Narrow resection margins are not associated with mortality or recurrence in patients with Merkel cell carcinoma: A retrospective study.

Background: Wide local excision constitutes the standard of care for Merkel cell carcinoma, but the optimal margin width remains controversial.
Objectives: To assess whether narrow margins (0.5-1 cm) were associated with outcome.
Methods: Patients were recruited from a retrospective French multicentric cohort and included if they had had excision of primary tumor with minimum lateral margins of 0.5 cm. Factors associated with mortality and recurrence were assessed by multivariate regression.
Results: Among the 214 patients included, 58 (27.1%) had undergone excision with narrow margins (0.5-1 cm) versus 156 (72.9%) with wide margins (>1 cm). During a median follow-up of 50.7 months, cancer-specific survival did not differ between groups (5-year specific survival rate 76.8% [95% confidence interval 61.7%-91.9%] and 76.2% [95% confidence interval 68.8%-83.6%], respectively). Overall survival, any recurrence-free survival, and local recurrence-free survival did not significantly differ between groups. Cancer-specific mortality was associated with age, male sex, American Joint Committee on Cancer stage III, and presence of positive margins.
Limitations: Retrospective design, heterogenous baseline characteristics between groups.
Conclusion: Excision with narrow margins was not associated with outcome in this cohort, in which most patients had clear margins and postoperative radiation therapy. Residual tumor, mostly found on deep surgical margins, was independently associated with prognosis.
Competing Interests: Conflicts of interest Dr Dreno reports personal fees from Board Merck Pfizer, outside the submitted work. Dr Saiag reports personal fees from Novartis, Pierre Fabre, BMS, MSD, Merk Serono, and Pfizer; and grants from Pierre Fabre and MSD outside the submitted work. Drs Jaouen, Kervarrec, Caille, Le Corre, Esteve, Wierzbiecka-Hainault, Maillard, Dinulescu, Blom, and Samimi have no conflicts of interest to declare.
(Copyright © 2020 American Academy of Dermatology, Inc. Published by Elsevier Inc. All rights reserved.)