Association of drug exposure with clinical response and toxicities in metastatic renal cell carcinoma patients (mRCC) receiving an alternative dosing (AD) regimen of sunitinib.

e13582 Background: An AD regimen of 37.5mg daily in repeated 4-weeks on, 2-weeks off cycle has been proposed to ameliorate frequent dose modifications due to toxicities as observed with the approved dosing regimen of sunitinib for mRCC. This study aims to determine the effect of drug exposure (sunitinib and active metabolite, SU12662) on clinical response and toxicities in patients receiving this AD regimen. Methods: All mRCC patients starting on sunitinib were invited to participate in this study. In week 4 of each cycle, toxicities were assessed and graded according to CTCAE and plasma AUCss was quantified using high-performance liquid chromatography. Clinical response was assessed after 2 treatment cycles; and was used with drug exposure and toxicities data for dose adjustments. Statistical tests such as Mann-Whitney U were used to compare the levels between groups. Results: 24 patients with a mean age of 58.8 ± 11.2 years were recruited. Majority were males (75%) and Chinese (87.5%). Among the 17 and ...