Merkel cell carcinoma (MCC) is an uncommon neuroendocrine cutaneous malignancy considered to have a high risk of local recurrence (LR). We investigated the true risk of LR in patients with MCC treated by surgical excision alone.

Patients with clinically localized MCC excised with pathologically negative surgical margins were identified from a prospectively maintained single-institution database from November 1980 through December 2022. The cumulative incidence of LR, defined as recurrence within 5 cm of the surgical scar, was estimated using death as a competing event.

Among 447 patients, 393 (88%) were treated with surgery alone, and 54 (12%) also received adjuvant radiotherapy (RT) to the primary site. LR occurred in eight patients, with seven recurrences detected within 12 months of treatment. All recurrences occurred in patients treated with surgery alone for a 1-year LR rate of 1.8% (95% confidence interval [CI] 0.8-3.6%). At a median follow-up of 8.8 years (95% CI 7.6-10) from presentation, of the six patients with LR alone, all treated with surgery and/or RT, four patients had no evidence of disease and two died of other causes. Two patients developed distant metastases at the time of LR; both received systemic therapy and died of disease. The low incidence of LR precluded analysis of risk factors.

Negative-margin surgery without adjuvant RT provides excellent local control, with an LR rate of 1.8%. LR was effectively treated with surgery and/or RT. These data do not support the routine use of adjuvant RT for all patients after complete excision of primary MCC.