Stage-specific conditional survival in renal cell carcinoma after nephrectomy

Objectives: Conditional survival (CS) represents the probability that a cancer patient will survive some additional number of years, given that the patient has already survived for a certain period of time. CS estimates, therefore, serve as better measures of survival probability compared to standard estimates as they incorporate patient survivorship. Stage-specific CS has not been widely investigated in the context of renal cell carcinoma (RCC) after nephrectomy. We aimed to examine this phenomenon. Materials and methods: We analyzed retrospective data on a population-based cohort of 87,225 surgically-treated RCC patients extracted from the Surveillance, Epidemiology, and End Results database (2004–2015) and on a similar validation cohort of 1,642 patients from our institution (1995–2015). 5-year cancer-specific CS estimates stratified by stage were obtained using the Kaplan–Meier method. Multivariable Cox regression analyses were performed to evaluate the possible variation in risk of cancer-specific mortality by stage at nephrectomy and with increasing postoperative survivorship. Results: 5-year cancer-specific survival rates at time of nephrectomy for stage I, II, III, and IV patients in the population-based cohort were 97.4%, 89.9%, 77.9%, and 26.7%, respectively. Improvement in 5-year CS was mainly observed in surviving patients with advanced-stage disease; given 1, 2, 3, 4, and 5 years of survivorship after nephrectomy, the subsequent 5-year cancer-specific survival rates were, respectively, 79.3% (+1.8% increase over previous survival probability), 81.3% (+2.5%), 83.3% (+2.5%), 84.3% (+1.2%), and 85.1% (+1.0%) for stage III, and 34.6% (+29.6%), 42.5% (+22.8%), 49.0% (+15.3%), 55.7% (+13.7%), and 58.6% (+5.2%) for stage IV. A similar trend was established in the validation cohort. Findings were confirmed upon multivariable analyses. Conclusions: CS after nephrectomy for RCC varies dramatically by stage of disease. Gains in CS over time occur primarily among patients with advanced-stage disease. Stage-specific CS estimates can help urologists better plan postoperative surveillance for RCC patients.