No difference in survival for primary cutaneous Merkel cell carcinoma after Mohs micrographic surgery and wide local excision.

Background: The preferred treatment for clinically node-negative Merkel cell carcinoma (MCC) is surgical excision in conjunction with sentinel lymph node biopsy. There is limited large-scale research on survival outcomes by surgical approach for management of the primary tumor.

Objective: To compare overall and MCC-specific survival outcomes in clinically and pathologically, node-negative MCC patients treated with wide-local excision (WLE) and Mohs micrographic surgery (MMS) in a nationally representative sample.

Methods: Overall and MCC-specific survival outcomes for primary MCC tumors contained in the SEER (Surveillance, Epidemiology, and End Results)-18 database from 1989 to 2015 were stratified by surgical modality and analyzed via competing risk analysis.

Results: A total of 2359 US adults with MCC were included in the analysis. For overall and MCC-specific survival, there was no significant difference in survival outcomes between WLE and MMS on multivariable analysis (hazard ratio, 1.04 [95% CI, 0.88-1.22]; subdistribution hazard ratio, 0.76 [95% CI, 0.53-1.09]). Sentinel lymph node biopsy was associated with improved overall survival and MCC-specific survival.

Limitations: Retrospective design of SEER and the lack of covariates such as comorbidities and immunostaining.

Conclusion: There is no survival disadvantage for MMS compared to WLE as the surgical modality for primary cutaneous MCC. Sentinel lymph node biopsy should be coordinated prior to MMS.