The UK government is known to be considering setting up a nationwide screening program for bowel cancer. Pilot studies are already under way. However, 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% 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%, and 0.5% 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. 15% of 151 people with the disease fell into this category.
The researchers also found that occurrence of the cancer in a close relative more than doubled the risk of developing it.
|85% of bowel cancers in individuals without family history.
|Journal of Medical Screening|
In addition, 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.
However, 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% of bowel cancers develop in people who do not have a family history of the disease.
Currently recognized genetic factors may account for only 5% of all bowel cancers detected, they say.
"Based on the prevalence estimates reported here, screening strategies targeted solely at people with a family history will have limited impact on reducing mortality from colorectal cancer, at the population level," concluded the authors.