Conditional survival estimates for merkel cell carcinoma reveal the dynamic nature of prognostication

Background and objectives: Conditional survival (CS) analysis has emerged as a dynamic prognostication methodology. The goal of this study was to determine disease-specific CS rates in Merkel cell carcinoma (MCC).

Methods: This retrospective study included patients with MCC from the Surveillance Epidemiology and End Results (SEER) registry (1988-2016). Stage-specific 5-year MCC-specific CS rates for study and survivor cohorts were estimated, and the significance of clinicopathologic factors to predict 1-year MCC-specific death was evaluated using multivariate logistic regression.

Results: Within stage, 5-year CS survival rates improved with increasing survivorship. Pathologic Stage I patients had the highest 5-year CS rate at diagnosis (89.1%) but the smallest increase over time (96% among 5-year survivors). Stage IV patients experienced the greatest change in 5-year CS rates from 25.4% (at diagnosis) to 88% (5-year survivors). At diagnosis stage, age, sex, and primary site were all significantly associated with 1-year MCC-related death in the multivariate analysis. In contrast, among 5-year survivors only sex and age at diagnosis were significant predictors.

Conclusions: MCC CS rates improved across all disease stages over time. Additionally, the relationships of prognostic factors with 1-year MCC-death changed with increasing survivorship. This perspective can provide a foundation for informed decision-making.