(A1100) A Comparative-Effectiveness Research of the Comprehensive Treatment Strategies for Resectable Sinonasal Mucosal Melanoma

Introduction: Sinonasal mucosal melanoma (SNMM) is a rare and aggressive malignancy. Unlike cutaneous melanoma, SNMM shows limited response to immunotherapy. The optimal treatment strategy remains undefined, and the role of immune checkpoint inhibitors in perioperative treatment of SNMM is unclear. Additionally, the efficacy of preoperative radiotherapy warrants further investigation.

Methods: From 2021 to 2023, three single-center Phase II clinical trials were initiated at our institution, enrolling patients with pathologically confirmed SNMM. In trials ChiCTR2100046498 and ChiCTR2100045797, eligible patients underwent postoperative chemoradiotherapy, with or without immune checkpoint inhibitors (anti-PD1 antibodies). Participants in trial ChiCTR2100049031 received preoperative radiotherapy. The primary efficacy endpoints were distant metastasis-free survival (DMFS) and overall survival (OS).

Results: A total of 57 patients were enrolled, with a mean age of 63 years (33 males [57.9%] and 24 females [42.1%]). Patients were allocated to the following groups: preoperative radiotherapy (n=7), postoperative chemoradiotherapy (n=15), postoperative chemoradiotherapy combined with immunotherapy (n=25), and surgery alone (n=10). OS rates at 1 and 2 years were 86.9% and 45.6%, while DMFS rates were 72.2% and 49.4%, respectively.During a median follow-up of 12 months, 23 patients died,18 patients developed metastases, with the majority (14/23, 60.9%) succumbing to metastases within the first year.The subgroup analysis revealed a significant association between tumor T stage and OS (p=0.001).The preoperative radiotherapy group demonstrated higher 1-year OS (83.3%) compared to other treatment groups (66.6%).Among patients who received postoperative chemoradiotherapy with and without immunotherapy, the 1-year OS showed no statistically significant difference (61.6% vs. 66.0%, p=0.946).

Conclusions: Preoperative radiotherapy may reduce the risk of distant metastasis. The survival benefit of adjuvant immunotherapy in combination with surgery and radiotherapy remains unclear.