Treatment and survival of Merkel cell carcinoma since 1993: A population-based cohort study in The Netherlands

Background: Merkel cell carcinoma (MCC) is a rare and potentially lethal skin cancer. MCC is known for its potential rapid growth and its propensity to metastasize. Objective: To describe the incidence, treatment, and survival of MCC in a population-based setting. Methods: All MCCs diagnosed in The Netherlands between 1993 and 2016 were selected from the Netherlands Cancer Registry. Patient and tumor characteristics, therapy, and vital status were obtained. Cox proportional hazards were computed, and relative survival analyses were performed. Results: Our cohort included 1977 patients with MCC. Incidence increased from 0.17 per 100,000 person-years in 1993 to 0.59 per 100,000 in 2016. The mean age at diagnosis was 75.5. Most MCCs (59.8%) were treated with surgery alone. Relative 5-year survival was low (63.0%) and did not improve. Mortality was higher among males (hazard ratio [HR], 1.24; 95% confidence interval [CI], 1.11-1.39), higher age (HR, 1.07; 95% CI, 1.06-1.07), and nodal (HR, 1.26; 95% CI, 1.08-1.48) and distant spread of disease (HR, 2.44; 95% CI, 1.99-2.99). Limitations: We lacked data on cause of death, comorbidity, and pathologic margins, which may have led to misinterpretation of the data. Conclusion: This study shows continuously increasing incidence rates of MCC in The Netherlands. Survival after a diagnosis of MCC remained low. Our results emphasize the need for implementation of new therapies.