Abstract P2-15-06: BRCA1/2 status, treatment patterns and safety outcomes in HER2- advanced breast cancer (ABC): Results from a US real-world study
Authors: Lux Michael P. , Lewis Katie , Rider Alex , Niyazov Alexander 
Published: March 2020

Background: Mutations in breast cancer susceptibility genes 1 and 2 (BRCA1/2) are known risk factors for developing breast cancer. Using the Adelphi Disease Specific Program, we assessed differences in real-world treatment patterns and safety outcomes based on BRCA1/2 mutation status in the US. Methods: Oncologists extracted data from medical charts in US adult women with human epidermal growth factor receptor 2-negative (HER2-) advanced breast cancer (ABC) via the Adelphi Advanced Breast Cancer Disease Specific Program. Data drawn from two different years of data collection (2015 and 2017) were merged across common variables (e.g. age, hormone receptor status, BRCA1/2 testing rates, BRCA status). Patients (pts.) were categorized into 3 mutually exclusive cohorts; BRCA mutations (BRCAm), wild type (BRCAwt), and unknown status (BRCAunk). BRCA1/2 testing rates were analyzed via Fisher Exact tests. Treatments received and adverse event (AE) rates were compared between BRCAm and BRCAwt using Fisher Exact tests. Results: The study included 1,285 US adult women with HER2- ABC; 75% pts were hormone receptor (HR)+/HER2-, 23% triple negative breast cancer (TNBC), and 2% had an unknown HR status. Overall, 50% of the 1,285 pts. received ≥1 BRCA1/2 test at the time of data abstraction [43% HR+/HER2-, 72% TNBC (P&lt;0.001)]. Out of the BRCA1/2 tested pts. (n=648), 112 (17%) were identified as BRCAm, 448 (69%) as BRCAwt, and 88 (14%) as BRCAunk. Pts. with HR+/HER2- ABC and BRCAm were more likely to receive a 1st line chemotherapy (CT) based regimen compared to BRCAwt (62% vs 49%; P=0.098) and less likely to receive endocrine +/- targeted therapies (36% vs 51%; P=0.051) [Table 1]. TNBC treatments consisted primarily of CT based regimens and were similar between BRCAm vs BRCAwt, (77% vs 80%; P=0.802) [Table 1]. Pts. with BRCAm (HR+/HER2-, TNBC, and unknown HR status) were significantly more likely to experience ≥1 AEs compared with those with BRCAwt (57% vs 33%; P&lt;0.001). Conclusions: In this study of US adult women with HER2- ABC, significantly lower BRCA1/2 testing rates were observed among HR+/HER2- vs TNBC pts. Pts. with HR+/HER2- and BRCAm were less likely to receive endocrine +/-targeted therapy and more likely to receive a chemotherapy-based regimen than those with HR+/HER2- and BRCAwt. Pts. with BRCAm were significantly more likely to report experiencing ≥1 adverse event than those with BRCAwt. Opportunities exist to improve safety outcomes in HER2- ABC pts. with BRCAm. Funding: Pfizer Inc.

Table 1. 1st line ABC Treatment Patterns Based on BRCA Status and HR SubtypeHR+/HER2-TNBCTreatments Received No. (%)BRCAm (N=53)BRCAwt (N=265)P valuesBRCAm (N=31)BRCAwt (N=111)P valuesCT based33 (62)130 (49)0.09824 (77)89 (80)0.802Endocrine +/-targeted19 (36)135 (51)0.0516 (19)13 (12)0.369Othera1 (2)0 (0)0.1671 (3)9 (8)0.691aIncludes “best supportive care” or “other therapy”

Citation Format: Michael P. Lux, Katie Lewis, Alex Rider, Alexander Niyazov. BRCA1/2 status, treatment patterns and safety outcomes in HER2- advanced breast cancer (ABC): Results from a US real-world study [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P2-15-06.