Article updated and reviewed by Kevin Knopf, MD, MPH; Director of Clinical Research, Annapolis Oncology Center and Associate Staff, Johns Hopkins Oncology Center on July 22, 2005.
Colorectal cancer is a disease in which cancerous growths (tumors) are found in the tissues of the colon and/or rectum. The colon and rectum are part of the digestive system. Together they form a long, muscular tube called the large intestine. The colon is the upper five to six feet of the large intestine; the rectum is the last 15 inches of the colon.
The colon and rectum are made of many kinds of cells. Normally, cells divide in an orderly way to produce more cells only when the body needs them. If cells keep dividing when new cells are not needed, a mass of extra tissue (called a tumor) forms. The tumor can be either benign (non-cancerous) or malignant (cancerous).
Colorectal cancer develops from either precancerous polyps (a benign tumor of mucous membranes) that protrude from the colon wall like small mushrooms (tubular polyps), or appear as flat, spreading growths along the colon surface (villous adenomas) or adenocarcinomas (malignant tumors), which arise in the epithelial tissue (or lining) of the colon.
Colorectal cancer spreads directly from the lining of the colon and into adjacent tissues. The tumor may spread (metastasize) to other parts of body, such as the lymph nodes, liver, lungs, bones, brain, kidneys and bladder.
Colorectal cancer is rare in young people. Fewer than 6 percent of cases occur before the age of 50 years old. Incidences increase markedly after the age of 50, continues to rise until the age of 75, and then tapers off. The average age at the time of diagnosis is 60 years old.
The causes of colorectal cancer include:
- Polyp formation
- Genetic defects on chromosomes 2, 5, 17, and 18
- Family history of colon cancer related to genetic syndromes, such as HNPCC (Hereditary nonpolyposis colorectal cancer) syndrome of familial adenomatous polyposis (FAP). Both are rare diseases.
- Eating a high-fat, low-fiber/calcium diet
- Lack of exercise
Some people are more at risk for developing colorectal cancer. The risk factors include:
- Being over 50 years of age
- Family history of colorectal cancer
- Evidence of or previous polyps in the colon and rectum
- Having FAP or HNPCC
- Having inflammatory bowel disease, such as ulcerative colitis (inflammation of the colon lining) or Crohn's disease (an ulcerative condition of the small and large bowels)
- Eating diets high in fat and low in fiber and calcium
When an illness affects the colon or rectum, a number of symptoms can appear. The ones listed below are warning signs of a possible problem:
The diagnosis of colorectal cancer includes the patient's personal and family medical history, a physical examination and various laboratory and diagnostic tests. The physical exam includes a digital rectal examination (DRE), which involves the doctor inserting a gloved and then lubricated finger into the rectum to feel for abnormalities. Laboratory tests will include a fecal occult blood test (FOB), and blood and urine samples.
The FOB test involves taking a small sample of the stool and smearing it on a slide that will be examined under the microscope to check for and hidden (occult) blood in the stool. The diagnostic tests will include a sigmoidoscopy, and if needed, a colonoscopy and lower GI series (barium enema).
The sigmoidoscopy involves inserting a lighted flexible tube (called a sigmoidoscope) into the rectum and lower part of the colon. The doctor then looks through the sigmoidoscope to check for polyps, tumors or other abnormalities.
The barium enema involves giving the patient an enema (an injection of fluid into the rectum) containing a white, chalky solution consisting of barium. The barium outlines the colon and rectum, and using x-rays, the doctor can look for tumors or other abnormalities.
A colonoscopy involves inserting a lighted flexible tube (longer than a sigmoidoscope) called a colonoscope into the entire colon. The doctor then looks through the colonoscope to check for polyps, tumors or other abnormalities. Colonoscopy reaches all the way up the colon whereas the sigmoidoscope reaches only the first two-thirds. In addition, the doctor can biopsy suspicious areas through a colonoscope which he cannot do with a barium enema, which only looks at the colon.
If a polyp or other abnormal growth is found during a sigmoidoscopy or colonoscopy, the growth is removed and checked for cancer cells. This is called a biopsy. If the growth is cancerous, the doctor needs to determine the stage (or extent) of the disease.
Staging exams and tests help the doctor find out whether the cancer has spread and, if so, what parts of the body are affected. The staging exams include x-rays, ultrasounds or CT/CAT scans of the chest, abdomen, and pelvic areas.. A CT scan is a series of detailed pictures of areas inside the body created by a computer linked to an x-ray machine. The staging test may include an additional blood test(called the carcinoembryonic antigen - CEA test. This test measures the blood level of CEA, a substance sometimes found in higher than normal amounts in many people with colorectal cancer.
After the staging exams and tests have been done, the doctor will be able to know what stage the cancer is in. The stages of colorectal cancer are:
- Stage 0 (or carcinoma in situ) Tumor is in innermost lining of colon wall
- Stage I (Dukes A) Tumor in innermost lining, second and third layers of colon wall
- Stage II (Dukes B) Tumor through colon wall
- Stage III (Dukes C) Colon tumor and malignant lymph nodes
- Stage IV (Dukes D) Colon tumor and has spread to other parts of the body
- Recurrent Cancer has come back after being treated
Treatment for colorectal cancer depends on the size and location of the tumor, the stage of the disease, the patient's general health and other factors. There are three primary ways to treat colorectal cancer: surgery, radiation therapy, and/or chemotherapy.
Surgery is the most common treatment for all stages (Stage 0 - Recurrent) of colorectal cancer. The location and size of the tumor determines the type of surgical procedure to be done. The types of procedures include a polypectomy, colectomy or colostomy.
- Polypectomy is the removal of a polyp using either a sigmoidoscope or colonoscope to locate the growth and another surgical instrument to remove the polyp. Polypectomy is sufficient for some benign polyps and some cases of carcinoma in situ, but surgery (i.e., colectomy) is recommended for true colon cancer.
- Colectomy is the removal of part of the colon or rectum (whichever is cancerous) and a small amount of surrounding healthy tissue. The healthy parts of the colon or rectum are then sewn back together. This part of the surgery is called anastomosis. Additionally, during this procedure, the doctor will take out lymph nodes near the intestine and examine them for cancerous growth.
- Colostomy is done if, after the portions of the colon, rectum and tissue are removed, the healthy tissues cannot be sewn back together. In this procedure, part of the colon is brought through an incision in the abdominal wall and formed into an artificial opening (stoma) to allow the discharge of feces into a lightweight bag attached to the skin. A colostomy may be temporary or permanent. A temporary colostomy is sometimes needed to allow the lower colon or the rectum to heal after surgery. Later, in a second surgery, the doctor reconnects the healthy sections of the colon or rectum. A permanent colostomy may be necessary when the tumor is in the rectum, and in very few cases, in the lower colon.
Laparoscopic colectomy has the advantage of using smaller incisions which heal quicker and therefore result in a shorter hospital stay. In capable hands – surgeons who have performed a substantial number of surgeries with laparoscopy – this has the same curative potential as laparotomy (which requires a much larger incision).
In radiation therapy (also called x-ray therapy, radiotherapy, cobalt treatment or irradiation), high-energy rays are used to stop the cancer cells from growing and multiplying. Radiation therapy is sometimes used before surgery to shrink the tumor. More often, it is used after surgery to destroy any cancer cells that may remain or to relieve pain.
Radiation may come from a machine outside of the body (called external radiation therapy) or from putting radioactive materials through thin plastic tubes into the intestinal area (called internal radiation therapy).
Radiation therapy may be used in combination with surgery to treat Stage II - IV colorectal cancer. Chemotherapy or radiation therapy with surgery may be used to treat recurrent colorectal cancer. Colon cancer rarely requires radiation therapy after surgery; patients with rectal cancer are often offered radiation therapy after surgery to avoid the tumor coming back in the area it was excised.
Chemotherapy is the use of drugs to kill cancer cells. Given orally or injected, these drugs enter the bloodstream and travel through the body to kill cancer cells outside of the colon. Chemotherapy may be given after surgery to kill any cancer cells that remain, or as a preventive measure after surgery to assure the cancer does not spread. This preventive measure is called adjuvant therapy. Anticancer drugs may also be used when there are signs that the cancer has spread.
Chemotherapy is almost always given as an outpatient procedure. It is most often given in cycles - a treatment period followed by a rest period, then another treatment, and so on.
Chemotherapy may be used in combination with surgery and radiation therapy for Stages II - IV. Chemotherapy or radiation therapy with surgery may be used to treat recurrent colorectal cancer. There are several new chemotherapy agents for colon and rectal cancer and several more in development. The drugs that have recently come into use include oxaliplatin (a chemotherapy drug), bevacuzimab (a drug that blocks blood vessel growth to cancer cells), and erbitux (a drug that interferes with growth by a different mechanism).
Follow-up of Colorectal Cancer
For patients who have had surgery with curative intent, with or without adjuvant chemotherapy and/or radiation therapy, the oncologist will follow the patient to determine that there has not been a recurrence. CEA is a blood test expressed by many colorectal cancers; if it is elevated, it may indicate that the patient has had a metastatic recurrence. However, it is not 100% accurate – it can be elevated in the absence of colorectal cancer and normal in the presence of colorectal cancer. In general intensive follow-up with CT scans, PET scans, MRIs, etc. are not performed.
Patients should have follow-up colonoscopies. The risk of a recurrence in the colon or rectum is low, but patients may be prone to developing a second colon or rectal cancer.
What tests are needed to diagnose the condition?
What tests are needed to determine the extent of the disease?
What stage of the disease is it?
Will surgery be required?
What are the risks?
What can be expected after the surgery?
Will radiation therapy be given?
At what point in the treatment?
What can be expected from the treatments?
Will chemotherapy be required?
What are the side effects?
How will it be given?
What is the prognosis?
Is there a clinical trial I can participate in?
Editorial review provided by VeriMed Healthcare Network.
Since cancer is highly curable in the early stages, screening is strongly recommended. All individuals should begin to receive screening at the age of 50. This screening should be comprised of annual fecal occult blood tests, sigmoidoscopy or both.
To minimize the chance of misleading results on the stool test, the test should be postponed if a woman is menstruating or if the individual has bleedinghemorrhoids, bleeding gums or blood in the urine. It is also important to avoid the following items during the test period and for two days beforehand: red meat, raw fruits and vegetables (particularly cauliflower, horseradish and other radishes), melons, turnips, aspirin or other non-steroidal anti-inflammatory drugs.
The following preventive measures appear to reduce the risk of developing colorectal cancer:
- Screen for colorectal cancer using FOB and a sigmoidoscopy (see DIAGNOSIS section).
- Eat a diet low in fat and high in fiber (25 g per day).
- Consume at least 1,000 mg of calcium each day.
- Eat foods that contain antioxidants, such as citrus fruits and dark-green and yellow vegetables.
- Exercise at least 30 minutes most days of the week.
- Stop smoking.
- Limit alcohol consumption. Older adults should consume no more then equivalent to one glass of wine daily.
- Have polyps and adenomas surgically removed upon discovery.