P-063: Pathogenic germline variants in hereditary cancer genes in patients with Multiple Myeloma

Background GWAS have identified common SNPs & rare high-penetrance variants that explain ~16% of the estimated heritability of multiple myeloma (MM)(PMID 30213928). Pathogenic/likely-pathogenic germline variants (PGV) in hereditary cancer genes (HCG) are common in adult cancer pts (~8%), but prevalence in MM is not known. The aim of our study is to investigate the occurrence of PGV in newly-diagnosed MM (NDMM) and describe clinical characteristics & outcomes of carriers. Methods We analyzed MMRF CoMMpass data & identified 895 NDMM pts with whole-exome sequencing of germline DNA. We used the clinical annotation pipeline from Sema4, a CLIA/CAP certified genetic testing laboratory, to identify pts with PGV according to ACMG variant classification guidelines. We compared clinical characteristics & disease phenotypes of PGV carriers vs non-carriers. We used Chi-Square and Fisher’s Exact tests to assess statistical significance. Results We identified 83 PGV in 31 distinct HCG in 79 (8.8%) of 895 NDMM pts (83% European ancestry). Most PGV involved DNA damage repair (DDR) genes (78%), & homologous recombination (HR) genes were the most commonly mutated (34%). PGV in CHEK2 were most common (n=10,1.1% of all MM pts). 2 pts carried PGV in TP53, & 6 pts had mismatch repair (MMR) gene defects (1:149). MM pts with family history (FH) of hematologic malignancy (HM) in a 1st or 2nd-degree relative were more likely to carry PGV (22 vs 7.6%,OR=3.3,p Conclusions PGV in HCG were common (8.8%) in this large cohort of NDMM pts of predominantly European ancestry, especially in those with FH of HM (1:4, with high prevalence of CHEK2 variants), and in those