Epidemiology of primary Merkel cell carcinoma in the United States

Background: Merkel cell carcinoma (MCC) is a rare, aggressive skin cancer. Objective: We sought to describe primary MCC incidence trends, epidemiology, and predictors of survival. Methods: The population covered by the Surveillance, Epidemiology, and End Results Program was analyzed as a prospective cohort. We measured age-adjusted incidence rates (per 100,000 person-years) and effect of age, anatomic site, and stage on survival. Results: Incidence was higher in males (0.34) than in females (0.17). Cases (n = 1034) occurred mostly in whites (94%), in people older than 65 years (76%), and at the head (48%). The 5-year relative Survival was 75%, 59%, and 25% for localized, regional, and distant MCC, respectively. Female sex, limb presentation, localized disease, and younger age were positive predictors of survival. Conclusion: The highest incidence of MCC was observed in whites, males, and in people older than 65 years. Only 49% of cases were reported as localized. Better survival was associated with limb localization, early-stage disease, younger age, and female sex.