Adjuvant short-course radiotherapy combined with chemotherapy and a PD-1 inhibitor for resected mucosal melanoma: study protocol for a single-arm, prospective, phase II trial

Introduction Mucosal melanoma (MM) carries a high risk of postoperative relapse and poorer survival than cutaneous disease. Prospective data from China support adjuvant temozolomide - cisplatin (TMZ/DDP) in resected MM, while radiotherapy (RT) may augment antitumour immunity and synergise with programmed death 1 (PD-1) inhibitor.

We therefore designed an adjuvant regimen combining short-course RT (SCRT) with chemotherapy and PD-1 inhibitor after curative-intent resection. Methods and analysis This investigator-initiated, single-arm, prospective, phase II study at Fudan University Shanghai Cancer Centre enrols adults (≥18 years) with histologically confirmed MM after R0/R1 resection, Eastern Cooperative Oncology Group (ECOG) performance status 0 - 1 and M0 disease.

Patients receive six 3-week cycles of systemic therapy: pucotenlimab 200 mg IV on day 1; TMZ 200 mg/m² orally on days 1 - 5 and DDP 25 mg/m² IV on days 1 - 3. (SCRT; 25 Gy in five fractions) is delivered after the first two cycles of systemic therapy, followed by four additional cycles of systemic therapy without RT.

The primary endpoint is 1-year recurrence-free survival (RFS). Secondary endpoints include locoregional RFS, distant metastasis-free survival, overall survival and safety (CTCAE V.5.0).

The planned sample size is 47 (44 evaluable), providing 80% power (one-sided α of 0.10) to detect an improvement in 1-year RFS from 55% to 70%. Time-to-event endpoints will be estimated using Kaplan - Meier methods with 95% CIs.

Ethics and dissemination The protocol was approved by the Ethics Committee of Fudan University Shanghai Cancer Centre (approval number: 2407300-5), and all participants will provide written informed consent. Findings will be disseminated in peer-reviewed journals and at scientific conferences.

Trial registration number ChiCTR2400093001.