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Gastrointestinal Cancers

Colon & Rectal Cancer

Background

Colon cancer is cancer of the large intestine (colon), the lower part of the digestive system. Rectal cancer is cancer of the last several inches of the colon, near the anus. Most cases of colon cancer begin as small, benign polyps. Polyps may be small and produce few, if any, symptoms. For this reason, doctors recommend regular screening tests to help prevent colon cancer by identifying polyps before they become colon cancer.

Symptoms

Signs and symptoms of colon cancer can include:

  • A change in bowel habits, including diarrhea or constipation or a change in the consistency/caliber of stool
  • Rectal bleeding or blood in the stool
  • Persistent abdominal discomfort, such as cramps, gas or pain
  • Feeling like the bowel is not emptying completely
  • Weakness or fatigue
  • Weight loss (non-intentional)

Many people with colon cancer experience no symptoms in the early stages of the disease. This emphasizes the importance of screening tests to help detect cancers at an early stage. The presence of symptoms does not necessarily indicate colon cancer, but warrants a visit to see a physician to discuss the appropriate workup and treatment.

Risk Factors

Factors that may increase the risk of colon cancer include:

  • Alcohol use
  • Smoking
  • Obesity and sedentary lifestyle
  • Colon cancer can occur in younger people, but it occurs much less frequently. About 90 percent of people diagnosed with colon cancer are older than 50.
  • A personal history of colorectal cancer or polyps
  • Being African-American; initial colon cancer screening is recommended at age 45
  • A low-fiber, high-fat diet. Some studies have found an increased risk of colon cancer in people who eat diets high in red meat and processed meats.
  • Long-standing inflammatory diseases of the colon, i.e., inflammatory bowel disease (Crohn's, ulcerative colitis)
  • Radiation therapy for cancer. Radiation therapy directed at the abdomen to treat previous cancers and repeated radiation exposure from previous radiological studies may increase the risk of colon cancer.
  • Genetic syndromes, such as familial adenomatous polyposis (FAP) and hereditary nonpolyposis colorectal cancer (HNPCC - also called Lynch syndrome)
  • A family history of colon cancer and colon polyps. If the family member developed colon cancer at an early age, or if more than one family member has a history of colon cancer or rectal cancer, the risk is even greater.

Staging

Stage 0 (Carcinoma in Situ): Abnormal cells are found in the innermost lining of the colon (mucosa). These abnormal cells may become cancer and spread into nearby normal tissue. Stage 0 is also called carcinoma in situ.

Stage I: Cancer has formed and spread beyond the innermost tissue layer of the colon wall to the middle layers. Stage I colon cancer is sometimes called Dukes A colon cancer.

Stage II: Stage II colon cancer, sometimes called Dukes B colon cancer, is divided into Stages IIA and IIB.

    Stage IIA: Cancer has spread beyond the middle tissue layers of the colon wall or has spread to nearby tissues around the colon or rectum.

    Stage IIB: Cancer has spread beyond the colon wall into nearby organs and/or through the peritoneum.

Stage III: Stage III colon cancer is divided into stage IIIA, stage IIIB, and stage IIIC.

    • beyond the middle tissue layers of the colon wall; or
    • to nearby tissues around the colon or rectum; or
    • beyond the colon wall into nearby organs and/or through the peritoneum.
    • to or beyond 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 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 three nearby lymph nodes and has spread:

    Stage IIIC: Stage III colon cancer, sometimes called Dukes C colon cancer, occurs when the cancer has reached four or more nearby lymph nodes and has spread:

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

Treatment

The type of treatment your doctor recommends will largely depend on the stage of cancer. The three primary treatment options are surgery, chemotherapy, and radiation, which are sometimes performed in combination.

Surgery for early-stage colon cancer
If the cancer is small, localized in a polyp and in a very early stage, your doctor may be able to remove it completely during a colonoscopy. If the pathologist determines that the cancer resides only within the polyp/mucosal layer without evidence of deeper colon layer involvement or vascular invasion, no further treatment (such as surgery, chemotherapy or radiation) may be required. However, close surveillance with repeat endoscopic procedures (flexible sigmoidoscopy or colonoscopy) will be required.

Surgery for invasive colon cancer
If the cancer has grown into or through the colon, a surgeon may recommend a partial colectomy to remove the part of your colon that contains the cancer. Nearby lymph nodes are usually removed and tested for cancer involvement. Your surgeon is often able to reconnect the healthy portions of your colon or rectum. However, when the cancer involves the very distal rectum (near the anus), you may need to have a permanent colostomy. This is where the end of the colon is attached to the outside of the abdominal wall with stool emptying into an attached bag.

Surgery for advanced colon cancer
If the cancer is very advanced or your overall health very poor, a surgeon may recommend an operation to relieve a blockage of the colon or other conditions to ease your symptoms. This type of surgery is referred to as palliative surgery. The goal of palliative surgery is not meant to be curative, but instead to relieve signs and symptoms, such as bleeding and pain, due to the cancer. In specific cases where the cancer has spread only to the liver and if your overall health is otherwise good, a doctor may recommend surgery to remove the cancerous lesion from your liver. Chemotherapy may be used before or after this type of surgery. This treatment may improve your prognosis.

Chemotherapy
Your doctor may recommend chemotherapy if your cancer has spread beyond the wall of the colon or if your cancer has spread to the lymph nodes. In people with rectal cancer, chemotherapy is typically used along with radiation therapy. The combination of chemotherapy and radiation may be performed either before or after surgery depending on the staging of the rectal cancer and your overall health.

Radiation therapy
Radiation therapy is rarely used in early-stage colon cancer, but is a routine part of treating rectal cancer, especially if the cancer has penetrated through the wall of the rectum or traveled to nearby lymph nodes. Radiation therapy, usually combined with chemotherapy, may be used before or after surgery to reduce the risk that the cancer may recur in the area of the rectum where it began.

Targeted drug therapy
Drugs that target specific defects that allow cancer cells to proliferate are available to people with advanced colon cancer, including bevacizumab (Avastin), cetuximab (Erbitux) and panitumumab (Vectibix). Targeted drugs can be given alone or along with chemotherapy. Targeted drugs are typically reserved for people with advanced colon cancer. Whether you are a candidate for such treatment should be discussed with your cancer specialist (oncologist).

References
National Cancer Institute, Mayo Clinic, Cancer Treatment Centers of America.