Updated on July 30, 2024.
Colorectal cancer is now the leading cause of cancer death in men younger than 50 years old, and the second leading cause of death for women in this age group, according to a new report from the American Cancer Society (ACS). “Colorectal cancer is no longer just a disease of older adults,” the U.S. Food and Drug Administration (FDA) cautions.
For the report, ACS researchers collected the latest data from central cancer registries to analyze cancer occurrence and outcomes among the U.S. population. They also examined data on deaths from cancer collected through 2021 by the National Center for Health Statistics.
They found that as rates of colorectal cancer (cancers of the colon or rectum) have fallen among older people (related to more awareness about screenings and prevention), new cases of this form of cancer among adults younger than 50—in their 40s and even younger—has increased steadily. To put this into perspective, just 20 years ago colorectal cancer was the fourth leading cause of cancer death in younger adults. Today, it ranks above all others for men; it is second and outranked only by breast cancer among women in this age group.
Complicating matters: scientists aren’t entirely sure what is causing this trend.
Why more younger adults are getting colorectal cancer
In 2023 alone, the ACS estimates there will be 106,970 new cases of colon cancer and 46,050 new cases of rectal cancer. Overall, the lifetime risk of developing the disease is about 1 in 23 for men and 1 in 26 for women. But your individual risk for this type of cancer also depends on your risk factors for the disease.
Risk factors are things that increase your odds of getting a disease. Some you may be able to control, others you can’t.
Risk factors for colorectal cancer that you can’t control include:
- Getting older: The risk of colorectal cancer goes up over time as you age.
- Your genes: Certain mutations as well as inherited genes or syndromes are tied to an increased risk for colorectal cancer.
- Having inflammatory bowel disease: If you’ve been diagnosed with inflammatory bowel disease (chronic inflammation of the digestive tract) your risk for colorectal cancer is higher.
- Having a history of colorectal cancer or polyps: If you’ve had this form of cancer, you’re more likely to develop it again. The chances of this happening are greater if your first colorectal cancer occurred at a relatively young age. Having a polyp (small clump of cells on the lining of the colon or rectum that may become cancerous) also increases your risk for the disease.
- Your race and ethnicity: In the U.S., American Indian and Alaska Native people have the highest rates of colorectal cancer. The disease is also more common among Black people. Jewish people of Eastern European (Ashkenazi) descent are also at higher risk for colorectal cancer.
- Having type 2 diabetes: Colorectal cancer and type 2 diabetes share certain risk factors, such as being inactive or obese. But even after taking that into account, people with type 2 diabetes are still at higher risk for this form of cancer.
Other risk factors you can control:
- Being inactive or sedentary: Studies show that getting regular exercise (at least 150 minutes per week of moderate-intensity aerobic activity like brisk walking or 75 minutes per week of vigorous aerobic activity like jogging or running) can reduce your risk for the disease by 24 percent.
- Following a low-fiber, high-fat diet: Also eating a lot of processed meats (such as hot dogs, bacon, and some deli meats) and red meats (like beef, pork, lamb, or liver) is linked to a higher risk.
- Cooking meats at very high temperatures: Frying, broiling, or grilling meats produces chemicals linked to increased risk for colorectal cancer.
- Vitamin D deficiency: Having a low blood level of vitamin D may increase colorectal cancer risk.
- Being overweight or obese: Being overweight raises the risk of colon and rectal cancer, and this link appears to be even stronger among men. Maintaining a healthy weight can help reduce this risk.
- Drinking alcohol: Even light-to-moderate alcohol intake has been linked with a higher risk for certain forms of cancer, including colorectal cancer. If you don’t drink, it’s best not to start. Men who choose to drink should have no more than two drinks per day, and women should have no more than one.
- Smoking: Research suggests the more people smoke and the longer they smoke, the greater their risk for colorectal cancer. But studies also show that when compared to current smokers, people who quit smoking for more than 25 years are at significantly lower risk for the disease.
Considering these risk factors for colon and rectal cancer, rising rates of obesity and more sedentary behavior may help explain a fraction of cases among younger adults. But it’s not the whole story. Experts agree that lifestyle factors alone can’t explain why rates of colorectal cancer have been rising among younger adults.
Meanwhile, rates of genetic syndromes, which tend to cause cancer at an earlier age, have been stable in recent years, and are unlikely to be responsible for this trend.
Scientists are still working to understand why more younger adults are getting and dying from colon and rectal cancers. It may be a genetic mutation that has not yet been identified, or possibly something else in the U.S. diet or the environment that’s causing the increase. Research to find a cause (or a combination of causes) is ongoing and more studies are needed to find answers.
When—and how—to be screened for colorectal cancer
In most cases, colorectal cancer doesn't cause symptoms until the disease has progressed and may be more difficult to treat. Those warning signs include:
- Changes in bowel habits
- Blood in the stool (bright red or very dark and tar-colored poop)
- Gastrointestinal issues, such as gas, pain, vomiting, unexplained weight loss, or bloating
If you develop any of these symptoms, which may be confused with other health issues, it’s important to talk to your healthcare provider (HCP) right away. Do not ignore these signs or wait to seek medical attention.
In its early stages, colorectal cancer usually starts from polyps or other growths in the rectum or the colon. The only way to find these growths is to undergo a screening test or procedure.
Amid rising rates of colorectal cancer among younger adults, in May 2021 the U.S. Preventive Services Task Force updated its recommendations, advising people to begin screening five years earlier than before. People at average risk should start screening at age 45. Those at higher risk for the disease should begin even earlier.
There are two main types of screenings recommended for colorectal cancer:
Stool (poop) sample tests: These tests can look for blood in the stool (fecal immunochemical test, or FIT as well as fecal occult blood test, or FOBT) or blood and altered DNA in the stool (FIT-DNA or stool DNA test) that could indicate colorectal cancer. Your HCP can prescribe an at-home stool test. Some tests are also available without a prescription online. Some types of these sample tests should be done once a year, while others should be done every three years. Talk to your HCP about what is best for you.
Visual screening procedures: For these procedures, a specially trained physician uses a medical device to look inside your colon and rectum for polyps or other abnormal growths that may be cancer or eventually become cancer. Among the visual screening tests available:
- Colonoscopy: A thin tube with a light and camera is used to look inside the rectum and entire colon for growths, other abnormal tissue, or cancer. Any precancerous polyps or abnormal growths found can be removed during the procedure.
- Flexible Sigmoidoscopy: A thin tube with a light and camera is used to look inside the rectum and lower-third of the colon for growths, other abnormal tissue, or cancer. Any precancerous polyps or abnormal growths found can be removed during the procedure.
- CT Colonography (“Virtual Colonoscopy”): For this test, the colon is temporarily inflated with air using a thin tube placed in the rectum. Then a series of X-rays of the colon are taken.
Shield blood test
On July 29, the U.S. Food and Drug Administration (FDA) approved a blood test for colorectal cancer screening. The Shield test, which is made by Guardant Health, is available by prescription for adults ages 45 and older who are at average risk for the disease. The test, which will reportedly cost $895, is also expected to be covered by Medicare. It works by finding the DNA that cancerous tumors release into the bloodstream.
Guardant Health recommends that the Shield test be taken every three years, like the FIT-DNA test. But experts have not yet made a formal recommendation on how often this blood test should be repeated.
The Shield test is a less invasive screening option, but it is not a replacement for colonoscopy, which remains the gold standard for colorectal cancer detection.
Here’s why: It is more likely to find cancer at a later stage, when it is more difficult to treat.
In clinical trials, the blood test correctly detected colorectal cancer in 83 percent of people confirmed to have the disease. These people had not yet developed symptoms. But it has more limited detection of precancerous growths and early stage colorectal cancers. Studies show it found only 55 to 65 percent of stage 1 cancers and missed up to 87 percent of advanced precancerous lesions, which can be found and removed during colonoscopy.
In trials, the Shield blood test also had a false positive rate of about 10 percent. (A false positive suggests that a disease is present when it really is not.) Anyone who tests positive—including false positives—would still need to undergo a follow up colonoscopy to confirm their result.
Similarly, a stool test alone cannot diagnose cancer. If your test results show blood or possible DNA from a polyp or tumor, you will still need to undergo a visual screening procedure to confirm or rule out a cancer diagnosis. Research has shown that people who had a positive stool sample test result but did not have a follow-up colonoscopy were twice as likely to die from colorectal cancer as those who did have a follow-up screening.
Colonoscopy is considered to be the best method (gold standard) for colorectal cancer screening. But each screening test for the disease comes with different risks and benefits. Talk to your HCP about which one is best for you, when you should start screening, and how often you should undergo repeat testing.
