Abstract P6-06-06: Comprehensive Analysis of BRCA (brcam) and Other Germline Mutations (grm) with a Clinicopathological Association in Breast Cancer: an Indian Study

Abstract Background: BRCAm and other GRm testing using next generation sequencing (NGS) in early diagnosed and/or metastatic breast cancer (BC) helps in the identification of both unambiguously defined deleterious mutations and sequence variants of unknown clinical significance (VUS). The early detection of these mutations in the proband and the family members help in risk stratification and instituting effective monitoring, surveillance and disease management strategies. Methods: Out of total 200 patients diagnosed with BC (April 2013-15) 77 unrelated individuals were consented to be profiled by NGS on MiSeq platform using TruSight Cancer panel (consisting of 94 genes including 13 genes highly associated with risk of inherited breast and/or ovarian cancer) in an IRB-approved prospective study in a CLIA compliant laboratory. Paired end sequencing was done with an average coverage of > 450X. Data was processed using STRAND software and interpreted using "Strand Omics" platform. The paired tumor samples were analysed for pathological stage, histological type and hormonal status. Results: GRm were detected in 61 cases (79%). Among all mutations detected, BRCA1/2 were found in 51% (31% in BRCA1, 20% in BRCA2) of cases. BRCA1 was found to be co-mutated with BRCA2 in 2 cases. Out of 37 deleterious mutations in BRCA1/2 genes only 10 were reported to be pathogenic (6 in BRCA1 and 4 in BRCA2) and rest were VUS. Mutation frequencies were higher among high grade IDC with HER2-ve tumors including TNBC (53%, p<0.05) with an early onset of the disease. TNBC with BRCAm were found to have no/incomplete pCR on conventional TAC regimen , subsequently started with platinum therapy and the outcome being monitored. Interestingly, 4 BRCA1 mutations including 3 non-sense and 1 frameshift mutation were found in two unrelated individuals suggesting them to be founder mutations in Indian population. The other GRm frequency (alone/ co-mutated with BRCA) was also found to be significantly high (49%) and include BRIP1, CHEK2, ERCC2, CDH1, SDHB, APC, MSH6, TP53, PALB2 and RAD51C. Stratification based on age of diagnosis(dx) showed a detection rate significantly higher in the age group of 25-50 yrs (74%) as compared to the 50-75 yrs (26%). Also a strong association of GRm status with the family history(Hx) of BC in 1st or 2nd degree relatives was indicated. Table 1: Correlation of GRm with Dx and HxGenen%Age at dx(yrs)Family Hx (Yes=Y, No=N,Unknown=UK)BRCA1193125-50 (n=23) 50-75(n=8)Y(n=13) N(n=3) UK(n=3)BRCA2122025-50(n=21) 50-75(n=9)Y(n=8) N(n=2) UK(n=2)PALB211.7>50YCHEK258.825-50 (n=4) 50-75(n=1)YATM610.525-50 (n=4) 50-75(n=2)Y(n=5) N(n=1)RAD5111.7<50Y Conclusions: Our study in a small cohort clearly highlighted the significance of germline testing and classifying the variant in larger cohort of BC patients with a strong family Hx of cancer particularly in BRCA1/2 positive families , and in women <50yrs for early detection and risk assessment. The study also indicates BRCAm to be an important contributor to the etiology of high grade HER2-/ TNBC in Indian patients. Expanded testing of this subtype is warranted to impact management of the disease with PARP inhibitors and/or platinum therapy. Citation Format: Ghosh M, ML S, Upasana M, Chodhury S, Mannan AU, Southekal S, Manjima C, Patil S, Murugan K, Mahesh B, Nayak R, Sridhar PSS, Rao N, Krishnamoorthy N, Gupta V, Satheesh CT, Subramanian K, Ajaikumar BS. Comprehensive analysis of BRCA (BRCAm) and other germline mutations (GRm) with a clinicopathological association in breast cancer: An Indian study. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P6-06-06.