Everything You Need to Know About Colorectal Cancer in Canada
Screening for colorectal cancer can save your life. Here’s what you need to know about the most commonly-diagnosed form of cancer in Canada.
Colorectal cancer in Canada: The numbers
Colorectal cancer is preventable if caught at a precancerous stage, highly treatable if caught at an early stage, and testing for it is easy. Nevertheless, an estimated 24,300 Canadians were diagnosed with colorectal cancer (CRC) in 2022, and about 9,400 died of the disease.
In this country, it is the most common cancer among men (tied with lung cancer) and the third most common among women (after breast cancer and lung cancer). While the disease accounts for 12 per cent of all cancer deaths, it needn’t be fatal. In fact, the five-year survival rate for CRC is 90 per cent when it’s caught before spreading out of the colon or rectum. “What’s more, if you survive for five years past diagnosis, your chance of dying is barely higher than that of the rest of the population your age,” says Dr. Heather Bryant, chief scientific officer for the Canadian Partnership Against Cancer.
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Colorectal cancer strikes both old and young
What puts us at risk of getting colorectal cancer—a malignancy in the large intestine, the last 15 centimetres of which is called the rectum—in the first place? The chances increase with age (those older than 50 make up nearly 95 per cent of all new cases), but it can strike younger people, as well.
The Canadian Cancer Society reports that while the incidence of CRC is falling in seniors, it’s on the rise in people under 50. Increasing numbers of older people are availing themselves of colorectal cancer screening, which can catch colon polyps (easily removable clumps of cells that form on the organ’s lining) before they turn into cancer. Meanwhile, younger Canadians, most of whom aren’t getting screened at this point, have a higher rate of obesity (an important CRC risk factor) compared to previous generations.
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Your diet plays a role in the development of colorectal cancer
Known risk factors can’t account for all cases of colorectal cancer in Canada, but there can be genetic factors, environmental factors or both working together. Among those we can control are physical inactivity, smoking and eating habits. “There’s some debate about various types of diets, but those that are high in animal fat, red meat or processed meat seem to increase the risk,” says Bryant. People who are obese or who have type 2 diabetes have a heightened risk, as well.
A study published in JAMA Oncology in January 2017 offers one reason why diet might affect your CRC risk. When we eat, we are feeding the trillions of micro-organisms living in our intestines. According to the lead author, Dr. Shuji Ogino, professor of pathology at Harvard University, some of those well-fed micro-organisms might pay you back by making you sick. Specifically, CRC tumour tissue often hosts bacteria called fusobacterium nucleatum. These microbes may help cancerous cells grow by suppressing the immune system’s response to tumours. The study found that people who ate a fibre-rich, healthful diet tended to have lower levels of these bacteria, as well as a lower risk of CRC influenced by them.
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Screening for colorectal cancer in Canada
Early detection is key to beating colorectal cancer. “Previous studies have suggested that screening causes a 30 per cent reduction in CRC mortality, plus a 20 per cent reduction in the number of cases that progress to cancer at all,” says Bryant. “But now, in part because of improvements to the screening tests, the impact could be even greater than that.”
The most common and readily accessible type of screening is a fecal test, which is both simple and inexpensive. Users can get a kit from their doctor or have one sent directly to them through a provincial screening program, follow the at-home directions for collecting a stool sample and take or mail everything to the specified hospital or medical lab. These tests look for blood in the sample that isn’t apparent to the naked eye. A positive result may be evidence of precancerous polyps or of cancer, or it may point to other health conditions, such as hemorrhoids, inflammatory bowel disease or ulcers. Your doctor will order more tests before making a diagnosis.
The Canadian Cancer Society recommends that people aged 50 to 74 get a stool test every two years. After 75, any new growths are less likely to have enough time to develop into something that could affect the length or quality of your life. But that’s not always the case. “It’s actually based on how good your health is generally,” says Dr. David Armstrong, chair of the National Colorectal Cancer Screening Network. “There are 75-year-olds who are perfectly healthy and who have a life expectancy of more than 10 years, so continuing screening past that age is definitely something an individual could discuss with their physician.”
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If a fecal test finds anything suspicious, you’ll normally go on to get a colonoscopy. In this procedure, the colon is examined with an endoscope, a thin tube with a light and a small video camera on the end. While the endoscope is inside your colon, your doctor can use it to take biopsies and cell samples that can be tested for cancer in the lab, and to remove any precancerous growths or early-stage tumours it finds.
Colonoscopies aren’t typically used for primary screening because of minuscule but real risks, such as bowel perforation, and also because of the hassle: you generally need to fast and then take laxatives to empty out your colon, as well as sedative pills to relax enough to let the endoscope pass through. On the plus side, colonoscopies provide such a good look at your colon that if the results come back clean, you’re considered up to date for CRC screening for the next 10 years.
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Colorectal cancer screening is on the rise—and it’s getting easier
There is room for improvement, but screening for colorectal cancer is on the rise. “I think what we’re seeing is an increased awareness that it makes a difference to our mortality, and the ‘ick factor’ isn’t enough to turn people away,” says Bryant. At the time of the latest available estimates, in 2012, around 55 per cent of Canadians aged 50 to 74 had completed a fecal test during the preceding two years, a colonoscopy or similar test during the preceding five years, or both.
All the provinces have an organized screening program, but not all the territories. Screening rates vary, with Manitoba leading the way at 68 per cent and the Northwest Territories trailing with 48 per cent. The former’s program is long-standing and convenient: it mails out invitations to everyone aged 50 to 74 who is registered for public health insurance. Residents can order a fecal test directly to their homes, without having to visit a hospital.
Putting off testing once you notice symptoms of CRC can be a bad decision. Even if you’ve been screened recently, tell your doctor about your symptoms, Armstrong says—fecal tests aren’t infallible.“The likelihood of surviving colorectal cancer increases almost ninefold when it’s treated in the early stages,” says Armstrong. By stage 3, when the cancer has spread to nearby lymph nodes, the five-year survival rate has fallen from 90 per cent to 71 per cent. At stage 4, when the cancer has made its way to other organs, it’s down to 13 per cent.
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If colorectal cancer runs in your family, take extra measures
Even if you’ve had colorectal cancer, there are steps you can take to mitigate the risk of recurrence. Try to live a healthier lifestyle, of course, and maintain a healthy weight.
When it comes to pharmaceuticals, Bryant says that there is evidence that daily Aspirin is useful for colorectal cancer prevention. In the long term, Aspirin does have potential side effects, including gastrointestinal bleeding, so it shouldn’t be taken solely to reduce cancer risk. However, if you’re also at risk of heart attack or stroke, that may tilt the balance in the drug’s favour. Don’t start an Aspirin regime without talking to your doctor first.
The evidence so far is mixed, but high amounts of vitamin D and calcium, from food and/or supplements, might also play a role in CRC prevention.
The most effective way to lower your risk, however, remains vigilance. If you are over age 50, you should talk to your doctor about screening. Up to a third of colorectal cancers have a genetic component, so if you have at least one first-degree relative (a parent, sibling or child) or two second-degree relatives (uncles, aunts, grandparents) who’ve had CRC, then you’ll probably need to get a colonoscopy every five to 10 years, rather than relying on fecal tests. People with Crohn’s disease or ulcerative colitis also run a higher-than-average risk and should see a specialist to determine their screening requirements.
As always, if you experience any of the symptoms associated with the disease, tell your doctor. Your life could depend on it.
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