Screening for colorectal cancer.

Colorectal cancer (CRC) causes 20 000 deaths per annum in the UK alone. Screening has been shown to reduce mortality but debate exists as to which approach to use. Direct visualization of the colorectum has the advantage that it detects lesions most effectively and is required at less frequent intervals, but the procedure is invasive and at present too costly for screening purposes. Faecal occult blood measurement, despite its limitations, is currently the recommended screening method, with follow-up of positive tests by colonoscopy or other visualization techniques. This strategy has been shown to reduce mortality from CRC by about 20% and screening trials directed towards individuals in the over 50 years age group are underway in the UK and elsewhere. Future developments in CRC screening include colorectal visualization by computed colonography -- a less-invasive alternative to colonoscopy. Developments in stool analysis are also occurring. Examination of faecal samples for cellular products derived from neoplasms (e.g. calprotectin) may prove more sensitive and specific than faecal occult blood measurements. In addition, detection of altered DNA in faeces is being investigated by molecular biology techniques. Using a multi-target assay panel to detect point mutations and other neoplasia-associated DNA abnormalities may be an effective strategy for CRC screening in the future.