Prognostic factors in Merkel cell carcinoma: Analysis of 240 cases

Background: Knowledge regarding behavior of and prognostic factors for Merkel cell carcinoma (MCC) is limited. Objective: We sought to further understand the characteristics, behavior, prognostic factors, and optimal treatment of MCC. Methods: A multicenter, retrospective, consecutive study of patients with known primary MCC was completed. Overall survival and survival free of locoregional recurrence were calculated and statistical analysis of characteristics and outcomes was performed. Results: Among the 240 patients, the mean age at diagnosis was 70.1 years, 168 (70.0%) were male, and the majority was Caucasian. The most common location was head and neck (111, 46.3%). Immunosuppressed patients had significantly worse survival, with an overall 3-year survival of 43.4% compared with 68.1% in immunocompetent patients. In our study, patients with stage II disease had improved overall survival versus those with stage I disease, in a statistically significant manner. Patients with stage III disease had significantly worse survival compared with stage I and with stage II. Primary tumor size did not predict nodal involvement. Conclusion: The data presented represent one of the largest series of primary MCC in the literature and confirm that MCC of all sizes has metastatic potential, supporting sentinel lymph node biopsy for all primary MCC. Because of the unpredictable natural history of MCC, we recommend individualization of care based on the details of each patient's tumor and clinical presentation.