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Colon cancer

Definition

Colon, or colorectal, cancer is cancer that starts in the large intestine (colon) or the rectum (end of the colon).

Other types of cancer can affect the colon. These include lymphoma, carcinoid tumors, melanoma, and sarcomas. These are rare. In this article, colon cancer refers to colon carcinoma only.

Alternative Names

Colorectal cancer; Cancer - colon; Rectal cancer; Cancer - rectum; Adenocarcinoma - colon; Colon - adenocarcinoma

Causes

In the United States, colorectal cancer is one of the leading causes of deaths due to cancer. Early diagnosis can often lead to a complete cure.

Almost all colon cancers start in the lining of the colon and rectum. When doctors talk about colorectal cancer, this is usually what they are talking about.

There is no single cause of colon cancer. Nearly all colon cancers begin as noncancerous (benign) polyps, which slowly develop into cancer.

You have a high risk of colon cancer if you:

  • Are older than 60
  • Are African American or of eastern European descent
  • Eat a a lot of red or processed meats
  • Have colorectal polyps
  • Have inflammatory bowel disease (Crohn disease or ulcerative colitis)
  • Have a family history of colon cancer
  • Have a personal history of breast cancer

Some inherited diseases also increase the risk of developing colon cancer. One of the most common is a type of polyp called familial adenomatous polyposis (FAP).

What you eat may play a role in getting colon cancer. Colon cancer may be linked to a high-fat, low-fiber diet and to a high intake of red meat. Some studies have found that the risk does not drop if you switch to a high-fiber diet, so this link is not yet clear.

Smoking cigarettes and drinking alcohol are other risk factors for colorectal cancer.

Symptoms

Many cases of colon cancer have no symptoms. If there are symptoms, the following may indicate colon cancer:

Exams and Tests

Through screening tests, colon cancer can be detected before symptoms develop. This is when the cancer is most curable.

Your doctor will perform a physical exam and press on your belly area. The physical exam rarely shows any problems, although the doctor may feel a lump (mass) in the abdomen. A rectal exam may reveal a mass in patients with rectal cancer, but not colon cancer.

A fecal occult blood test (FOBT) may detect small amounts of blood in the stool. This may suggest colon cancer. A sigmoidoscopy, or more likely a colonoscopy, will be done to evaluate the cause of blood in your stool.

Only colonoscopy can see the entire colon. This is the best screening test for colon cancer.

Blood tests may be done for those diagnosed with colorectal cancer, including:

If you are diagnosed with colorectal cancer, more tests will be done to see if the cancer has spread. This is called staging. CT or MRI scans of the abdomen, pelvic area, chest, or brain may be used to stage the cancer. Sometimes, PET scans are also used.

Stages of colon cancer are:

  • Stage 0: Very early cancer on the innermost layer of the intestine
  • Stage I: Cancer is in the inner layers of the colon
  • Stage II: Cancer has spread through the muscle wall of the colon
  • Stage III: Cancer has spread to the lymph nodes
  • Stage IV: Cancer has spread to other organs outside the colon

Blood tests to detect tumor markers, such as carcinoembryonic antigen (CEA) may help the doctor follow you during and after treatment.

Treatment

Treatment depends on many things, including stage of the cancer. Treatments may include:

Surgery

Stage 0 colon cancer may be treated by removing the cancer cells. This is done using colonoscopy. For stages I, II, and III cancer, more extensive surgery is needed to remove the part of the colon that is cancerous. This surgery is called colon resection.

Chemotherapy

Almost all patients with stage III colon cancer should receive chemotherapy after surgery for 6 to 8 months. This is called adjuvant chemotherapy.

Chemotherapy is also used to improve symptoms and prolong survival in patients with stage IV colon cancer.

You may receive just one type of medicine or a combination of medicines.

Radiation

Radiation therapy is sometimes used for colon cancer. It is usually used in combination with chemotherapy for patients with stage III rectal cancer.

For patients with stage IV disease that has spread to the liver, treatment directed at the liver can be used. This may include:

  • Burning the cancer (ablation)
  • Delivering chemotherapy or radiation directly into the liver
  • Freezing the cancer (cryotherapy)
  • Surgery

Support Groups

You can ease the stress of illness by joining a colon cancer support group. Sharing with others who have common experiences and problems can help you not feel alone. 

Outlook (Prognosis)

In many cases, colon cancer is treatable when caught early.

How well you do depends on many things, especially the stage of the cancer. When treated at an early stage, many patients survive at least 5 years after diagnosis. This is called the 5-year survival rate.

If the colon cancer does not come back (recur) within 5 years, it is considered cured. Stages I, II, and III cancers are considered possibly curable. In most cases, stage IV cancer is not considered curable, although there are exceptions.

Possible Complications

  • Blockage of the colon, causing bowel obstruction
  • Cancer returning in the colon
  • Cancer spreading to other organs or tissues (metastasis)
  • Development of a second primary colorectal cancer

When to Contact a Medical Professional

Call your health care provider if you have:

  • Black, tar-like stools
  • Blood during a bowel movement
  • Change in bowel habits
  • Unexplained weight loss

Prevention

Colon cancer can almost always be caught by colonoscopy in its earliest and most curable stages. Almost all men and women age 50 and older should have a colon cancer screening. Patients at higher risk may need earlier screening.

Colon cancer screening can often find polyps before they become cancerous. Removing these polyps may prevent colon cancer.

Changing your diet and lifestyle is important. Medical research suggests that low-fat and high-fiber diets may reduce your risk of colon cancer.

Some studies have reported that NSAIDs (aspirin, ibuprofen, naproxen, celecoxib) may help reduce the risk of colorectal cancer. But these medicines can increase your risk of bleeding and heart problems. Your health care provider can tell you more about the risks and benefits of the medicines and other ways that help prevent colorectal cancer.

References

Itzkowitz SH, Potack J. Colonic polyps and polyposis syndromes. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger and Fordtran's Gastrointestinal and Liver Disease Pathophysiology/Diagnosis/Management. 9th ed. Philadelphia, Pa: Elsevier Saunders; 2010:chap 122.

National Cancer Institute: PDQ Colon Cancer Treatment. Bethesda, Md: National Cancer Institute. Date last modified 02/08/2013. Available at http://cancer.gov/cancertopics/pdq/treatment/colon/HealthProfessional. Accessed November 11, 2013.

National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines): Colon cancer. Version 2.2014. Available at http://www.nccn.org/professionals/physician_gls/pdf/colon.pdf. Accessed November 11, 2013.

National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines): Colorectal cancer screening. Version 2.2013. Available at http://www.nccn.org/professionals/physician_gls/pdf/colorectal_screening.pdf. Accessed November 11, 2013.


Review Date: 10/30/2013
Reviewed By: Yi-Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.
The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.
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