Colorectal cancers used to be rare in younger adults. But both diagnoses are increasing at an alarming pace for this age group, with 1 in 5 new colorectal cancer cases now occurring in people under 55.
Colon and rectal cancers are typically grouped together as colorectal cancer since both affect the large intestine, with the rectum closer to the outside of the body. While they cause similar symptoms, they are distinct cancers.
The latest research, which hasn’t yet been published in a peer-reviewed journal, highlights that rectal cancer in particular is increasing at a strikingly high rate.
“Based on our estimation, in adults ages 35 to 44, colon cancer deaths are rising slowly, by about half a percent each year. Rectal cancer rates are increasing much more rapidly, at nearly 2 percent per year,” says lead author Mythili Menon Pathiyil, MBBS, a gastroenterology fellow at SUNY Upstate Medical University in Syracuse, New York.
“While the numbers appear modest at first glance, the concern isn’t just how many additional deaths there are today, but that the curve is moving in the wrong direction and accelerating in young, otherwise low-risk individuals,” says Dr. Pathiyil.
Pathiyil stresses that just because rectal cancer cases are growing at a faster clip, doesn’t make colon cancer any less of a concern.
Findings Based on Decades of Research
For the study, Pathivil and her collaborators analyzed deaths due to early-onset colorectal cancers among adults ages 20 to 44 using a federal database of U.S. death records from 1999 to 2023.
Applying a machine learning model computer program, the scientists calculated that rectal cancer mortality among adults ages 35 to 44 (the core of the millennial generation) will escalate through 2035, as colon cancer mortality in the same age group rises more slowly.
“It is surprising that these cancers are increasing among younger adults, because we have traditionally considered colorectal cancer to be relatively slow growing, so this makes us wonder if these cancers are starting at an even earlier age,” says Cindy Kin, MD, an associate professor of surgery at Stanford Health Care in Palo Alto, California, who specializes in colon and rectal surgery.
What Might Be Driving the Rise in Rectal Cancer?
The reasons behind this upswing in rectal cancer deaths aren’t yet clear, and the topic needs more scientific investigation, Dr. Kin says.
“If I were to hazard a guess, the rise could be due to chronic exposure from a young age — most likely in the food — that leads to chronic inflammation or an unhealthy microbiome in the colon, which then leads to the development of cancer cells,” she says.
Younger adults are not routinely screened for colon or rectal cancers, so symptoms are often missed or attributed to benign causes like stress or hemorrhoids, adds Pathiyil.
“This leads to diagnosis at an advanced [cancer] stage, and that in itself could be the reason why the mortality rates are rising,” she says.
What Are the Signs and Symptoms of Rectal Cancer?
Common symptoms of colon cancer and rectal cancer include:
- Persistent changes in bowel habits (diarrhea or constipation)
- Rectal bleeding or blood in the stool
- Unexplained weight loss
- Persistent abdominal pain or cramps
- Fatigue
In the early stages, colon and rectal cancer may not produce any symptoms — one reason routine screenings are vital.
Symptoms of rectal cancer can be more readily apparent than those of colon cancer because of its location near the outside of the body, according to Rachel Gordon, MD, a physician who is double board-certified in colorectal and general surgery at Episcopal Health Services in Queens, New York.
When a cancer tumor stretches the rectum, she explains, you’re more likely to feel it and have difficulty passing stool or to experience anal or pelvic pain.
The colon has more room to stretch, and a cancer deeper in the body may be harder to detect.
“With colon cancer, you are less likely to notice bright red blood on the stool or the toilet paper because the blood from colon cancer has time to mix in with the stool before the stool reaches the anus,” Dr. Kin says. “Colon cancers are more likely to cause black stools.”
How Is Rectal Cancer Treated Compared With Colon Cancer?
Rectal cancer that reaches the muscle layer of the bowel wall or nearby lymph nodes is commonly treated with radiation and chemotherapy first, then surgery if necessary, according to Kin and Gordon.
That is a different approach than that used for the vast majority of colon cancers, for which treatment generally starts with surgery followed by chemotherapy if the cancer has spread to the lymph nodes.
For metastatic disease (meaning cancer that has spread to farther-away parts of the body), treatment generally starts with chemotherapy for both colon and rectal cancer.
Screening at Younger Ages May Help
People at increased risk are advised to consult with their healthcare provider about screening at a younger age. Higher-risk individuals include:
- People with one or more family members who have had colon or rectal cancer
- People who have had certain types of polyps removed during a colonoscopy
- People who have had colon or rectal cancer
- People who have had radiation to the abdomen or pelvic area to treat a prior cancer
- People with inflammatory bowel disease (Crohn’s disease or ulcerative colitis)
- People known or suspected to have certain genetic syndromes
“I’ve moved my threshold for getting a colonoscopy to a younger age than 45 in some cases,” says Gordon. “If someone comes to me now in their thirties and they had some rectal bleeding,” she will recommend a colonoscopy so she can rule out cancer, she says.
What Is the Outlook for Rectal Cancer?
The prognosis for both rectal and colon cancer is generally favorable if the cancer is found early. Survival rates decrease as the disease spreads.
Again, screening is key to early detection. Colonoscopy is considered the gold standard, and it covers the entire colon and rectum. Pathiyil says that greater use of flexible sigmoidoscopy (a slightly less invasive procedure) could help increase the number of rectal cancers detected.
Is There Any Way to Lower Your Risk?
To decrease your chances of getting rectal or colon cancer, the American Cancer Society advises:
- Begin regular screenings at age 45.
- Maintain a healthy weight.
- Stay physically active.
- Eat a diet rich in fruits, vegetables, and whole grains.
- Limit red and processed meats.
- Avoid tobacco.
- Limit alcohol intake.
Pathiyil emphasizes that rectal bleeding and changes in bowel habits in people less than 45 years old should not automatically be attributed to hemorrhoids or stress by both patients and doctors without a thorough evaluation.
“Just being aware that mortality rates are increasing in this age group may encourage young adults to not brush off symptoms without being evaluated by a healthcare professional,” she says.
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