Axitinib-induced proteinuria and efficacy in patients with metastatic renal cell carcinoma

Background No report has evaluated axitinib-induced proteinuria as a biomarker for predicting treatment efficacy and survival of patients with metastatic renal cell carcinoma (mRCC). Methods The subjects were patients with mRCC treated with axitinib at Kinki University Hospital from February 2008 to November 2014. Clinical records were retrospectively reviewed including baseline patient characteristics, time-dependent changes of urinary protein status, computed tomography scans of metastatic lesions, treatment duration with axitinib, and survival time. Results A total of 45 patients were evaluable. Median tumor shrinkage rates were 32.3 and 35.0 % in patients with urinary protein increases ≥+2 and <+2, respectively ( p = 0.496). Objective response rates were also similar between the two groups. Median progression-free survival (PFS) times with axitinib were 13.5 months [95 % confidence interval (CI) 0.0–27.5] and 11.0 months (95 % CI 0.0–26.7) in patients with urinary protein increases ≥+2 and <+2, respectively ( p = 0.975). The maximum tumor shrinkage rate with axitinib was significantly associated with PFS with axitinib as a result of multivariate analysis ( p = 0.002). Median overall survival (OS) times were 39.8 months (95 % CI 12.7–67.0) and 25.4 months (95 % CI 11.2–39.6) in patients with axitinib-induced urinary protein increases ≥+2 and <+2, respectively ( p = 0.250). The number of metastatic sites ( p = 0.006), the MSKCC risk ( p = 0.009), and the maximum tumor shrinkage rate with axitinib ( p = 0.019) were significantly associated with OS as a result of multivariate analysis. Conclusions The degree of urinary protein increase during axitinib treatment was not associated with objective response, PFS, and OS in mRCC patients treated with axitinib.