10591 Background: Clinically relevant cancer genetic data from Sub-Saharan Africa (SSA) are limited, despite the observation that cancers in this region are frequently diagnosed at an early age and follow an aggressive course. A prospective pilot study was undertaken to explore the feasibility of implementing germline genetic testing (GGT) and counseling in breast and prostate cancer patients in Rwanda. Methods: Consecutive female breast (FBC), male breast (MBC) and prostate (PC) cancer patients from hospitals in Rwanda underwent GGT. Demographic, disease, and treatment information were collected. A commercial 84-gene multi-cancer panel (Invitae Corp.) was used to identify pathogenic variants (PV) and variants of uncertain significance (VUS). Descriptive statistics were utilized. Results: 342 total patients underwent GGT: PV were observed in 32/175 (18.3%) FBC, 7/161 (4.3%) PC, and 1/6 (16.7%) MBC patients. PV were most frequently identified in BRCA2: FBC (n=14), MBC (n=1), PC (n=2). BRCA1 was almost common in FBC (n=11). The majority of PV in FBC cases were in established breast cancer susceptibility genes (94%), while 43% of PV in PC involved PC susceptibility genes. Notably, of 40 total PV identified, 35 (88%) were in DNA damage repair (DDR) genes. 224 patients (65%) had > 1 VUS in the absence of a PV finding, including 109 (68%) in PC and 115 (64%) in FBC/MBC combined. Recurrent PV were observed in BRCA1, BRCA2, or ATM in apparently unrelated FBC cases. Conclusions: The high proportion of PV, observed in these Rwandan breast and prostate cancer cases, particularly in DDR genes, suggest that GGT should be more routinely implemented into cancer care and prevention strategies in this population. More widespread GGT may also help to resolve the high VUS rates. The recurrent variants identified warrant further investigation into founder effects. [Table: see text]
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