379PStudy of germline mutations in high risk cancer patients from a tertiary care center in India.

Background About 10% cancers are due to cancer susceptibility genes. Testing of high risk patients according to NCCN guidelines is important for detection of hereditary cases and at-risk relatives for secondary prevention of cancer. The exact burden of germline mutations in Indian population is not known because of lack of education and unaffordability. We undertook this study for detection of hereditary cancer cases from Western India. Methods All patients who underwent testing from June 2015 to June 2019 for extended germline mutation panel of 96 genes using next generation sequencing (NGS) on Illumina platform were selected. Clinical data was analysed and correlated with the results. Results Out of total 290 patients counselled, 84 (28.9%) underwent genetic testing. Mutations were found in 63 % (53/84) patients whose median age was 44 years. 24.5% (13/53) had no positive family history of cancer. Most common malignancies were breast, 31; of which 15 were triple negative breast cancers, followed by ovary, 13 and colon, 4 cases. BRCA1/BRCA2 mutations were seen in 66% (35/53), MSH2 in 3 and MLH1 and RAD51D mutation in 2 patients each. 38 mutations were pathogenic, 4 likely pathogenic and 11 were Variant of Unknown Significance (VUS). Three novel BRCA1 mutations (c.1039delC, c.42_44dupGCT, c.68-5_77del) and one novel BRCA2 mutation (c.7342A>T) was identified. A rare TP53 mutation (c.(-29 + 1_-28-1)_(672 + 1_673-1)dup) was also identified in one patient, who had three metachronous malignancies. Conclusions Hereditary breast and ovarian cancer syndrome due to BRCA1/2 mutations was commonest in our study followed by Lynch syndrome due to MSH2 mutation. 20% VUS, 4 novel and 1 rare mutation were identified. Negative family history does not rule out hereditary predisposition. The knowledge shared would assist in further genetic testing and enable detection of more hereditary cancer cases. Legal entity responsible for the study The authors. Funding Has not received any funding. Disclosure All authors have declared no conflicts of interest. [ABSTRACT FROM AUTHOR]