Colorectal Cancer

Colorectal cancer is an abnormal growth of tissue (tumor) in the colon or rectum that is cancerous (malignant). Unlike noncancerous (benign) tumors, malignant tumors can spread to other parts of your body. The colon is the large bowel or large intestine. The rectum is the last several inches of the colon.


The exact cause of colon cancer is unknown.


The majority of patients do not have identifiable risk factors, but the following factors may increase your chances of getting colon cancer:

  • Age. Most colorectal cancers occur in people older than 50 years.

  • Having abnormal growths (polyps) on the inner wall of the colon or rectum.

  • Diabetes.

  • Being African American.

  • Family history of hereditary nonpolyposis colon cancer. This condition is caused by changes in the genes that are responsible for repairing mismatched DNA.

  • Family history of familial adenomatous polyposis (FAP). This is a rare, inherited condition in which hundreds of polyps form in the colon and rectum. It is caused by a change in the APC gene. Unless FAP is treated, it usually leads to colorectal cancer by age 40.

  • Personal history of cancer. A person who has already had colorectal cancer may develop it a second time. Also, women with a history of ovarian, uterine, or breast cancer are at a somewhat higher risk of developing colorectal cancer.

  • Inflammatory bowel disease, including ulcerative colitis and Crohn's disease.

  • Being obese or eating a diet that is high in fat (especially animal fat) and low in fiber, fruits, and vegetables.

  • Smoking. A person who smokes cigarettes may be at increased risk of developing polyps and colorectal cancer.

  • Heavy alcohol use.


Early colorectal cancer often does not cause symptoms. As the cancer grows, symptoms may include:

  • Diarrhea.

  • Constipation.

  • Feeling like the bowel does not empty completely after a bowel movement.

  • Blood in the stool.

  • Stools that are narrower than usual.

  • Abdominal discomfort, pain, bloating, fullness, or cramps.

  • Unexplained weight loss.

  • Constant tiredness.

  • Nausea and vomiting.


Your caregiver will ask about your medical history. He or she may also perform a number of procedures, such as:

  • A physical exam.

  • Blood tests. This may include a routine complete blood count and iron level testing. Your caregiver may also check for carcinoembryonic antigen (CEA) and other substances in the blood. Some people who have colorectal cancer have a high CEA level. These levels may be used to follow the activity of your colon cancer.

  • Chest X-rays, computed tomography (CT) scans, or magnetic resonance imaging (MRI).

  • Taking a tissue sample (biopsy) from the colon or rectum. The sample is examined under a microscope to look for cancer cells.

  • Sigmoidoscopy. With this test, your caregiver can see inside your colon. A thin flexible tube (sigmoidoscope) is placed into your rectum. This device has a light source and a tiny video camera in it. Your caregiver uses the sigmoidoscope to look at the last third of your colon.

  • Colonoscopy. This test is like sigmoidoscopy, but your caregiver looks at the entire colon. This test usually requires medicine that helps you relax (sedative).

  • Endorectal ultrasound. With this test, your caregiver can see how deep a rectal tumor has grown and whether the cancer has spread to lymph nodes or other nearby tissues. A tool (probe) is inserted into the rectum. The probe sends out sound waves to the rectum and nearby tissues, and a computer uses the echoes to create a picture.

Your cancer will be staged to determine its severity and extent. Staging is a careful attempt to find out the size of the tumor, whether the cancer has spread, and if so, to what parts of the body. You may need to have more tests to determine the stage of your cancer. The test results will help determine what treatment plan is best for you.


  • Stage 0. The cancer is found only in the innermost lining of the colon or rectum.

  • Stage I. The cancer has grown into the inner wall of the colon or rectum. The cancer has not yet reached the outer wall of the colon.

  • Stage II. The cancer extends more deeply into or through the wall of the colon or rectum. It may have invaded nearby tissue, but cancer cells have not spread to the lymph nodes.

  • Stage III. The cancer has spread to nearby lymph nodes but not to other parts of the body.

  • Stage IV. The cancer has spread to other parts of the body, such as the liver or lungs.

Your caregiver may tell you the detailed stage of your cancer. In that case, the stage will include both a number and a letter.


Depending on the type and stage, colorectal cancer may be treated with surgery, radiation therapy, or chemotherapy. Some patients have a combination of these therapies.

  • Surgery may be done to remove the polyps from your colon. In early stages, your caregiver may be able to do this during a colonoscopy. In later stages, surgery may be done to remove part of your colon.

  • Radiation therapy uses high-energy rays to kill cancer cells. This is usually recommended for patients with rectal cancer.

  • Chemotherapy is the use of drugs to kill cancer cells. Caregivers also give chemotherapy to help reduce pain and other problems caused by colorectal cancer. This may be done even if the cancer is not curable.


  • Only take over-the-counter or prescription medicines for pain, discomfort, or fever as directed by your caregiver.

  • Maintain a healthy diet.

  • Consider joining a support group. This may help you learn to cope with the stress of having colorectal cancer.

  • Seek advice to help you manage treatment side effects.

  • Keep all follow-up appointments as directed by your caregiver.

  • Inform your cancer specialist if you are admitted to the hospital.


  • Your diarrhea or constipation does not go away.

  • You have alternating constipation and diarrhea.

  • You have blood in your stools.

  • Your abdominal pain gets worse.

  • You lose weight without trying.

  • You notice new fatigue or weakness.

  • You develop a fever during chemotherapy treatment.