The SIGN guideline’s recommendations on screening do not go far enough, argues Dr Mark Cottrill

Diagnosing early colorectal cancer in primary care is notoriously difficult. Sadly, about a third of patients will present as emergencies, with obstruction or perforation.

The new SIGN guideline emphasises the importance of early referral for patients at high risk – those aged over 50 years with rectal bleeding and a change in bowel habit to looseness, or with rectal bleeding but no anal symptoms. Careful abdominal and rectal examinations are recommended to detect a mass. The guideline also advocates investigating iron deficiency anaemia to exclude a colonic cause.

The section on prevention advocates healthier lifestyles and includes recommendations to reduce weight, increase levels of physical activity, stop smoking and eat more fruit and vegetables.

The same section covers population screening – or the lack of it. No national screening programme yet exists. However, the results of two large pilot studies are awaited, and specialist units should be making plans for screening, as screening in some form is on the way. It is estimated that screening could prevent or cure up to 90% of cases of colorectal cancer. The disease is an ideal candidate for screening because treatment of the pre-malignant condition, the adenoma, reduces the risk of cancer.

In the United States, the US Preventative Services Task Force recently gave a grade A recommendation for screening all men and women over 50 years of age.1 Regular screening by faecal occult blood testing, radiology or endoscopy was also recommended by the American Gastroenterological Association’s (AGA) updated guidelines.2

The SIGN guideline recommends "screening” patients who have had an adenoma or inflammatory bowel disease diagnosed. This is technically surveillance, as is the advice contained in the section on genetics, to "screen” patients at risk because of their family history.

An individual with a first degree relative who has the disease has a two to three times greater risk; if the relative developed the disease before 50 years of age or two first degree relatives are affected, the risk is increased by three to four times.2

The SIGN guideline is at variance with AGA advice,2 which is to offer colonoscopy every 10 years from 40 years of age onwards (or 10 years before the age that the affected relative was diagnosed). SIGN recommends a single colonoscopy for patients in the ‘moderate’ risk group and a repeat examination some 20-25 years later. The guideline does not recognise a significant increased risk for an individual with one first degree relative affected over 45 years of age at diagnosis.

Although the SIGN recommendation may be all that might realistically be achieved because of pressures in secondary care, I feel it is a short-sighted strategy.

The document also contains interesting information on palliative care and the impact of the disease on patients and their families. There is also a section devoted to advice for patients and their carers, which GPs will find useful.

References

  1. US Preventative Services Task Force. Screening for colorectal cancer: recommendations and rationale. Ann Intern Med 2002; 137: 129-31.
  2. Colorectal Cancer Screening and Surveillance: Clinical Guidelines and Rationale - Update based on New Evidence. Gastroenterology 2003; 124: 544-60.

SIGN 67: Management of Colorectal Cancer – A national clinical guideline can be downloaded free of charge from the SIGN website: www.sign.ac.uk