Early Tumor Shrinkage Under Treatment with First-line Tyrosine Kinase Inhibitors as a Predictor of Overall Survival in Patients with Metastatic Renal Cell Carcinoma: a Retrospective Multi-Institutional Study in Japan.

Abstract

Prognostic significance of early tumor shrinkage following treatment with tyrosine kinase inhibitors (TKIs) in patients with metastatic renal cell carcinoma (mRCC) has not been fully elucidated. The aim of this study was to assess the impact of early tumor shrinkage induced by first-line TKIs on overall survival (OS) in mRCC patients. This study retrospectively included 185 consecutive Japanese patients with mRCC treated with either sunitinib or sorafenib for at least 3months as first-line molecular-targeted therapy between April 2011 and December 2014 at Kobe University Hospital and its affiliated institutions. Median OS in the 185 patients was 33.6months. At 12weeks after the introduction of TKIs, 9 patients had achieved tumor shrinkage from -100 to -50%, 43 from -49 to -25%, 61 from -24 to 0%, and the remaining 72 patients showed an increase in tumor size. The median OS stratified according to tumor shrinkage as shown above was 59.2, 39.1, 31.4, and 16.1months, respectively. Univariate analysis identified prior nephrectomy, Memorial Sloan Kettering Cancer Center (MSKCC) risk classification, C-reactive protein (CRP) level, liver metastasis, number of metastatic organs, histological subtype, sarcomatoid feature, and early tumor shrinkage as significant predictors of OS. Of these significant factors, only the MSKCC classification, CRP level, liver metastasis, and early tumor shrinkage were shown to be independently associated with OS on multivariate analysis. Early tumor shrinkage could be a useful predictor of OS in mRCC patients receiving TKIs as a first-line molecular-targeted agent.