Immunotherapy use without approval: Patterns, biases, and biomarkers in patients with ovarian cancer.

e17588 Background: Immunotherapy use has attracted increasing attention in ovarian cancer but currently has no disease specific FDA indications. We determined the factors and tumor biomarkers associated with immunotherapy use in ovarian cancer over the last 17 years. Methods: This was a retrospective analysis of the 2022 submission of the National Cancer Database (NCDB) epithelial ovarian cancer cohort. This cohort included women aged 18 and older diagnosed with ovarian cancer from 2004-2021 with information on immunotherapy use. Patient factors included age at diagnosis, race/ethnicity, insurance status, and comorbidities. Cancer factors included disease stage, histology, and tumor size. Patients with epithelial ovarian cancer who underwent testing at a commercial laboratory (2010-2025) were identified from the Myriad Collaborative Research Registry V2. Myriad Precise tumor testing results were used to identify incidence of immunotherapy related tumor biomarkers such as mismatch repair instability (MSI), tumor mutational burden (TMB) and PD-L1 positivity. P-values