Importance of Surgical Margins in Patients with Early-Stage Merkel Cell Carcinoma

The National Comprehensive Cancer Network (NCCN) recommends excision of the primary tumor using 1-2-cm surgical margins and sentinel lymph node biopsy (SLNB) as the initial management of early-stage Merkel cell carcinoma (MCC). However, there is no clear consensus on the appropriate size of the surgical margins and/or the use of Mohs micrographic surgery (MMS). Our aim was to demonstrate that, independent of the type of surgery, obtaining negative surgical margins is associated with enhanced overall survival (OS).

A retrospective study was performed using early-stage MCC patients from the National Cancer Database (NCDB) who were diagnosed between 2004 and 2020 and underwent surgical excision (SE) of their primary tumor. Patients were stratified into three groups based on the surgical treatment they received: < 1 cm excision margin, ≥ 1 cm excision margin, or MMS. OS was assessed with Kaplan-Meier curves, log-rank tests, and multivariable risk-adjusted Cox proportional-hazards regression.

Of the 4,607 patients included in this study; 53% underwent SE of ≥ 1 cm (n = 2,474), 41% had SE < 1 cm (n = 1,905), and the remainder had MMS (n = 228). 75% of patients had an SLNB, and 56% received adjuvant radiation to the primary site and/or nodal basin. While no difference in OS was observed between the three surgical treatments, negative surgical margins (hazard ratio (HR) 0.78; 95% confidence interval (CI) 0.65-0.94) and receipt of radiation to the primary site (HR 0.82; 95% CI 0.73-0.92) were both independently associated with improved OS.

Achieving negative surgical margins is associated with improved OS in MCC, suggesting that MMS and conventional excision are both suitable approaches for the treatment of primary MCC.