Oregon Health & Science University, McMaster University in Hamilton, McGill University in Montreal and Mayo Clinic in Phoenix were among the institutions taking part.
The research is due to be published in Gastroenterology, the official journal of the American Gastroenterological Association. It makes 19 evidence-based recommendations, which will guide the choice of screening test and frequency of use among people who have close relatives with colon cancer or pre-cancerous growths.
Examining the correct screening methods for bowel cancer
Head of the Graduate Entry Medical School at UL and co-lead author on the study, Prof Des Leddin, said the results will have a massive impact on how bowel cancer is managed worldwide.
Leddin said: “The guidelines will, we hope, reduce mortality from this common disease and ensure that screening resources are optimally used. The impact of this work, which was co-led by UL, will be global in reach and will affect screening for a large segment of the population.”
Having a family history of colorectal cancer significantly increases the risk of developing the disease, but the correct screening programme can substantially reduce its incidence and mortality. The disease is the second-leading cause of cancer deaths in Ireland, the US and Canada.
Nearly 60 people in Ireland are diagnosed with colon cancer on a weekly basis and one in 25 people will develop the disease over a lifetime. Most people have an average risk of developing the disease; screening this segment of the population involves stool sample analysis. A smaller section of the population have an inherited genetic abnormality, meaning their risk of developing the disease is very high; colonoscopy is used here.
Helping a specific patient group
The research from UL has created guidelines for a third group: those who have a relative with bowel cancer but who do not meet the criteria for a hereditary form of the disease. “Some people have a close relative with bowel cancer but do not have a demonstrable genetic abnormality.
“Between one in 10 and one in 20 people has a relative with colon cancer and one in two may have a relative with pre-cancerous growths. Evidence-based guidelines have not previously been developed for this group. The purpose of this study was to correct this gap in cancer screening by carefully sifting through all of the evidence to draw up best-practice guidelines for consumers and healthcare providers.”
The researchers examined 35,000 papers, and experts at nine universities took three years and more than $350,000 to tackle this issue. Screening reduces the risk and likelihood of death by detecting polyps and stopping the progression to cancer, and by finding cancer at an earlier, curable stage.
“The takeaway from this for the general population is clear,” said Leddin. “If you have a parent, a sibling or a child with colorectal cancer or certain types of precancerous tumours, you are at an increased risk of developing the disease. Talk to your family doctor about appropriate screening.”
The elevated risk of a family history of the disease means screening at a younger age is crucial, either between the ages of 40 and 50, or 10 years younger than the family member at their own diagnosis.
There should also be a shorter interval of five years between screening tests for those with two or more close family members with colorectal cancer, and every five to 10 years for those with a family history of one close relative with bowel cancer or documented advanced adenoma. Despite very low-quality evidence, the group recommends colonoscopy in individuals with a close relative with cancer as the preferred test.
The good news is that the risk of getting bowel cancer if the only affected family members are aunts, uncles or cousins is not much different than average and the people in this category can be screened according to average-risk guidelines.
The researchers said that well-designed prospective studies are important in order to make definitive screening-age recommendations based on evidence.
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