Dr. David Hodgson
Dr. David Hodgson, lead author of the study, is a Cancer Clinical Research Unit (CCRU) member at the Princess Margaret Cancer Centre. (Photo: UHN)

There are many rites of passage in life: driving a car at 16, voting at 18 – and screening for colon cancer at 50.

Though it can sound uncomfortable, this one is just as important as life's other milestones. According to the National Cancer Institute in the United States, regular colonoscopies can reduce your risk of dying from colorectal cancers by up to 70 per cent.

For people with a higher risk of developing colon cancer, guidelines often call for increased screening with colonoscopies, starting at a younger age. However, for young cancer survivors there are no clear guidelines in place.

Cancer therapies, such as radiation therapy, are known to increase the risk of developing cancer years later. When this happens, these cancers are sometimes referred to as "secondary cancers." But to create guidelines for screening for secondary cancers, evidence is needed to show that these cancers can be detected at early stages and that screening with colonoscopies would actually help.

To address this issue, Dr. David Hodgson of Princes Margaret Cancer Centre and colleagues recruited a group of cancer survivors aged 35 to 49 who had received radiation therapy to the abdomen in the past. They were then screened with a standard colonoscopy.

The team found that despite their younger age, the cancer survivors had abnormal growths (polyps) in their colons that were comparable to what would be found in people age 50 or older. In addition, the prevalence of a certain type of polyp (adenomatous polyps) was similar to that found for patients known to be at high risk of developing colon cancer.

"This study provides the first evidence that early-onset colorectal cancer in people who received prior radiation therapy does have a preclinical phase that can be detected with colonoscopy screening," said Dr. Hodgson. "The prevalence of polyps found here is comparable to other groups for whom screening is recommended.

"This bolsters the case for the creation of guidelines for cancer survivors that initiate screening at younger ages."

This work was supported by the Canadian Cancer Society Research Institute, the Pediatric Oncology Group of Ontario and The Princess Margaret Cancer Foundation.

blue ribbon
The blue ribbon brings awareness to colorectal cancer—the second most commonly diagnosed cancer in Canada; the risk of this cancer is 4.5-25 times higher in cancer survivors treated with radiation therapy. (Photo: iStock)

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