Abstract P6-08-09: BRCA1/2 testing in adult women with 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 gene 1 or 2 (BRCA1/2) are known risk factors for developing cancer, especially for breast cancer (BC) and ovarian cancer (OC). Recently, BC guidelines have expanded the eligibility criteria for BRCA1/2 testing. This real-world study assessed somatic and/or germline BRCA1/2 testing rates in human epidermal growth factor receptor 2-negative (HER2-) adult women with advanced breast cancer (ABC) in the United States (US). Methods: Patient (pt.) demographics/clinical characteristics in adult women with HER2- ABC were abstracted from pt. medical charts by oncologists via the Adelphi Advanced Breast Cancer Disease Specific Program. Data collected from 2 different years (2015 and 2017) were merged across common variables (e.g. age, hormone receptor status, BRCA1/2 testing rates, BRCA status). Differences in pt. demographics/characteristics among BRCA1/2 tested/untested pts. were analyzed via t-tests and Fisher exact tests. BRCA1/2 testing rates were analyzed via Fisher exact tests. Analyses of BRCA1/2 testing rates were stratified by hormone receptor status [hormone receptor positive (HR+)/HER2- or triple negative breast cancer (TNBC)] and HR status by family history (FHx) of BC or OC. Results: 1,285 records were provided by 176 oncologists in the US. The mean age was 62.6 yrs. 75% of pts. were HR+/HER2-, 23% were TNBC, and 2% had an unknown HR status. Compared to BRCA1/2 untested pts., BRCA1/2 tested pts. were significantly younger [59.2 vs 66.1 yrs. (p&lt;0.001)] and significantly more likely to have TNBC [33% vs 13% (p&lt;0.001)]. Additionally, pts. who received a BRCA1/2 test were significantly more likely to have received surgery [18% vs 9% (p=0.006)]. The BRCA1/2 testing rate observed for the overall sample was 50% with significantly lower BRCA1/2 testing seen among HR+/HER2- vs TNBC pts [43% vs 72% (p&lt;0.001)]. Among HR+/HER2-, lower BRCA1/2 testing rates were observed among pts. known not to have a FHx of BC or OC (Table 1). Conclusions: In this real-world analysis of adult women with HER2- ABC, pts. who received BRCA1/2 testing were significantly younger and more likely to have received surgery vs BRCA1/2 untested pts. Among HER2- ABC pts., significantly lower BRCA1/2 testing rates were observed in HR+/HER2- vs TNBC; among HR+/HER2- pts., significantly lower BRCA1/2 testing rates were observed among pts. known not to have a FHx of BC or OC. With the broadening of testing eligibility criteria in BC guidelines, there is a high need to increase BRCA1/2 testing rates which may inform treatment decisions based on BRCA status. Funding: Pfizer Inc.

Table 1. BRCA1/2 Testing by HR Status and known FHx of BC or OCHR+/HER2- with FHx (n=141)HR+/HER2- without FHx (n=713)TNBC with FHx (n=48)TNBC without FHx (n=211)aPts. tested No. (%)97 (69)289 (41)36 (75)146 (69)P Value&lt;0.0010.487aPts. unsure of their family history (n=172) were excluded from this analysis

Citation Format: Michael P. Lux, Katie Lewis, Alex Rider, Alexander Niyazov. BRCA1/2 testing in adult women with 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 P6-08-09.