Postoperative Radiotherapy and Overall Survival in Head and Neck Merkel Cell Carcinoma: A Population-Based Cohort Study (SEER 2004–2021)

This supplementary dataset accompanies the manuscript entitled “Postoperative Radiotherapy and Overall Survival in Head and Neck Merkel Cell Carcinoma: A Population-Based Cohort Study (SEER 2004–2021).” This study focused on head and neck Merkel cell carcinoma (HN-MCC), a rare but highly aggressive neuroendocrine tumor. Using data from the SEER database (2004–2021), the investigators conducted a population-based cohort analysis to evaluate the impact of postoperative radiotherapy (PORT) on overall survival (OS). A total of 1,776 patients with non-metastatic HN-MCC who underwent curative-intent resection and had known radiotherapy status were included, of whom 52.9% received PORT. Because baseline risk was higher in the PORT group (e.g., greater nodal burden and poorer differentiation), 1:1 nearest-neighbor propensity score matching (PSM) was performed to balance covariates, yielding 655 well-matched pairs.

Results showed that PORT was significantly associated with improved OS both before and after matching (adjusted HR = 0.804, 95% CI 0.696–0.928, P < 0.001; post-PSM P = 0.006). In the matched cohort, the absolute improvements in 3-year and 5-year OS were 4.1% and 8.2%, respectively, with a 3.0-month gain in restricted mean survival time (RMST) over 60 months, indicating a clinically meaningful survival benefit.

Subgroup analyses revealed that the greatest benefit of PORT was observed among high-risk patients, including those aged > 65 years, with tumors > 2 cm, T2–T4 stage, > 4 positive nodes, cutaneous primaries, and diagnoses between 2016–2021. In contrast, no OS benefit was seen in low-risk subgroups (e.g., T1 stage, small tumors, minimal nodal disease), suggesting that selective de-escalation may be appropriate for these patients.

Although limited by the lack of detailed radiotherapy parameters and comorbidity data in the registry, the consistency of results across multiple analytic approaches supports the robustness of these findings. Overall, this study demonstrates that PORT significantly improves OS in resected HN-MCC, particularly among high-risk patients, and supports a risk-adapted, individualized approach to adjuvant radiotherapy.