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Colon cancer is increasing among adults under 50 — but new research has identified four key symptoms linked to early onset. Aaron Thomas/Stocksy
  • New research has identified key symptoms linked to an increased risk of early-onset colorectal cancer in younger adults.
  • Symptoms to watch for include abdominal pain, rectal bleeding, diarrhea, and iron deficiency anemia.
  • Risk factors for colon cancer may include a history of inflammatory bowel disease (IBD), personal or family history of colorectal polyps, or a genetic predisposition.
  • An individual’s health status and dietary or lifestyle habits may also play a role.
  • Younger adults could lower their risk by maintaining healthy lifestyles, receiving colon screenings when recommended, and considering genetic screening.

In recent years, colorectal cancer has nearly doubled among young adults. Researchers are currently exploring the reasons for this increased risk.

According to a recent study, published in the Journal of the National Cancer Institute, four signs and symptoms have been linked to a heightened risk of early-onset colorectal cancer among younger adults. Early onset is defined as being diagnosed with cancer before age 50.

“We want younger adults to be aware of and act on these potentially very telling signs and symptoms — particularly because people under 50 are considered to be at low risk, and they don’t receive routine colorectal cancer screening,” senior study author Yin Cao, ScD, MPH, an associate professor of surgery in the Public Health Sciences Division, and a research member of Siteman Cancer Center at Barnes-Jewish Hospital and Washington University School of Medicine, said in a statement.

The incidence of colon and rectal cancer in people under 55 has almost doubled over the past 20 years from 11% to 20%.

Risk factors associated with the increasing incidence of colon cancer among younger adults include:

  • family history of colon and rectal cancer in a first-degree relative (i.e., parent, child, or sibling) without an identifiable genetic mutation
  • high cholesterol or triglycerides
  • increased alcohol consumption

Colon cancer is also more common in males than females.

In addition, racial and ethnic disparities in developing colorectal cancer exist. Individuals of Black American, Native American, and Alaskan Native American descent face a higher risk of disease incidence and mortality.

For the study, researchers examined the health insurance data of more than 5,000 patients with early-onset colorectal cancer.

They discovered four key signs and symptoms in subjects younger than 50 years old between three months and two years before their diagnosis:

  • abdominal pain
  • anorectal bleeding (dark or bright red blood in the toilet bowl, on toilet paper, or in the stool)
  • diarrhea
  • iron deficiency anemia (with or without chronic fatigue)

The researchers also found that having one of the symptoms nearly doubled the risk of developing colon cancer. Two symptoms increased the risk by more than 3.5 times and having three or more increased the risk by more than 6.5 times.

Dr. Tracey Childs, board certified in general and colorectal surgery and vice chair of surgery at Providence Saint John’s Health Center in Santa Monica, CA, told Medical News Today:

“Symptoms (subjective experiences) and signs (objective findings) could be an indication of polyps or colon and rectal cancer which should not be ignored if experienced and persist.”

Other symptoms of early-onset colon cancer may include a significant change in bowel habits (i.e., difficulty passing stool or passing small or narrow stools) or unexplained weight loss.

While the study findings provide compelling insight into early-onset colon cancer, additional research in young adults is needed to support the findings.

Dr. Austin Chiang, MPH, triple board-certified gastroenterologist and advanced endoscopist and assistant professor of medicine at Jefferson Health in Philadelphia, PA, told MNT the reasons why colon cancer rates are increasing among younger adults are not fully understood.

“While some factors, including environmental contributions and obesity, have been suggested, these alone do not appear to fully account for the significant impact we are witnessing. Further research is required to gain a comprehensive understanding of the complex interplay of factors contributing to this concerning trend.”

Dr. Austin Chiang, MPH, triple board-certified gastroenterologist and advanced endoscopist

Dr. Misagh Karimi, a medical oncologist specializing in gastrointestinal cancers at City of Hope Orange County Lennar Foundation Cancer Center in Irvine, CA, noted to MNT that a matched case-control study can have its limitations.

“This study tests a hypothesis around the link between specific symptoms and outcome, but an association does not always mean that having these symptoms indicates an increased risk of early-onset colorectal cancer,” Dr. Karimi said.

A person’s health status, diet, or lifestyle may play a role in their risk of developing colon and rectal cancer. These risk factors may include:

Dr. Childs cited other risk factors for developing colorectal cancer that may determine whether a person receives earlier screening. These include:

Younger and older adults alike concerned about developing colon cancer can take action to minimize their risk.

Colon screening

Colon cancer screening starting around age 45 is essential to early detection and prevention.

Dr. Karimi explained that polyps containing cancer cells could remain in the colon wall for not just months but for years. Some people with colorectal cancer may not always exhibit symptoms, or their symptoms may resemble other gastrointestinal issues.

“We know that once severe symptoms arise, the cancer has usually progressed to a more advanced stage. This is one of many reasons why people should know their family medical history and tell their physician if something feels wrong. If the symptoms might be caused by colorectal cancer, there are screening tests that can [be] done to find the cause.”

– Dr. Misagah Karimi, medical oncologist

In high-risk populations, colon screening involves a colonoscopy or CT colonography (a virtual colonoscopy done with a CT scan), Dr. Childs explained.

Average-risk populations may also receive a colonoscopy or CT colonography, or start with a stool test screening, which may lead to a recommendation for a colonoscopy.

In addition, individuals with a family history of colorectal cancer may choose to receive screening 10 years before the age of the family member’s cancer diagnosis.

Genetic screening

Dr. Childs noted that around one-third of colon cancers in younger people are associated with a genetic predisposition or genetic mutation. She recommends genetic screening for individuals with a family history of colorectal cancer in a first-degree relative (parent, sibling, or child).

Genetic screening for colon and rectal cancer involves a simple blood test that can identify the genetic mutation and other malignancies.

Healthy diet and exercise

In addition to following recommended screening guidelines, experts recommend:

  • following a balanced diet
  • exercising regularly
  • maintaining a healthy weight
  • limiting alcohol consumption
  • avoiding smoking

“The majority of people with colorectal cancer do not have inherited conditions that signal higher risk,” Dr. Karimi said.

“For most people, making healthy lifestyle choices and getting screened as their physician recommends are the most important things they can do to lower their risk of colorectal cancer.”