Efficacy of Cabozantinib for Papillary Compared With Clear-cell Renal Cell Carcinoma Following Immune Checkpoint Inhibitor Treatment

BACKGROUND: The efficacy of combined immunotherapy for papillary renal cell carcinoma (pRCC) based on prolonged progression-free survival (PFS) and overall survival in several clinical trials remains unknown. We aimed to compare the efficacy of cabozantinib in patients with pRCC and those with clear-cell renal cell carcinoma (ccRCC). PATIENTS AND METHODS: This retrospective study included 27 patients with metastatic RCC who received cabozantinib as second-line or later therapy between June 2020 and October 2021. Objective response, PFS, and toxicity were compared between the ccRCC and pRCC groups. RESULTS: Out of 27 patients, seven and 20 were diagnosed with pRCC and ccRCC, respectively. Out of the seven patients with pRCC, cabozantinib was used as second-line treatment in four patients and as third-line treatment in three patients, and all seven patients had had prior immunotherapy. One and two patients achieved complete and partial responses, respectively; four patients had stable disease, and none had progressive disease. The rates of objective response (43% vs. 30%, p=0.65) and disease control (100% vs. 85%, p=0.54) were similarly high in patients with pRCC and ccRCC. Changes in the target lesions were -19% and -10% (p=0.11), respectively. With a median follow-up of 7.1 months, the median PFS tended to be longer in patients with pRCC than in those with ccRCC (not reached vs. 10.7 months, p=0.12). Discontinuation due to toxicity was observed in four (57%) patients with pRCC and 10 (50%) patients with ccRCC. CONCLUSION: Cabozantinib is effective for pRCC, similar to ccRCC. This information may help physicians to select treatment options for pRCC.