GSTM1 and colorectal carcinoma: Genetic variants for GSTP1 exon 5 (Ile105Val), GSTP1 exon 6 (Ala114Val), GSTM1 (homozygous deletion), and GSTT1 (homozygous deletion) were examined in a cohort of 64 OXA-treated CRC patients, among whom 15 had grade 3 chronic OXAIPN.