Merkel cell carcinoma: Clinical outcome and prognostic factors in 351 patients

Background Merkel cell carcinoma (MCC) is a rare and aggressive neuroendocrine carcinoma of the skin. Aim To describe clinical outcome and prognostic factors of MCC patients in two expert‐centers. Method Patients with histologically confirmed MCC in 1990‐2014 were included. Data on patient, tumor characteristics and treatment were retrospectively collected. Results A total of 351 Patients were evaluated, 153 (44%) males, median age 74 years (range 28‐94). Median follow‐up time was 28 months (IQR 13‐58). Median primary tumor size was 17 mm (range 2‐135). At time of diagnosis 112 (32%) patients had lymph node metastases. The cohorts′ 5‐year overall survival (OS) was 58%. Using a competing risk analysis the 5‐year relapse and MCC related death was 42% and 22%. Adjuvant radiation therapy (XRT) was associated with reduced recurrence (SDH 0.54; CI 0.3‐0.9). Nodal involvement (SDH 2.7; CI 1.1‐6.6) and the male gender were associated with higher MCC related death (SDH 3.1; CI 1.2‐7.9) Conclusion In a large cohort a low MCC related death, in the presence of a low OS was seen. This indicates that a significant number of MCC patients die due to other causes than MCC. Adjuvant XRT was associated with relapse. Male gender and nodal metastasis were associated with MCC related death.