Abstract PS7-66: Real-world clinical outcomes of patients with BRCA-mutated (BRCAm) HER2-negative metastatic breast cancer: A CancerLinQ^®study

Abstract Background: Limited epidemiological data exist on the real-world outcomes in patients with BRCA-mutated (BRCAm), HER2− metastatic breast cancer (mBC). This study describes clinical outcomes in this population according to germline BRCA mutation (gBRCAm) and hormone receptor (HR) status. Methods: Patients diagnosed with HER2− mBC between January 1, 2010 and December 31, 2018 were retrospectively selected from the American Society of Clinical Oncology (ASCO)’s CancerLinQ Discovery® database. The primary objective was to describe, as a surrogate for progression-free survival, the time to first subsequent therapy or death (TFST; whichever came first), calculated from date of mBC diagnosis, according to gBRCAm status (gBRCAm, gBRCA wild-type [gBRCAwt] or unknown gBRCA [gBRCAu]) and HR status (+/−). TFST was also calculated from first-line systemic therapy initiation. The secondary objective was to describe overall survival (OS), calculated from date of mBC diagnosis. Kaplan-Meier medians and 95% confidence intervals (CIs) were estimated. Results: 3744 patients with HER2− mBC were identified (gBRCAwt, n=460; gBRCAm, n=83; gBRCAu, n=3201); 2738 patients were HR+. Median (Q1, Q3) age was 63.0 (54.0, 73.0) years. Median (95% CI) TFST (months), calculated from date of mBC diagnosis, was 9.2 (8.6, 9.9) in HR+ patients, 5.4 (5.1, 6.0) in HR− patients, and 7.1 (5.0, 9.2), 6.9 (6.1, 8.1) and 8.4 (7.9, 9.1) in gBRCAm, gBRCAwt and gBRCAu cohorts, respectively. Median (95% CI) OS (months) was 34.30 (32.70, 36.40) in HR+ patients, 12.0 (11.1, 13.3) in HR− patients, and 31.5 (23.1, 42.8), 34.7 (28.9, 44.5), 27.6 (26.1, 29.5) in gBRCAm, gBRCAwt and gBRCAu cohorts, respectively. Median TFST and OS stratified by both HR and BRCA mutation status are shown in Table 1. Conclusions: When stratified by HR status, median TFST and OS were broadly similar for patients with mBC, regardless of BRCA mutation status, as captured in the CancerLinQ Discovery® database. Outcomes may have been affected by class of first-line treatment received in a time preceding poly (ADP-ribose) polymerase inhibitor introduction as a targeted treatment for BRCAm patients. Further studies will be required to support these findings. Funding: This study was funded by AstraZeneca. Table 1. Median TFST and OSCohort TFST, n (events)a,bMedian TFST from mBC diagnosis, months (95% CI)Median TFST from first-line treatment initiation, months (95% CI)OS, n (events)aMedian OS, months(95% CI)gBRCAm, HR+(n=47)45 (40)7.7 (5.0, 11.2)6.6 (3.2, 9.0)47 (21)41.1 (31.5, NR)gBRCAm, HR−(n=29)20 (19)5.4 (3.9, 12.4)3.1 (2.2, 8.9)29 (18)13.7 (11.1, NR)gBRCAwt, HR+(n=296)277 (234)8.3 (6.6, 10.2)6.5 (5.7, 8.7)296 (128)55.1 (43.5, 65.5)gBRCAwt, HR−(n=130)113 (101)5.6 (4.7, 6.6)4.1 (3.4, 5.2)130 (91)14.4 (10.7, 17.0)gBRCAu, HR+(n=2395)2174 (1949)9.4 (8.7, 10.1)7.3 (6.9, 8.0)2395 (1431)33.0 (31.3, 34.8)gBRCAu, HR−(n=609)466 (425)5.4 (5.0, 6.2)4.2 (3.7, 4.6)609 (448)11.7 (10.3, 12.8)an refers to the number of patients at risk.bFor patients with no indication of a further line of therapy or death, TFST was censored at the last activity date.CI, confidence interval; gBRCAm, germline BRCA-mutated; gBRCAu, unknown germline BRCA mutation; gBRCAwt, germline BRCA wild-type; HR, hormone receptor; NR, not reached; OS, overall survival; TFST, time to first subsequent therapy or death. Citation Format: Robert S Miller, Stella Mokiou, Aliki Taylor, Miao Jiang, Ping Sun, Susan McCutcheon. Real-world clinical outcomes of patients with BRCA-mutated (BRCAm) HER2-negative metastatic breast cancer: A CancerLinQ® study [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS7-66.