Based on the multivariate Cox regression analysis, older, female patients with good performance status, impaired liver function (alanine transaminase; ALT⩾16 U l−1 or bilirubin⩾12 μmol l−1) and renal function (urea⩾4.8 mmol/l−1) who develop early grade 1 PPE alone or in combination with diarrhoea could be considered for early dose reduction, at the time of development of early toxicity, as this group of patients is at the highest risk of grade 2 or worse PPE and stomatitis. The gene discussed is GPT; the disease is stomatitis.