Colorectal cancer (CRC) is a type of cancer that begins in the large intestine or colon. The colon is the last part of the gastrointestinal (GI) system and serves to absorb nutrients and eliminate feces.

CRC most commonly starts as a precancerous growth, or polyp, that grows slowly over years in the colon. CRC generally forms on the inner lining of the colon, but it can also grow through the wall of the colon and spread to other organs.

How common is colon cancer?

Colorectal cancer is the second leading cause of cancer deaths in the United States and the fourth most common cancer diagnosed. The American Cancer Society estimates 152,810 new diagnoses of colorectal cancer in 2024. CRC affects men and women equally, but a larger number of men are diagnosed with rectal cancer.  

Is colon cancer occurring in younger people?

Yes, this is true. According to SEER data, diagnosis rates of CRC in people under the age of 50 have been increasing steadily since 2012. The reason for this increase is unclear; however, it may be related to diet, obesity and sedentary lifestyles. There are multiple ongoing studies trying to determine the underlying causes.

What are colon cancer symptoms and signs?

Most early colorectal cancers have no symptoms. As CRCs grow, they can bleed and cause a low red blood cell count, known as anemia. Other symptoms of CRC include a change in bowel habits (such as new constipation), rectal bleeding, dark stools (called melena, due to slow internal bleeding), abdominal pain or unintentional weight loss.

Are there any early signs of colon cancer?

Quite simply, colorectal cancer can be prevented through screening. Because there are typically no signs of CRC in its earliest stages, screening tests like colonoscopy are so important—they can identify cancers early, before symptoms appear and when they are most treatable.  Successful screening can identify precancerous polyps and your physician can remove them before they become cancer.

Who should be screened for colon cancer?

Most guidelines recommend starting colon cancer screening at age 45 for individuals with average risk of CRC. Patients with risk factors, such as family history of CRC, inflammatory bowel disease or certain genetic disorders, may need screening even earlier. Talk with your doctor about what is most appropriate for you.

Healthcare providers agree that the best screening test for colon cancer is a colonoscopy, as it can not only detect precancerous polyps, but also remove them and effectively prevent cancer development. There are other less invasive modalities available such as Cologuard or FIT stool testing, which test stool samples for signs of cancer, or computed tomography (CT) colonography, which can potentially visualize polyps as well.

How do you detect colon cancer?

While there are other screening methods, colonoscopy is the only one that can both diagnose and remove early forms of cancer—CRC screening can directly save lives. Your doctor can talk with you about the best screening method for you.

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Shannon Simmons, MD

Shannon Simmons, MD

Dr. Shannon Simmons is a gastroenterologist at Lifespan Physician Group. Dr. Simmons is especially interested in general gastroenterology, colorectal cancer screening and prevention, and women’s health.