Professor John Northover, of the Imperial Cancer Research Fund Colorectal Cancer Unit, St. Marks Hospital, London, said that surgery had been "the mainstay of treatment" for more than a century. Screening could help to improve surgical success rates by identifying people with the disease before they developed symptoms.
Colorectal cancer is the second biggest cancer killer in the UK and other European countries - as well as in the USA and Australia.
Professor Northover said: "Almost nowhere has colorectal cancer screening been introduced as national policy as robust evidence of efficacy has not been available. It has taken almost 20 years to conduct and interpret the necessary randomised trials of faecal occult blood testing" (FOBT). Data from three such trials have shown that death rates could be cut by up to 20 per cent if governments rose to the challenge".
But Professor Göran Ekelund, of the Department of Surgery, University Hospital of Malmo, Sweden, challenged the suggestion that screening would necessarily be beneficial. He said: "The idea of prevention of disease and early detection of cancer is very attractive - especially so when people are told that screening can reduce mortality in cancer by up to 30 per cent. But it is not that simple. There are many sources of bias and error in the studies performed".
Professor Ekelund added that the studies only provided data about the differences in mortality between screened patients and control groups. They had not been informed about how many 'extra survival years' screened people got. This advantage had to be balanced against the discomfort and number of complications occurring in people who did not benefit from screening and any treatment that follows.
"Before any decision is taken, we should have that information which is not yet available. We cannot yet calculate how many people will need to suffer from unnecessary screening. What we can calculate is the NNT (Numbers Needed to Treat), i.e. how many people must be screened bi-annually for ten years to avoid one death in colo-rectal cancer. That figure is around one thousand. The exact cost for a screening programme is not available." Professor Ekelund asked if the resources/costs for screening would need to be taken from other health care resources, leading to additional medical problems.
Professor Northover said that the UK government had set up pilot centres covering two million people to examine the potential of setting up a FOBT based programme. He added: "This will check that a service of the necessary quality can be delivered and establish the true costs. These studies are due to be completed in 2003".
The St. Marks Colorectal Cancer Unit in London is also evaluating the use of a single flexible sigmoidoscopy (FS) to screen people aged around 60 for colorectal cancer. About 170,000 people were randomised, of whom 40,000 received screening.
In his concluding remarks, Professor Ekelund highlighted the importance of addressing and analysing a difficult problem in a balanced way that took account of ethical issues.
Abstracts nos. 1355 (Professor Northover) and 1356 (Professor Ekelund)
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