Colon cancer

The colon and rectum form a long, muscular tube called the large intestine or large bowel. The colon is the upper 5 to 6 feet of the large bowel, and the rectum is the last 6 to 8 inches. 

Colon cancer (also known as colorectal cancer) begins when cells begin to grow out of control. Most cancers begin as growths on the inner lining of the colon or rectum called polyps. 

Colon cancer is the fourth most common cancer and the second leading cause of cancer death in the United States. It responds best to treatment when it is diagnosed and treated as early as possible, especially before it has a chance to spread outside of the colon.

Colon cancer risk factors

Studies have found that certain things may increase a person’s risk of getting colon cancer. These include:

  • Being ages 50 or older
  • Previously having colon polyps (small noncancerous growths)
  • A family history of colon cancer
  • Personal history of:
    • Colon cancer
    • Rectum cancer
    • Ovarian cancer
    • Endometrium cancer
    • Breast cancer
  • Having inflammatory bowel disease, such as ulcerative colitis or Crohn’s disease
  • Hereditary conditions
    • Familial adenomatous polyposis
    • Hereditary nonpolyposis colon cancer (HNPCC; Lynch Syndrome)
  • Eating a high fat, low fiber diet
  • Being part of African American and Ashkenazi Jew populations
  • Obesity
  • Smoking
  • Alcohol intake
  • Inactive lifestyle

Colon cancer symptoms

Colon cancer can cause a wide range of symptoms. Signs to watch for include:

  • Change in usual bowel habits (i.e. used to have 1 bowel movement a day, now having 2 to 3 movements a day)
  • Blood in the stool, either dark red or bright red
  • Fatigue or tiredness
  • Stools that are more narrow than usual
  • Abdominal pain or discomfort such as:
    • Gas pains
    • Cramping
    • Bloating
    • Feeling of fullness
  • Loose or watery bowel movements or hard, difficult to pass stools, that continue for over 2 weeks
  • Feeling as if bowel does not empty completely
  • Weight loss for no reason

These same symptoms may be caused by problems other than cancer. Only a doctor can find out the cause. If you have any of these symptoms, you should see your doctor.

Colon cancer prevention

There are steps you can take to help prevent colon cancer.

Eat a diet high in fiber and/or fruits and vegetables

It is not known if a diet low in fat and high in fiber, fruits, and vegetables lowers the risk of colon and rectal cancers. However, some studies have shown that a diet high in protein, fat, calories, and meat increases the risk of colon cancer.

Increase your activity level

Research has connected an inactive lifestyle with a higher risk of colon and rectal cancer. A person is considered physically active if they exercise for at least 30 minutes a day.

Limit your alcohol intake

Drinking more than 1 drink per day for women and 2 drinks per day for men has been shown to raise the risk of mouth, esophagus, pharynx, larynx, and liver cancers in both women and men and breast cancer in women. Heavy alcohol use has been shown to increase the risk of colon cancer.

Have regular screenings

Screening exams can find and remove precancerous polyps before they turn into cancer. Follow your doctor’s advice about having tests for colon cancer.

Colon cancer screening

You can take an active role in the prevention and early detection of colon cancer by getting screened regularly after the age of 50. Screening is when doctors order tests in people who are not having any symptoms to look for early cancer or polyps. Talk to your doctor about which test you should have.

These tests are commonly used to screen for colorectal cancer:

Fecal Occult Blood Test (FOBT)
A test to see if there is hidden blood in the stool. A positive result may be a sign of cancer or polyps.
A test that looks in the rectum and entire colon by using a long fiber optic telescope that is lighted and flexible. It may reveal polyps, cancer, colitis, or diverticulosis. Tissue can be removed for a doctor to look at under a microscope to make a diagnosis. May require sedation. Before the test, laxatives must be used to clean the bowel.
An examination of the rectum and lower (sigmoid) colon with a hollow lighted tube. It is used to find colon polyps, cancer, and/or to find the cause of bleeding. Tissue can be removed for a doctor to look at under a microscope to make a diagnosis. Before the test, laxatives are used to clean the bowel.
Virtual colonoscopy (also called CT colonoscopy)
A CT (computerized tomography) scan creates cross section images of the body, which may show cancer or its spread to other organs. Before the test, laxatives must be used to clean the bowel.
DNA stool test
A stool sample is examined for abnormal DNA that may be a sign of colon cancer. This technology is still undergoing testing to see if it is more effective at finding cancer cells earlier than other screening options.

Thinking about getting screened for colon cancer?

We have put together a short guide for your use.

Colon cancer treatment

The treatment for colon cancer depends on the stage of the cancer when it is diagnosed. There are three standard treatments used to fight colon cancer: surgery, chemotherapy, and radiation therapy.


An operation is done to remove the cancer. It is the most common treatment for all stages of colon cancer. Doctors use several types of operations to remove colon cancer:

Local excision
When the cancer is in a very early stage, the doctor can remove it without making a cut or incision on the abdomen. The doctor will put a tube into the colon and cut the cancer out through the tube. If cancer is found in a polyp, the surgery is called a polypectomy.
If the cancer is larger, the doctor will perform a partial colectomy. This means removing the part of the colon where the cancer is and some of healthy tissue surrounding the cancer. The doctor may then do an anastomosis, which is sewing the healthy parts of the colon together. The doctor will usually remove lymph nodes near the colon and examine them under a microscope to see if they contain cancer cells.
Resection and colostomy
If the doctor is not able to sew the two ends of colon back together, an opening (stoma) is made on the outside of the body for bowel movements to pass through. This operation is called a colostomy. A bag is connected to the stoma to collect the waste. Colostomies sometimes are needed only until the lower colon has healed, then the colon can be sewn back together. Sometimes, however, a colostomy is permanent.
Radiofrequency ablation
A special probe with small electrodes is used to kill cancer cells. The probe is often inserted directly through a cut in the skin and only local anesthesia is needed. If a larger cut is made, then general anesthesia is used.
Abnormal tissue is frozen and killed by an instrument. This is also called cryotherapy.

Chemotherapy and colon cancer

Chemotherapy is medicine that can kill cancer cells or stop them from growing. Chemotherapy can be taken in a pill form, given in the vein through an IV, or it may be given in the muscle with a needle. The medicine will travel through the bloodstream and kill cancer cells throughout the entire body. This is called systemic chemotherapy. 

If the chemotherapy is placed into an organ or a body cavity like the abdomen, the medicine will try to affect only the cancer cells in that area. This is called regional chemotherapy. Most often with colon cancer the term intraperitoneal chemotherapy is used because the medicine is placed in the abdominal (peritoneal) cavity using a thin tube.


This is for patients whose colon cancer has spread to the liver. Doctors block the artery that feeds the liver with blood and inject chemotherapy drugs into the artery between the blockage and the liver so the drugs will go directly to the liver. Only a small amount of the chemotherapy will reach other cells.

Radiation therapy

Radiation therapy uses X-rays or other types of energy to kill cancer cells or keep them from growing. Usually, radiation is given outside the body using a machine, this is called external radiation. Internal radiation uses radioactive substances like needles, seeds, wires, or catheters that are put directly in or near the cancer.

Biological therapy for colon cancer

This is treatment uses substances to encourage the body’s own immune system to fight the cancer. It can also be called immunotherapy or biotherapy.

Stages of colon cancer

Colon cancer tests will also determine the stage of the cancer. The stage of colon cancer tells how big the tumor is, how deep it is, and if it has spread to another part of the body. The treatment of cancer is given according to the stage of the disease. The stage also gives information on the overall outlook of the cancer. The lower the stage, the better the outlook.

Stage 0

The abnormal cells are found in the inner most lining of the colon only. Abnormal cells can become cancerous and spread into the normal tissue. This stage is also called “carcinoma in situ.”

Stage I

The cancer has spread past the inner most tissue layer of the colon wall to the middle layers. Stage I colon cancer is sometimes called “Dukes A colon cancer.”

Stage II

Colon cancer is divided into stage IIA and IIB.

Stage IIA
Cancer has spread past the middle tissue layers of the colon wall or has spread to nearby tissues around the colon or rectum.
Stage IIB
Cancer has spread past the colon wall into nearby organs and/or through the peritoneum.

Stage II colon cancer is sometimes called “Dukes B colon cancer.”

Stage III

Colon cancer is divided into stage IIIA, stage IIIB, and IIIC.

Stage IIIA
Cancer has spread from the innermost tissue layer of the colon wall to the middle layers and has spread to as many as three lymph nodes.
Stage IIIB
Cancer has spread to as many as 3 nearby lymph nodes and has spread:
  • past the middle tissue layers of the colon wall; or
  • to nearby tissues around the colon or rectum; or
  • past the colon wall into nearby organs and or through the peritoneum.
Stage IIIC
Cancer has spread to 4 or more lymph nodes and has spread:
  • to or past the middle tissue layers of the colon wall; or
  • to nearby tissues around the colon or rectum; or
  • to nearby organs and/or through the peritoneum.

Stage III colon cancer is sometimes called “Dukes C colon cancer.”

Stage IV

Cancer has spread to nearby lymph nodes and other parts of the body, such as the liver or lungs. Stage IV colon cancer is sometimes called “Dukes D colon cancer.”

Recurrent colon cancer

Cancer that has recurred (come back) after it has been treated. The cancer may come back in the colon or in other parts of the body, such as the liver, lungs, or both.

Last reviewed: 
January 2017
Alternative Names: 
Colorectal cancer

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