Predictors of survival and recurrence in the surgical treatment of merkel cell carcinoma of the extremities.

PURPOSE: Merkel cell carcinoma (MCC) is a rare and aggressive malignancy that originates within the extremities in about 40% of cases. Treatment approaches to this tumor have not been standardized. The purpose of this study was to examine treatment approaches to extremity MCC and to determine predictors of recurrence and patient survival.

METHODS: A retrospective review of 38 consecutive patients with surgically treated extremity MCC was performed. Patient demographics, histologic tumor stage and location and pre-existing malignancies were recorded. Patients were treated by wide-local excision (WLE) or Mohs' technique. Clinically negative regional lymph nodes were either observed (n = 16) or staged with elective lymphadenectomy or sentinel lymph node dissection (SLND) (n = 17), and clinically positive nodes underwent therapeutic node dissection (n = 5). Adjuvant radiotherapy (n = 21) and chemotherapy (n = 6) were noted, as well as time to tumor recurrence and overall patient survival. Predictors of recurrence and survival were analyzed using Kaplan-Meier method and log rank test.

RESULTS: There was no difference in local recurrence rates when comparing Mohs' technique to WLE for the treatment of primary tumors. Although there was no survival advantage to lymph node dissection, lymph node status was effective in predicting the risk of regional recurrence. Radiation reduced the local recurrence rate (HR = 0.29, 95% CI [0.10, 0.85]), but did not lead to improved overall survival.

CONCLUSION: Margin-negative excision of the MCC remains the mainstay of treatment. Surgical staging, preferably with SLND, identifies patients that may develop regional recurrence. This study further supports the important role of adjuvant radiation therapy in improving locoregional tumor control in the patients with MCC.