Activity of Tivozanib in Non-clear Cell Renal Cell Carcinoma: Subgroup Analysis From a Phase II Randomized Discontinuation Trial

BACKGROUND: Non-clear cell renal cell carcinoma (nccRCC) is a blanket term for a collection of heterogeneous and biologically diverse RCC histologies, including but not limited to papillary, chromophobe, and unclassified subtypes. Tivozanib is a selective vascular endothelial growth factor receptor (VEGFR) tyrosine kinase inhibitor (TKI) that demonstrated activity in RCC with clear cell component. The objective of this analysis was to determine the efficacy of tivozanib in histologically unclassified/mixed RCC. METHODS: We identified patients with nccRCC enrolled in Study 201 (NCT00502307) between October 2007 and July 2008. This was a phase II randomized discontinuation trial of tivozanib in patients with RCC who had no prior VEGFR-targeted treatment. Clinical outcomes including investigator-assessed objective response rate (ORR), disease control rate (DCR, defined by complete response + partial response + stable disease), and progression-free survival (PFS) were examined. RESULTS: Of the 272 patients enrolled, 46 (16.9%) patients had nccRCC: 11 (4%) papillary, 2 (0.7%) chromophobe, 2 (0.7%) collecting duct, and 31 (11.4%) mixed/unclassified. Of the 46 patients with nccRCC, 38 were continuously treated with tivozanib and the best ORR was 21.1% (confirmed) and 31.6% (confirmed and unconfirmed). The DCR was 73.7% and median PFS was 6.7 months (95% confidence interval, 125-366 days). There were no new safety signals compared to the ITT population. Limitations include the small number of individual nccRCC subtypes and the randomized discontinuation design. CONCLUSION: Tivozanib demonstrated activity and a favorable safety profile in patients with nccRCC. These data add to the body of evidence supporting the use of VEGFR-TKI in advanced nccRCC.