Exemestane plus everolimus and palbociclib in metastatic breast cancer: clinical response and genomic/transcriptomic determinants of resistance in a phase I/II trial

The landscape of cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) resistance is still being elucidated and the optimal subsequent therapy to overcome resistance remains uncertain. Here we present the final results of a phase Ib/IIa, open-label trial (NCT02871791) of exemestane plus everolimus and palbociclib for CDK4/6i-resistant metastatic breast cancer. The primary objective of phase Ib was to evaluate safety and tolerability and determine the maximum tolerated dose/recommended phase II dose (100 mg palbociclib, 5 mg everolimus, 25 mg exemestane). The primary objective of phase IIa was to determine the clinical benefit rate (18.8%, n = 6/32), which did not meet the predefined endpoint (65%). Secondary objectives included pharmacokinetic profiling (phase Ib), objective response rate, disease control rate, duration of response, and progression free survival (phase IIa), and correlative multi-omics analysis to investigate biomarkers of resistance to CDK4/6i. All participants were female. Multi-omics data from the phase IIa patients (n = 24 tumor/17 blood biopsy exomes; n = 27 tumor transcriptomes) showed potential mechanisms of resistance (convergent evolution of HER2 activation, BRAFV600E), identified joint genomic/transcriptomic resistance features (ESR1 mutations, high estrogen receptor pathway activity, and a Luminal A/B subtype; ERBB2/BRAF mutations, high RTK/MAPK pathway activity, and a HER2-E subtype), and provided hypothesis-generating results suggesting that mTOR pathway activation correlates with response to the trial's therapy. Our results illustrate how genome and transcriptome sequencing may help better identify patients likely to respond to CDK4/6i therapies.

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.

Concurrent predictors of an immune responsive tumor microenvironment within tumor mutational burden-high breast cancer

Background

Data supporting high tumor mutational burden (TMB-H) as a lone biomarker for an immune-responsive tumor microenvironment (TME) in metastatic breast cancer (MBC) are weak, yet tumor agnostic approval in TMB-H advanced tumors provides immune checkpoint inhibition (ICI) as a clinical option. We evaluated concurrent predictors of immune-responsive and non-responsive TME within MBC.

Methods

Tumor samples from patients with MBC (N=5621) were analyzed by next-generation sequencing of DNA (592-gene panel or whole exome) and RNA (whole transcriptome) at Caris Life Sciences (Phoenix, AZ). TMB-H threshold was set to ≥ 10 muts/Mb. PDL-1 was evaluated using SP142 antibody. Gene expression profiling and RNA deconvolution were used to estimate immune and stromal cell population abundance in the TME, and transcriptomic signature of immunotherapy response (T cell-inflamed score).

Results

461 (8.2%) TMB-H MBC samples were identified. Consistent with prior studies, TMB-H tumors exhibited significant dMMR/MSI-H enrichment (7 vs. 0%, p<0.0001) and PD-L1+ expression (36 vs. 28%, p<0.05) compared to TMB-L. Across all samples, T cell-inflamed scores were weakly correlated with TMB. TMB-H was not associated with significantly increased immune responsive cell types (CD8+ T-cells, NK cells, or B cells) or immune response gene signatures (e.g. antigen presentation), yet positive trends were observed, while immunosuppressive fibroblasts were significantly decreased in TMB-H tumors (0.84-fold change compared to TMB-L, P<0.05). HR+/HER2- breast cancer was the only subtype in which TMB-H tumors exhibited increased T cell-inflamed scores vs. TMB-L. Concurrent PD-L1+ or dMMR/MSI-H with TMB-H was associated with high T cell-inflamed scores in both HR+/HER2- and TNBC. Among several associated biomarkers, B2M mutations and CD274 amplifications were positively associated with T-cell inflamed scores in TMB-H tumors; CDH1 and ERBB2 mutations were negatively associated.

Conclusion

High TMB alone does not strongly correlate with immune infiltrate or immune-related gene signatures in MBC. TMB-H predicts T-cell inflamed signature compared to TMB-L in HR+/HER2- tumors only. Along with MSI-H and PD-L1+, several biomarkers, including B2M mutation and CD274 amplification, may help predict ICI benefit amongst TMB-H tumors. Co-occurring biomarkers within TMB-H breast cancer warrant evaluation in larger cohorts for response or resistance to ICI to develop composite predictive biomarkers in MBC.

Tumor Mutational Burden in Breast Cancer: Current Evidence, Challenges, and Opportunities

Tumor mutational burden (TMB) correlates with tumor neoantigen burden, T cell infiltration, and response to immune checkpoint inhibitors in many solid tumor types. Based on data from the phase II KEYNOTE-158 study, the anti-PD-1 antibody pembrolizumab was granted approval for treating patients with advanced solid tumors and TMB ≥ 10 mutations per megabase. However, this trial did not include any patients with metastatic breast cancer; thus, several questions remain unanswered about the true role of TMB as a predictive biomarker of benefit to immune checkpoint inhibitor therapy in breast cancer. In this review, we will discuss the challenges and opportunities in establishing TMB as a predictive biomarker of benefit to immunotherapy in metastatic breast cancer.

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 P5-03-19: Frequency of germline TP53 p.R337H variant among women at risk of hereditary breast cancer in a public health system of Central-West of Brazil

Background: Breast Cancer (BC) is one of the most common cancers diagnosed in Li-Fraumeni Syndrome (LFS). Most studies about the frequency of germline pathogenic variant (PV) TP53 p.R337H have been conducted in the South and Southeastern regions of Brazil reaching rates as high as 8% of detection. There is a lack of data on the frequency of this germline PV in other Brazilian regions, especially among patients without access to genetic tests. Objective: This study aims to evaluate the detection rate of TP53 p.R337H in patients (pts) at risk of hereditary breast cancer (HBC) and describe the clinical and demographic profile of the study cohort. Methodology: Hereditary cancer risk assessment based on the National Comprehensive Cancer Network Criteria (NCCN), version 1.2020, was performed in women with BC who were being followed in a public hospital (DF, Brazil) between January 2021 and January 2022. All pts eligible for germline genetic testing according to HBC NCCN criteria were referred for genetic counseling and genetic testing. For those patients who could not afford a comprehensive genetic test, a real time PCR test specifically searching for TP53 p.R337H variant was performed. In case of TP53 p.R337H detection in the proband, genetic counseling and familial variant testing were offered to family members. Results: Among 221 pts eligible for this study, 180 pts performed germline testing, including 100 pts tested only for the TP53 p.R337H variant (real-time PCR) and 80 pts performed out of pocket BC multigene panel testing (including TP53 sequencing). This cohort was mostly represented by pts from Central-West (47%) and Northeast (35%) regions of Brazil. The median age of BC diagnosis was 44 y.o. (18 - 78). Invasive ductal carcinoma represented 92% (n=203) of the tumors, 50% were ER/PR+ HER2-, 25% HER2 +, 25% ER/PR- HER2- (triple negative). Regarding stage at diagnosis, 59% (n=130) were stages IIB-IIIC and 13% IV. The detection rate of TP53 p.R337H was 1.1% (2/180). Among the pts who met the revised Chompret criteria for LFS, this frequency was 5% (2/40). One of them was diagnosed with a stage IIIB IDC ER/PR+HER2- at 28 y.o. and had no relevant family history of cancer. The other pt was diagnosed with a stage IV IDC ER/PR+HER2- at 44 y.o. and the family history revealed four sisters and one niece with BC, and one nephew with brain tumor at 4 y.o. The family members from these two families received genetic counseling and genetic testing. Cascade testing was able to identify 12 additional carriers. All carriers were referred for post-testing follow-up. Conclusion: According to these results, we expect to identify at least one p.R337H carrier in each 90 BC pts treated in the Federal’s District Public Health setting who fulfill HBC NCCN criteria. In a limited resources setting, in Brazil, testing the TP53 p.R337H variant with PCR is a low-cost test that should be considered at least for pts that meet the revised Chompret criteria. The overall detection rate of TP53 p.R337H carriers was lower in comparison to other Brazilian studies from the South/Southeast of the country. Both cases identified in this cohort had advanced local disease or metastatic disease at BC diagnosis, raising the concern about the importance of LFS diagnosis, and high-risk surveillance and risk reduction strategies in this subgroup of pts. Despite the low detection rate of TP53 p.R337H in this cohort, there was a high familial impact through cascade testing.

Citation Format: Tatiana S. Correa, Renata L. Sandoval, Eduarda S. Oliveira, Ana Carolina R. Leite, Luiza Nardin Weis, Maria Isabel Achatz, Claudiner P. Oliveira, Paula Fontes Asprino, Romualdo Barroso-Sousa. Frequency of germline TP53 p.R337H variant among women at risk of hereditary breast cancer in a public health system of Central-West of Brazil [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 P5-03-19.

Abstract PD18-01: Adjuvant Trastuzumab Emtansine Versus Paclitaxel plus Trastuzumab for Stage I HER2+ Breast Cancer: 5-year results and correlative analyses from ATEMPT (TBCRC033)

Background: The ATEMPT trial primary analysis found that one year of adjuvant trastuzumab emtansine (T-DM1) achieved a 3-year iDFS of 97.8% for patients with stage I HER2+ breast cancer, but was not associated with fewer clinically relevant toxicities (CRTs) compared with paclitaxel and trastuzumab (TH). In this end-of-study analysis, we report 5-year survival outcomes and correlative analyses from the trial. Methods: Patients with stage I centrally confirmed HER2+ breast cancer were randomly assigned 3:1 to adjuvant T-DM1 for one year or TH and received T-DM1 3.6 mg/kg IV every 3 weeks for 17 cycles or paclitaxel 80 mg/m2 IV with weekly trastuzumab IV followed by trastuzumab for 9 months. The co-primary objectives were to compare the incidence of CRTs between the 2 arms and to evaluate iDFS in patients receiving T-DM1. To investigate proteomic correlates of recurrence, spatial proteomic analyses were performed on samples from 13 patients experiencing iDFS events (cases) and 24 matched controls using the NanoString GeoMx Digital Spatial Profiler. The impact of HER2 heterogeneity on outcomes was investigated among 17 cases and 51 matched controls by fluorescence in-situ hybridization (FISH). HER2 genetic heterogeneity was assessed by scrutinizing the whole tumor area and defined as the occurrence of HER2 gene amplification in &gt;5% but &lt; 50% invasive tumor cells. The risk of recurrence was evaluated centrally with the HER2DX genomic assay from 225 primary tumor samples. Germline whole genome sequencing (WGS) was conducted among 55 patients experiencing T-DM1-induced thrombocytopenia and/or bleeding and 55 matched controls to identify genomic correlates for this side effect. Results: A total of 497 patients who initiated protocol therapy were included in this analysis (383 T-DM1 and 114 TH). After a median follow up 5.8 years, among patients receiving T-DM1 there were a total of 11 iDFS events, with 3 distant recurrences. The 5-year iDFS for T-DM1 was 97.0% (95% CI, 95.3-98.8%), the 5-year recurrence-free interval (RFI) was 98.6% (95% CI: 97.4-99.8%) and the 5-year overall survival (OS) for T-DM1 was 97.8 % (95% CI, 96.3-99.3%). Although the study was not powered to evaluate the efficacy of TH, among the 114 patients receiving TH, a total of 9 iDFS events were observed, including 2 distant events; the 5-year iDFS with TH was 91.3% (95% CI: 86.0-96.9%), 5-year RFI was 93.3% (95% CI: 88.6-98.2%) and 5-year OS was 97.9% (95% CI: 95.2-100%). A total of 56 samples were evaluable for heterogeneity analyses, among which 14% (n=8) harbored HER2 genetic heterogeneity. Spatial proteomic analyses found that NF1 (adjusted p=0.72 × 10-6) and CTLA-4 (adjusted p=0.15 × 10-3) were significantly upregulated in primary samples from cases, while cleaved caspase 9, CD25, GITR, ICOS, p53 and PD-L2 were significantly upregulated in controls (all with adjusted p&lt; 0.05). Germline WGS found that the top gene associations with thrombocytopenia and thrombocytopenia or bleeding were ALMS1 (p=0,19 × 10-3) and APBA3 (p=0,23 × 10-3), respectively, although none reaching the threshold for genome wide significance. rs62143195 and rs114169776 were the top single nucleotide polymorphisms associated with thrombocytopenia and thrombocytopenia or bleeding, respectively. Data on the impact of HER2 heterogeneity and of HER2DX score on survival outcomes will be presented. Conclusion: With longer follow-up, adjuvant T-DM1 confirmed outstanding long-term outcomes among patients with stage I HER2+ breast cancer, demonstrating a 5-year RFI of 98.6%. Spatial proteomic analyses identified a potential association between NF1 and CTLA-4 expression with recurrence. Details on the impact of HER2 heterogeneity and HER2DX assay on prognosis will be presented.

Citation Format: Paolo Tarantino, Nabihah Tayob, Chau T Dang, Denise Yardley, Steven J. Isakoff, Vicente Valero, Meredith Faggen, Therese Mulvey, Ron Bose, Douglas Weckstein, Antonio C. Wolff, Katherine Reeder-Hayes, Hope Rugo, Bhuvaneswari Ramaswamy, Dan Zuckerman, Lowell Hart, Vijayakrishna K. Gadi, Michael Constantine, Kit Cheng, Audrey Merrill Garrett, Paul K. Marcom, Kathy S. Albain, Patricia DeFusco, Nadine Tung, Blair Ardman, Rita Nanda, Rachel C. Jankowitz, Mothaffar Rimawi, Vandana Abramson, Paula R. Pohlmann, Catherine Van Poznak, Andres Forero-Torres, Minetta C. Liu, Kathryn Ruddy, Yue Zheng, Romualdo Barroso-Sousa, Adrienne Waks, Michelle K. DeMeo, Molly K. DiLullo, Giuseppe Curigliano, Harold Burstein, Ann Partridge, Eric Winer, Giuseppe Viale, Winnie Hui, Elizabeth A. Mittendorf, Bryan P. Schneider, Aleix Prat, Ian Krop, Sara Tolaney. Adjuvant Trastuzumab Emtansine Versus Paclitaxel plus Trastuzumab for Stage I HER2+ Breast Cancer: 5-year results and correlative analyses from ATEMPT (TBCRC033) [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 PD18-01.

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.

Adjuvant paclitaxel and trastuzumab for node-negative, HER2-positive breast cancer: final 10-year analysis of the open-label, single-arm, phase 2 APT trial

BACKGROUND

We aimed to report on long-term outcomes of patients with small, node-negative, HER2-positive breast cancer treated with adjuvant paclitaxel and trastuzumab and to establish potential biomarkers to predict prognosis.

METHODS

In this open-label, single-arm, phase 2 study, patients aged 18 years or older, with small (≤3 cm), node-negative, HER2-positive breast cancer, and an Eastern Cooperative Oncology Group performance status of 0-1, were recruited from 16 institutions in 13 cities in the USA. Eligible patients were given intravenous paclitaxel (80 mg/m²) with intravenous trastuzumab (loading dose of 4 mg/kg, subsequent doses 2 mg/kg) weekly for 12 weeks, followed by trastuzumab (weekly at 2 mg/kg or once every 3 weeks at 6 mg/kg) for 40 weeks to complete a full year of trastuzumab. The primary endpoint was 3-year invasive disease-free survival. Here, we report 10-year survival outcomes, assessed in all participants who received protocol-defined treatment, with exploratory analyses using the HER2DX genomic tool. This study is registered on ClinicalTrials.gov, NCT00542451, and is closed to accrual.

FINDINGS

Between Oct 29, 2007, and Sept 3, 2010, 410 patients were enrolled and 406 were given adjuvant paclitaxel and trastuzumab and included in the analysis. Mean age at enrolment was 55 years (SD 10·5), 405 (99·8%) of 406 patients were female and one (0·2%) was male, 350 (86·2%) were White, 28 (6·9%) were Black or African American, and 272 (67·0%) had hormone receptor-positive disease. After a median follow-up of 10·8 years (IQR 7·1-11·4), among 406 patients included in the analysis population, we observed 31 invasive disease-free survival events, of which six (19·4%) were locoregional ipsilateral recurrences, nine (29·0%) were new contralateral breast cancers, six (19·4%) were distant recurrences, and ten (32·3%) were all-cause deaths. 10-year invasive disease-free survival was 91·3% (95% CI 88·3-94·4), 10-year recurrence-free interval was 96·3% (95% CI 94·3-98·3), 10-year overall survival was 94·3% (95% CI 91·8-96·8), and 10-year breast cancer-specific survival was 98·8% (95% CI 97·6-100). HER2DX risk score as a continuous variable was significantly associated with invasive disease-free survival (hazard ratio [HR] per 10-unit increment 1·24 [95% CI 1·00-1·52]; p=0·047) and recurrence-free interval (1·45 [1·09-1·93]; p=0·011).

INTERPRETATION

Adjuvant paclitaxel and trastuzumab is a reasonable treatment standard for patients with small, node-negative, HER2-positive breast cancer. The HER2DX genomic tool might help to refine the prognosis for this population.

FUNDING

Genentech.

Abstract OT3-07-01: Real-World Data on First-line Treatment of HR-positive, HER2-negative, Metastatic Breast Cancer in Brazil (BRAVE Study/LACOG 0221)

Background: It is estimated that 50 thousand patients live with metastatic breast cancer (MBC) in Brazil. A recent Brazilian registry (LACOG 0312) on MBC demonstrated a median overall survival (OS) by breast subtype of 15 months for triple negative, 23 months for HER2 positive, and 42 months for Luminal tumors, which are very similar to developed countries except the HER2 positive group which have limited access to targeted agents in the public health system. Recently, CDK 4/6 inhibitors were approved for the treatment of HR+ HER2-negative MBC with an improvement in progression-free survival (PFS) and ribociclib and abemaciclib demonstrating benefit in OS over endocrine therapy alone, establishing the standard of care in first-line setting for this BC subtype. In Brazil, disparities exist in the incorporation of novel anticancer agents between public and private health systems limiting treatment options for patients with HR+ HER2- negative MBC in the public system, which covers most of the population. The BRAVE study aims to describe the patient journey and current patterns of care for HR+ HER2-negative MBC to identify possible gaps and how health insurance type influences treatment patterns in Brazil. Trial Design: This is an observational, retrospective cohort study. All patients diagnosed with mBC (either de novo or recurrent) in the period of January 2018 to December 2020 at participating centers will be included. Data will be collected from medical records. No interventions are proposed. Enrollment of a total of 300 patients (150 patients from public health care system and 150 patients from private health care system) is planned. ClinicalTrials.gov identifier: NCT05034393. Eligibility: Inclusion criteria: women ≥18 years old; histologically confirmed HR-positive HER2-negative invasive breast cancer; HR-positive, defined as 1% to 100% of tumor nuclei positive for ER and/or PgR as per ASCO/CAP Guideline 2020 or Allred score of ≥3; HER2-negative, defined as IHC result is 0/1+ or 2+ with ISH negative as per ASCO/CAP Guideline 2018; diagnosed with de novo or recurrent metastatic breast cancer between January 2018 and December 2020. Exclusion criteria: male BC; first-line treatment for mBC received through clinical trial. Specific Aims: Primary objective is to describe the first-line (1L) treatment of HR-positive, HER2-negative mBC in Brazil. Secondary objectives are to describe progression-free survival (PFS) in the 1L setting until month 24; describe and compare the 1L treatment of HR-positive, HER2-negative mBC and PFS until month 24 according to the health care coverage (public vs. private); describe timelines from symptoms, histopathological diagnosis, molecular test, and treatment; describe the mBC pathological characterization; describe frequency of diagnostic tests to define breast cancer molecular subtypes; describe the subsequent line of treatment and corresponding PFS; describe overall survival (OS); evaluate PFS and OS according to visceral vs. non-visceral metastatic disease, primary endocrine resistance vs. acquired endocrine resistance, de novo versus recurrent disease, public vs. private health system and pre vs postmenopausal status. Statistical Methods: No a priori sample size calculation was performed. The expected sample size of 150 patients in each group allows description of the proportion of patients using CDK 4/6 inhibitors with two-sided 90% confidence interval ranging from 53.4% to 66.6% when the expected proportion is 60% in the private health system. Present Accrual and Target Accrual: A total of 12 sites of 14 planned were activated. The first patient was enrolled on February 8, 2022. As of June 24, 2022, a total of 122 patients were enrolled, 86 from public and 36 from private health system. The target accrual of 300 patients is expected to be completed by November 2022. Results are expected to be presented by April 2023. Funding: Novartis. Acknowledgements: SAS.

Citation Format: Gustavo Werutsky, Tomás Reinert, Daniela D. Rosa, Romualdo Barroso-Sousa, Heloísa Resende, Poliana A. Signorini, Juliana G. Martins Fagundes, Jose Marcio B. Figueiredo, Eduardo Cronemberger, Aline C. Vieira, Jorge Henrique Santos Leal, Luiza Nardin Weis, Ludmila Thommen, Rafaela G. Jesus, Gustavo Gössling, José Bines. Real-World Data on First-line Treatment of HR-positive, HER2-negative, Metastatic Breast Cancer in Brazil (BRAVE Study/LACOG 0221) [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 OT3-07-01.

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 PD18-02: Adjuvant Paclitaxel and Trastuzumab Trial (APT) for Node-Negative, Human Epidermal Growth Factor Receptor 2–Positive (HER2+) Breast Cancer: final 10-year analysis

Background: The APT trial evaluated the activity of adjuvant paclitaxel and trastuzumab (TH) among patients with small, node negative HER2+ breast cancer. This regimen showed a 7-year invasive disease-free survival (iDFS) of 93%, a recurrence-free interval (RFI) of 97.5% with only four (1.0%) distant recurrences, and a 7-year overall survival (OS) of 95%. In this end-of-study analysis, we report the survival outcomes at 10 years and assess the role of HER2DX testing in predicting long-term outcomes with adjuvant TH.

Methods: APT was a single-arm multicenter investigator-initiated phase II study in which patients with HER2+ breast cancer with tumors ≤3 cm and negative nodes (one single micrometastatic node allowed) received IV weekly paclitaxel (80 mg/m2) with IV weekly trastuzumab for 12 weeks, followed by IV trastuzumab for 9 months. The primary endpoint was 3-year iDFS. Here we report 10-year iDFS, RFI, breast cancer–specific survival (BCSS) and OS. In an exploratory analysis, the risk of recurrence was evaluated with the HER2DX genomic assay.

Results: A total of 410 patients were enrolled from October 2007 to September 2010, of which 406 started the study treatment and were included in the intent to treat analysis. Median age at enrollment was 55 years (range, 24 to 85 years), and most patients (67%) had hormone receptor (HR)-positive disease. Fifty percent of patients had tumors 1.0 cm or smaller and only 9% of patients had tumors between 2 cm to 3 cm. Mean tumor size was 1.1 cm. After a median follow-up of 10.2 years (122 months), 36 iDFS events were observed, consistent with a 10-year iDFS of 89.7% (95% CI, 86.3%-93.1%). Ten-year iDFS was 90.2% (95% CI, 86.3%-94.3%) and 88.5% (95% CI, 82.4%-95.1%) for patients with HR-positive and HR-negative tumors at baseline, respectively. 10-year RFI was 96.8% (95% CI, 95.0%-98.7%), 10-year OS was 94.2% (95% CI, 91.6%-96.8%) and 10-year BCSS was 99.1% (95% CI, 98.1%-100.0%). Of the iDFS events observed in the trial, 6 were non-breast cancer related deaths and 9 were contralateral tumors, all but one locally found to be HER2-negative upon biopsy (Table 1). Among patients experiencing an iDFS event, 7 patients (1.7%) had distant recurrences, including 1 with a T2 tumor, 3 with a T1c tumor and 3 with a T1b tumor. At baseline, 6 of them had HR-positive disease, 1 had HR-negative disease, and 6 had high-grade disease. Upon biopsy of metastatic lesions, 5 of the 7 distant recurrences were locally found to be HER2+, 1 was HER2-negative and 1 had unknown HER2 status. HER2DX testing was conducted on available baseline archival tumor tissue and analyses of patients’ survival outcomes based on the HER2DX score will be presented.

Conclusion: After 10 years of follow-up, adjuvant TH confirmed excellent long-term outcomes for small, node-negative HER2+ breast cancer, with a 10-year RFI of 96.8% and a 10-year BCSS of 99.1%.

Table 1: iDFS events with adjuvant paclitaxel plus trastuzumab after 10.2 years of follow up

Citation Format: Sara Tolaney, Paolo Tarantino, Noah Graham, Nabihah Tayob, Chau T Dang, Denise Yardley, Beverly Moy, Paul K. Marcom, Kathy S. Albain, Hope Rugo, Matthew Ellis, Iuliana Shapira, Antonio C. Wolff, Lisa Carey, Romualdo Barroso-Sousa, Michelle K. DeMeo, Molly K. DiLullo, Ann Partridge, Adrienne Waks, Clifford Hudis, Ian Krop, Harold Burstein, Aleix Prat, Eric Winer. Adjuvant Paclitaxel and Trastuzumab Trial (APT) for Node-Negative, Human Epidermal Growth Factor Receptor 2–Positive (HER2+) Breast Cancer: final 10-year analysis [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 PD18-02.

Real-world treatment outcomes in HR+ HER2- metastatic breast cancer patients treated with CDK4/6 inhibitors: Results from a reference center in Brazil

BACKGROUND

Cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) have been recently developed and introduced into clinical practice.

METHODS

We retrospectively analyzed data from patients with confirmed HR+/HER2 metastatic breast cancer treated with hormonal therapy in combination with ribociclib (R), palbociclib (P), or abemaciclib (A).

OUTCOMES

median progression-free survival (mPFS), time to treatment discontinuation (mTTD), and objective response rate (ORR).

RESULTS

Between January 2016 - June 2021, 142 patients were treated with an CDK4/6i (79 P, 42 R, 21 A). The median age was 59 years and 67.6% had recurrent disease. Roughly 35.2%, 36.6%, 28.2% of the patients had 1, 2 or 3+ metastatic sites, respectively, and 55.6% of the patients received CDK4/6i as a first-line treatment. The mPFS was 28m(R) vs. 14m(P) vs. 6m(A) (P = 0.002), with a higher proportion of patients receiving R in the first-line setting. However, no difference was seen when the analysis was restricted to the first-line scenario (P = 0.193). Sixty-four patients required one dose reduction, and 19 patients required two. ORR was 76.2% (R) vs 62% (P) vs 42.9% (A). More patients achieved a complete response with R and P, with no difference in the incidence of partial response and stable disease. Adverse events occurred in 94.4% of the population, with the most common grade 3-4 AE being neutropenia (59.1%).

CONCLUSIONS

Our results confirm the efficacy and tolerability of CDK4/6i in routine clinical practice. This is the first real-world data describing and comparing the efficacy and toxicity of CDK4/6i in the Brazilian population.

Cost-effectiveness analysis of Oncotype DX from a Brazilian private medicine perspective: a GBECAM multicenter retrospective study

Background

Oncotype DX (ODX) is a validated assay for the prediction of risk of recurrence and benefit of chemotherapy (CT) in both node negative (N0) and 1-3 positive nodes (N1), hormone receptor positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) early breast cancer (eBC). Due to limited access to genomic assays in Brazil, treatment decisions remain largely driven by traditional clinicopathologic risk factors. ODX has been reported to be cost-effective in different health system, but limited data are available considering the reality of middle-income countries such as Brazil. We aim to evaluate the cost-effectiveness of ODX across strata of clinical risk groups using data from a dataset of patients from Brazilian institutions.

Methods

Clinicopathologic and ODX information were analyzed for patients with T1-T3, N0-N1, HR+/HER2- eBC who had an ODX performed between 2005 and 2020. Projections of CT indication by clinicopathologic criteria were based on binary clinical risk categorization based on the Adjuvant! Algorithm. The ODX score was correlated with the indication of CT according to TAILORx and RxPONDER data. Two decision-tree models were developed. In the first model, low and high clinical risk patients were included while in the second, only high clinical risk patients were included. The cost for ODX and CT was based on the Brazilian private medicine perspective.

Results

In all, 645 patients were analyzed; 411 patients (63.7%) had low clinical risk and 234 patients (36.3%) had high clinical risk disease. The ODX indicated low (<11), intermediate (11-25), and high (>25) risk in 119 (18.4%), 415 (64.3%), and 111 (17.2%) patients, respectively. Among 645 patients analyzed in the first model, ODX was effective (5.6% reduction in CT indication) though with an incremental cost of United States Dollar (US$) 2288.87 per patient. Among 234 patients analyzed in the second model (high clinical risk only), ODX led to a 57.7% reduction in CT indication and reduced costs by US$ 4350.66 per patient.

Conclusions

Our study suggests that ODX is cost-saving for patients with high clinical risk HR+/HER2- eBC and cost-attractive for the overall population in the Brazilian private medicine perspective. Its incorporation into routine practice should be strongly considered by healthcare providers.

PD-1/PD-L1 inhibition enhances chemotherapy-induced neuropathic pain by suppressing neuroimmune antinociceptive signaling

Cytotoxic agents synergize with immune checkpoint inhibitors and improve outcomes for patients with several cancer types. Nonetheless, a parallel increase in the incidence of dose-limiting side effects, such as peripheral neuropathy, is often observed. Here, we investigated the role of the PD-1/PD-L1 axis in the modulation of paclitaxel-induced neuropathic pain. We found that human and mouse neural tissues, including the dorsal root ganglion (DRG), expressed basal levels of PD-1 and PD-L1. During the development of paclitaxel-induced neuropathy, an increase in PD-L1 expression was observed in macrophages from the DRG. This effect depended on Toll-like receptor 4 (TLR4) activation by paclitaxel. Furthermore, PD-L1 inhibited pain behavior triggered by paclitaxel or formalin in mice, suggesting that PD-1/PD-L1 signaling attenuates peripheral neuropathy development. Consistent with this, we observed that the combined use of anti–PD-L1 plus paclitaxel increased mechanical allodynia and chronic neuropathy development induced by single agents. This effect was associated with higher expression of inflammatory markers (Tnf, Il6, and Cx3cr1) in peripheral nervous tissue. Together, these results suggest that PD-1/PD-L1 inhibitors enhance paclitaxel-induced neuropathic pain by suppressing PD-1/PD-L1 antinociceptive signaling.

What can we learn from more than 1,000 Brazilian patients at risk of hereditary cancer?

Background

Identifying individuals at a higher risk of developing cancer is a major concern for healthcare providers. Cancer predisposition syndromes are the underlying cause of cancer aggregation and young-onset tumors in many families. Germline genetic testing is underused due to lack of access, but Brazilian germline data associated with cancer predisposition syndromes are needed.

Methods

Medical records of patients referred for genetic counseling at the Oncogenetics Department at the Hospital Sírio-Libanês (Brasília, DF, Brazil) from July 2017 to January 2021 were reviewed. The clinical features and germline findings were described. Detection rates of germline pathogenic/likely pathogenic variant (P/LPV) carriers were compared between international and Brazilian guidelines for genetic testing.

Results

A total of 1,091 individuals from 985 families were included in this study. Most patients (93.5%) had a family history of cancer, including 64% with a family member under 50 with cancer. Sixty-six percent of patients (720/1091) had a personal history of cancer. Young-onset cancers (&lt;50 years old) represented 62% of the patients affected by cancer and 17% had multiple primary cancers. The cohort included patients with 30 different cancer types. Breast cancer was the most prevalent type of cancer (52.6%). Germline testing included multigene panel (89.3%) and family variant testing (8.9%). Approximately 27% (236/879) of the tested patients harbored germline P/LPVs in cancer susceptibility genes. BRCA2, BRCA1, and TP53 were the most frequently reported genes, corresponding to 18.6%, 14.4%, and 13.5% of the positive results, respectively. Genetic testing criteria from international guidelines were more effective in identifying carriers than the Brazilian National Agency of Supplementary Health (ANS) criteria (92% vs. 72%, p&lt;0.001). Forty-six percent of the cancer-unaffected patients who harbored a germline P/LPV (45/98) would not be eligible for genetic testing according to ANS because they did not have a family variant previously identified in a cancer-affected relative.

Conclusion

The high detection rate of P/LPVs in the present study is possibly related to the genetic testing approach with multigene panels and cohort’s characteristics, represented mainly by individuals with a personal or family history of young-onset cancer. Testing asymptomatic individuals with suspicious family history may also have contributed to a higher detection rate. A significant number of carriers would not have been identified using ANS criteria for genetic testing.

Management of patients with early-stage triple-negative breast cancer following pembrolizumab-based neoadjuvant therapy: What are the evidences?

New therapy options have changed the treatment landscape of early-stage triple-negative breast cancer (TNBC) in recent years. Most patients are candidates for neoadjuvant chemotherapy, which helps to downstage the tumor and tailor adjuvant systemic therapy based on pathologic response. Capecitabine, pembrolizumab, and olaparib have been incorporated into the armamentarium of adjuvant treatment for selected patients. The KEYNOTE-522 trial, that demonstrated the benefit of pembrolizumab, given in addition to neoadjuvant chemotherapy and adjuvantly after surgery, represented a paradigm shift for early-stage TNBC treatment. Pembrolizumab was continued in the adjuvant setting irrespective of response to neoadjuvant therapy, and other adjuvant therapies were not administered in the trial. Many questions were then raised on the selection of adjuvant therapy regimens for patients with residual disease (RD). Prior to the routine use of immune-checkpoint inhibitors (ICI), the value of adjuvant capecitabine for patients with RD after neoadjuvant polychemotherapy was demonstrated. Given the poor prognosis of some patients with RD after neoadjuvant chemo-immunotherapy, while the survival advantage of adding capecitabine during the adjuvant phase of pembrolizumab is unknown, it does appear safe and can be considered. Regarding patients harboring germline BRCA mutations with RD after neoadjuvant ICI-containing regimens, the combination of olaparib with pembrolizumab can be an option based on existing safety data.

Multidimensional Molecular Profiling of Metastatic Triple-Negative Breast Cancer and Immune Checkpoint Inhibitor Benefit

PURPOSE

In metastatic triple-negative breast cancer (mTNBC), consistent biomarkers of immune checkpoint inhibitor (ICI) therapy benefit remain elusive. We evaluated the immune, genomic, and transcriptomic landscape of mTNBC in patients treated with ICIs.

METHODS

We identified 29 patients with mTNBC treated with pembrolizumab or atezolizumab, either alone (n = 9) or in combination with chemotherapy (n = 14) or targeted therapy (n = 6), who had tumor tissue and/or blood available before ICI therapy for whole-exome sequencing. RNA sequencing and CIBERSORTx-inferred immune population analyses were performed (n = 20). Immune cell populations and programmed death-ligand 1 expression were assessed using multiplexed immunofluorescence (n = 18). Clonal trajectories were evaluated via serial tumor/circulating tumor DNA whole-exome sequencing (n = 4). Association of biomarkers with progression-free survival and overall survival (OS) was assessed.

RESULTS

Progression-free survival and OS were longer in patients with high programmed death-ligand 1 expression and tumor mutational burden. Patients with longer survival also had a higher relative inferred fraction of CD8+ T cells, activated CD4+ memory T cells, M1 macrophages, and follicular helper T cells and enrichment of inflammatory gene expression pathways. A mutational signature of defective repair of DNA damage by homologous recombination was enriched in patients with both shorter OS and primary resistance. Exploratory analysis of clonal evolution among four patients treated with programmed cell death protein 1 blockade and a tyrosine kinase inhibitor suggested that clonal stability post-treatment was associated with short time to progression.

CONCLUSION

This study identified potential biomarkers of response to ICIs among patients with mTNBC: high tumor mutational burden; presence of CD8+, CD4 memory T cells, follicular helper T cells, and M1 macrophages; and inflammatory gene expression pathways. Pretreatment deficiencies in the homologous recombination DNA damage repair pathway and the absence of or minimal clonal evolution post-treatment may be associated with worse outcomes.

Cost-effectiveness analysis of Oncotype DX from a Brazilian private medicine perspective: A GBECAM multicenter retrospective study

e18822

Background: Oncotype DX (ODX) is a validated tool for the prediction of risk of recurrence and benefit of chemotherapy (CH) in both node negative (N0) and positive (N1), hormone receptor positive (HR+), HER2 negative (HER2-) early breast cancer (eBC). Due to limited access to novel genomic assays in Brazil, treatment decisions remain largely driven by traditional clinicopathologic risk factors. ODX has been reported to be cost-effective, but limited data is available considering the reality of middle-income countries such as Brazil. We aim to evaluate the cost-effectiveness of ODX across strata of clinical risk groups using data from a large dataset of patients from various Brazilian institutions. Methods: Clinicopathologic and ODX information were analyzed for patients with T1-T3, N0-N1, HR+/HER2- eBC who had an ODX performed between 2005 and 2020. Projections of CH indication by clinicopathologic criteria were based on binary clinical risk categorization based on the Adjuvant! algorithm, as used in the MINDACT study. The ODX score was correlated with the indication of CH according to TAILORx and RxPONDER data. Two decision-tree models were developed. In the first model, low and high clinical risk patients were included the model. In the second model, only high clinical risk patients were included. The cost for ODX and CH (U$2,846 and U$14,464, respectively) were based on the Brazilian private medicine perspective. Uncertainty was assessed using deterministic and probabilistic sensitivity analyses. Results: Six hundred and forty-five patients were analyzed. 411 patients (63.7%) had low clinical risk and 234 patients (36.3%) had high clinical risk disease. The ODX indicated low (< 11), intermediate (11-25) and high (> 25) risk in 119 (18.4%), 415 (64.3%) and 111 (17.2%) patients, respectively. Among 645 patients analyzed in the first model, 234 (36.2%) had clinical and 198 (30.6%) had genomic indication for CH, respectively. In this model, ODX was modestly effective (5.6% reduction in CH indication) though with an incremental cost of US$ 2,040 per patient. Among 234 patients analyzed in the second model (high clinical risk only), 99 (42.3%) patients had genomic indication of CH. In this model, ODX led to a 57.7% reduction in CH indication and reduced costs by US$5,491 per patient (table). The results remained robust in the 1,000 probabilistic simulations. Conclusions: Our study suggests that ODX is cost-saving for patients with high clinical risk HR+/HER2- eBC in the perspective of the Brazilian private health system. Its incorporation into routine practice should be strongly considered by health care providers.[Table: see text]

Targeting PARP1 to Enhance Anticancer Checkpoint Immunotherapy Response: Rationale and Clinical Implications

Reinvigorating the antitumor immune response using immune checkpoint inhibitors (ICIs) has revolutionized the treatment of several malignancies. However, extended use of ICIs has resulted in a cancer-specific response. In tumors considered to be less immunogenic, the response rates were low or null. To overcome resistance and improve the beneficial effects of ICIs, novel strategies focused on ICI-combined therapies have been tested. In particular, poly ADP-ribose polymerase inhibitors (PARPi) are a class of agents with potential for ICI combined therapy. PARPi impairs single-strand break DNA repair; this mechanism involves synthetic lethality in tumor cells with deficient homologous recombination. More recently, novel evidence indicated that PAPRi has the potential to modulate the antitumor immune response by activating antigen-presenting cells, infiltrating effector lymphocytes, and upregulating programmed death ligand-1 in tumors. This review covers the current advances in the immune effects of PARPi, explores the potential rationale for combined therapy with ICIs, and discusses ongoing clinical trials.

Abstract P4-01-06: Genomic and transcriptomic analysis reveals known and novel resistance mechanisms to CDK4/6 inhibitors and sensitivity factors for the response to triplet therapy (palbociclib + everolimus + exemestane) in a phase I/IIb study in hormone-receptor positive (HR+)/HER2- metastatic breast cancer (MBC) after progression on a CDK4/6 inhibitor (CDK4/6i)

Background: Multiple studies in HR+/HER2- MBC have identified a variety of genomic resistance mechanisms to CDK4/6 inhibitors, but the complete landscape of resistance mechanisms is still being elucidated. A clinical trial evaluating the benefit of continued CDK4/6 blockade after disease progression on a prior CDK4/6i provides a unique setting to study the landscape of resistance to CDK4/6 inhibitors. Methods: We analyzed genomic data from a Phase I/II trial (NCT02871791) of triplet therapy: palbociclib (CDK4/6i) + everolimus (mTOR inhibitor) + exemestane (endocrine therapy) in patients (pts) with HR+/HER2− MBC who had progressed on prior CDK4/6i. For the phase IIa pts, a research tumor biopsy at baseline and serial research blood collection for circulating tumor DNA (ctDNA) analysis were mandatory. Additionally, when possible, we acquired tumor biopsies that preceded the patient's prior exposure to a CDK4/6i, which would allow us to identify acquired genomic resistance mechanisms to the prior CDK4/6i. The genomic data consisted of whole exome sequencing (WES) data from 23 tumor biopsies (19 pts) and 17 ctDNA samples (12 pts), and RNA sequencing (RNA-seq) from 27 tumors (22 pts). 4 pts had a biopsy or ctDNA sample at baseline and a biopsy that preceded their prior exposure to a CDK4/6i. WES data was used to identify mutations and copy number alterations, which was used to perform evolutionary analysis on the pts with multiple biopsies or ctDNA samples. RNA-seq data was used to make research-grade PAM50 calls and calculate gene expression signature scores. Results: For the baseline biopsy or ctDNA sample of most pts, we found genomic alterations in previously identified pathways and genes that could explain the tumor’s resistance to the prior CDK4/6i (16/19 pts) or to the prior endocrine therapies (17/19 pts). These pathways and genes include the PI3K/AKT/MTOR pathway (e.g. PTEN, AKT), the RAS/MAPK pathway (e.g. NF1), receptor tyrosine kinases (RTKs) (e.g. ERBB2, FGFR1), cell-cycle genes (e.g. RB1), and estrogen receptor signaling (e.g. ESR1, FOXA1). Two novel potential genomic resistance mechanisms in these pathways were identified: an activating MTOR T1977R mutation (PI3K/AKT/MTOR pathway) and an activating BRAF V600E mutation (RAS/MAPK pathway). Notably, the patient with the activating MTOR mutation responded to the triplet therapy (progression free survival of 8 months), consistent with prior work linking these mutations to sensitivity to everolimus. Evolutionary analysis revealed metastatic tumors with distinct lineages but derived from the same primary tumor (e.g. two lineages, one with activating ESR1 mutations and one with an activating MTOR mutation), some of which converged to activating the same pathway (e.g. two lineages with distinct activating ERBB2 mutations). Transcriptomic analysis found that activating mutations in ERBB2 and BRAF were correlated with the HER2-E PAM50 and that the expression signatures for MTOR and RTKs were correlated with clinical benefit to triplet therapy. Conclusions: Analysis of the genomic and transcriptomic data of baseline biopsies and ctDNA samples from NCT02871791 not only recapitulates genes and pathways previously implicated in resistance to endocrine therapy and CDK4/6i but also identified novel potential mechanisms of resistance including activating mutations in BRAF and MTOR. Evolutionary analysis demonstrates the complexity of resistance including both convergent and divergent paths to resistance. Integration of genomic and transcriptomic data may better identify pts likely to respond to CDK4/6i combinations.

Citation Format: Jorge Gomez Tejeda Zanudo, Romualdo Barroso-Sousa, Esha Jain, Jorge Buendia-Buendia, Tianyu Li, Nabihah Tayob, Rebecca Rees, Alyssa Pereslete, Arlindo R. Ferreira, Daniel L. Abravanel, Karla Helvie, Ann H. Partridge, Beth Overmoyer, Eric P. Winer, Nikhil Wagle, Sara M. Tolaney. Genomic and transcriptomic analysis reveals known and novel resistance mechanisms to CDK4/6 inhibitors and sensitivity factors for the response to triplet therapy (palbociclib + everolimus + exemestane) in a phase I/IIb study in hormone-receptor positive (HR+)/HER2- metastatic breast cancer (MBC) after progression on a CDK4/6 inhibitor (CDK4/6i) [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 P4-01-06.

Abstract GS2-10: Nimbus: A phase 2 trial of nivolumab plus ipilimumab for patients with hypermutated her2-negative metastatic breast cancer (MBC)

Background: While high tumor mutational burden (TMB-H) has been used as a tissue-agnostic biomarker for approval of immune checkpoint inhibitors (ICI), there is a paucity of data regarding efficacy of ICI in TMB-H MBC. The aim of this study was to evaluate if patients with TMB-H HER2-negative MBC benefit from the combination of nivolumab plus ipilimumab. Methods: This is an open-label, single-arm, multicenter, phase 2 study assessing the efficacy of nivolumab 3 mg/kg intravenously (IV) every 14 days plus ipilimumab 1 mg/kg IV every 6 weeks in subjects with TMB-H HER2-negative MBC. Eligible patients were required to have measurable HER2-negative MBC, TMB ≥9 Mut/Mb assessed by a cancer-gene panel evaluating &gt; 300 genes and performed in a CLIA-certified laboratory, and 0-3 prior lines of chemotherapy in the advanced setting. The primary objective was overall response rate (ORR) according to RECIST 1.1. Secondary objectives include safety and tolerability, progression-free survival (PFS), and overall survival (OS). The study followed a two-stage design. In the first stage, 14 patients were enrolled. The study required at least 1 objective response in order to continue to the second stage where an additional 16 patients were enrolled. At least 4 objective responses among the 30 patients would suggest the regimen is worthy of further study. If the true response rate is 25%, the chance that the regimen is declared worthy of further study is &gt; 90%. Tumor biopsies, peripheral blood mononuclear cells, circulating tumor DNA, and stool collection were mandatory and were obtained at baseline and on treatment (end of cycle 1). Results: From February 2019 to June 2021, 31 patients were enrolled across 3 different academic institutions. Among 30 patients who initiated study treatment, the median age was 63 yo, 20 had hormone-receptor positive (HR+) breast cancer and 10 had triple-negative breast cancer (TNBC), and median number of prior lines of chemotherapy was 1.5 (0-3). Among the 10 patients with TNBC, PD-L1 status was known in 7 patients (3 positive and 4 negative). Median TMB was 10.9 Mut/Mb and 16.7% (n = 5) of patients had a TMB ≥14 mut/Mb. After a median follow-up of 9.7 (4.4 - 16.4) months, 4 (13.3%) patients achieved a confirmed objective response (all partial responses) meeting the primary endpoint of this study. The median duration of response has not been reached and 3 of these patients are still progression-free for at least 15 months. Two patients have short follow-up, and one has an unconfirmed partial response and the other has a stable disease at the time of the data cut. Median PFS and OS was respectively 1.4 (95% CI 1.3 - 9.5) months and 8.8 (95% CI 4.2 - not reached). Exploratory analysis did not show a difference in response rate according to HR status and PD-L1 status (data not shown) but tumors with TMB ≥14 mut/Mb had a response rate of 60% vs 4% in the group with TMB between ≥9 and &lt;14 mut/Mb (p = 0.01). The treatment was associated with a favorable toxicity profile, with only three patients developing grade 3 immune-related adverse events (1 had adrenal insufficiency and cardiac troponin elevation, and two other had hepatitis). There were no reported grade 4-5 events. Data regarding TIL, PD-L1 and CD8 immunohistochemistry will be presented at the symposium. Conclusion: This study of nivolumab plus ipilimumab in TMB-H MBC achieved the primary endpoint and demonstrated a confirmed ORR of 13.3%. While patients with TMB ≥ 14 Mut/Mb were minority in this study, the 60% of ORR in this subgroup highlights the need to better evaluate the optimal TMB cutoff to predict benefit to immunotherapy in MBC.

Citation Format: Romualdo Barroso-Sousa, Tianyu Li, Sangeetha Reddy, Leisha A. Emens, Beth Overmoyer, Paulina Lange, Molly K Dilullo, Victoria Attaya, Jeffrey Kimmel, Eric P. Winer, Elizabeth A. Mittendorf, Nabihah Tayob, Sara M. Tolaney. Nimbus: A phase 2 trial of nivolumab plus ipilimumab for patients with hypermutated her2-negative metastatic breast cancer (MBC) [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 GS2-10.

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.

Cancer control in Latin America and the Caribbean: recent advances and opportunities to move forward

The increasing burden of cancer represents a substantial problem for Latin America and the Caribbean. Two Lancet Oncology Commissions in 2013 and 2015 highlighted potential interventions that could advance cancer care in the region by overcoming existing challenges. Areas requiring improvement included insufficient investment in cancer control, non-universal health coverage, fragmented health systems, inequitable concentration of cancer services, inadequate registries, delays in diagnosis or treatment initiation, and insufficient palliative services. Progress has been made in key areas but remains uneven across the region. An unforeseen challenge, the COVID-19 pandemic, strained all resources, and its negative effect on cancer control is expected to continue for years. In this Series paper, we summarise progress in several aspects of cancer control since 2015, and identify persistent barriers requiring commitment of additional resources to reduce the cancer burden in Latin America and the Caribbean.