Analysis of real-world (RW) data for metastatic breast cancer (mBC) patients (pts) with somatic <i>BRCA1/2</i> (<i>sBRCA</i>) or other homologous recombination (HR)-pathway gene mutations (muts) treated with PARP inhibitors (PARPi).
Felipe Batalini, Russell W. Madison, Dean C. Pavlick, Ethan Sokol, Tamara Snow, Arjun Sondhi, Garrett M. Frampton, C. David Jenkins, Judy E. Garber, Gerburg M. Wulf, Jeffrey M. Venstrom, Nadine Tung, Emily Castellanos, Alexa B. Schrock, Kimberly McGregor
Abstract
10512 Background: PARPi are approved for treatment of pts w/ HER2-negative mBC and germline BRCA1/2 (g BRCA) pathogenic or likely pathogenic variants (muts); however, clinical benefit has also been demonstrated in mBC pts w/ sBRCA or other HR-pathway gene muts. Using a RW Clinico-Genomic Database (CGDB), we assessed outcomes for pts w/ gBRCA muts compared to pts w/ either s BRCA or other HR-pathway muts treated w/ PARPi. Methods: 6,329 mBC pts from ̃280 US cancer clinics were included in the Flatiron Health (FH) -Foundation Medicine (FM) CGDB, which includes comprehensive genomic profiling (CGP) linked to de-identified, electronic health record (EHR)-derived clinical data. Eligible pts had mBC, received care in the FH network from 1/1/2011-9/1/2020, and had tissue CGP by FM. Pts classified as gBRCA: positive germline result in EHR and BRCA mut predicted germline per FM’s somatic, germline, zygosity algorithm (SGZ) (Sun et al PMID 29415044). Non-g BRCA: negative germline results in EHR and a somatic BRCA (s BRCA) mut per SGZ or BRCA wild-type w/ another HR mut per CGP result. Pts w/o a documented gBRCA result in EHR, unknown FM BRCA SGZ result, or conflicting results were excluded. RW overall survival (rwOS) and RW progression-free survival (rwPFS) from start of PARPi for pts w/ gBRCA and non- gBRCA mBC were compared using Kaplan-Meier analysis and Cox regression adjusted for mBC line number, prior platinum, age at PARPi initiation, race, and receptor status. Results: Among pts who received PARPi in the mBC setting, 44 had gBRCA and 18 had non -gBRCA: 9 s BRCA (5 BRCA1, 4 BRCA2), 4 PALB2, 2 ATM, and 1 each of ATM+CDK12, BARD1+FANCF+RAD54L, and CHEK2. Of HR muts 76% were confirmed biallelic: 33/44 gBRCA (11 unknown), 8/9 sBRCA, 3/4 PALB2, and 3/5 other (1 unknown). Neither median rwPFS nor rwOS from start of PARPi were significantly different between the non-g BRCA and g BRCA cohorts (rwPFS: 7.0 [4.6-11.3] vs 5.5 [4.3-7.2] months (mos), aHR: 1.19 [0.57 – 2.43]; rwOS: 15.0 [7.95-16.3] vs 11.5 [9.46-NA] mos, aHR: 0.85 [0.36-1.98]). For 9 pts w/ sBRCA mut, median rwPFS was 7.1 mos (range 1.4-12.4) and all pts had progressed by data cut off. Conclusions: Despite small pt numbers and limitations from RW data, our results suggest that pts w/ biallelic non-g BRCA mBC may derive similar benefit from PARPi when tumor CGP detects a s BRCA mut or germline or somatic mut in other HR-pathway genes. These findings are consistent w/ the results from TBCRC-048 (Tung et al PMID 33119476) and support further randomized trials exploring the efficacy of PARPi in this population.[Table: see text]