Retrospective Analysis of Fifth-Line Targeted Therapy Efficacy in Patients with Metastatic Renal Cell Carcinoma

<b><i>Objectives:</i></b> Current evidence of sequence-targeted therapy (TT) for patients with metastatic renal cell carcinoma (mRCC) beyond fourth-line is sparse. The aim of this study was to describe the efficacy and toxicity of fifth-line TT in patients with mRCC. <b><i>Methods:</i></b> Out of 406 patients treated in first-line, 25 patients (6.16%) with more than 4 lines of TT were retrospectively reviewed at a German academic high-volume cancer center. Response was assessed by the use of standard Response Evaluation Criteria in Solid Tumors version 1.0, and toxicity was graded according to the Common Toxicity Criteria for Adverse Events version 3.0. Progression-free survival (PFS) and overall survival (OS) were estimated using the Kaplan-Meier method. Cox proportional hazard models were applied to explore predictors of PFS and OS in univariable and multivariable analyses. <b><i>Results:</i></b> Disease control rate for fifth-line treatment was 20%. Median OS from the beginning of first-line therapy was 50.2 months (IQR (interquartile range) 38.9-76.7). Median OS from the time of initiation of fifth-line therapy was 6.2 months (IQR 3.1-23.8). Median PFS for fifth-line TT was 4.1 months (IQR 1.81-9.07) and did not correlate to treatment response in first-line TT. <b><i>Conclusions:</i></b> Highly selected patients might benefit from fifth-line treatment independently from treatment response in first-line TT.