BRCA-like classification in ovarian cancer: Results from the AGO-TR1-trial

5546 Background: BRCA associated cancers show a distinct pattern of genomic gains and losses that is associated with impaired repair of DNA double-strand breaks via homologous recombination (HR). We investigated whether BRCA1- and BRCA2-like classifiers could predict BRCA1 and BRCA2 mutation status in ovarian cancer. In addition, we explored whether promoter hypermethylation or mutations in other genes involved in DNA repair associate with a BRCA-like profile in ovarian cancer. Methods: The AGO-TR1 cohort study (NCT02222883 ) enrolled 525 consecutive patients with primary (PR) and platinum sensitive relapsed (RE) ovarian cancer to perform paired mutational analysis of germline and tumor tissue. We performed mutation panel sequencing, BRCA1 promoter hypermethylation and low-coverage whole genome sequencing to classify samples as BRCA1-like or BRCA2-like in 298 ovarian cancer samples (PR: n = 159, RE: n = 139). Results: A BRCA-like profile was observed in 58.1% of the samples without germline or somatic mutation in BRCA1/2 (n = 179; BRCA1-like: n = 26, BRCA2-like: n = 23, BRCA1- and 2-like: n = 55). There was no significant difference between PR- and RE-cases (54.5% vs 61.3%). 64 of 70 BRCA1 germline mutation carriers could be identified by the BRCA1-like classifier (sensitivity: 0.91). The BRCA2-like classifier identified BRCA2 germline mutation carrier with a sensitivity of 0.71 (17 of 24). The complementary use of both classifiers led to the detection of 22 of 25 somatic mutations in BRCA1 (16/16) or - 2 (6/9). Remarkably, 12 of 13 tumor samples from germline RAD51C mutation carriers were recognized by the BRCA1-like classifier (sensitivity: 0.92). No correlation of PALB2 mutation status (n = 7) with BRCA-like profile was observed. Of 28 tumor samples with a BRCA1 promoter hypermethylation 26 had a BRCA1-like profile (sensitivity: 0.93). Conclusions: A high number of ovarian cancer cases display a BRCA-like profile. Mutations (germline and somatic) in BRCA1, BRCA2, RAD51C as well as BRCA1 hypermethylation strongly associate with a BRCA-like profile and can explain 146 of 212 cases. Future studies will investigate whether the classifiers identify patients who benefit from HR-deficiency directed approaches beyond the BRCA mutation status. Clinical trial information: NCT02222883.