Immunotherapy for colorectal cancer: a challenge to clinical trial design.

Colorectal cancer is a leading cause of morbidity and mortality with about 18 000 deaths in the UK and 56 000 in the USA each year. Despite improvements in surgical technique, radiotherapy, and adjuvant chemotherapy, 50% of patients apparently 'cured' by surgery subsequently relapse and die of the disease. There is an obvious need to develop novel rational therapies based on understanding the molecular signatures that separate tumour from normal colorectal epithelium.