The role of polymorphisms occurring in BRCA1/2 genes in determining ovarian cancer risk.

e17551 Background: Ovarian cancer (OC) is the 10th tumor occurring in women, it accounts for 30% of all malignant tumor affecting female genital tract in Italy. There are several factors that contribute to OC development; in 15-25% of cases family history of breast and ovarian cancer represent the main risk factor. It is well known that pathogenic variants (PVs) occurring in BRCA1/2 genes strongly increase the risk of developing OC, ranging from 50% in BRCA1 PVs carriers to 30% in BRCA2 PVs carriers. Recently genetic polymorphism has been shown to increase cancer risk, consequently polymorphisms in BRCA1/2 genes could represent low penetrance susceptibility alleles and contribute to determine specific clinicopathological features in OC patients harboring BRCA1/2 PVs. Methods: From 2015 to 2021, 338 patients diagnosed with epithelial OC (not mucinous, not borderline) were subjected to BRCA1/2 analysis. After obtaining informed consent, blood samples were processed for genomic DNA isolation; DNA was used for library preparation with the BRaCa Screen kit. Sequencing was performed on the IonS5 platform; variant annotation was performed with Amplicon Suite software. We collected data of both PVs and polymorphisms in BRCA1/2 genes with the aim to evaluate whether a cluster of specific polymorphisms could impact clinicopathological features in BRCA1 PVs carriers. Results: Among the 338 screened EOC, BRCA1/2 PVs were reported in 85 patients (25%). 66% of patients harbored BRCA1 PVs and 34% in BRCA2. The most frequent BRCA1 PVs were the c.4964_4982del (5083del19), c.514delC and c.181T > G; the first and the last are known for their founder effect in Italy and Eastern Europe. Looking at BRCA1 gene, in 75% of patients we identified a polymorphisms cluster (c.2082C > T, c.2311T > C, c.2612C > T, c.3113A > G, c.3548A > G, c.4308T > C, c.4837A > G). The c.514delC and c.181T > G PVs are always associated with the cluster and two additional polymorphisms, the c.2077G > A and the c.1067A > G respectively. Conversely, the cluster seems not to be associated with the PVs 5083del19. Interestingly in BRCA1-5083del19 PV carriers median age at OC diagnosis was 50 years (range 45-69). On average, these patients developed ovarian cancer 6 years earlier than other BRCA1 PV carriers (median age at diagnosis 57 years; range 30-81). Bilateral tumors were frequent and occurred in 57% of the patients versus 33% in OC patients carrying other BRCA1 PVs. Therefore, it seems that the cluster has a “protective” effect and that its absence reduces age at diagnosis. Conclusions: Despite this study has the main limitation of a small sample size, we have reported a possible association between polymorphisms cluster and clinicopathological features in BRCA1 PVs carriers. By further investigating this aspect in a larger cohort, we might be able to prove the role of this cluster in increasing or reducing OC risk and providing clinicians more information useful for patients’ stratification.