Treatment of Locally Advanced Merkel Cell Carcinoma—A Multi-Center Study

SIMPLE SUMMARY: Merkel cell carcinoma (MCC) is a rare skin cancer with unfavorable outcomes. Surgery remains the standard of care in the treatment of locally advanced disease. Perioperative radiotherapy and chemotherapy can be considered in selected patients. Analyzing 161 patients with locally advanced MCC treated with curative intent, we found that over one-third of patients developed disease recurrence. The use of perioperative radiotherapy decreased the risk of disease recurrence by over 50%. The 5-year overall survival rate was 55%. Moreover, we identified male gender, age above 70, metastases in lymph nodes at diagnosis, and no sentinel lymph node biopsy as factors associated with shorter overall survival. ABSTRACT: Merkel cell carcinoma (MCC) is a rare, aggressive skin cancer with a high risk of recurrence and poor prognosis. The treatment of locally advanced disease involves surgery and radiotherapy. To analyze real-life treatment patterns and clinical outcomes, we conducted a retrospective analysis of data from 161 MCC patients treated with curative intent in four oncological centers in Poland. The median age at diagnosis was 72 years (30–94); 49.7% were male. Lymph node (LN) involvement at diagnosis was found in 26.9% of patients. Sentinel lymph node biopsy (SLNB) was performed in 36.5% of patients (positive in 10.5%), and 51.9% of patients received perioperative treatment. The relapse rate was 38.3%. With the median follow-up of 2.3 years, the median disease-free survival (DFS) was not reached, and the 1-year rate was 65%. The negative independent risk factors for DFS were male gender, metastases in LN at diagnosis, no SLNB in patients without clinical nodal metastases, and no perioperative radiotherapy. The estimated median overall survival (OS) was 6.9 years (95% CI 4.64–9.15). The negative independent risk factors for OS were male gender, age above 70, metastases in LN at diagnosis, and no SLNB in patients without clinical nodal metastases. Our results confirm that the MCC treatment should be conducted in an experienced multidisciplinary team; however, the outcomes are still unsatisfactory.