The magnitude of best tumor shrinkage during second-line targeted therapy affects progression-free survival but not overall survival in patients with metastatic renal cell carcinoma

Abstract

Objective: The present study aimed to evaluate the influence of the magnitude of best tumor shrinkage during second-line targeted therapy after first-line tyrosine kinase inhibitor failure on metastatic renal cell carcinoma prognosis. Methods: Fifty-two patients were enrolled. The magnitude of tumor shrinkage was assessed according to the Response Evaluation Criteria in Solid Tumors v. 1.1, and evaluated as a continuous variable and by categorical classification: good responders (greater than or equal to -30%), mild responders (-0.1 to -29.9%), poor responders (0 to +19.9%) and non-responders (greater than or equal to +20% or new lesions). Overall survival and progression-free survival after second-line therapy initiation were evaluated according to the categorical classification. Factors predicting overall survival and progression-free survival were also examined. Results: The mean magnitude of tumor shrinkage was -1.29%, and there were 9, 21, 11 and 11 good responders, mild responders, poor responders and non-responders, respectively. The overall survival and progression-free survival significantly improved as the magnitude of tumor shrinkage increased according to the categorical classification (overall survival: not reached, 27.8, 18.2 and 4.67 months; progression-free survival: 13.4, 8.19, 5.18 and 1.84 months, respectively; P< 0.0001 for both). For overall survival, the magnitude of tomor shrinkage was not demonstrated as an independent indicator in the multivariate analysis (P= 0.0872 for the categorical classification, P= 0.133 for the continuous variable) whereas for second-line progression-free survival, the magnitude of tumor shrinkage according to both the categorical classification and continuous variable was found to be an independent factor in the multivariate analysis (P< 0.0001 for both). Conclusions: The magnitude of tumor shrinkage is an independent predictive factor for progression-free survival, and may represent a surrogate marker for overall survival.