Prognostic Significance of Early Tumor Shrinkage Under Second-Line Targeted Therapy for Metastatic Renal Cell Carcinoma: A Retrospective Multi-Institutional Study in Japan.

Abstract

The prognostic significance of early tumor shrinkage (ETS) under second-line targeted therapy for metastatic renal cell carcinoma (mRCC) has not been fully documented. The objective of this study was to evaluate the impact of ETS induced by a second-line targeted agent on overall survival (OS) in mRCC patients. This study retrospectively included 271 consecutive Japanese patients with mRCC who received second-line targeted therapy for at least 3months. ETS was defined as the degree of tumor shrinkage at the first post-baseline radiological evaluation conducted 4-8weeks after initiating second-line targeted therapy. Of the 271 patients, 26 had ETS from -100 to -50%, 70 from -49 to -25%, 84 from -24 to 0%, and the remaining 91 failed to achieve a reduction in the tumor size. The median OS following the initiation of second-line targeted therapy stratified according to ETS was 45.8, 30.9, 22.1 and 14.2months, respectively. Univariate analysis identified prior nephrectomy, the Memorial Sloan-Kettering Cancer Center (MSKCC) risk classification, C-reactive protein (CRP) level, number of metastatic organs, sarcomatoid feature, introduced second-line agent and ETS induced by a second-line agent as parameters significantly associated with OS, of which, only the MSKCC classification, CRP level and ETS appeared to have independent impacts on OS on multivariate analysis. These findings suggest that ETS at the first post-baseline assessment under treatment with a second-line targeted agent could serve as a useful parameter with an independent impact on OS in mRCC patients receiving second-line targeted therapy.