Abstract LB561: Germline mutational profiling of TNBCs in an Indian cohort
Authors: Koppiker Chaitanyanand , Bapat Ashwini , Gahlaut Siddharth , Luke Naveen , John Jisha , Mishra Rupa , Konnur Aishwarya , Namewar Namrata , Reddy Ruhi , Shaikh Shaheen , Banale Rituja , Nare Smeeta , Busheri Laleh , Reddy Asha , Mannan Ashraf , Radhakrishnan Sabarinathan , Radhakrishna Selvi , Dixit Santosh 
Published: June 2022

Abstract
Breast cancer is the most common cancer in Indian women with a high incidence of triple negative breast cancer (TNBC), an aggressive subtype of breast cancer associated with poor prognosis. The high TNBC prevalence (&gt;25%) in India as compared to the western population (10-15%) remains to be a challenge in clinical management. The association of germline BRCA1/2 mutations in TNBCs is well-established as a predisposing factor for hereditary breast cancer risk. However, these studies are predominantly from germline profiling of TNBCs representative of western population. Therefore, we aimed to investigate the germline profiles of breast cancer patients in India using a multi-institutional TNBC cohort based on ACMG consensus multi-gene NGS panel. Of 193 TNBC patients, we identified 57 pathogenic mutations (diagnostic yield = 29.53%) from various genes of which BRCA1 (41/57, 71.93%) and BRCA2 (8/57, 14.03%) were most commonly mutated. We observed a high prevalence of BRCA1 mutations (41/193, 21.24%) and BRCA2 mutations (8/193, 4.14%) in our cohort as compared to published literature. Additionally, 8 pathogenic mutations were also reported in non-BRCA cancer pre-disposing genes associated with the HR pathway like ATM, CHEK2, PALB2. 10 novel mutations were identified in 3 genes namely BRCA1, BRCA2 and PALB2. The most common type of mutations was found to be frame-shift which may cause protein truncation and loss of function. Furthermore, we identified 48 variants of unknown significance (24.9%) of which about 7% were in the BRCA1/2 genes. Data mining from global databases like TCGA, Genome Asia indicated that the novel mutations were unique to the Indian population compared to the germline profiles of different ethnicities. Our study confirms the major contribution of BRCA1/2 genes in TNBCs as reported in the literature. A high percentage of the women were found to be associated with young age onset which may be attributed to BRCA mutations. We have also assessed the association of clinicopathological parameters such as tumor grade, stage, recurrence to the germline mutational status. Our analysis shows significant association of germline mutational status with family history thus underlin the importance of multi-gene panel testing as recommended by NCCN guidelines. Moreover, our results also emphasize the need for designing/implementing guidelines specific to Indian population. In summary our results indicate that Indian TNBCs have a high prevalence of BRCA1/2 mutations. Large scale studies in future are warranted to validate these preliminary findings.
Citation Format: Chaitanyanand Koppiker, Ashwini Bapat, Siddharth Gahlaut, Naveen Luke, Jisha John, Rupa Mishra, Aishwarya Konnur, Namrata Namewar, Ruhi Reddy, Shaheen Shaikh, Rituja Banale, Smeeta Nare, Laleh Busheri, Asha Reddy, Ashraf Mannan, Sabarinathan Radhakrishnan, Selvi Radhakrishna, Santosh Dixit. Germline mutational profiling of TNBCs in an Indian cohort [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB561.