Cabozantinib for the treatment of patients with metastatic non-clear cell renal cell carcinoma: A retrospective analysis

Background: Cabozantinib prolongs overall survival (OS) and progression-free survival (PFS) in patients with metastatic clear cell renal cell carcinoma (RCC) that progressed on first-line vascular endothelial growth factor receptor–tyrosine kinase inhibitor (VEGFR-TKI). The role of cabozantinib has not been established in non-clear cell renal cell carcinoma (nccRCC). Methods: This is a retrospective study of 30 patients with nccRCC who received cabozantinib from January 2013 to January 2017. Information collected included baseline characteristics, toxicity, dose reductions, PFS and OS. A fellowship trained abdominal radiologist, blinded to patient history and clinical data, assessed radiographic response using RECIST, v1.1. Results: With a median follow-up of 20.6 months (95% confidence interval [CI]: 11.4–28.8), median PFS was 8.6 months (95% CI: 6.1–14.7), and median OS was 25.4 months (95% CI: 15.5–35.4). Of the 28 patients with measurable disease, 4 had partial responses (2 papillary, 1 chromophobe and 1 unclassified RCC), 18 had stable disease (64.2%) and 6 had progressive disease (21.4%), resulting in a 14.3% objective response rate and a 78.6% disease control rate. Two patients with papillary RCC who had experienced disease progression on savolitinib achieved durable partial response and stable disease, respectively, following treatment with cabozantinib. Of the 21 patients who started cabozantinib at 60 mg/d, 12 (57.1%) required dose reduction due to toxicity. Conclusion: In this retrospective study, cabozantinib produced a clinically meaningful benefit in patients with metastatic nccRCC, the majority of whom had disease progression on prior VEGFR-TKIs. Prospective trials of cabozantinib in nccRCC are warranted.