Colorectal cancer is the second leading cause of cancer death in the United States, according to the National Cancer Institute. However experts say many of those deaths could be prevented.
Colorectal cancer is one of the cancers for which effective screening exists. For one thing, colorectal cancer nearly always develops from precancerous polyps in the colon or rectum, and doctors can identify them with screening tests and remove them before they turn into cancer.
Additionally, colorectal screening helps doctors spot cancer early when treatments are most successful. When colorectal cancer is caught early, the five-year survival rate is around 90 percent, according to the Cleveland Clinic.
Colonoscopy, in which a camera is threaded through the colon, has always been considered the gold standard screening tool for colorectal cancer, because doctors can literally see inside the colon to look for abnormalities.
But, for a variety of reasons, not everyone is willing or able to undergo this procedure. Sometimes, the colonoscopy prep, which requires a liquid diet prior to the test and medication to clear out the colon, intimidates people, or takes too much time. Sometimes, people are afraid of the test itself and not willing to undergo it. During the pandemic, it was hard to get colorectal screening because centers were closed because of infection risk — a fact that may lead to an uptick in incidence of the disease and delayed diagnoses.
The U.S. Preventive Services Task Force (USPSTF), which offers colorectal screening guidelines, recommends that all adults between ages 45 and 75 be screened for colorectal cancer. Decisions for screening adults ages 76 and older should be made on an individual basis, according to the USPSTF.
While colonoscopy is truly considered the gold standard, it’s important to know that if you’re not able or willing to undergo a colonoscopy, there are other options in colorectal cancer screening.
What Are the Types of Screening for Colorectal Cancer?
Colorectal screening tests are divided into two main categories, according to the American Cancer Society.
- Visual exams Colonoscopy, sigmoidoscopy, and virtual colonoscopy all involve using scopes to see inside the colon.
- Stool-based tests Doctors analyze feces for signs of colorectal cancer or polyps.
All approaches have pluses and minuses. The most important thing is to get screened. Here are some of the factors you and your doctor will discuss when deciding on a screening strategy.
- Your preferences Do you have reservations about being under anesthesia? Do you have the time and transportation necessary to prep and undergo colonoscopy?
- Your family or personal history of colorectal cancer or polyps. If you have a family history, your doctor may lean toward recommending colonoscopy.
- Other medical conditions Some conditions may necessitate that you undergo less intensive screening.
- Genetic syndromes, such as Lynch syndrome, can put you at a higher risk for colorectal cancer. Genetic syndromes may mean colonoscopy is the best screening method for you.
- Your medical resources Doctors can work with what your insurance will cover.
Colonoscopy: The Screening Gold Standard
A colonoscopy lets doctors see inside the large intestine, which includes the rectum and colon. Physicians insert a lighted tube with an attached camera into the rectum to view parts of the digestive system. One benefit of the procedure is that it allows doctors to identify any problems and remove precancerous polyps at the same time.
The American Cancer Society recommends a colonoscopy every 10 years for average-risk people. You may need to undergo screening at a younger age and more often if you have risk factors for colorectal cancer, such as a family history or a genetic mutation that puts you at higher risk.
Recently, research triggered a controversy over colonoscopy exams.
A large European study published in October 2022 in the New England Journal of Medicine sparked some controversy over the benefits of colonoscopy screening. Results showed that people who were invited to be screened for a colonoscopy and those in a usual care group had nearly the same death rates 10 years later.
A key piece of information explains the findings: Only 42 percent of the participants who were invited to have a colonoscopy actually had the exam.
“The other patients, who did not accept, were not screened,” explains Douglas A. Corley, MD, PhD, MPH, a research scientist at the Kaiser Permanente Northern California Division of Research in Oakland, California. “This study only allowed an evaluation of how effective a program for inviting people to colonoscopy might be. It did not directly evaluate the effectiveness of colonoscopy.”
When the study researchers analyzed only those who had the screening, they found colonoscopies reduced the risk of death from colorectal cancer by about 50 percent.
“Preventive cancer screenings, including colonoscopy, are the best and most trusted way to save lives,” commented the American Cancer Society, in response to the study.
“That’s why the American Cancer Society recommends colorectal screening, including colonoscopy, for adults beginning at age 45. There’s no reason to change that direction. Recommended cancer screenings should be a routine part of good health,” the society wrote.
A flexible sigmoidoscopy is a procedure that’s similar to a colonoscopy, but it doesn’t examine the entire colon. With this exam, a flexible tool that contains a light and a camera is inserted into the rectum and moved through the lower part of the colon. Doctors can view less than half of the colon and the entire rectum with a sigmoidoscopy.
Because a flexible sigmoidoscopy doesn’t let doctors see the entire colon, it’s possible that it won’t detect cancer or polyps farther into the colon, according to the Mayo Clinic.
A flexible sigmoidoscopy is a good screening test when done every 5 years or every 10 years if it’s combined with an annual fecal test, according to the Centers for Disease Control and Prevention (CDC).
Virtual Colonoscopy (CT Colonography)
A virtual colonoscopy is an exam in which you follow the prep used to clean out the colon for a regular colonosocpy, but it is not invasive. Instead of using a scope to examine the inside of the colon, doctors use X-rays and CT scans to generate images of the colon. When it’s performed correctly, a virtual colonoscopy can be as effective as traditional colonoscopy at detecting cancer and most polyps, according to the Mayo Clinic. The CDC says this test should be performed every five years as a screening tool for colorectal cancer.
Stool tests are used to detect abnormalities in feces. There are different types, including:
- Fecal immunochemical test (FIT) FIT uses antibodies to detect blood in the stool. It’s performed once a year as a screening tool.
- FIT-DNA test This test combines FIT with a technology that detects abnormal DNA in the stool. It’s done once every three years.
- Guaiac-based fecal occult blood test (gFOBT) With this test, the chemical guaiac detects blood in the stool. Experts recommend that it should be done once a year.
“These [stool] tests are thought to have similar effectiveness in decreasing deaths from colorectal cancer, when used as recommended,” Dr. Corley says. Most medical centers offer both colonoscopies and stool tests to achieve the highest screening rates, he says. If an abnormality it detected in a stool test, it will often be followed up with a colonoscopy.
The Bottom Line
While colorectal cancer screenings may not be something most people look forward to, these tests can reduce the number of cancer cases and save lives.
What’s more, colorectal cancer screening tests shouldn’t cost you. The Affordable Care Act requires that both private insurance companies and Medicare cover colorectal screening tests for qualified people, according to the American Cancer Society. You should check with your provider about specific benefits.
It's a good idea to discuss the different colorectal screening tests with your doctor. But most importantly, pick the option that works for you, and don’t wait to be screened.
“Screening tests only provide benefit if they are completed,” says Corley. “The best test is the one that gets it done.”