Changeable Conditional Survival Rates and Associated Prognosticators in Patients with Metastatic Renal Cell Carcinoma Receiving First Line Targeted Therapy

Purpose: In this study we evaluated conditional survival probabilities in patients with metastatic renal cell carcinoma who underwent first line tyrosine kinase inhibitor therapy. We also identified predictors of conditional survival with time. Materials and Methods: We retrospectively reviewed clinical data on 1,659 individuals with metastatic renal cell carcinoma in the Korean Renal Cancer Study Group database, of whom the records of 1,131 were finally analyzed. The primary end point was conditional overall survival. Kaplan-Meier survival analysis was used to calculate conditional overall survival probabilities using the formula, conditional survival (α│β) = S(α + β)/S(β), indicating the likelihood of additional α years survivorship in person who has already survived for β years after initial therapy. S(χ) represents the actual survival rate. Multivariate Cox regression model was used to identify predictors of conditional survival with time. Results: Six, 12, 18, 24 and 36-month conditional overall survival gradually increased in patients at all additional survival times after initial treatment compared to patient baseline survival estimations. While the actual overall survival rate decreased with time, the 36-month conditional overall survival rate was calculated as 7.3% higher in patients who had already survived 36 months compared to baseline estimations at the time of initial tyrosine kinase inhibitor treatment. Furthermore, predictors of conditional overall survival changed with time. Only previous metastasectomy remained a key prognosticator of conditional overall survival until 36 months of survival following initial tyrosine kinase inhibitor treatment. Conclusions: Conditional survival improved with time after initial tyrosine kinase inhibitor treatment in patients with metastatic renal cell carcinoma. Our study offers valuable information for practical survival estimations and relevant prognosticators in patients with metastatic renal cell carcinoma who receive first line tyrosine kinase inhibitor.