Illustration of colorectal cancer

Colorectal Cancer Overview

Colorectal cancer is very common, and it’s on the rise among young adults. Early detection and treatment are crucial, which is why people need to be familiar the symptoms of colon and rectal cancer and get regular colorectal cancer screenings.

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Colorectal cancer (often called colon cancer, for short) starts in the colon or rectum. While any adult can develop colorectal cancer, it's more common in men than women and in people of African American descent. The risk of developing colorectal cancer goes up as you get older. Other risk factors include smoking, eating a meat-heavy diet, being physically inactive, having inflammatory bowel disease, or having a family history of colorectal cancer or growths called polyps. Watch out for symptoms such as blood in the stool, a change in bowl habits, cramping or abdominal pain, or unexplained weight loss.

In recent years, the rate of colorectal cancer cases in the US has been on the rise among younger adults. Routine screening for colorectal cancer is now recommended starting at age 45—or even sooner for people with risk factors. The earlier colorectal cancer is detected and treated, the better the outcome.

What Is It?

Colorectal cancer, as the name implies, is a cancer of the large, muscular tube known as the colon, or cancer of the rectum, which sits at the end of the digestive tract. These organs process and remove waste.

It's the third most common cancer diagnosed in men and women in the US.

Colorectal cancer often begins as a polyp, or growth, on the inner lining of the colon or rectum. Not all polyps are cancerous, but if cancer develops in a polyp, it can spread to the wall of the colon or rectum and beyond. That's why colorectal cancer screening is so important: You want your doctor to find and remove any polyps before they have a chance to become cancerous.


While different types of colorectal cancers exist, 95% of them are adenocarcinomas. If you are diagnosed with cancer of the colon or rectum, it's likely to be an adenocarcinoma.

  • Adenocarcinoma. Cancer begins in mucus-making cells lining the colon and rectum.
  • Carcinoid tumor. A type of cancer that starts in hormone-producing cells in the intestines.
  • Gastrointestinal stromal tumor (known as GIST). A cancer that develops in special cells (called interstitial cells of Cajal) in the wall of the gastrointestinal (GI) tract. These tumors are rarely found in the colon.
  • Lymphoma. An immune system cancer that usually begins in the lymph nodes. It's a rare type of GI tumor.
  • Sarcoma. A rare type of colorectal cancer often arising from smooth muscle cells.


Colorectal cancer may not cause symptoms, especially early in the disease. (Again, this is why routine screening is so important.) If you happen to have symptoms, you may experience:

  • A change in bowel habits.
  • Blood on or in your stool. (The blood can be bright red, dark brown, or black.)
  • Diarrhea or constipation.
  • A feeling that your bowel hasn't emptied completely, even after a BM.
  • Cramping or abdominal pain.
  • Unexplained weight loss.
  • Weakness or fatigue.

If you're having colorectal cancer symptoms, it's important to see a physician right away.


Most colorectal cancers begin when polyps on the inner lining of the colon or rectum become cancerous. Exactly why the cells that make up these growths begin to mutate and divide isn't clear, but scientists believe certain factors can increase a person's risk of developing colorectal cancer. These include:

  • Age. It's more common in adults over 50 (although younger adults can develop it too).
  • Having a personal or family history of colorectal polyps or colorectal cancer.
  • Having inflammatory bowel disease.
  • Race or ethnicity. African Americans and people of Ashkenazi (Eastern European) Jewish descent have higher rates of colorectal cancer.
  • Having an inherited genetic syndrome, such as familial adenomatous polyposis or Lynch syndrome.
  • Being overweight or obese.
  • Being physically inactive.
  • Consuming a diet high in red or processed meats.
  • Tobacco use.
  • Heavy alcohol use.
  • Having type 2 diabetes.


If you have symptoms of colorectal cancer or if colorectal cancer is suspected, your doctor may recommend:

  • A physical exam, including a digital rectal exam.
  • A stool-based test to look for hidden blood in the stool or other signs of cancer.
  • Blood tests.
  • Diagnostic colonoscopy to inspect the entire colon and rectum and remove any polyps.
  • Proctoscopy to test for rectal cancer.
  • Biopsy (a lab procedure to examine suspicious tissue for cancer).
  • Imaging tests (such as ultrasound, MRI, or CT).

Once a diagnosis of colorectal cancer has been determined, the cancer is "staged" based on the size of the tumor, whether it has spread to nearby lymph nodes, and the extent to which it has traveled to distant lymph nodes and other organs of the body. A stage 0 cancer means it's in its earliest stage; stage 4 cancer is advanced, meaning the cancer has spread or "metastasized."


The treatment for colorectal cancer depends on factors such as the cancer's location and stage. But surgery is usually the main treatment.

The type of surgery depends on the size of the polyp and whether the cancer has spread. If it's a small, early-stage cancer contained within a polyp, treatment may simply involve removing the polyp during colonoscopy. More advanced cancer might require a colectomy, a procedure that involves cutting out all or part of the colon. If the colon or rectum are diseased, a colostomy or ileostomy may be performed. These are surgeries to create an opening in the abdomen so that waste can be collected in an external pouch.

Chemotherapy, radiation, targeted drug therapy, or immunotherapy may be recommended.


The number one way to reduce your risk of colorectal cancer is to get screened. Several different screening tests may be used to look for possible colorectal cancer:

  • Stool tests. These tests look blood in the stool or signs of cancer.
  • Flexible sigmoidoscopy. (A test to examine the rectum and lower part of the colon.)
  • Colonoscopy. (This procedure allows the doctor to see the entire colon and remove any polyps that may be present.)
  • CT colonography, aka virtual colonoscopy. (Displays computer images of the colon.)

Talk to your doctor about which test is best for you. People with a family history of colorectal cancer may also want to consider genetic counseling to assess their risk.

In addition, you may be able to reduce your risk of developing colorectal cancer by modifying your diet and exercise habits. Specifically:

  • Maintain a healthy weight.
  • Exercise regularly.
  • Eat more fruits, veggies, and whole grains and limit your intake of red or processed meat.
  • Limit your alcohol intake, or don't drink at all.
  • Stop smoking.

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