Anti–programmed cell death-1 monotherapy is a typical treatment for cutaneous melanoma, although it is ineffective against mucosal melanoma. Researchers assessed the efficacy and safety of atezolizumab plus bevacizumab as a first-line treatment for advanced mucosal melanoma. This phase II multicenter, single-arm, open-label trial utilized Simon’s 2-stage design. Atezolizumab (1,200 mg fixed dose) and bevacizumab (7.5 mg/kg) was delivered intravenously every 3 weeks. The primary outcome measure was the objective response rate (ORR), as measured by RECIST v1.1. 

Secondary objectives included progression-free survival (PFS), overall survival, duration of response (DOR), and safety, with adverse events (AE) summarized using NCI-CTCAE version 5.0. About 43 patients were included, including 20 (46.5%) with unresectable mucosal melanoma and 23 (53.5%) with metastatic disease. The 13.4 months was the median duration of follow-up at the time the data was cut off (July 30, 2021). About 40 patients were evaluable for response; the overall response rate (ORR) was 45.0% [95% CI: 29.3%–61.5%; 1 complete response, 17 partial responses]. 

The median PFS was 8.2 months (95% CI, 2.7–9.6); the 6- and 12-month PFS rates were 53.4% (95% CI, 36.6%–67.6%) and 28.1% (95% CI, 14.2%–43.6%), respectively. The median OS could not be determined (NR; 95% CI, 14.4–NR). The 6-month OS rates were 92.5% (95% CI, 78.5%–97.5%), and the 12-month OS rates were 76.0% (95% CI, 57.1%–87.5%). The median DOR was 12.5 months (95% confidence interval [CI], 5.5–NR) Overall, 90.7% (39/43) of patients encountered treatment-related adverse events, with 25.6% (11/43) experiencing occurrences of grade 3. In patients with advanced mucosal melanoma, the combination of atezolizumab and bevacizumab exhibited promising effectiveness and tolerable tolerability.