Prevalence of pathogenic germline cancer risk variants in high-risk urothelial carcinoma.

Purpose: To date, there has not been a large, systematic evaluation of the prevalence of germline risk variants in urothelial carcinoma (UC).

Methods: We evaluated the frequency of germline pathogenic and likely pathogenic variants in 1038 patients with high-risk UC who underwent targeted clinical germline testing. Case-control enrichment analysis was performed to screen for pathogenic variant enrichment in 17 DNA repair genes in 1038 UC patients relative to cancer-free individuals.

Results: Among 1038 patients with UC, the cumulative frequency of patients with pathogenic variants was 24%; 18.6% of patients harbored ≥1 actionable germline variant with preventive or therapeutic utility. MSH2 (34/969, 3.5%) and BRCA1/2 (38/867, 4.4%) germline variants had the highest frequency. Germline variants in DNA damage repair genes accounted for 78% of pathogenic germline variants. Compared to the cancer-free cohort, UC patients had significant variant enrichment in MSH2 (odds ratio [OR]: 15.4, 95% confidence interval [CI]: 7.1-32.7, p < 0.0001), MLH1 (OR: 15.9, 95% CI: 4.4-67.7, p < 0.0001), BRCA2 (OR: 5.7, 95% CI: 3.2-9.6, p < 0.0001), and ATM (OR: 3.8, 95% CI: 1.8-8.3, p = 0.02).

Conclusion: In this study, 24% of UC patients harbored pathogenic germline variants and 18.6% had clinically actionable variants. MLH1 and MSH2 were validated as UC risk genes while ATM and BRCA2 were highlighted as potential UC predisposition genes. This work emphasizes the utility of germline testing in selected high-risk UC cohorts.