Rectal cancer is a disease in which malignant (cancer) cells form in the tissues of the rectum.
How is it caused?
The following are possible risk factors for rectal cancer:
- A family history of cancer of the colon or rectum.
- A personal history of cancer of the colon, rectum, ovary, endometrium, or breast.
- A personal history of ulcerative colitis (ulcers in the lining of the large intestine) or Crohn disease.
- Certain hereditary conditions, such as familial adenomatous polyposis and hereditary nonpolyposis colon cancer (HNPCC; Lynch syndrome).
What are the symptoms?
Possible signs of rectal cancer include a change in bowel habits or blood in the stool.
These and other symptoms may be caused by rectal cancer. Other conditions may cause the same symptoms. A doctor should be consulted if any of the following problems occur:
- A change in bowel habits.
- Blood (either bright red or very dark) in the stool.
- Diarrhea, constipation, or feeling that the bowel does not empty completely.
- Stools that are narrower than usual.
- General abdominal discomfort (frequent gas pains, bloating, fullness, or cramps).
- Weight loss for no known reason.
How is it diagnosed?
Tests used in diagnosing rectal cancer include the following:
- Fecal occult blood test: A test to check stool (solid waste) for blood that can only be seen with a microscope. Small samples of stool are placed on special cards and returned to the doctor or laboratory for testing.
- Digital rectal exam: An exam of the rectum. The doctor or nurse inserts a lubricated, gloved finger into the lower part of the rectum to feel for lumps or anything else that seems unusual.
- Barium enema: A series of x-rays of the lower gastrointestinal tract. A liquid that contains barium (a silver-white metallic compound) is put into the rectum. The barium coats the lower gastrointestinal tract and x-rays are taken. This procedure is also called a lower GI series.
Sigmoidoscopy: A procedure to look inside the rectum and sigmoid (lower) colon for polyps, abnormal areas, or cancer. A sigmoidoscope (a thin, lighted tube) is inserted through the rectum into the sigmoid colon. Polyps or tissue samples may be taken for biopsy.
Colonoscopy: A procedure to look inside the rectum and colon for polyps, abnormal areas, or cancer. A colonoscope (a thin, lighted tube) is inserted through the rectum into the colon. Polyps or tissue samples may be taken for biopsy.
What is the treatment?
Three types of standard treatment are used:
Surgery
Surgery is the most common treatment for all stages of rectal cancer. A doctor may remove the cancer using one of the following types of surgery:
Local excision: If the cancer is found at a very early stage, the doctor may remove it without cutting into the abdomen. If the cancer is found in a polyp (a growth that protrudes from the rectal mucous membrane), the operation is called a polypectomy.
Resection: If the cancer is larger, the doctor will perform a resection of the rectum (removing the cancer and a small amount of healthy tissue around it). The doctor will then perform an anastomosis (sewing the healthy parts of the rectum together, sewing the remaining rectum to the colon, or sewing the colon to the anus). The doctor will also take out lymph nodes near the rectum and examine them under a microscope to see if they contain cancer.
Rectal cancer surgery with anastomosis. The rectum and part of the colon are removed, and then the colon and anus are joined.
Resection and colostomy: If the doctor is not able to sew the rectum back together, a stoma (an opening) is made on the outside of the body for waste to pass through. This procedure is called a colostomy. A bag is placed around the stoma to collect the waste. Sometimes the colostomy is needed only until the rectum has healed, and then it can be reversed. If the doctor needs to remove the entire rectum, however, the colostomy may be permanent.
Even if the doctor removes all the cancer that can be seen at the time of the operation, some patients may be given chemotherapy or radiation therapy after surgery to kill any cancer cells that are left. Treatment given after surgery to increase the chances of a cure is called adjuvant therapy.
Radiation therapy
Radiation therapy is a cancer treatment that uses high-energy x-rays or other types of radiation to kill cancer cells. There are two types of radiation therapy. External radiation therapy uses a machine outside the body to send radiation toward the cancer. Internal radiation therapy uses a radioactive substance sealed in needles, seeds, wires, or catheters that are placed directly into or near the cancer. The way the radiation therapy is given depends on the type and stage of the cancer being treated.
Chemotherapy
Chemotherapy is a cancer treatment that uses drugs to stop the growth of cancer cells, either by killing the cells or by stopping the cells from dividing. When chemotherapy is taken by mouth or injected into a vein or muscle, the drugs enter the bloodstream and can reach cancer cells throughout the body (systemic chemotherapy). When chemotherapy is placed directly in the spinal column, an organ, or a body cavity such as the abdomen, the drugs mainly affect cancer cells in those areas (regional chemotherapy). The way the chemotherapy is given depends on the type and stage of the cancer being treated.
After treatment, a blood test to measure amounts of carcinoembryonic antigen (a substance in the blood that may be increased when cancer is present) may be done to see if the cancer has come back.
