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 colorectal cancer only.
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 higher risk for colon cancer if you:
Some inherited diseases also increase the risk of developing colon cancer. One of the most common is 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.
Many cases of colon cancer have no symptoms. If there are symptoms, the following may indicate colon cancer:
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 people 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 a full 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, or chest may be used to stage the cancer. Sometimes, PET scans are also used.
Stages of colon cancer are:
Blood tests to detect tumor markers, such as carcinoembryonic antigen (CEA) may help the doctor follow you during and after treatment.
Treatment depends on many things, including the stage of the cancer. Treatments may include:
Stage 0 colon cancer may be treated by removing the tumor. This is often 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 (colectomy).
Almost all people with stage III colon cancer receive chemotherapy after surgery for 6 to 8 months. This is called adjuvant chemotherapy. Even though the tumor was removed, chemotherapy is given to treat any cancer cells that may be left.
Chemotherapy is also used to improve symptoms and prolong survival in people with stage IV colon cancer.
You may receive just one type of medicine or a combination of medicines.
Radiation therapy is sometimes used for colon cancer.
For people with stage IV disease that has spread to the liver, treatment directed at the liver can be used. This may include:
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.
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 people 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.
Complications may include:
Call your health care provider if you have:
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. People 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 for colon cancer.
Some studies have reported that NSAIDs (aspirin, ibuprofen, naproxen, and celecoxib) may help reduce the risk for colorectal cancer. But these medicines can increase your risk of bleeding and heart problems. Your provider can tell you more about the risks and benefits of the medicines and other ways that help prevent colorectal cancer.
Reviewed By: Richard LoCicero, MD, private practice specializing in hematology and medical oncology, Longstreet Cancer Center, Gainesville, GA. Review provided by VeriMed Healthcare Network. Internal review and update on 04/15/2019 by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.