Immunosuppression Outweighs Clinical AEIOU Heuristics in Predicting Disease Progression of Merkel Cell Carcinoma: A Retrospective Cohort Study

Merkel cell carcinoma (MCC)is a rare but aggressive cutaneous malignancy with increasing incidence and poor prognosis. Host immune status is a key determinant of MCCmerkel cell carcinoma development and outcome. While the AEIOU criteria are widely used to facilitate clinical recognition, their value for prognostic assessment remains unclear. To evaluate the association between individual AEIOU presentation features and disease progression in patients with merkel cell carcinoma, with particular emphasis on immunosuppression. We performed a retrospective single-centre cohort study including 400 patients diagnosed with merkel cell carcinoma. Disease progression, defined as local recurrence, nodal involvement or distant metastasis, served as the primary endpoint. AEIOU criteria were assessed at diagnosis and analysed using logistic regression. Complete follow-up data were available for 241 patients, of whom 81 (33.6%) experienced disease progression. Patients with progression were significantly older and more frequently male. Among the AEIOU components, immunosuppression was the only criterion significantly associated with disease progression, conferring an increased risk compared with immunocompetent patients (p<0.001). Other AEIOU features showed no consistent prognostic association. Complete follow-up data were available for 241 patients, of whom 81 (33.6%) experienced disease progression. Patients with progression were significantly older and more frequently male. Among the AEIOU components, immunosuppression was the only criterion significantly associated with disease progression, conferring an increased risk compared with immunocompetent patients (p<0.001). Other AEIOU features showed no consistent prognostic association.