Pharmacogenetic testing of uridine diphosphate glucuronosyltransferase 1A1 (UGT1A1) \*6/\*28 is recommended in clinical practice prior to the administration of irinotecan (CPT-11)-based regimens, such as FOLFIRI regimen in patients with advanced colorectal cancer. To avoid severe toxicity of irinotecan, such as severe neutropenia and diarrhea, patients with UGT1A1 \*6/\*28 mutation often start with a reduced dose of irinotecan. However, it remains unclear whether high-dose CPT-based regimen (FOLFIRI) could increase clinical efficacy in CRC patients when compared with standard-dose FOLFIRI or FOLFOX-6 regimens. This trial aims to compare the efficacy, safety of high-dose FOLFIRI and standard-dose FOLFIRI or FOLFOX-6 in advanced colorectal cancer patients with UGT1A1\*6 G/G and \*28 TA6/6.
