Clinical characteristics and immunotherapy in Chinese patients with Merkel cell carcinoma: a retrospective analysis

Merkel cell carcinoma (MCC) is a rare but highly aggressive cutaneous malignancy with limited epidemiological and therapeutic data in Asian populations. While immunotherapy works in Western patients, its efficacy in Chinese MCC patients remains unexplored.

We retrospectively analyzed 40 histologically confirmed MCC cases treated at our institution between November 2011 to November 2024. Sixteen patients with complete records underwent detailed analysis of demographics, treatments, and responses.

The cohort included 25 female and 15 male patients (median age 71 years, range 25-91). Of the 16 patients with detailed information, 15 (94%) patients underwent extensive resection while 1 did not. Among surgical patients, 1 (7%) patient operative area received postoperative adjuvant radiotherapy, and 2 (13%) had additional lymph node dissection. Immunohistochemical analysis showed that out of 10 evaluable patients, 8 (80%) were MCPyV positive and 3 (30%) were PD-L1 positive. Among the patients receiving systemic treatment, four were administered Pembrolizumab at a dose of 200 mg every three weeks. Remarkably, three of these patients (75%) achieved a complete response (CR) by radiographic evaluation, with two of the treated specimens showed no residual malignant cells detected in post-treatment biopsy specimens. The treatment was well-tolerated, with no grade 3 or higher adverse events reported during the observation period.

This study describes MCC characteristics in Chinese patients, with preliminary indications of female predominance and favorable immunotherapy responses. The findings highlight the need for standardized treatment approaches.