The lack of a survival advantage for tumours with defective MMR status may be related to the sample size and/or the observation that colon cancers with defective MMR do not respond to adjuvant 5-fluorouracil, whereas those with intact MMR receive a survival benefit from 5-fluorouracil treatment (Ribic et al, 2003). The gene discussed is MRC1; the disease is malignant colon neoplasm.