Rectal cancer is a disease in which malignant (cancer) cells form in the tissues of the rectum.

The rectum is part of the body’s digestive system. The digestive system removes and processes nutrients (vitamins, minerals, carbohydrates, fats, proteins, and water) from foods and helps pass waste material out of the body. The digestive system is made up of the esophagus, stomach, and the small and large intestines. The first 6 feet of the large intestine are called the large bowel or colon. The last 6 inches are the rectum and the anal canal. The anal canal ends at the anus (the opening of the large intestine to the outside of the body).

Age and family history can affect the risk of developing rectal cancer.

The following are possible risk factors for rectal cancer:

• Age 50 or older.
• 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's disease.
• Certain hereditary conditions, such as familial adenomatous polyposis and hereditary nonpolyposis colon cancer (HNPCC; Lynch syndrome).

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.
• Feeling very tired.
• Vomiting.

Tests that examine the rectum and colon are used to detect (find) and diagnose rectal cancer.

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.
  
• Biopsy: The removal of cells or tissues so they can be viewed under a microscope to check for signs of cancer. Certain factors affect prognosis (chance of recovery) and treatment options.

The prognosis (chance of recovery) and treatment options depend on the following:

• The stage of the cancer (whether it affects the inner lining of the rectum only, involves the whole rectum, or has spread to other places in the body).
• The patient’s general health.
• Whether the cancer has just been diagnosed or has recurred (come back).

After rectal cancer has been diagnosed, tests are done to find out if cancer cells have spread within the rectum or to other parts of the body.

The process used to find out whether cancer has spread within the rectum or to other parts of the body is called staging.

The information gathered from the staging process determines the stage of the disease. It is important to know the stage in order to plan treatment. The following tests and procedures may be used in the staging process:

• 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.
  
• CT scan (CAT scan): A procedure that makes a series of detailed pictures of areas inside the body, taken from different angles. The pictures are made by a computer linked to an x-ray machine. A dye may be injected into a vein or swallowed to help the organs or tissues show up more clearly. This procedure is also called computed tomography, computerized tomography, or computerized axial tomography.
  
• MRI (magnetic resonance imaging): A procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas inside the body. This procedure is also called nuclear magnetic resonance imaging (NMRI).
  
• Sigmoidoscopy or colonoscopy and biopsy: A procedure to look inside the rectum and colon for polyps, abnormal areas, or cancer. A sigmoidoscope or colonoscope is inserted through the rectum into the colon. Polyps or tissue samples may be taken for biopsy.
  
• Endoscopic ultrasound (EUS): A procedure in which an endoscope (a thin, lighted tube) is inserted into the body. The endoscope is used to bounce high-energy sound waves (ultrasound) off internal tissues or organs and make echoes. The echoes form a picture of body tissues called a sonogram. This procedure is also called endosonography.

There are different types of treatment for patients with rectal cancer.

Different types of treatment are available for patients with rectal cancer. Some treatments are standard (the currently used treatment), and some are being tested in clinical trials. Before starting treatment, patients may want to think about taking part in a clinical trial. A treatment clinical trial is a research study meant to help improve current treatments or obtain information on new treatments for patients with cancer. When clinical trials show that a new treatment is better than the standard treatment, the new treatment may become the standard treatment.

Clinical trials are taking place in many parts of the country. Choosing the most appropriate cancer treatment is a decision that ideally involves the patient, family, and health care team.

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.
  
• 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.

New types of treatment are being tested in clinical trials. These include the following:

Biologic therapy

Biologic therapy is a treatment that uses the patient’s immune system to fight cancer. Substances made by the body or made in a laboratory are used to boost, direct, or restore the body’s natural defenses against cancer. This type of cancer treatment is also called biotherapy or immunotherapy.