What to know about colorectal cancer

Colon cancer is often referred to as the “silent killer.” Learn about the symptoms, causes and screening options.

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Updated on April 10, 2024.

Colorectal cancer is the second leading cause of cancer-related deaths in the United States, according to the U.S. National Cancer Institute. Although colorectal cancer death rates are declining overall, deaths among people younger than 50 rose 2 percent every year from 2012 to 2016. Early detection and regular screenings can help prevent the disease and often cure it.

What is colorectal cancer?

Colorectal cancer is cancer that starts in the inner lining of the colon (the large intestine) or rectum (the last several inches of the large intestine). The cancer usually begins as a polyp (a small growth of irregular tissue) inside the intestine, which eventually develops into cancer cells that can break free and spread to other parts of the body. It's important to remember that polyps are often benign (not cancer), but some may lead to cancer. 

Who’s at risk?

Both men and women are at risk for colorectal cancer. Men have a 1 in 23 chance of developing the cancer; women have a 1 in 25 chance. Experts aren't sure why, but African Americans have an even higher risk.

What causes colorectal cancer?

Studies show that certain factors may increase your risk of developing colon cancers, but why and how they affect the disease is still unknown. Being overweight or inactive, eating a diet rich in red or processed meats, smoking and heavy drinking can all increase your risk. People over age 50 or those with inflammatory bowel disease (chronic inflammation of the digestive tract) have an increased risk, too.

Most instances of colorectal cancer are found in people who do not have a history of colorectal cancer. But up to 20 percent of people with colon cancer have a family history of the disease.

“Patients who had family members with colon cancer, rectal cancer or polyps are most at risk," says Theodoros Voloyiannis, MD, a colon and rectal surgeon at Clear Lake Regional Medical Center in Houston, Texas.

Are there any symptoms?

Colon cancer is sometimes called a "silent killer" because it often has no symptoms until the disease has progressed and become more advanced or spread to other areas of the body. “The symptoms can sometimes be confused with other conditions, and in general, many patients have no symptoms or warning signs until the cancer has advanced,” says Dr. Voloyiannis. Here are some symptoms that may indicate colon cancer:

  • Prolonged bowel problems like diarrhea and constipation
  • Feeling like you still have to go after a bowel movement
  • Rectal bleeding, which may be seen on toilet paper or in stool (poop)
  • Blood in the stool, which can appear dark red or black like tar
  • Decreased stool quality, such as narrowing of the stool
  • Unintended weight loss
  • Weakness and fatigue
  • Abdominal discomfort, pain or cramping
  • Anemia, or low red blood cells which carry oxygen throughout your body

What are the screening options?  

Screening can help healthcare providers (HCPs) find polyps and remove them early before cancer develops, or diagnose cancer and suggest treatment. Both the U.S. Preventive Services Task Force (USPSTF) and the ACS recommend screenings for people with average risk of colorectal cancer beginning at age 45. Earlier screenings may be recommended for those who have an increased risk of colorectal cancers, Voloyiannis adds.

Here are some of the most common types of screenings:

  • Colonoscopy: “This is the preferred method of screening,” notes Voloyiannis. During the procedure, a flexible tube with a camera is inserted into the colon and rectum to check for irregular growths. If polyps are found, they are usually removed for testing. Should be done every 10 years, or earlier depending on the findings. 
  • Stool tests: These tests look for blood or cancer cells in stool. You collect a sample at home and mail it in for analysis. Should be done every 1 to 3 years, depending on the test.
  • Flexible sigmoidoscopy: A flexible tube is inserted into the rectum and lower part of the colon to check for irregular growths. Should be done every 5 years.

Many people put off getting their colonoscopies due to concerns that the process will be uncomfortable and time-consuming. While the bowel preparation the night before can be uncomfortable and requires drinking a solition that causes diarrhea to clean out the colon, the actual colonoscopy procedure is short and usually painless.

“Nowadays, the bowel preparation and fluid you drink to clean up the bowels prior to the colonoscopy is more tolerable than it used to be. You don’t have to drink as much fluid and you can drink water in between,” explains Voloyiannis. Most colonoscopies today are also being done under IV anesthesia, which administers medication to make you sleepy directly into a vein. “You’re completely asleep so you don’t feel the pain or cramps, then you wake up right after the procedure, and only have to take one day off of work.”

What are the treatment options?

If you are diagnosed with colorectal cancer, the cancer’s stage, location and type of cancer cells will be used to find a treatment option is right for you. Options include:

  • Surgery
  • Radiation therapy (high-dose X-rays)
  • Chemotherapy (chemo, or drugs that go throughout the body to kill cancer cells and can also damage healthy cells)
  • Targeted therapy (drugs that target cancer cells for killing and minimizes damage to healthy cells)
  • Immunotherapy (drugs that work on the immune system to help it fight cancer)  
  • Combination therapy, using more than one cancer therapy 

How can you lower your risk?

While you can’t control your genes, there are other things you may be able to do that can lower your risk of colorectal cancer. In addition to the recommended screenings, here are ways to lower your risk of colorectal cancer:

  • Aim for maintaining a healthy weight.
  • Quit smoking if you smoke.
  • Stay active and exercise regularly, as you are able.
  • Avoid red meat, deli meat like hot dogs and cold cuts, and limit processed foods; try to include plenty of fresh fruits, vegetables, and whole grains in your diet
  • Limit alcoholic beverages to no more than 2 drink a day for men, and 1 drink a day for women.

If detected early, polyps can be removed before they turn into cancer. Keeping your appointments for your own personal screening recommendations is the best way to prevent colorectal cancer. Taking care of your overall health can also lower your risk.

Article sources open article sources

American Cancer Society. “Key Statistics for Colorectal Cancer.” Last Revised: January 12, 2021.

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