Background: Survival curves following surgical treatment of cutaneous melanoma are heavily influenced by early deaths. Therefore, survival estimates may be misleading for long-term cancer survivors. We examined whether conditional survival (CS) is more accurate in predicting long-term melanoma survival.
Methods: We used the Surveillance, Epidemiology, and End Results database (1992-2005) to identify patients who underwent surgical treatment for melanoma. We included patients with T2-T4 disease and with known nodal status. Patients were stratified into low-risk (T2-3N0M0) and high-risk (T4N0M0 or T2-4N1-3M0) categories. We defined CS as time-specific estimates conditioned on living to a certain point in follow-up, and calculated 10-year cancer-specific survival curves conditioned on annual survival. We adjusted for potential confounders using a Cox proportional hazards regression model (alpha = 0.05).
Results: A total of 8647 patients met inclusion criteria (low-risk, 5987 [69.2%]; high-risk, 2660 [30.8%]). At diagnosis, low-risk patients had a significantly better 10-year survival rate (low-risk, 79.6%; high-risk, 41.2%; P < 0.001). On CS analysis, survival differences remained until 8 years after treatment, after which 10-year cancer-specific survival rates were no longer significantly different (P = 0.51) for low-risk (95.4%) and high-risk (91.7%) groups. Multivariate analysis demonstrated that age, gender, location, and ulceration (initial predictors of survival) were no longer predictive after 8 years of survival.
Conclusions: For patients who survive 8 years after surgical treatment of melanoma, CS data become discordant with traditionally used estimates. Our findings have important implications for patient counseling, as high-risk melanoma survivors may require no more intensive surveillance than low-risk survivors 8 years after treatment.