Editor's note: This story was updated in March 2022 with the latest statistics and the current recommended age for starting colorectal cancer screening: 45 years old, a reduction from 50.
It’s the second-most common cancer killer in the U.S., but misconceptions about colorectal cancer can keep people from accessing the preventive care and treatment they might need.
We asked colorectal cancer experts at Fred Hutchinson Cancer Research Center for the top misunderstandings they encounter about this disease, which is diagnosed in nearly 150,000 Americans each year.
Hutch experts came up with six, but here are the Cliffs Notes takeaways: Screening saves lives. And so does a healthy diet. Read on:
Screening for colorectal cancer saves lives by detecting early cancers and precancers that are more easily treated than late-stage disease. In fact, a 2015 study estimated that 50% fewer people have died of colorectal cancer in recent years thanks to screening.
“We are lucky to have screening tests for colorectal cancer. Many cancers do not,” said Dr. Stacey Cohen, an oncologist and scientist at Fred Hutch and the University of Washington who specializes in high-risk gastrointestinal cancers.
Fast facts: Colorectal cancer in the U.S.
Colorectal cancer is the fourth-most common* cancer in the U.S., but the second-most common cause of cancer death in the U.S. (after lung cancer).
*Not counting basal cell and squamous carcinomas, two very common skin cancers that are not usually deadly.
Yet a common belief is that screening is only necessary for those who are experiencing signs and symptoms of colorectal cancer — such as bleeding from the rectum, persistent changes in bowel movements, belly pain or unexpected weight loss — said the Hutch’s Dr. Rachel Issaka. But that’s not true, she said.
“Colorectal cancer is, for the most part, a really silent disease. It takes years to progress to a point where you experience symptoms,” said Issaka, a gastroenterologist who studies how health systems can increase rates of colorectal cancer screening.
By the time a patient begins noticing problems, the disease is often more advanced and more difficult to treat, she explained.
U.S. Preventive Services Task Force guidelines recommend that all adults age 45 to 75 be screened for cancers of the colon and rectum. The guidelines add that those who have certain risk factors — like a personal or immediate-family history of colon cancer or certain precancerous growths (or polyps) — should talk to their doctors about starting at earlier ages.
Because the guidelines, until recently, recommended that most people start screening at age 50, some assume that this group of cancers simply does not occur in younger adults, Cohen said.
Colorectal cancer does, in fact, strike younger people. And while it’s still uncommon, the rate in this population is rising in a “pretty dramatic” way, said Fred Hutch colorectal cancer physician-scientist Dr. William Grady.
According to data from the National Cancer Institute’s Surveillance, Epidemiology and End Results Program, or SEER, while the overall rate of new cases of colorectal cancer has dropped for the past 20 years, that decrease has been concentrated in older age groups. For adults in two younger age groups — 20-39 and 40-54 — the rate of new cases has actually increased every year since the mid-1980s.
Why the increase? No one knows, but it’s possible that changes in diet or shifts in the kinds of bacteria living in our guts are having an effect, Cohen and Grady said.
This increase prompted experts to begin recommending age 45 as the time to begin screening. Screening recommendations are built from the best available evidence about the benefits (i.e., catching a cancer early) versus the risks (like costs and side effects). On the whole, the risks of colon cancer screening outweigh the benefits for the average person under age 45.
The problem is that an individual person is not an average. Cohen said that it’s important that younger adults experiencing troubling gastrointestinal symptoms advocate for themselves with their doctors until they get answers.
“Don’t ignore the symptoms you are having. This is true of a lot of cancer types, but if something doesn’t feel right, be persistent in talking to your doctor about it,” Cohen said. “Because maybe you’re one of the people who doesn’t fit the standard criteria, but that doesn’t mean that something’s not wrong.”
In the meantime, researchers at Fred Hutch and other institutions are gathering evidence to inform more nuanced screening recommendations for this cancer and developing more low-risk screening methods. The goal is to detect cancers and precancers earlier in more people, no matter their age.
The most common colorectal cancer screening test in the U.S., and the most definitive, is colonoscopy. In a colonoscopy, a doctor inserts a long, flexible fiber-optic instrument into the rectum and intestines to look for growths and remove any that are found.
That sounds like it would be painful. But it’s not, Issaka said.
“If anything, most patients say that the prep is the most uncomfortable part of it,” she said. Patients prepare for colonoscopy by emptying their colon; this often involves eating a special diet and taking a laxative or using an enema. “Patients often say that the bowel prep is uncomfortable because of the large amount of liquid they need to drink in a relatively short time,” she explained.
During the procedure itself, patients are sedated into a “twilight state,” Issaka said, in which they are conscious and can respond to directions but don’t feel any pain and often forget the whole thing once the sedation wears off.
“With sedation, which is the standard of care in the United States, it tends to be a very smooth process,” she said.
But, Issaka emphasized, colonoscopy isn’t the only way to screen for colorectal cancer, a fact that many people don’t realize.
There are also very simple home-based tests that look for tiny amounts of blood in the stool. With such tests, patients take a stool sample after having a bowel movement in the privacy of their own bathroom then mail the sample off to a lab for analysis. If the test comes back positive — indicating that it detected a microscopic amount of blood — the patient should come in for colonoscopy. “Patients with a positive stool-based test carry an increased risk of colon cancer, so completing a follow-up colonoscopy is very important,” Issaka stressed. If the test is negative, the patient is good to go until they’re due for their next test.
The USPSTF guidelines recommend that patients choose whichever of many different screening options they and their doctors prefer, from home kits to imaging to traditional colonoscopy. In fact, research has shown that eligible patients are more likely to opt for screening when their doctors present them with options, Issaka said.
According to data from the National Health Interview Survey, one-third of Americans over age 50 do not receive the recommended colorectal cancer screening. The most important thing is for people to get screened in any fashion, experts say.
“Please get screened and please encourage friends and family members to do the same,” Cohen urged.
Cancers of the colon and rectum are a bit more common in men, but not by much: SEER data show that about 56%, or slightly more than half, of new diagnoses are in men.
Yet the idea that it’s a “man’s cancer” is the misconception that Grady hears the most.
“Women tell me, ‘I’m not going to get that; women don’t get that type of cancer,’” Grady said.
He’s not sure why the perception exists, but whatever the reason, it’s a problem if a woman doesn’t receive potentially lifesaving screening tests as a result.
In short: Gals, ask your doctor if a colorectal cancer screening test is warranted. If so, do it.
OK, there’s no denying that a juicy rack of barbequed ribs is delicious. But a diet high in red meat is linked to an increased risk of colorectal cancer, a fact that Grady said surprises many of his patients. Many are also unaware of a potential risk from the way that meat is cooked, he added.
Grady sees patients with inherited syndromes that significantly increase their risk of developing colorectal and other cancers at a younger age. So for these patients, a change in diet can really have a big impact on their health. But a healthful diet benefits everyone else, too.
According to the International Agency for Research on Cancer, meat releases cancer-causing substances when it is cooked at high temperatures or in direct contact with a flame or hot surface (i.e., on a barbeque or frying pan).
A recent review by an international panel of experts concluded that it is “probable” that eating red meat (regardless of cooking method) causes colorectal cancer, especially if one eats more than 500 grams a week. At the recommended portion — the size of a deck of cards — that’s six servings. In comparison, the evidence is even stronger — “convincing,” the experts wrote — that colorectal cancer risk rises if one eats just 50 grams per day of a processed meat like bacon, deli meat or sausage. (Two slices of bacon weigh in at 50 grams, by the way.)
In contrast, a diet rich in fruits, vegetables and whole grains decreases risk. Here are five things you can do to reduce your risk of colorectal cancer.
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Susan Keown was a staff editor and writer at Fred Hutchinson Cancer Center from 2014-2022 who has written about health and research topics for a variety of research institutions. Find her on Twitter @sejkeown.