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 <0.05 were considered statistically significant. Results: From 2004-2021, 196,087 patients were identified in the NCDB database. In total, 7,767 (4.0%) of patients were treated with immunotherapy. Patients who received immunotherapy were more likely to be older (18-39 years: 2.0% vs 65+: 4.7%, p<0.001), be of Asian race (White: 3.8% vs Asian 4.7%, p<0.001), have more medical comorbidities (Charlson-Deyo Comorbidity Score 0: 3.9% vs 2+: 4.7%, p<0.001), and have higher stage disease (Stage 1: 0.4% vs Stage IV: 8.4%, p<0.001) compared to those who did not receive immunotherapy. After adjusting for confounders, patients with stage IV had an adjusted odds ratio (aOR) of 16.12 [95% CI: 13.99-18.57, p<0.001] of receiving immunotherapy. Clear cell histology was associated with increased use of immunotherapy (aOR: 1.18 [1.05-1.32], p<0.001. Patients who were treated with surgery for their cancer were less likely to get immunotherapy (3.8 vs 5.6%, p<0.001). Patients who did not get treated with chemotherapy were unlikely to get immunotherapy alone (0.1% vs 5.1%, p<0.001). Use of immunotherapy has increased over the last 17 years. From 2008-2021, immunotherapy use in ovarian cancer increased 50.6% per year [42.2-64.2, p<0.001]. In 2021, 16.0% of patients were treated with immunotherapy, compared to 0.5% in 2004. In the Myriad data, 3,095 patients received Precise tumor testing. The rate of MSI positivity was 1.13% (N=35), the rate of PD-L1 positivity was 15.61% (N=483), and the rate of TMB high was 7.08% (N=219). Conclusions: Immunotherapy use in ovarian cancer has increased substantially over 17 years in the absence of an FDA-specific indication, with evidence of PD-L1 enrichment in studied populations.