Abstract PO2-17-06: Real world treatment patterns and clinical outcomes by germline BRCA (gBRCA) mutation status in patients with HER2-negative early breast cancer in the US community oncology setting: a retrospective observational chart-review study

Abstract Background: Women with early-stage breast cancer (eBC) who have inherited BRCA1 or BRCA2 mutations (gBRCAm) are typically diagnosed at a younger age and often require more intensive treatment. In the randomized, double-blind OlympiA trial of HER2-negative (HER2–) gBRCAm patients, olaparib, a targeted poly (ADP-ribose) polymerase inhibitor (PARPi), significantly improved invasive disease free survival (IDFS), distant disease free survival (DDFS) and overall survival (OS) and was subsequently approved for adjuvant treatment of gBRCAm HER2– high-risk eBC patients. This study examined the real-world patient characteristics, treatment patterns and clinical outcomes by gBRCA status among patients with HER2– eBC in a US community oncology setting prior to olaparib US approval for treatment of eBC. Methods: This retrospective observational study used chart review data from The US Oncology Network's iKnowMed database to examine adult patients diagnosed with HER2– eBC (stage I-III) initiating systemic neoadjuvant or adjuvant therapy with chemotherapy and/or endocrine therapy between January 1, 2012 and December 31, 2018. Patients with valid gBRCAm test results (all gBRCAm and randomly selected BRCAwt patients) were included and followed through December 31, 2021. Patients were excluded if they had HER2+ tumors and progressed to stage IV within 6 months after initiation of neoadjuvant therapy or were diagnosed with another primary cancer. Descriptive analyses assessed patient characteristics. Kaplan Meier methods and multivariate Cox proportional hazard models (CPHM) were used to evaluate IDFS, DDFS and OS by gBRCA status and by HR+/HER2– or TNBC eBC subsets. Results: Among 298 BC patients meeting initial criteria, 42% had gBRCAm (n=124, 43% hormone receptor positive HR+, 56% triple-negative BC TNBC, 1% unknown), and 58% had gBRCAwt (n=174, 74% HR+, 22% TNBC). Median (interquartile) age at surgery was numerically lower in gBRCAm (45 36,55 years) than gBRCAwt (48 41,55 years) patients. A numerically higher proportion of gBRCAm patients received neoadjuvant therapy compared with gBRCAwt (Neoadj: gBRCAm 37.1% vs gBRCAwt 12.6%) but the reverse was true for adjuvant (Adj: gBRCAm 42.7% vs gBRCAwt 65.5%) and neoadjuvant + adjuvant use was numerically similar (Neoadj+Adj: gBRCAm 20.1% vs gBRCAwt 21.8%). The majority of TNBC patients received neoadjuvant therapy while the majority of HR+ patients received adjuvant therapy (Neoadj: TNBC 51.4% vs HR+ 6.6%, Adj: TNBC 29.0% vs HR+ 71.4%, Neoadj+Adj: TNBC 19.6% vs HR+ 22.0%). Median IDFS, DDFS, and OS in both study cohorts were not reached. Median follow-up from surgery was 5 years (overall 59.0 months; gBRCAm 50.6 months; gBRCAwt 61.3 months). At 60 months, in gBRCAm and gBRCAwt respectively, estimated IDFS were 85.5% and 90.9%, estimated DDFS 88.1% and 92.2%, and estimated survival 91.9% and 95.2%. At 60 months, in HR+/HER2– and TNBC respectively, estimated IDFS were 92.4% and 81.2%, estimated DDFS 93.9% and 85.7%, and estimated survival 96.3% and 90.9%. CPHM results showed that risks of invasive disease (HR 1.74; 95% CI 0.83-3.64; p=0.15), distant disease (HR 1.24; 95% CI 0.50-3.07; p=0.65) and death (HR 1.79; 95% CI 0.52-6.13; p=0.353) were similar between gBRCAm and gBRCAwt patients. Between HR+/HER2– and TNBC patients, risks of invasive disease (HR=0.63; 95% CI 0.21-1.89; p=0.41), distant disease (HR=0.42; 95% CI 0.11-1.67; p=0.22) and death (HR 0.48; 95% CI 0.09-2.70; p=0.41) were similar. Conclusions: This real-world chart review study of data through 2021 (before PARPi approval for eBC) with limited follow up of 5 years found that gBRCAm patients had a numerically shorter survival (IDFS, DDFS and OS) than gBRCAwt, but this difference was not statistically significantly different. Given that the follow-up period was too short to draw conclusions, further studies examining clinical outcomes over a longer follow-up period after approval of PARPi may be of interest. Citation Format: Jay Andersen, Jagadeswara Earla, Nicole Fulcher, Juliet Ndukum, Nicholas J Robert, Mark Robson, Weiyan Li, Jaime Mejia. Real world treatment patterns and clinical outcomes by germline BRCA (gBRCA) mutation status in patients with HER2-negative early breast cancer in the US community oncology setting: a retrospective observational chart-review study abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-17-06.