Association of cabozantinib dose reductions for toxicity with clinical effectiveness in metastatic renal cell carcinoma (mRCC): Results from the Canadian Kidney Cancer Information System (CKCis).

Abstract

316 Background: Cabozantinib (cabo) is an oral multi-targeted tyrosine kinase inhibitor (TKI) with activity in mRCC. TKI toxicity, an indicator of adequate drug exposure, has been associated with clinical effectiveness for sunitinib, pazopanib, and axitinib. We explored whether cabo dose reductions (a surrogate for toxicity) were associated with improved clinical outcomes in mRCC. Methods: Using the CKCis database, we performed an analysis of patients treated with cabo in the second-line or later between 2011-2021. We divided the cohort into those needing a dose reduction (DR, defined as less than the starting dose at time of treatment discontinuation) and those who did not (no-DR). We compared outcomes by dose reduction status, including objective response rate (ORR), time to treatment failure (TTF), and overall survival (OS). Results: We identified 260 patients who received cabo, of which 103 (41.0%) needed a DR. Across all lines, the ORR was similar between the DR and non-DR groups: 19.6% vs. 18.9% (p = 0.903) respectively. The median TTF was 12.75 months (95% CI 10.38 – 17.64) in the DR group vs. 6.44 months (95% CI 5.49 – 8.67) in the no-DR group. After adjusting for IMDC risk, the hazard ratio (HR) for TTF comparing DR vs. no-DR was 0.69 (95% CI 0.50 - 0.97, p-value = 0.03). The median OS was 29.6 months (95% CI 19.58 – 42.64) in the DR group vs. 15.28 (95% CI 11.04 – 22.64) in the no-DR group. After adjusting for IMDC risk, the HR for OS comparing DR vs. no-DR was 0.65 (95% CI 0.43 - 0.98, p = 0.04). Conclusions: Cabozantinib dose reductions, a surrogate for toxicity and adequate drug exposure, appear to be associated with improved TTF and OS in mRCC. Toxicity driven/individualized dosing strategies for cabo alone and in combination with immunotherapy, warrant further investigation.[Table: see text]