Prognostic Factors Influencing Oncologic Outcomes in Merkel Cell Carcinoma: A Retrospective Population‐Based Cohort Study

Aim/Objectives Merkel cell carcinoma (MCC) is a rare, aggressive neuroendocrine skin cancer with a poorly understood etiology and lacking high‐level evidence to guide its management. This study examined the presentation and outcome related to MCC treatment at a Canadian center. Materials and Methods The electronic and paper records of a population‐based cohort of 74 cases of MCC identified by the Manitoba Cancer Registry between 2000 and 2019 to be treated with potential curability intent were retrospectively reviewed. Age, gender, stage of disease at initial presentation, treatment intent and modalities used, and their oncological outcome were recorded and analyzed using SPSS 27·0. A two‐sided Pearson test was used for intergroup comparisons. Disease‐specific survival (DSS) was estimated by the Kaplan–Meier product limit method, and the effect of individual prognostic factors on survival was assessed using the log‐rank test. The Cox‐proportional hazard model was used to determine the independent influence of prognostic factors on DFS and DSS. Results The mean age at diagnosis was 75.9 years; 51% were female, 35% had a history of nonmelanoma skin cancer, 4% had a history of melanoma, and 12% had a history of immunosuppression. Eighty‐three percent of patients were treated with curative intent. Five‐year DSS and DFS were 57.2% and 45.7%, respectively. The head and neck were the most common sites involved (59%); however, the location of MCC did not influence DSS. Forty percent of patients had pathologic Stage III/IV disease. For the patients treated with curative intent, the patient’s gender or treatment modality did not impact the DSS. The stage of disease (HR = 1.04; 95% CI = 1.00–1.08; p < 0.001) and the age of disease (HR = 1.04; 95% CI = 1.00–1.08; p = 0.046) independently influenced DSS at presentation. Conclusion The stage at presentation and age at diagnosis but not the site of MCC or radical treatment modality were identified as independent predictors of DSS.