Multicenter retrospective study of clinical genetic testing in patients with sarcoma.

10511 Background: Sarcomas are rare and diverse malignancies with a subset developing in the context of heritable cancer predisposition syndromes. Data surrounding the frequency of inheritance and patient/genomic findings are limited. We aimed to describe the characteristics of patients with sarcoma referred for clinical genetic testing and to determine the prevalence of pathogenic/likely pathogenic germline variants (PGV/LPGV). Methods: We performed retrospective chart reviews of patients with sarcoma referred to Michigan Medicine Cancer Genetics Clinic between 12/2006 and 1/2020 and Vanderbilt Hereditary Cancer Clinic between 1/2005 and 1/2019. Reviewers obtained medical/family history, cancer phenotype, and results of germline genetic testing. Descriptive analyses were performed to assess the prevalence of germline variants classified as pathogenic/likely pathogenic according to American College of Medical Genetics criteria. Associations with clinical factors were tested for using Fisher’s exact test or Wilcoxon rank-sum test. Results: One-hundred sixteen patients with sarcoma underwent genetic evaluation during a 15-year period. Mean age at time of visit was 46 years (SD, 17.6 years; range, 1-80 years). Sixty-nine patients (59%) were female. The most common reasons for referral were personal history of multiple malignancies (n = 69, 59.4%), first degree relative (FDR) with malignancy (n = 67, 57.7%) and young age at diagnosis (age ≤ 18, n = 18, 15.5%). Forty-eight patients (41.4%) had both a history of multiple malignancies and a FDR with a malignancy. Eight patients had a FDR with sarcoma (6.9%). Of the 110 patients who underwent germline testing, 53 patients (48.2%) had a PGV/LPGV. Identified germline variants and frequencies are listed in the Table. There was no statistical significance between young age at diagnosis, history of personal malignancies, FDR with sarcoma, FDR with one or more malignancies, or multiple FDRs with malignancy and presence of a PGV/LPGV. Conclusions: In this multicenter study, approximately half of patients with sarcoma referred for cancer genetic testing had a PGV/LPGV associated with hereditary predisposition to cancer. There was no identified positive predictive factor for germline variants. Though TP53 was the most common, over 20 genetic variants were identified, supporting the consideration of multigene panel testing. Our study is limited to patients who were both referred to and attended genetic evaluation. Yet, the high frequency of pathogenic germline variants observed highlights the necessity for further investigation of the prevalence of and predictive factors for germline mutations in all sarcoma patients. Identified germline variants. [Table: see text]