The expression of UGT1A has been associated with the response to the epidermal growth factor receptor (EGFR) inhibitor erlotinib in patients with non-small-cell lung cancer (NSCLC) or head and neck cancer.35,36 Although studies were conducted by using a limited number of patients, the tumour levels of UGT1A mRNA were threefold higher in non-responding patients with head and neck cancer, and those of UGT1A6 mRNA were eightfold higher in non-responding patients with NSCLC prior to treatment. Here, UGT1A1 is linked to neoplasm.