Associations between UGT1A1 (TA)n, UGT1A1 –3156G>A, SLCO1B1*1b 388A>G and ABCC1 IVS11 –48C>T genotypes and drug response (tumour DS, ypT0, OS and RFS) to 5-FU+irinotecan were evaluated for the 35 patients of group 2. The gene discussed is UGT1A1; the disease is neoplasm.