81 Cytological samples for detection of BRCA 1/2 mutations in patients with high grade serous ovarian cancer

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Introduction/Background* Since approval of PARP inhibitor olaparib, testing for germline BRCA 1/2 (gBRCA) gene mutations from blood and testing from formalin-fixed-paraffin-embedded (FFPE) tumor tissue for detection of somatic BRCA 1/2 (sBRCA) gene mutation has become standard procedure for patients with high-grade serous ovarian cancer (HGSOC). Since the DNA extracted from FFPE is of poor quality, the new alternative materials are being investigated. Cytological samples (CS) from malignant ascites or other metastatic sites provide intact DNA material for BRCA 1/2 gene testing. The aim of study was to determine if CS can be used for BRCA 1/2 gene testing in patients with HGSOC. Methodology For patients with HGSOC to be eligible three samples were obtained: blood sample, FFPE (tumor block) and CS from malignant ascites or other metastatic sites. From FFPE and CS status of gBRCA 1/2 or sBRCA 1/2 gene mutations status was obtained, from blood samples status of gBRCA 1/2 gene mutations was obtained. Comparison of reliability in BRCA 1/2 gene testing between all three samples was performed. BRCA 1/2 gene testing was performed by next generation sequencing. Result(s)* Overall 122 patients were included in the period from 2015-2020, 63 (52%) of them were eligible for analysis. BRCA 1/2 gene mutation had 21/63 (33%) of patients: 18 (28%) gBRCA 1/2 and 3 (5%) sBRCA 1/2 gene mutation. There was 98% correlation (62/63) between CS and FFPE in determination of BRCA 1/2 gene mutational status. One patient had sBRCA 2 gene mutation present in FFPE but not in CS (ascites). Conclusion* In experienced oncology centers cytological samples can be used for BRCA 1/2 gene mutation testing in patients with HGSOC.

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