Older patients were more likely to discontinue neratinib treatment due to diarrhoea. The incidence of acute renal failure was also increased in this population. Older patients are at increased risk of complications of diarrhoea, including renal impairment, and should be carefully monitored. Rash and PPE syndrome were reported more commonly by Asian patients compared to White patients. Patients with mild renal impairment were more likely to discontinue treatment due to diarrhoea and dehydration, and should be carefully monitored if diarrhoea develops.