'Irrefutable' evidence that fall in death rates is attributable to screening programs
Screening for colorectal cancer (CRC) in European countries is highly effective in reducing mortality from the disease. Some of the resources currently being devoted to breast and prostate screening programmes, where the evidence of effectiveness is much less clear-cut, should be reallocated to the early detection of CRC, the 2013 European Cancer Congress (ECC2013) will hear today (Sunday).
Professor Philippe Autier, Vice President, Population Studies, at the International Prevention Research Institute, Lyon, France, will report on results extracted from data on CRC collected as part of the Survey of Health, Ageing, and Retirement in Europe (SHARE) project on exposure to screening in men and women aged 50 and over in 11 European countries between 1989 and 2010. Using the World Health Organisation cause of death database, the researchers calculated changes in death rates from CRC in the different countries, and related them to the scope and take-up of CRC screening activities.
Screening involves either a faecal occult blood test (FOBT), which checks a sample of faeces for hidden blood, or endoscopy, where a tiny camera is introduced into the large bowel to look for the polyps that can be a precursor of cancer. Screening activities were either part of national programmes, for example FOBT screening in France and in the UK, FOBT or endoscopy in Germany and some Italian regions, or the result of decisions made by individuals and their doctors. Endoscopic screening is often carried out without a prior FOBT examination.
"We saw quite clearly that the greater proportions of men and women who were screened, the greater the reductions in mortality," Prof Autier will say. "Reduced death rates from CRC were not noticeable in countries where screening was low, even though healthcare services in those countries were similar to those in countries where screening was more widespread."
In Austria, where 61% of all those studied reported having undertaken a FOBT, deaths from CRC dropped by 39% for men and 47% for women during the period. In Greece, however, where only 8% of males had had an endoscopic examination as opposed to 35% in Austria, death rates from CRC rose during the period by 30% for men and 2% for women.
Overall, in all the European countries studied, 73% of the decrease in CRC mortality over ten years in males, and 82% in females, could be explained by their having had one or more endoscopic examination of the large bowel over the last ten years. "The evidence could not be clearer," Prof Autier says, "and it is therefore very disappointing that national differences in the availability of CRC screening programmes are still so pronounced."
The researchers believe that the large differences in screening rates between different European countries are due to a number of factors. "First, many countries still do not have a national CRC screening programme. Second, the acceptability of screening methods is often low, sometimes due to cultural differences between countries. There is also the question of the availability of qualified personnel. In some countries, there are insufficient gastroenterologists available to perform endoscopy. Even with FOBT screening, an endoscopy is needed if the test is positive," says Prof Autier.
Since the main goal of CRC screening is to remove polyps in the bowel, the risk of over-diagnosis is low, unlike that seen in breast and prostate cancer screening. "The risk of bowel perforation with endoscopy, while not non-existent, is very low and so far no trial has reported rates of perforation that could compromise the feasibility of screening on either practical or ethical grounds," Prof Autier says.
The researchers now intend to gather further data on screening and to include those from the USA, Canada, and Australia. "There are signs that CRC screening can reduce the incidence of this cancer as well as mortality from it, in exactly the same way as is happening with cervical cancer screening. We would also like to investigate the cost-effectiveness of CRC screening, since we believe that it has the potential to bring about economic gains associated with averted CRC cases and deaths, and hence to more than pay for its initial cost," says Prof Autier.
"If two-thirds of eligible people in each country attend screening, we believe that we could see a considerable reduction in CRC mortality in a minimum of ten years. National healthcare services need to put more effort into organising screening programmes based on FOBT or endoscopy, and into informing people aged 50 and over about the availability of these tests so that they can make a choice."