Positive Surgical Margins Affect Nodal Metastasis and All-Cause Mortality in Merkel Cell Carcinoma: A National Cancer Database Study 2004 to 2022.

BACKGROUND: Merkel cell carcinoma (MCC) is a highly aggressive cutaneous malignancy. Guidelines recommend surgical excision with histologically negative margins for clinically node-negative disease. Adjuvant radiation therapy (aRT) is recommended for positive margins; however, its ability to offset the adverse impact of residual microscopic disease remains uncertain. OBJECTIVE: Evaluate the association between surgical margin status and oncologic outcomes among patients treated with excision and aRT. METHODS: Using the National Cancer Database (2004-2022), the authors identified patients with cN0 MCC who underwent excision followed by aRT with documented margin status. Multivariable logistic regression assessed predictors of regional lymph node metastasis, and Cox modeling evaluated all-cause mortality. RESULTS: Among 7,510 patients, 11.7% had positive surgical margins. Margin positivity was more common in older patients, head and neck tumors, and higher T-stage disease. Positive margins were independently associated with increased odds of regional lymph node metastasis (aOR 1.57, 95% confidence interval CI 1.24-1.99; p < .001) and higher all-cause mortality (HR 1.60, 95% CI 1.43-1.78; p < .001). CONCLUSION: Their findings suggest that positive surgical margins are an adverse prognostic factor despite aRT. Achieving histologically negative margins remains an important prognostic consideration in the management of MCC.