Genetic polymorphisms of the adenosine triphosphate-binding cassette transporters (ABCG2, ABCB1) and gefitinib toxicity.

The purpose of this study is to investigate associations between allelic variations of ABCG2 and ABCB1 with skin toxicity, diarrhea, liver injury and interstitial lung disease (ILD) in gefitinib-treated patients. A prospective clinical study of 83 Japanese patients with non-small-cell lung cancer was performed. Polymorphic loci in ABCG2 and ABCB1 were genotyped, and their effects on gefitinib toxicities were evaluated. ABCG2 34G>A was statistically associated with occurrence of skin rash; 13 (42%) of the 32 patients with at least one variant ABCG2 34G>A allele (G/A and A/A) developed grade 2 or worse skin rash, whereas only 10 (19%) of 51 patients homozygous for the reference allele (G/G) for the wild-type sequence for both alleles did so (P=0.046). There was no significant association between severe toxicities and polymorphisms of ABCG2 421C>A nor ABCB1 3435C>T. The results suggested that ABCG2 34G>A would be useful for predicting grade 2 or worse skin rash.