First-line Immunotherapy for Metastatic Merkel Cell Carcinoma

Background: Immune checkpoint inhibitors are a promising new therapy for advanced Merkel Cell Carcinoma (MCC). We investigated real-world utilization and survival outcomes of first-line immunotherapies in a contemporary cohort. Methods: Using the National Cancer Database (NCDB), we identified 759 patients with MCC between 2015 and 2020 with stage IV disease and known status of first-line systemic therapy. Univariable and multivariable analyses were used to determine predictors of immunotherapy usage. Overall survival (OS) was compared for patients receiving immunotherapy, chemotherapy, or no systemic therapies. Results: We identified 759 patients meeting our inclusion criteria: 329 patients received immunotherapy, 161 received chemotherapy, and 269 received no systemic therapy. Adjusting for demographic, clinical, and facility factors, high facility volume significantly predicted first-line immunotherapy use (OR 1.99; P=0.017). Median OS was 16.2, 12.3, and 8.7 months, among patients who received immunotherapy, chemotherapy, or no systemic therapy, respectively (P<0.001). On Cox multivariable survival analysis, first-line immunotherapy treatment (HR=0.79, P=0.041) and treatment at high-volume centers (HR=0.58, P=0.004) were associated with improved OS. Conclusions: Consistent with clinical trial results, first-line immunotherapy associated with improvement in median overall survival for patients with stage IV MCC, significantly outperforming chemotherapy in this real-world cohort. Treatment at high-volume centers associated with first-line immunotherapy utilization suggesting that familiarity with this rare disease is important to achieving optimal outcomes for metastatic MCC.