Skip Navigation
NIH MedlinePlus the Magazine, Trusted Health Information from the National Institutes of Health

Colorectal Cancer

The Importance of Early Detection

Cancer of the colon or rectum is called colorectal cancer. The colon and the rectum are part of the large intestine, which is part of the digestive system. Colorectal cancer occurs when tumors form in the lining of the large intestine.

Colorectal cancer accounts for almost 10 percent of all cancer deaths in the United States. It is common in both men and women.

Today there are more ways than ever to treat colorectal cancer. As with almost all cancers, the earlier it is found, the more likely that the treatment will be successful. If colon cancer is detected in its early stages, it is up to 90 percent curable.

Risk Factors

Scientists don't know exactly what causes colorectal cancer, but they have been able to identify some risk factors for the disease.

  • Age: Colorectal cancer is more likely in people over age 50.
  • Polyps: Polyps are benign, or non-cancerous, growths on the inner wall of the colon and rectum. They are fairly common in people over age 50. Some types of polyps increase a person's risk of developing colorectal cancer. Not all polyps become cancerous, but nearly all colon cancers start as polyps.
  • Diet: The link between diet and colorectal cancer is not firmly established. However, there is evidence that smoking cigarettes and drinking three or more alcoholic beverages daily may be associated with an increased risk.
  • Personal history: Research shows that women with a history of cancer of the ovary, uterus, or breast have a somewhat increased chance of developing colorectal cancer.
  • Family history: The parents, siblings, and children of a person who has had colorectal cancer are somewhat more likely to develop this type of cancer themselves.
  • Ulcerative colitis: Having this condition increases a person's chance of developing colorectal cancer.
  • Genetic mutations: Researchers have identified genetic mutations, or abnormalities, that may be linked to the development of colon cancer. They are working to unravel the exact ways these genetic changes occur.

Common Signs and Symptoms

When colorectal cancer first develops, there may be no symptoms. But as the cancer grows, it can cause changes that people should watch for:

  • Changes in the frequency of bowel movements
  • Diarrhea, constipation, or feeling that the bowel does not empty completely
  • Bright red or very dark blood in the stool
  • Stools that are narrower than usual
  • General abdominal discomfort such as frequent gas pains, bloating, fullness, and/or cramps
  • Weight loss with no known reason
  • Constant tiredness
  • Vomiting

Standard Treatments

The three standard treatments for colon cancer are surgery, chemotherapy, and radiation. The choice of treatment depends on the size, location, and stage of the cancer and on the patient’s general health. Doctors may suggest several treatments or combinations of treatments.


Surgery is the most common first step in the treatment for all stages of colon cancer. A doctor may remove the cancer using several types of surgery.

  • Local excision: If the cancer is found at a very early stage, the doctor may remove it without cutting through the abdominal wall. Instead, the doctor may put a tube up the rectum into the colon and cut the cancer out. This is called a local excision.
  • Colectomy: If the cancer is larger, the surgeon will remove the cancer and a small amount of healthy tissue around it. This is called a colectomy. The surgeon may then sew the healthy parts of the colon together.
  • Colostomy: If the doctor is unable to sew the two ends of the colon back together, an opening called a stoma is made on the abdomen for waste to pass out of the body before it reaches the rectum. This procedure is called a colostomy. Sometimes the colostomy is needed only until the lower colon has healed, and then it can be reversed. But if the doctor needs to remove the entire lower colon or rectum, the colostomy may be permanent.


Chemotherapy is the use of anti-cancer drugs to kill cancer cells. Chemotherapy may be taken by mouth, or it may be put into the body by inserting a needle into a vein or muscle.

One form of chemotherapy is called systemic treatment because the drugs enter the bloodstream, travel through the body, and can kill cancer cells throughout the body. The other form of chemotherapy is called targeted therapy because the drug affects only the factors that are causing the cancer and does not perturb the rest of the body.

Radiation Therapy

Radiation therapy is the use of X-rays or other types of radiation to kill cancer cells and shrink tumors. Most often, doctors use it for patients whose cancer is in the rectum.

Doctors may use radiation before surgery to shrink a tumor in the rectum and make it easier to remove. Or they may use it after surgery to destroy any cancer cells that remain in the treated area.

The radiation may come from a machine or from implants placed directly into or near the tumor. Radiation that comes from a machine is called external radiation. Radiation that uses implants is known as internal radiation. Some patients have both kinds of therapy.

Find Out More

Read More "Colorectal Cancer" Articles

Colorectal Cancer: A Personal Journey / The Importance of Early Detection / Developments in Colorectal Cancer Screening

Summer 2016 Issue: Volume 11 Number 2 Page 19-20