Doctors are seeing more cases of colorectal cancer before the age of 50, the recommended age for screenings to begin.

Colon and rectal cancers are often conditions doctors focus on with patients over the age of 50, but recent trends show an uptick in those cancers among people as young as their 20s.

Experts say the increase in diagnoses is attributable to a variety of factors, including people’s familiarity with colonoscopy and other colorectal cancer screenings.

Dr. Allen Kamrava, a colorectal surgeon in private practice in Los Angeles, said when someone has blood in their rectum it’s much easier to get a colonoscopy done now than in years prior.

Patients with bleeding in their rectum, especially those under 40, usually have hemorrhoids, not rectal cancer. However, that’s also when a doctor should look at the big picture.

“The worst thing to do in a young patient is to diagnose their cancer late,” Kamrava told Healthline. “I have seen several young patients — 40 years or younger — that presented with what seemed to be hemorrhoidal bleeding and were treated as such. Ultimately, when the bleeding would not stop, they had colonoscopies, only to find cancer that had advanced.”

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A review of 35 years of data on colon and rectal cancers in the United States found that incidence rates have been falling since 1998.

However, among patients ages 20 to 34 years, the rates of colorectal cancers are rising.

According to a study published in JAMA Surgery, if current trends continue, by the year 2030 the colon cancer rate will increase 90 percent and rectal cancer 124 percent in people 20 to 34 years old.

For people ages 35 to 49, those rates are expected to go up as much as 46 percent.

Although the percentages might be alarming, the numbers are still low. Of the cases diagnosed in the JAMA study period, only 1 percent of them occurred in people under 35, and 6.8 percent were between the ages of 35 and 49.

That means roughly 9 out of 10 people diagnosed were 50 years old or older.

The cause of these trends, however, continues to evade researchers, but it does have some experts questioning when routine screening should begin for people with risk factors for colorectal cancers.

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Aspects of the typical American diet and lifestyle can increase a person’s risk of colon or rectal cancers.

These include diets high in red or processed meats and fried foods but low in vegetables. Obesity, physical inactivity, smoking, and heavy alcohol use are also risk factors for colorectal and other kinds of cancers.

People with type 2 diabetes are also at an increased risk for colorectal cancers and often fare worse after being diagnosed.

Age isn’t the only uncontrollable factor. African-Americans have the highest rate of colorectal cancers of all racial groups in the United States, and it’s not exactly clear why.

This has led groups like the American Society for Gastrointestinal Endoscopy to suggest that African-Americans should be screened beginning at 45, not 50.

“I know many gastroenterologists that believe that should become a universal recommendation, regardless of race. Generally speaking, the old standard of 50 has remained so,” Kamrava said. “However, for any patient that presents with bleeding between the ages of 40 and 50, a serious discussion regarding colonoscopy should be undertaken. Even if it is painfully obvious that the bleeding is hemorrhoidal.”

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Besides race, genetics play a large role in cases of colorectal cancers in younger patients.

According to the American Cancer Society, people with a personal history of inflammatory bowel disease, a family history of colorectal cancer, or inherited gene defects, such as familial adenomatous polyposis, have an increased risk of colorectal cancers.

“All of us have seen colon cancer in patients in younger ages from their 20s to their 40s. In general, we consider colon cancers in younger patients to be more familial in nature,” Kamrava said. “Simply having a family member with colon cancer does not mean you are at a higher risk. It depends on the pattern, the type of cancer, the age of onset, etc. But if you do have a family history of colon cancer, it’s important for your physician to know.”

Some of these trends have doctors altering what tests they order for suspected colorectal cancers.

Kamrava says that genetic-based colon cancers are more likely to be on the right side of the colon, where a sigmoidoscopy would miss it (a flexible sigmoidoscopy only evaluates the left side of the colon and rectum, so it would be unable to detect a right-side colon lesion).

As colonoscopies have become more standard, right-side lesions are being detected at a higher rate and thus being found in younger patients.

“Overall, however, it is much more common for patients in their 40s to undergo colonoscopy,” said Kamrava. “In general, many physicians these days have a very low threshold to perform a colonoscopy for younger patients when presented with any symptoms from the gastrointestinal tract. This is a gross generalization, but in general it is true.”