Relationships between sunitinib plasma concentration and clinical outcomes in Japanese patients with metastatic renal cell carcinoma

Background The aim was to investigate the relationships between total sunitinib plasma concentrations (sunitinib plus its active metabolite; N- desethyl sunitinib) and clinical outcomes in Japanese patients with metastatic renal cell carcinoma (mRCC). Methods Twenty patients with mRCC were enrolled following treatment with sunitinib. To assess safety, the total sunitinib concentration range up to discontinuation of treatment and dosage reduction associated with adverse events within 6 weeks from initiating administration were analyzed. The longest administered sunitinib dosage was defined as the maintenance dose, and the relationship between total sunitinib concentration at the maintenance dosage and sunitinib efficacy was investigated. Results Total sunitinib concentration was significantly higher in patients who discontinued treatment or had dosage reduction due to adverse events within 6 weeks after initiation of sunitinib than in patients who continued treatment with the initial dosage. The time to treatment failure, progression-free survival, and overall survival were better in patients with total sunitinib concentrations