Prevalence and family history of colorectal cancer: implications for family screening 2001; 8: 69-72
If screening for bowel cancer is to get the go-ahead, it must include everyone, not just those with a family history, who are known to be at increased risk, reports research in the Journal of Medical Screening.
The UK government is known to be considering setting up a nationwide screening programme for bowel cancer, and pilot studies are already under way. But whom and exactly how to screen have not yet been decided.
A population study of over 30,000 people in Norfolk showed that just under 7 per cent reported a family history of the disease in at least one parent or sibling. Levels of bowel cancer among those with a family history ran to 1 per cent and 0.5 per cent in people with no known family history.
The findings showed that people who had a history of the disease in their family were at greater risk, with 15 per cent of 151 people with the disease falling into this category. Occurrence of the cancer in a close relative more than doubled the risk of developing it. And those with a relative under 45 diagnosed with bowel cancer, or with two relatives with the disease, had up to five times the risk of getting this type of cancer themselves.
But the numbers of cases among people with no family history were far higher, particularly in older age groups and among men. Indeed, the authors comment that around 85 per cent of bowel cancers develop in people who do not have a family history of the disease. Currently recognised genetic factors may account for only five per cent of all bowel cancers detected, they say. "Based on the prevalence estimates reported here," conclude the authors, "screening strategies targeted solely at people with a family history will have limited impact on reducing mortality from colorectal cancer at the population level."
Dr Majinder Sandhu, Department of Public Health and Primary Care, Institute of Public Health, University of Cambridge.