido-Castro, Samuel M. Niman, Marie Claire Remolano, Jennifer M. Rosenbluth, Caroline Block, Laura E. Warren, Jennifer Bellon, Beth T. Harrison, Faina Nakhlis, Meredith Regan, Beth Overmoyer. Clinical outcomes in de novo metastatic HER2-positive inflammatory breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS10-34.

Abstract PD9-06: Peripheral blood gene signatures predict response to neoadjuvant chemotherapy in breast cancer patients

Purpose: Neoadjuvant chemotherapy (NAC), the standard of care for a subset of breast cancer patients, is known to have immunologic effects. With emerging data showing improved response rates with anti-PD-1/PD-L1 immunotherapy in combination with chemotherapy, the effects of NAC on systemic and local anti-tumor immunity require further study. Biomarkers of anti-tumor immunity are needed to identify which patients are most likely to respond to immunotherapy. Our previous work has shown that changes in the peripheral blood can be observed over the course of NAC for breast cancer. Peripheral blood biomarkers are attractive because of the relative ease of sampling compared to site of disease. Residual cancer burden (RCB) is a useful surrogate marker of long-term prognosis, as patients who experience a pathologic complete response (pCR) have better outcomes than those with residual disease (RD). Methods: We previously identified an 8 gene signature of cytotoxicity, derived from single cell RNA sequencing of PD-1Hi CD8+ T cells, which are enriched for tumor-reactive T cells. Using a custom NanoString panel, we tested expression of this gene signature in whole blood collected prior to definitive surgery in 88 breast cancer patients (TNBC, n=21; HER2+, n=17; ER+, n= 54; PR+, n=53) across two cohorts (VUMC, n=58; DFCI, n=30), 64 of whom had received NAC (pCR, n=11; RD, n=53). We further investigated peripheral blood gene expression using RNA sequencing (n=58; 34 post-NAC, 24 untreated). Results: In two cohorts of breast cancer patients, expression of the 8 gene signature (FGFBP2 + GNLY + GZMB + GZMH + NKG7 + LAG3 + PDCD1 - HLA-G) was highest in patients with RD who experienced a recurrence within three years compared to those with pCR (p&lt;0.01) or those with the highest RCB (RCB III) compared to those with RCB 0/I/II who did not have a recurrence with three years (p&lt;0.05). RNA sequencing showed higher expression of interferon alpha, interferon gamma, and complement gene sets in patients experiencing a pCR compared to those with RD by gene set enrichment analysis (FDR-corrected q-values &lt; 0.05). Conclusions: Expression of immune-related genes in the peripheral blood may predict response to NAC in breast cancer patients and be a useful biomarker for those who would benefit from additional therapies. These results will be further tested in a large cohort of longitudinal samples from breast cancer patients receiving NAC alone or in combination with pembrolizumab from the I-SPY-2 trial, to determine whether peripheral blood gene signatures can predict response to immunotherapy in breast cancer.

Citation Format: Margaret L Axelrod, Paula I Gonzalez-Ericsson, Xiaopeng Sun, Riley E Bergman, Joshua Donaldson, Sara M Tolaney, Ian E Krop, Ana C Garrido-Castro, Melinda E. Sanders, Ingrid A Mayer, Justin M Balko. Peripheral blood gene signatures predict response to neoadjuvant chemotherapy in breast cancer patients [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PD9-06.

Genomic Characterization of de novo Metastatic Breast Cancer

PURPOSE

In contrast to recurrence after initial diagnosis of stage I-III breast cancer [recurrent metastatic breast cancer (rMBC)], de novo metastatic breast cancer (dnMBC) represents a unique setting to elucidate metastatic drivers in the absence of treatment selection. We present the genomic landscape of dnMBC and association with overall survival (OS).

EXPERIMENTAL DESIGN

Targeted DNA sequencing (OncoPanel) was prospectively performed on either primary or metastatic tumors from 926 patients (212 dnMBC and 714 rMBC). Single-nucleotide variants, copy-number variations, and tumor mutational burden (TMB) in treatment-naïve dnMBC primary tumors were compared with primary tumors in patients who ultimately developed rMBC, and correlated with OS across all dnMBC.

RESULTS

When comparing primary tumors by subtype, MYB amplification was enriched in triple-negative dnMBC versus rMBC (21.1% vs. 0%, P = 0.0005, q = 0.111). Mutations in KMTD2, SETD2, and PIK3CA were more prevalent, and TP53 and BRCA1 less prevalent, in primary HR⁺/HER2^- tumors of dnMBC versus rMBC, though not significant after multiple comparison adjustment. Alterations associated with shorter OS in dnMBC included TP53 (wild-type: 79.7 months; altered: 44.2 months; P = 0.008, q = 0.107), MYC (79.7 vs. 23.3 months; P = 0.0003, q = 0.011), and cell-cycle (122.7 vs. 54.9 months; P = 0.034, q = 0.245) pathway genes. High TMB correlated with better OS in triple-negative dnMBC (P = 0.041).

CONCLUSIONS

Genomic differences between treatment-naïve dnMBC and primary tumors of patients who developed rMBC may provide insight into mechanisms underlying metastatic potential and differential therapeutic sensitivity in dnMBC. Alterations associated with poor OS in dnMBC highlight the need for novel approaches to overcome potential intrinsic resistance to current treatments.

Phase 2 study of buparlisib (BKM120), a pan-class I PI3K inhibitor, in patients with metastatic triple-negative breast cancer

BACKGROUND

Treatment options for triple-negative breast cancer remain limited. Activation of the PI3K pathway via loss of PTEN and/or INPP4B is common. Buparlisib is an orally bioavailable, pan-class I PI3K inhibitor. We evaluated the safety and efficacy of buparlisib in patients with metastatic triple-negative breast cancer.

METHODS

This was a single-arm phase 2 study enrolling patients with triple-negative metastatic breast cancer. Patients were treated with buparlisib at a starting dose of 100 mg daily. The primary endpoint was clinical benefit, defined as confirmed complete response (CR), partial response (PR), or stable disease (SD) for ≥ 4 months, per RECIST 1.1. Secondary endpoints included progression-free survival (PFS), overall survival (OS), and toxicity. A subset of patients underwent pre- and on-treatment tumor tissue biopsies for correlative studies.

RESULTS

Fifty patients were enrolled. Median number of cycles was 2 (range 1-10). The clinical benefit rate was 12% (6 patients, all SD ≥ 4 months). Median PFS was 1.8 months (95% confidence interval [CI] 1.6-2.3). Median OS was 11.2 months (95% CI 6.2-25). The most frequent adverse events were fatigue (58% all grades, 8% grade 3), nausea (34% all grades, none grade 3), hyperglycemia (34% all grades, 4% grade 3), and anorexia (30% all grades, 2% grade 3). Eighteen percent of patients experienced depression (12% grade 1, 6% grade 2) and anxiety (10% grade 1, 8% grade 2). Alterations in PIK3CA/AKT1/PTEN were present in 6/27 patients with available targeted DNA sequencing (MSK-IMPACT), 3 of whom achieved SD as best overall response though none with clinical benefit ≥ 4 months. Of five patients with paired baseline and on-treatment biopsies, reverse phase protein arrays (RPPA) analysis demonstrated reduction of S6 phosphorylation in 2 of 3 patients who achieved SD, and in none of the patients with progressive disease.

CONCLUSIONS

Buparlisib was associated with prolonged SD in a very small subset of patients with triple-negative breast cancer; however, no confirmed objective responses were observed. Downmodulation of key nodes in the PI3K pathway was observed in patients who achieved SD. PI3K pathway inhibition alone may be insufficient as a therapeutic strategy for triple-negative breast cancer.

TRIAL REGISTRATION

NCT01790932 . Registered on 13 February 2013; NCT01629615 . Registered on 27 June 2012.

Clinical Pan-Cancer Assessment of Mismatch Repair Deficiency Using Tumor-Only, Targeted Next-Generation Sequencing

PURPOSE

Given regulatory approval of immune checkpoint inhibitors in patients with mismatch repair-deficient (MMR-D) cancers agnostic to tumor type, it has become important to characterize occurrence of MMR-D and develop cost-effective screening approaches. Using a next-generation sequencing (NGS) panel (OncoPanel), we developed an algorithm to identify MMR-D frequency in tumor samples and applied it in a clinical setting with pathologist review.

METHODS

To predict MMR-D, we adapted methods described previously for use in NGS panels, which assess patterns of single base-pair insertion or deletion events occurring in homopolymer regions. Tumors assayed with OncoPanel between July 2013 and July 2018 were included. For tumors tested after June 2017, sequencing results were presented to pathologists in real time for clinical MMR determination, in the context of tumor mutation burden, other mutational signatures, and clinical data.

RESULTS

Of 20,301 tumors sequenced, 2.7% (553) were retrospectively classified as MMR-D by the algorithm. Of 4,404 samples with pathologist sign-out of MMR status, the algorithm classified 147 (3.3%) as MMR-D: in 116 cases, MMR-D was confirmed by a pathologist, five cases were overruled by the pathologist, and 26 were assessed as indeterminate. Overall, the highest frequencies of OncoPanel-inferred MMR-D were in endometrial (21%; 152/723), colorectal (9.7%; 169/1,744), and small bowel (9.3%; 9/97) cancers. When algorithm predictions were compared with historical MMR immunohistochemistry or polymerase chain reaction results in a set of 325 tumors sequenced before initiation of pathologist assessment, the overall sensitivity and specificity of the algorithm were 91.1% and 98.2%, respectively.

CONCLUSION

We show that targeted, tumor-only NGS can be leveraged to determine MMR signatures across tumor types, suggesting that broader biomarker screening approaches may have clinical value.

Identifying ERBB2 Activating Mutations in HER2-Negative Breast Cancer: Clinical Impact of Institute-Wide Genomic Testing and Enrollment in Matched Therapy Trials

PURPOSE

The yield of comprehensive genomic profiling in recruiting patients to molecular-based trials designed for small subgroups has not been fully evaluated. We evaluated the likelihood of enrollment in a clinical trial that required the identification of a specific genomic change based on our institute-wide genomic tumor profiling.

PATIENTS AND METHODS

Using genomic profiling from archived tissue samples derived from patients with metastatic breast cancer treated between 2011 and 2017, we assessed the impact of systematic genomic characterization on enrollment in an ongoing phase II trial (ClinicalTrials.gov identifier: NCT01670877). Our primary aim was to describe the proportion of patients with a qualifying ERBB2 mutation identified by our institutional genomic panel (OncoMap or OncoPanel) who enrolled in the trial. Secondary objectives included median time from testing result to trial registration, description of the spectrum of ERBB2 mutations, and survival. Associations were calculated using Fisher's exact test.

RESULTS

We identified a total of 1,045 patients with metastatic breast cancer without ERBB2 amplification who had available genomic testing results. Of these, 42 patients were found to have ERBB2 mutation and 19 patients (1.8%) were eligible for the trial on the basis of the presence of an activating mutation, 18 of which were identified by OncoPanel testing. Fifty-eight percent of potentially eligible patients were approached, and 33.3% of eligible patients enrolled in the trial guided exclusively by OncoPanel testing.

CONCLUSION

More than one half of eligible patients were approached for trial participation and, significantly, one third of those were enrolled in NCT01670877. Our data illustrate the ability to enroll patients in trials of rare subsets in routine clinical practice and highlight the need for these broadly based approaches to effectively support the success of these studies.

Changes in Peripheral and Local Tumor Immunity after Neoadjuvant Chemotherapy Reshape Clinical Outcomes in Patients with Breast Cancer

PURPOSE

The recent approval of anti-programmed death-ligand 1 immunotherapy in combination with nab-paclitaxel for metastatic triple-negative breast cancer (TNBC) highlights the need to understand the role of chemotherapy in modulating the tumor immune microenvironment (TIME).

EXPERIMENTAL DESIGN

We examined immune-related gene expression patterns before and after neoadjuvant chemotherapy (NAC) in a series of 83 breast tumors, including 44 TNBCs, from patients with residual disease (RD). Changes in gene expression patterns in the TIME were tested for association with recurrence-free (RFS) and overall survival (OS). In addition, we sought to characterize the systemic effects of NAC through single-cell analysis (RNAseq and cytokine secretion) of programmed death-1-high (PD-1^HI) CD8⁺ peripheral T cells and examination of a cytolytic gene signature in whole blood.

RESULTS

In non-TNBC, no change in expression of any single gene was associated with RFS or OS, while in TNBC upregulation of multiple immune-related genes and gene sets were associated with improved long-term outcome. High cytotoxic T-cell signatures present in the peripheral blood of patients with breast cancer at surgery were associated with persistent disease and recurrence, suggesting active antitumor immunity that may indicate ongoing disease burden.

CONCLUSIONS

We have characterized the effects of NAC on the TIME, finding that TNBC is uniquely sensitive to the immunologic effects of NAC, and local increases in immune genes/sets are associated with improved outcomes. However, expression of cytotoxic genes in the peripheral blood, as opposed to the TIME, may be a minimally invasive biomarker of persistent micrometastatic disease ultimately leading to recurrence.

Tumor Mutational Burden and PTEN Alterations as Molecular Correlates of Response to PD-1/L1 Blockade in Metastatic Triple-Negative Breast Cancer

PURPOSE

Few patients with metastatic triple-negative breast cancer (mTNBC) benefit from immune checkpoint inhibitors (ICI). On the basis of immunotherapy response correlates in other cancers, we evaluated whether high tumor mutational burden (TMB) ≥10 nonsynonymous mutations/megabase and PTEN alterations, defined as nonsynonymous mutations or 1 or 2 copy deletions, were associated with clinical benefit to anti-PD-1/L1 therapy in mTNBC.

EXPERIMENTAL DESIGN

We identified patients with mTNBC, who consented to targeted DNA sequencing and were treated with ICIs on clinical trials between April 2014 and January 2019 at Dana-Farber Cancer Institute (Boston, MA). Objective response rate (ORR), progression-free survival (PFS), and overall survival (OS) were correlated with tumor genomic features.

RESULTS

Sixty-two women received anti-PD-1/L1 inhibitors alone (23%) or combined with targeted therapy (19%) or chemotherapy (58%). High TMB (18%) was associated with significantly longer PFS (12.5 vs. 3.7 months; P = 0.04), while PTEN alterations (29%) were associated with significantly lower ORR (6% vs. 48%; P = 0.01), shorter PFS (2.3 vs. 6.1 months; P = 0.01), and shorter OS (9.7 vs. 20.5 months; P = 0.02). Multivariate analyses confirmed that these associations were independent of performance status, prior lines of therapy, therapy regimen, and visceral metastases. The survival associations were additionally independent of PD-L1 in patients with known PD-L1 and were not found in mTNBC cohorts treated with chemotherapy (n = 90) and non-ICI regimens (n = 169).

CONCLUSIONS

Among patients with mTNBC treated with anti-PD-1/L1 therapies, high TMB and PTEN alterations were associated with longer and shorter survival, respectively. These observations warrant validation in larger datasets.

Incidence of Endocrine Dysfunction Following the Use of Different Immune Checkpoint Inhibitor Regimens: A Systematic Review and Meta-analysis

Importance

If not promptly recognized, endocrine dysfunction can be life threatening. The incidence and risk of developing such adverse events (AEs) following the use of immune checkpoint inhibitor (ICI) regimens are unknown.

Objective

To compare the incidence and risk of endocrine AEs following treatment with US Food and Drug Administration-approved ICI regimens.

Data Sources

A PubMed search through July 18, 2016, using the following keywords was performed: "ipilimumab," "MDX-010," "nivolumab," "BMS-963558," "pembrolizumab," "MK-3475," "atezolizumab," "MPDL3280A," and "phase."

Study Selection

Thirty-eight randomized clinical trials evaluating the usage of these ICIs for treatment of advanced solid tumors were identified, resulting in a total of 7551 patients who were eligible for a meta-analysis. Regimens were categorized by class into monotherapy with a PD-1 (programmed cell death protein 1) inhibitor, a CTLA-4 (cytotoxic T-lymphocyte-associated protein-4) inhibitor, or a PD-L1 (programmed cell death 1 ligand 1) inhibitor, and combination therapy with PD-1 plus CTLA-4 inhibitors.

Data Extraction and Synthesis

The data were extracted by 1 primary reviewer (R.B.-S.) and then independently reviewed by 2 secondary reviewers (W.T.B. and A.C.G.-C.) following Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Inferences on the incidence of AEs were made using log-odds random effects models.

Main Outcomes and Measures

Incidence of all-grade hypothyroidism, hyperthyroidism, hypophysitis, primary adrenal insufficiency, and insulin-deficient diabetes.

Results

Overall, 38 randomized clinical trials comprising 7551 patients were included in this systematic review and meta-analysis. The incidence of both hypothyroidism and hyperthyroidism was highest in patients receiving combination therapy. Patients on the combination regimen were significantly more likely to experience hypothyroidism (odds ratio [OR], 3.81; 95% CI, 2.10-6.91, P < .001) and hyperthyroidism (OR, 4.27; 95% CI, 2.05-8.90; P = .001) than patients on ipilimumab. Compared with patients on ipilimumab, those on PD-1 inhibitors had a higher risk of developing hypothyroidism (OR, 1.89; 95% CI, 1.17-3.05; P = .03). The risk of hyperthyroidism, but not hypothyroidism, was significantly greater with PD-1 than with PD-L1 inhibitors (OR, 5.36; 95% CI, 2.04-14.08; P = .002). While patients who received PD-1 inhibitors were significantly less likely to experience hypophysitis than those receiving ipilimumab (OR, 0.29; 95% CI, 0.18-0.49; P < .001), those who received combination therapy were significantly more likely to develop it (OR, 2.2; 95% CI, 1.39-3.60; P = .001). For primary adrenal insufficiency and insulin-deficient diabetes no statistical inferences were made due to the smaller number of events.

Conclusions and Relevance

Our study provides more precise data on the incidence of endocrine dysfunctions among patients receiving ICI regimens. Patients on combination therapy are at increased risk of thyroid dysfunction and hypophysitis.

Abstract PD9-01: Genomic alterations associated with loss of HR expression in metastatic breast cancer

Background: Discordance in hormone receptor (HR) status between primary (p) tumors and metastatic (m) recurrences has been widely described. Loss of estrogen and progesterone receptor expression occurs in ˜12% of asynchronous recurrences, leading to triple-negative (TN) status in the metastasis. Genomic mechanisms driving HR loss and its prognostic and therapeutic implications have not been fully elucidated.

Methods: Targeted NGS (Oncopanel, OP) at Dana-Farber Cancer Institute using multiplexed copy number variation and mutation (mut) detection across the full coding regions of 300 genes and selected intronic regions of 35 genes was prospectively performed on either archival primary or metastatic samples collected in patients (pts) with metastatic breast cancer (MBC). Receptor status at initial diagnosis and recurrence were reviewed using a 1% cutoff to define HR-positivity and excluding HER2+ cases. Fisher´s exact test was used to compare frequency of alterations. Tumor mut burden (TMB) was computed normalizing the sum of reported exon mut in each pt by the exonic-bait-set size of the panel.

Results: Between 8/2013-9/2016, 929 pts with MBC underwent OP testing. Of 517 pts diagnosed with primary HR+/HER2- breast cancer, at time of recurrence 388 remained HR+/HER2- (pHR+/mHR+), 39 switched to HR-/HER2- (pHR+/mTN, of which 23 (59%) had initial HR expression &gt;10%), 10 switched to HER2+ and 80 had unknown metastatic receptor status. Comparison between primary samples in pHR+/mHR+ (n=245) and pHR+/mTN (n=24) showed that pHR+/mTN was significantly more likely to harbor mut in TP53, STK11 and MSH6, amplifications (amp) in CCNE1 and FGFR2, and less likely to have PIK3CA mut or CCND1 amp. Median TMB in primary pHR+/mHR+ was 6.05 mut/Mb (0-37.5) and 5.68 mut/Mb (1.2-10.9) in pHR+/mTN (p=0.45). Metastatic samples in pHR+/mTN (n=15) were enriched in ARID1A, CRTC2 and CDH1 mut compared to metastases (n=40) in pts who remained TN (pTN/mTN). Deletions in CDKN2A/2B and RB1, and mut in TP53, NOTCH2 and ERCC2 were more prevalent in recurrent tumors of pHR+/mTN than pHR+/mHR+. In metastases, TMB was higher in pHR+/mTN than pTN/mTN or pHR+/mHR+ (10.9 vs. 7.0 vs. 7.3 mut/Mb, respectively; p=0.002). Median OS from initial diagnosis was 9.4 yrs in pHR+/mTN, less than pHR+/mHR+ (15.9 yrs; p=0.009) and greater than pTN/mTN (4.3 yrs; p=0.008). Median OS from MBC diagnosis was 1.8 yrs in pHR+/mTN, less than pHR+/mHR+ (6.4 yrs; p=0.001) but not significantly different than pTN/mTN (1.5 yrs, p=0.3).

 pHR+/mHR+ (n=245)pHR+/mTN (n=24)p value NFreq (%)NFreq (%) MutTP536325.72083.3&lt;0.00001PIK3CA9438.4000GATA33514.3000.053STK1152.0312.50.026MSH641.6312.50.017AmpFGFR20028.30.008CCNE10028.30.008CCND14418.0000.018

Conclusion: Targeted NGS shows that alterations in DNA damage and cell-cycle regulation pathways in primary HR+ tumors are associated with HR loss in the metastatic setting. Primary tumors that lose HR appear more similar to basal-like than luminal tumors, despite &gt;10% baseline HR expression in most pts, and once metastatic, survival is comparable to pTN/mTN. Metastases with HR loss have higher TMB than those that remain HR+ or TN throughout the course of the disease. These findings, if confirmed, may influence treatment and pt selection for clinical trials.

Citation Format: Garrido-Castro AC, Hughes ME, Cherniack A, Barroso-Sousa R, Bychkovsky BL, Di Lascio S, Berger A, Mittendorf EA, Files JL, Guo H, Kumari P, Cerami E, Krop IE, Wagle N, Lindeman NI, MacConaill LE, Dillon DA, Winer EP, Lin NU. Genomic alterations associated with loss of HR expression in metastatic breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD9-01.

Abstract P5-12-02: PTEN alterations and tumor mutational burden (TMB) as potential predictors of resistance or response to immune checkpoint inhibitors (ICI) in metastatic triple-negative breast cancer (mTNBC)

Purpose: To date no biomarker has been identified that predicts response to ICI in mTNBC. This study aimed to explore if tumor genomic alterations correlate with efficacy of PD-1/PD-L1 inhibition in patients (pts) with mTNBC. Methods: Demographic, treatment response, and long-term outcome data were collected on patients with mTNBC treated at Dana-Farber Cancer Institute (DFCI) under several clinical trials incorporating PD-1/PD-L1 inhibitors, given as monotherapy or combined with chemotherapy (CT). Pts included in this analysis had available results of targeted exon sequencing performed using Oncopanel, our institutional gene sequencing panel, on archival tumor tissue. TMB was calculated by determining the number of non-synonymous somatic mutations that occur per megabase of exonic sequence data across all genes on the panel. High TMB was defined as 310 mutations/megabase. TMB and gene alterations were correlated with objective response rate (ORR) per RECIST 1.1, progression-free (PFS) and overall survival (OS). Results: A total of 50 pts with mTNBC were included in this analysis. At baseline, the median age was 55.9 years (31.8–75.9), 60% had ECOG 0 and 40% had ECOG 1, 72% had visceral metastasis, and 46% had received 31 prior lines of systemic therapy in the metastatic setting. While 26% of pts received monotherapy [pembrolizumab (n=7, NCT02447003); atezolizumab (n=6; NCT01375842)], 74% received combination with CT [pembrolizumab plus eribulin (n=31; NCT02513472); atezolizumab plus nab-paclitaxel (n=6; NCT01633970)]. PTEN alterations were present in 30% of pts (mutations = 7; one copy number loss = 7; two copy number loss = 1). Median follow-up was 14 months (1–40). Pts with tumors harboring PTEN alterations had lower ORR (7% vs 57%; P&lt;0.001), shorter median PFS (2.3 vs 6.3 months; P=0.027), and shorter median OS (8.1 vs 20.1 months; P=0.012) compared to pts without PTEN alterations. The median TMB was 6.6 mut/Mb (1.2–50.8), and 23% of pts had a high TMB. While high TMB was not associated with higher ORR (P=0.56), it was associated with better median PFS (16.5 vs 2.4 months; P=0.017), and better median OS (not reached vs 13.5 months; P=0.026). Both PTEN status and TMB remained significantly associated with PFS in the multivariable model. Only PTEN status remained significantly associated with OS in the multivariable analysis with the same covariables. Ongoing analysis to better understand if these predictors are specific for predicting benefit to immunotherapy and/or a marker of chemotherapy resistance will be presented at the symposium. Conclusion: PTEN genomic alterations and TMB may impact benefit from PD-1/PD-L1 inhibitors largely administered with chemotherapy in mTNBC. These observations warrant prospective validation and may inform the importance of stratifying pts according to these characteristics in future randomized studies with ICI.

Table 1.Multivariable analysis for PFS Hazard ratioConfidence Intervalp-valueCombination therapy0.420.16 – 1.130.009Visceral metastasis1.310.63 – 2.770.46Previous lines of therapy1.020.09 – 0.700.85ECOG 12.11.06 – 1.280.034PTEN altered3.741.65 – 8.440.002Hypermutated tumors0.850.75 – 0.970.011

Citation Format: Barroso-Sousa R, Tyekucheva S, Pernas-Simon S, Exman P, Jain E, Garrido-Castro AC, Hughes M, Bychkovsky B, Di Lascio S, Umeton R, Files J, Lindeman NI, MacConaill LE, Hodi FS, Krop IE, Dillon D, Winer EP, Wagle N, Lin NU, Mittendorf EA, Tolaney SM. PTEN alterations and tumor mutational burden (TMB) as potential predictors of resistance or response to immune checkpoint inhibitors (ICI) in metastatic triple-negative breast cancer (mTNBC) [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-12-02.

Insights into Molecular Classifications of Triple-Negative Breast Cancer: Improving Patient Selection for Treatment

Triple-negative breast cancer (TNBC) remains the most challenging breast cancer subtype to treat. To date, therapies directed to specific molecular targets have rarely achieved clinically meaningful improvements in outcomes of patients with TNBC, and chemotherapy remains the standard of care. Here, we seek to review the most recent efforts to classify TNBC based on the comprehensive profiling of tumors for cellular composition and molecular features. Technologic advances allow for tumor characterization at ever-increasing depth, generating data that, if integrated with clinical-pathologic features, may help improve risk stratification of patients, guide treatment decisions and surveillance, and help identify new targets for drug development. SIGNIFICANCE: TNBC is characterized by higher rates of relapse, greater metastatic potential, and shorter overall survival compared with other major breast cancer subtypes. The identification of biomarkers that can help guide treatment decisions in TNBC remains a clinically unmet need. Understanding the mechanisms that drive resistance is key to the design of novel therapeutic strategies to help prevent the development of metastatic disease and, ultimately, to improve survival in this patient population.

Modulating Bone Marrow Hematopoietic Lineage Potential to Prevent Bone Metastasis in Breast Cancer

The presence of disseminated tumor cells in breast cancer patient bone marrow aspirates predicts decreased recurrence-free survival. Although it is appreciated that physiologic, pathologic, and therapeutic conditions impact hematopoiesis, it remains unclear whether targeting hematopoiesis presents opportunities for limiting bone metastasis. Using preclinical breast cancer models, we discovered that marrow from mice treated with the bisphosphonate zoledronic acid (ZA) are metastasis-suppressive. Specifically, ZA modulated hematopoietic myeloid/osteoclast progenitor cell (M/OCP) lineage potential to activate metastasis-suppressive activity. Granulocyte-colony stimulating factor (G-CSF) promoted ZA resistance by redirecting M/OCP differentiation. We identified M/OCP and bone marrow transcriptional programs associated with metastasis suppression and ZA resistance. Analysis of patient blood samples taken at randomization revealed that women with high-plasma G-CSF experienced significantly worse outcome with adjuvant ZA than those with lower G-CSF levels. Our findings support discovery of therapeutic strategies to direct M/OCP lineage potential and biomarkers that stratify responses in patients at risk of recurrence.Significance: Bone marrow myeloid/osteoclast progenitor cell lineage potential has a profound impact on breast cancer bone metastasis and can be modulated by G-CSF and bone-targeting agents. Cancer Res; 78(18); 5300-14. ©2018 AACR.

ESCMID Study Group for Infections in Compromised Hosts (ESGICH) Consensus Document on the safety of targeted and biological therapies: an infectious diseases perspective (Cell surface receptors and associated signaling pathways)

BACKGROUND

The present review is part of the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) Study Group for Infections in Compromised Hosts (ESGICH) consensus document on the safety of targeted and biologic therapies.

AIMS

To review, from an infectious diseases perspective, the safety profile of therapies targeting cell surface receptors and associated signaling pathways among cancer patients and to suggest preventive recommendations.

SOURCES

Computer-based Medline searches with MeSH terms pertaining to each agent or therapeutic family.

CONTENT

Vascular endothelial growth factor (VEGF)-targeted agents (bevacizumab and aflibercept) are associated with a meaningful increase in the risk of infection, likely due to drug-induced neutropaenia, although no clear benefit is expected from the universal use of anti-infective prophylaxis. VEGF tyrosine kinase inhibitors (i.e. sorafenib or sunitinib) do not seem to significantly affect host's susceptibility to infection, and universal anti-infective prophylaxis is not recommended either. Anti-epidermal growth factor receptor (EGFR) monoclonal antibodies (cetuximab or panitumumab) induce neutropaenia and secondary skin and soft tissue infection in cases of severe papulopustular rash. Systemic antibiotics (doxycycline or minocycline) should be administered to prevent the latter complication, whereas no recommendation can be established on the benefit from antiviral, antifungal or anti-Pneumocystis prophylaxis. A lower risk of infection is reported for anti-ErbB2/HER2 monoclonal antibodies (trastuzumab and pertuzumab) and ErbB receptor tyrosine kinase inhibitors (including dual-EGFR/ErbB2 inhibitors such as lapatinib or neratinib) compared to conventional chemotherapy, presumably as a result of the decreased occurrence of drug-induced neutropaenia.

IMPLICATIONS

With the exception of VEGF-targeted agents, the overall risk of infection associated with the reviewed therapies seems to be low.

CDK4/6 Inhibition in Breast Cancer: Mechanisms of Response and Treatment Failure

PURPOSE OF REVIEW

To describe the role of D-type cyclins and CDKs 4 and 6 in breast cancer, and to discuss potential biomarkers for sensitivity or resistance to CDK4/6 inhibitors.

RECENT FINDINGS

A small number of preclinical and clinical studies have explored potential mechanisms of CDK4/6 inhibitor response and resistance in breast cancer. Putative markers of response include ER-positivity, luminal patterns of gene expression, high cyclin D1 levels, and low p16 levels. Possible resistance mechanisms include loss of Rb function, overexpression/amplification of cyclin E, and CDK6 amplification. Most these remain speculative and have not been validated in clinical specimens.

SUMMARY

If early successes with CDK4/6 inhibitors are to be capitalized upon, it is critical that our understanding of CDK4/6 biology in breast cancer extends beyond its current rudimentary state. Only then we will be able to develop rational therapeutic combinations that further enhance the efficacy of these agents.

Increased myo-inositol in parietal white and gray matter as a biomarker of poor prognosis in neuropsychiatric lupus: a case report

Neuropsychiatric manifestations can be a serious complication of systemic lupus erythematosus, affecting nearly 56% of these patients. Frequently, acceptable clinical outcome is observed in neurolupus with immunosuppressive therapy. Different metabolites identified with MR spectroscopy may be associated with modifications in the natural history of this disease, specifically in the central nervous system. We report a case of neurolupus with progressive neurologic impairment despite aggressive immunosuppressive treatment. We describe clinical features, laboratory and MRI results, as well as characteristic findings on MR spectroscopy. Serial MRI identified atrophy of the left temporal lobe. MR spectroscopy showed an increase of myo-inositol/creatine ratio intensity, accompanied by a decrease of N-acetylaspartate/creatine ratio in both parietal white and gray matter. During follow-up, the patient developed progressive cognitive deficiency despite the intensification of therapy. Neurolupus manifestations are common and immunosuppressive treatment often avoids severe complications. Characteristic findings on MR spectroscopy may be useful for clinicians to determine poor prognosis and resistance to therapy.