While overall colorectal cancer cases have declined in the United States since the mid-1980s, diagnoses are rising in people under the age of 50.

According to a 2017 study in the Journal of the National Cancer Institute, people born around 1990 have double the risk of colon cancer and quadruple the risk of over their lifetimes compared with people born around 1950. Last year, the American Cancer Society revised its screening guidelines to recommend that people with average risk for colorectal cancer begin regular screening at age 45 rather than at 50.

(People are considered average risk if they do not have a family history of colorectal cancer and do not suffer from inflammatory bowel disease, or IBD, among other genetic factors.)

About 1 in 22 men and 1 in 24 women will be diagnosed with colorectal cancer in their lifetime.

Reezwana Chowdhury, an assistant professor of medicine at Johns Hopkins and expert in colon cancer screening, has been diagnosing cancer in more patients under 50.

“I have had a 30-year-old patient who had no family history of colon cancer or IBD and no genetic factors who was diagnosed with colon cancer,” she says. “Luckily, she was found early because she had a colonoscopy, and her complaint was rectal bleeding.”

Chowdhury says researchers are investigating reasons behind this frightening trend. Some studies indicate genetic differences in younger colorectal patients compared with their older counterparts and different tumor characteristics in early onset colorectal cancer versus more typical colorectal cancer.

She recommends that her patients under 50 receive colonoscopies on a case-by-case basis depending on their risk factors, family history and other patient-specific traits. She recently discussed screening methods for colorectal cancer, its changing demographics and risk factors.

Q: Why are colonoscopies the standard in colorectal cancer screening?

A: Most colorectal cancers don’t cause symptoms in the early stages, but doctors can often spot cancer during a routine colonoscopy. In this procedure, a doctor uses a flexible tube with a light and camera on the end to look at the inside of a patient’s colon. The patient is sedated, and the doctor will remove any polyps found during the procedure, which decreases the risk of cancer. The procedure can also be therapeutic. For example, if someone is bleeding from the rectum, we can often treat the bleeding source.

Q: Are there any colorectal cancer screening alternatives for patients who don’t want to undergo an invasive procedure?

A: Other options include a fecal immunochemical (FIT) test, which is a stool test; a virtual colonoscopy CT scan; a colon capsule, which is a pill-sized camera; and flexible sigmoidoscopy, which looks at the left part of the colon. I don’t think any of them are as precise as a colonoscopy, which is what I would recommend if any of these other tests came back positive.

Q: Do health insurers recognize the American Cancer Society’s new recommendation of screening at age 45?

A: That standard hasn’t yet been adopted by every gastroenterology society. Because of this, an insurance company may not cover the test unless a doctor determines that a younger patient shows symptoms of disease.

Q: What are some warning signs?

A: They include sudden changes in bowel movements, persistent blood in the stool or black stools, and abdominal pain. A diagnosis of iron deficiency anemia when someone has never been anemic, and without visible blood loss, could signal blood loss from the gastrointestinal tract.

Q: What risk factors are associated with colorectal cancer?

A: Although potential risk factors include smoking, obesity, eating red meat and moderate to heavy alcohol use, it’s not clear if these factors are linked to the increase in younger patients. Another 2017 study found that a person’s risk for colorectal cancer increases as their body mass index increases, and that weight gain between early adulthood and midlife is associated with a significant increase in risk. The study also found that regular physical activity was associated with a 24 to 31 percent reduction in risk when comparing the most active with the least active people.

Q: What else is known about colorectal cancer patients in their 20s and 30s?

A: Even though increased screening is catching more incidences of cancer in younger patients, it is being diagnosed at a later stage, perhaps because younger patients wait to seek help or because physicians may not think a patient’s symptoms are indicative of cancer. There are questions about whether these younger patients may have a more aggressive type of tumor that has yet to be identified.

Learn more about colon cancer and rectal cancer treatment.