ABCB1 and Hand-foot syndrome: Recent studies to re-evaluate the associations of ABCG2 and ABCB1 polymorphisms with sunitinib-induced toxicity and efficacy in renal cell carcinoma indicate that the ABCG2 rs2231142 A allele is associated with increased risk of thrombocytopenia and hand-foot syndrome (HFS) in Asians, with no apparent effect on sunitinib-induced hypertension or neutropenia.