RESUMO
BACKGROUND: Cabozantinib is highly effective against advanced renal cell carcinoma (RCC). However, approximately 60% of the patients require a dose reduction due to severe adverse events. Although associations between trough concentrations of cabozantinib and its efficacy and safety have been reported in other countries, reports on Japanese patients are unavailable. Therefore, we investigated the association of cabozantinib trough concentration with therapeutic efficacy and adverse events in Japanese patients with RCC and evaluated the usefulness of therapeutic drug monitoring. METHODS: In this prospective observational study, we measured the trough concentrations of cabozantinib in 10 Japanese patients with RCC enrolled between May 2022 and September 2023. The associations of trough concentration with treatment response, as determined by RECIST 1.1, and the occurrence of grade 2 or higher adverse events were assessed. RESULTS: Trough concentration was higher in patients with controlled cancer than in those with progressive cancer (1024 ± 352 versus 457 ± 216 ng/mL, P = 0.035). In addition, patients with grade 2 or higher adverse events showed a significantly higher trough concentration than those without (1560 ± 513 versus 807 ± 319 ng/mL, P = 0.032). In particular, grade 2 or higher dysgeusia, anorexia, fatigue, and dyspepsia significantly correlated with trough concentrations. CONCLUSIONS: This is the first clinical study to demonstrate a correlation between cabozantinib trough concentration, therapeutic efficacy, and adverse events in Japanese patients with RCC. The therapeutic drug monitoring of cabozantinib could be useful for improving therapeutic efficacy and avoiding serious adverse events.
RESUMO
Cabozantinib is an oral small-molecule tyrosine kinase inhibitor that has become a standard of care for advanced renal cell carcinoma (RCC). However, cabozantinib is associated with a high rate of adverse events. Therefore, individualised cabozantinib administration and monitoring could help maximise its therapeutic efficacy and avoid serious adverse events. This study developed and validated a method to determine cabozantinib concentration in plasma using HPLC-UV. Sorafenib, an internal standard, was added to the plasma sample containing cabozantinib. A calibration curve for cabozantinib showed good linearity (R2 = 1.00), between 25 and 4,000 ng/ml. The recovery rate was above 92.1%, and the intra- and inter-day coefficients of variation were smaller than 5.2 and 6.8%, respectively. Then, we applied the method for monitoring cabozantinib blood levels in three patients with advanced RCC who were taking cabozantinib at a dose of 20, 40 or 60 mg/day. Grade 3 adverse events were more likely to occur in patients with high dosing and blood level of cabozantinib. Owing to its simplicity, the developed method can be used in general hospitals, and is expected to help maximise drug efficacy and minimise serious adverse events in many patients with RCC undergoing cabozantinib treatment.