UGT1A1 and cancer: However, we also found that the prevalence of certain pharmacophenotypes was variable by ancestry; for instance, there were significantly more poor metabolizers among Indians (17.4%) compared to Chinese (3.2%, p = 7.28 × 10−66) and Malays (1.3%, p = 6.50 × 10−51) for UGT1A1, which metabolizes irinotecan-based drugs frequently used in cancer treatments, due to a higher allele frequency of UGT1A1*28 among Indians.