Prevalence of BRCA1 and BRCA2 mutations in an unselected cohort of Indian women with breast cancer.

Abstract

e13004 Background: Familial breast cancer accounts for 10-15% of breast cancer cases. The prevalence of germline pathogenic mutations in breast cancer susceptibility genes 1 and 2 ( BRCA1/2) among female breast cancer patients remained variable across studies depending on the population/settings studied. The estimate varied between 8-10% of the unselected female breast cancer population. There is a lack of data regarding the prevalence of BRCA1/2 among female breast cancer patients in India. Methods: This prospective observational study included consecutive patients with breast cancer in females, registered at All India Institute of Medical Sciences (AIIMS), New Delhi, India between the period of 1st September 2022 to 25th January 2023(5 months duration). The staging description was done as per anatomic TNM staging according to AJCC 7th edition. Mutation testing was performed in all patients by a standard next-generation sequencing (NGS) assay covering the BRCA1/2 gene. The reflex multiplex ligation by probe amplification method was performed in all cases that were negative by NGS. For patients with detected germline mutations in BRCA1/2, post-test counseling was done, and family screening was also advised. Results: A total of 210 female patients with breast cancer were sequentially included in the study. Young breast cancer (less than 35 years of age) constituted 40 (19.04%) cases. Thirty-eight patients (18.09%) women had a positive significant family history. The median age of the cohort was 46 years (range 18-85 years). Synchronous breast cancer was present in 7 (3.3%) cases. The stage distribution was stage I, 11(5.23%); stage II, 73 (34.76%); stage III, 83 (39.52%); and stage IV, 43 (20.47) %. One hundred and ten patients (52.38%) were hormone-receptor-positive, whereas 66 (31.42%) patients were HER2/neu positive. Triple-negative breast cancer (TNBC) was found in 65 (30.95%) cases. Overall, the prevalence of germline BRCA1/2 mutations was 35/210 (16.6%), which included BRCA 1 and 2 mutations in 22 (10.47%) and 12 (5.71) cases respectively. One case had mutations in both BRCA 1 and BRCA2. Young ( < 35) TNBCs (22 cases/210, 10.47%) have a high propensity for detecting pathogenic BRCA1 mutation (8/22, 36.36%). Conclusions: The prevalence of pathogenic BRCA1/2 in 16.6% of our cohort of unselected consecutive breast cancer patients. It is higher than that reported in the Western population likely due to the younger population and more proportion of triple-negative breast cancer patients in our cohort.