Avelumab real-world use in advanced Merkel cell carcinoma: a systematic review and non-comparative meta-analysis

AIM: Programmed death (ligand) 1 inhibitors (e.g., avelumab, pembrolizumab, and retifanlimab) are first-line treatment options for patients with locally advanced or metastatic Merkel cell carcinoma (MCC). In the absence of comparative and randomized trials, we aimed to systematically identify and synthesize real-world evidence (RWE) on the effectiveness and safety of immunotherapies in patients with advanced MCC. METHODS & MATERIALS: MEDLINE and Embase searches were conducted for observational RWE studies in locally advanced or metastatic MCC from January 2017 to December 2023. Avelumab was the only immunotherapy with sufficient data for analysis. Landmark 12-month overall survival (OS) and progression-free survival (PFS) were assessed by meta-analysis. RESULTS: Screening of 1731 records identified 37 publications eligible for inclusion (16 unique studies), of which eight were included in the meta-analysis. In line with results from the JAVELIN Merkel 200 trial, pooled 12-month OS rates of 77.7% in stage III and 63.0% in stage IV MCC and 12-month PFS rates of 53.3% and 39.3%, respectively, were estimated. Although safety data were insufficient for meta-analysis, two retrospective studies reported lower adverse event rates than JAVELIN Merkel 200. CONCLUSIONS: The results of this study support broader use of avelumab in advanced MCC.