Importance of UDP-glucuronosyltransferase 1A1∗6 for irinotecan toxicities in Japanese cancer patients

Abstract Recent pharmacogenetic studies on irinotecan have revealed the impact of UDP glucuronosyltransferase (UGT) 1A1 ∗ 28 on severe irinotecan toxicities. Although the clinical role of UGT1A1 ∗ 6, which is specifically detected in East Asian patients, in irinotecan toxicities is suggested, clear evidence remains limited. To examine the impact of ∗ 6, the association of UGT1A1 genotypes with severe irinotecan toxicities was retrospectively investigated in Japanese cancer patients. A significant ∗ 6 -dependent increase in the incidence of grade 3 or 4 neutropenia was observed in 49 patients on irinotecan monotherapy ( p  = 0.012). This study further clarifies the clinical importance of ∗ 6 in irinotecan therapy in East Asians.