Colon cancer: Should Canada change screening recommendations?

Data from both the U.S. and Canada show colorectal cancer rates are rising among young adults, but no changes to screening policies are on the horizon for Canada just yet, according to one expert.

A new report from the American Cancer Society (ACS), released in early March, found that colorectal cancer cases in Americans under the age of 55 now account for 20 percent of all cases nationwide.

This is nearly double the incidence of colorectal cancer in this age group in the United States 30 years ago.

And Canadian data shows a similar increase. According to a 2019 study in JAMA Network, there was a 31 percent increase in young adults with colorectal cancer between 2006 and 2015.

In the US, colorectal cancer screening is recommended starting at age 45 as of 2018, but Canada still recommends starting when a patient is 50 years old.

Colon cancer usually affects older people. So why are we seeing more cases in young adults?

Tom McFarlane, a clinical oncology pharmacist based in Waterloo, Ont., told CTV’s “Your Morning” that scientists “don’t know exactly why” at this stage, although there are theories.

“Obviously there are lifestyle factors that can play a role here – lifestyle factors, I mean obesity, poor diet, alcohol intake and so on, but they increase the risk for almost everyone, so there’s something going on that’s not entirely clear.” he said.

“There are probably some combination of risk factors that have yet to be determined that researchers haven’t found yet.”

According to the ACS report, the US is also seeing more cases of advanced stages of colorectal cancer. In the mid-2000s, 52 percent of colorectal diagnoses were advanced-stage cases, but in 2019 it was 60 percent.

In 2023, it is estimated that more than 153,000 people in the United States will be diagnosed with colorectal cancer and 52,000 people will die, according to the report.

“We know that rates are increasing in young people, but it’s alarming to see how quickly the entire patient population is getting younger, despite the decline in the general population,” said Rebecca Siegel, senior scientific director of surveillance research at the American Cancer Society and head. author of the report said in the press release. “The trend towards more advanced disease in people of all ages is also surprising and should encourage everyone aged 45 and over to be screened.”

McFarlane said that while the increase in young patients diagnosed with colorectal cancer is concerning, it is unlikely to prompt a change in screening recommendations in Canada at this stage.

“I guess it depends on what the trends are, but we may have to revisit it if we see these rates continue to rise,” he said. “But for now, we still recommend screening in patients 50 and older.”

She added that young adults who have a close relative with or a family history of colorectal cancer are encouraged to get regular screening earlier.

One of the main problems doctors face when younger Canadians develop colorectal cancer is that they are less likely to notice the early signs, he said.

“I think really the problem that we see more often with younger patients is that they ignore the symptoms because they don’t think it’s likely that colorectal cancer is causing these symptoms,” McFarlane said.

“If you have a younger patient who ignores the symptoms, the cancer will potentially progress to a point where it’s at a higher stage, at which point it will be much more difficult to treat.

He believes that instead of changing screening recommendations to help young adults get a diagnosis, the most important thing is to emphasize awareness of the symptoms.

“That includes things like blood in the stool, which includes things like unusually shaped stool or changes in bowel habits where you have diarrhea or constipation for a few weeks when you never had it before,” he said. “And also severe fatigue that cannot be explained in any other way.”

These are all symptoms you should mention to your doctor if you experience any of them, she said.

“As far as screening goes, we don’t really have the evidence to change our screening policy at this point,” McFarlane said.

“We usually base them on epidemiological data or screening data that show it’s cost-effective or beneficial.”

He said the current data do not yet suggest that a change in screening policy will balance these interests.

“These are still a fairly low number of total cases that we’re seeing, even though we’re seeing such a rapid increase,” he said.

There are some positive signs in the ACS report, including that the rate of colorectal cancer is declining in people age 65 and older, and has been declining since 2011.

However, since then, the incidence rate has increased by two percent per year among people younger than 55 years of age.

And if the incidence rate continues to rise in Canada as well, the question of screening may arise again.

“We may need to revisit this and talk about it if we continue to see an increase in these cases in the young adult population,” McFarlane said.