TPMT and cancer: With a median follow‐up of 11·3 years, we have not observed an excess of second cancers in TPMT heterozygotes as reported in the NOPHO and St Jude total therapy trials; the latter studies linking lower TPMT activity with second brain tumours in children who received radiotherapy and with etoposide mediated myeloid leukaemias (Relling et al, 1998, 1999c; Schmiegelow et al, 2009b).