Purpose: The aim of this study was to investigate the pharmacogenetic determinants of sunitinib-related toxicity and ethnic difference in metastatic renal cell carcinoma (mRCC) among Korean patients. Methods: A pharmacogenetic study was performed in 65 patients with mRCC treated with the standard schedule of sunitinib (50 mg orally once daily for 4 weeks-on/2 weeks-off). Detailed data regarding the toxicity of sunitinib, including thrombocytopenia, neutropenia, anemia, and hand-foot syndrome (HFS), were prospectively collected in a clinical trial program (n = 38) or standard oncology practice (n = 27). Total of 12 genetic polymorphisms in 8 candidate genes (CYP1A1, CYP3A5, ABCB1, ABCG2, PDGFRα, VEGFR2, RET, and FLT3) were analyzed for an association with treatment-related toxicity from sunitinib using Pearson χ 2 test. Results: Common grade 3 or grade 4 treatment-related toxicities were thrombocytopenia (36.9 %, 24/65), neutropenia (18.4 %, 12/65), anemia (7.7 %, 5/65), and HFS (12.3 %, 8/65). Patients carrying an ABCG2 421 AA genotype developed significantly more grade 3 or grade 4 thrombocytopenia, neutropenia, and HFS adjusted for age, sex, and Eastern Cooperative Oncology Group performance status, and body surface area (odds ratio compared with AC/CC genotypes [OR] 9.90, P = 0.04, thrombocytopenia; OR 18.20, P = 0.02, neutropenia; and OR 28.46, P = 0.01, HFS). In addition, total and surface protein ABCG2 protein expression was decreased in ABCG2 421 AA mutant cells compared to wild type. Conclusion: Among 12 genetic polymorphisms, polymorphism in the ABCG2 421C>A gene may be mostly associated with the risk of sunitinib-related toxicity in mRCC patients. Considering the high frequency of 421C>A SNP in Asian, this may be related to differential toxicities among ethnic groups.
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