2009PNon-BRCA1/2 hereditary breast and ovarian cancer: Findings from a multidisciplinary program

Abstract Background Non-BRCA1/2 pathogenic variants have increasingly been associated with breast and ovarian cancer (BOC). In this study, we analyze the clinical and molecular characteristics of non-BRCA1/2 BOC identified in our program. Methods Index pts without BRCA1/2 pathogenic variants identified between 2004-2018, were counselled for multigene sequencing after multidisciplinary decision. Either the BRCA Hereditary Cancer MASTR Plus (Multiplicom) or the Trusight (Ilumina) were performed in the MiSeq platform (Illumina). Counselling included the possibility of opt out. Results From all 4277 index pts tested, 377 non-BRCA1/2 (96,3% breast and 22,6% ovarian cancer) consented on reanalysis and in 31 (8.2%) a pathogenic variant was identified. All but one (with both ATM and PALB2 mutated) pt harbored one pathogenic variant (Table). For 38 pts (10,1%) only selected genes from the panel were studied and 11 (2,9%) opted out of TP53. Table . 2009P Gene Pathogenic variant CHECK2 c.1100delC (1) c.319 + 2T>A (6) c.593-1G>T (1) PALB2 c.1192delG (1) c.2257C>T; p.Arg753Ter (2) c.172_175delTTGT; p.Gln60ArgfsTer7 (1) c.751C>T (1)* RAD51C c.404G>A; p.C135Y (2) c.709C>T;p.Arg237 (1) c.887_896del10 (1) c.8890_899delTTGTTCCTGC;p.Leu297HisfsTer2 (1) ATM c.3802delG;p.Val1268Ter (1) c.8264_8268delATAAG (2)* c.8292_8293delTG; p.Ser2764ArgfsTer4 (1) TP53 c.586C>T;p.Arg196Ter (1) c.725G>A (1) c.1010G>A;p.Arg337His (1) BLM c.298_299delCA; p.Gln100Glufs (1) c.2206dupT; p.Tyr376LeufsTer5 (1) RAD50 c.2516_2517insA;p.Asp840ArgfsTer5 (2) BRIP1 c.3874 + 2T>C (1) c.484C>T; p.Arg162Ter (1) FAM175A c.1106dupG;p.Ser370iLefsTer2 (1) Predictive factors for positive tests were a lower median age of BC diagnosis (37vs41) and a complex phenotype (9.7%vs3.8%). Neither the family male: female ratio (3,2% vs 7,2%) or prostate cancer (19.4%vs21,4%) were predictive, but other cancers were more frequent in hereditary cases (83.9%vs78,8%). All individuals were invited for prospective follow up. Conclusions A recurrent CHECK2 event explained 19% of all cases and opt out, as well as incomplete panels, may have underestimated the relevance of the TP53 gene. Younger age at BC diagnosis, complex phenotype and aggregation with other cancers were predictive for positive test. Additional follow up will add to the impact of non-BRCA1/2 tests in clinical practice. Legal entity responsible for the study The authors. Funding Has not received any funding. Disclosure All authors have declared no conflicts of interest.