Higher-risk people are shunning colon cancer screens

It is difficult to make colon cancer screening effective, according to a follow-up study conducted by the Swedish medical university Karolinska Institutet of a screening programme from 1999. Many of the people who would probably have benefited most from the survey opted not to take part.

An acknowledged problem in public health surveys is that those who take part are generally more health conscious and healthier than those who do not. If this is also true of colon cancer screening, it means, at worst, that the people at greatest risk of developing the disease are not being screened, even though they would benefit most from the procedure.

A new study from Karolinska Institutet has confirmed these fears. Nine years ago, a team of researchers invited 2,000 people between the ages of 59 and 61 to take part in a colon cancer screening programme. Thirty-nine per cent of them accepted, but 61 per cent chose not to. A follow-up of these two groups has now shown that a larger percentage of the non-participants have since developed colon cancer or died, either from colon cancer or other diseases, compared with the participants.

“We do not think that the difference in incidences of cancer and death between the two groups is due to any effect the screening might have had, but believe it was down to the selection of people who took part,” says Johannes Blom, one of the researchers behind the study. “What we have here is the self-selection of more health conscious and healthier people , who perhaps don’t benefit as much from taking part.”

The team believes that those who opted out of the programme have less healthy lifestyles. This is supported by the findings that more of the non-participants have developed other forms of smoking-related cancer and that they run more than double the risk of dying from cardiovascular disease.

“If higher-risk people choose not to take part, public screening programmes will become very cost inefficient,” says Dr Blom. “One of the greatest challenges is therefore to encourage participation, so that the less motivated are also screened.”

On 1 January, the Stockholm County Council became the first health authority in Sweden to launch a screening programme for colon cancer.