Conditional recurrence-free survival in patients with primary stage I-II cutaneous malignant melanoma - a population-based study.

Conditional survival in patients with localized primary cutaneous malignant melanoma (CMM) is well described. However, conditional recurrence-free survival (RFS) has not been investigated before. The aim of this study was to determine conditional RFS and test for time dependency in prognostic factors in patients with localized stage I-II CMM. This study included 1437 CMM patients registered in one region of Sweden during 1999-2012 followed up through 31 December 2012. To identify first recurrence of CMM disease, data from a care data warehouse, the pathology and radiology department registries were used. Patients were also followed through a Census Register and the National Cause of Death Register. The time-dependent risk of recurrence was analysed in a Cox's proportional hazard regression. The 5-year conditional RFS increased from 86% (95% confidence interval: 84-88) at diagnosis to 96% (95% confidence interval: 94-98) at 5 years after diagnosis. Women showed a 60% lower risk of recurrence than men and this effect was stable over time (P=0.39). Patients aged greater than or equal to 65 years had a 40% higher risk of recurrence than patients aged less than 65 years, and this effect was stable over time (P=0.65). Patients with tumour ulceration showed a 70% higher risk of recurrence than nonulcerated patients, but this effect disappeared after 2 years (P=0.04). For patients with T3-T4 CMM, the hazard ratios decreased over time and were similar to hazard ratio of patients with T2 CMM after 2 years and later. The decreasing impact of tumour thickness and ulceration over time could have important implications for CMM patients in terms of counselling and follow-up.