Genetic testing outcomes and pathogenic germline mutation prevalence in renal cell carcinoma.

10601 Background: Germline mutations have been observed in renal cell carcinoma (RCC) with varying frequencies reported from 5% to 18% of patients. Due to the prevalence of germline mutations, current guidelines by the National Comprehensive Cancer Network (NCCN) recommend genetic testing for patients with RCC and high-risk factors such as young age, bilateral or multifocal tumors, family history of RCC, as well as certain RCC histologies. However, the germline mutational landscape in RCC has not been fully characterized. Here, we report the genetic testing results and clinicopathologic factors of patients with RCC who were referred for germline testing. Methods: All patients with a diagnosis code of kidney cancer and referred to the Cancer Genetics clinic at the University of Michigan between 2004 and 2022 were identified. Patients were excluded if they had erroneous RCC diagnosis codes, no history of RCC diagnosis, known familial/hereditary mutation or syndrome, or did not undergo germline testing. Genetic testing outcomes, germline mutation frequency, and clinical factors were obtained through chart review and analyzed using descriptive statistics. Results: A total of 322 patients with a history of RCC and referred for genetic testing were identified. The median age at diagnosis in all patients was 47 (interquartile range: 38-58). Males accounted for 56.8% of the cohort. Most patients (62.4%) had clear cell histology at initial diagnosis, whereas 30.7% had non-clear cell histology. The majority of patients (61.5%) were diagnosed at stage 1. Bilateral and multifocal tumors at diagnosis accounted for 18.9% and 12.7%, respectively. Pathogenic or likely pathogenic variants (P/LP) were identified in 43 patients (13.4%); 225 patients had negative germline testing (69.9%); 54 patients (16.8%) had a variant of unknown significance (VUS). The most frequently mutated RCC-associated genes were FLCN (n=10, 3.1%), SDHA/B/D (n=7, 2.2%), VHL (n=4, 1.2%), MLH1 (n=3, 0.9%), and FH (n=2, 0.6%). Common mutations in other cancer-related genes were CHEK2 (n=4, 1.2%), ATM (n=2, 0.6%), and RAD50 (n=2, 0.6%). Most patients (81.4%) with a P/LP test result had at least 1 of the following: diagnosis age ≤ 46 years, bilateral or multifocal tumors, or at least 1 first-degree relative with RCC. Out of the patients with a P/LP result, 18 patients (39.1%) had a potentially actionable mutation. Conclusions: Among patients with RCC who were unselected for a known familial/hereditary predisposition, P/LP variants were present in 13.4% which is consistent with previous studies. The prevalence of FLCN mutations was higher in our cohort (3.1%) compared to prior observations. Most patients with a P/LP variant met the NCCN criteria for genetic testing. Future studies should optimize the current genetic testing criteria to identify a broader group of patients who may have germline mutations given potential cascade testing and therapeutic implications.