Treatment patterns and clinical outcomes among patients (pts) with HER2+ advanced breast cancer (ABC) and germline BRCA1/2 mutation(s) (gBRCA1/2mut): Results from a US real-world study.

Abstract

e13076 Background: g BRCA1/2mut ABC represents ~5% of all breast cancer (BC) including pts with HER2+ BC. While HER2-targeted therapy remains an effective tx for those pts, limited information is available on the use and effectiveness of PARP inhibitors (PARPi) for pts with HER2+ g BRCA1/2mut ABC. Recently, NCCN updated its guidelines (v1.2020) to support the use of PARPi in pts with g BRCA1/2mut metastatic BC regardless of subtype. In order to establish a baseline reference point, we assessed real-world tx patterns and clinical outcomes among pts with g BRCA1/2mut HER2+. Methods: Oncologists retrospectively reviewed charts (July-Oct 2019) of randomly selected pts ≥18 y, with g BRCA1/2mut HER2+ABC who received ≥1 cytotoxic chemotherapy (CT) regimen(s) for ABC between Jan 2013-April 2018. Descriptive analysis was performed for 1st line ABC tx patterns. Clinical outcomes (1st line ABC PFS rates) were estimated using the Kaplan-Meier method. PARPi clinical outcomes data was immature given its recent launch. Additional analyses evaluating outcomes in pts receiving PARPi are planned. Results: Of the 225 pts with g BRCA1/2mut ABC included in the study, 48 (21%) female pts had HER2+ disease. Of the g BRCA1/2mut HER2+ pts, 77% were white with a median age of 58 y. Clinical characteristics: 42% HR+/HER2+, 56% HR-/HER2+, 2% had unknown HR/HER2+ ABC. Txs in the 1st line setting for HR+/HER2+ ABC pts (n = 20) included: CT (75%), CT + HER2-targeted therapy (25%) (Table). First-line txs used for HR-/HER2+ ABC pts (n = 27) included: CT + HER2-targeted therapy (78%), CT (15%), other (7%) (Table). 12-month PFS for 1st line HR+/HER2+ pts was 73% and for HR-/HER2+ pts was 69% (Table). Later line tx patterns will be presented. Conclusions: In this analysis of pts with g BRCA1/2mut HR+/HER2+, unexpectedly low rates of HER2-targeted therapy were observed. As expected, high rates of HER2-targeted therapy with CT were observed among g BRCA1/2mut HR-/HER2+ pts. Clinical outcome findings demonstrate the need for more efficacious tx options. Studies assessing clinical outcomes among g BRCA1/2mut HER2+ ABC pts receiving PARPi +/- HER2-targeted tx are warranted. This is a limited sample size; additional data collection including median PFS is ongoing. [Table: see text]