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Colorectal Cancer
This article discusses the definition, risk factors, symp- toms, diagnosis, common screening tests, progression and treatment of colorectal cancer. Includes photos, diagrams and endoscopy videos. • Article added October 22, 2003
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What is colorectal cancer?
The term colorectal cancer refers to cancers that affect the colon or the rectum. Together, the colon and the rectum form the large intestine, the final portion of the body's digestive system. The colon is the first 6 feet of this large, muscu- lar tube and the rectum is the final 8 to 10 inches. Colorectal cancer is one of the most common forms of cancer in the world. Like other cancers, it occurs when abnormal cells begin to grow and divide uncontrollably and form a mass, called a malignant tumor, in tissues or organs. Cancerous cells from these masses can enter the bloodstream or lymphatic system and spread to other organs or tissues.
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Endoscopy videos courtesy of Gastrolab • The Gastrointestinal Site 
Gastrolab is a medical research centre in Vasa, Finland dedicated to endoscopic examinations of the digestive canal. The centre was founded in 1983. Videos are used with permission.
View an endoscopy video of cancer in the sigmoid colon.
View an endoscopy video of cancer in the rectum.
View an endoscopy video of a malignant rectal polyp.
Risk Factors
People who have the following characteristics may be at increased risk of developing colorectal cancer:
- Age 50 or older
- Family history of colon or rectal cancer, especially in a parent, sibling, or child
- Personal history of colon, rectal, ovary, uterine, or breast cancer; or of ulcers in the lining of the large intestine, called ulcerative colitis
- Hereditary conditions, including familial adenomatous polyposis and hereditary nonpolyposis colon cancer
- Personal history of polyps in the colon
While treatment options and chances of recovery depend on the extent of the cancer at the time of diagnosis and a patient's general health, colorectal cancer is highly treatable. Even if cancer has spread beyond the tissue of the colon or rectum, surgery, chemotherapy, and radiation therapy are often successful at prolonging a patient's survival. [Top]
How is Colorectal Cancer Diagnosed?
Below are some of the common signs and symptoms of colorectal cancer. Bear in mind that these symptoms may be caused by a condition other than colorectal cancer. Consult a doctor if you notice:
- A change in bowel habits
- Diarrhea, constipation, or feeling that the bowel does not empty completely
- Blood, either bright red or very dark, in the stool
- Stools that are narrower than usual
- General abdominal discomfort such as frequent gas pains, bloating, fullness, and cramps
- Weight loss with no known reason
- Constant tiredness and vomiting
Common Screening Tests
Digital rectal examination • During this examination, the doctor feels for lumps or abnormal areas by inserting a lubricated, gloved finger into the first few inches of the rectum. Most often, patients receive a digital rectal exam as part of a routine gynecology exam (women), a routine prostate exam (men), or before two other screening tests: sigmoidoscopy and colonoscopy. Scientific evidence doesn't show that digital rectal examination decreases rates of death from colorectal cancer.
Fecal occult blood test • Test examines a patient's stool for hidden – or “occult” – blood. The test is given to the patient to be performed at home. There are some dietary instructions to be followed before starting the test. Certain foods – like red meat, some fruits and vegetables, as well as Vitamin C tablets and medications like aspirin and ibuprofen – may interfere with the test result and need to be avoided for a period of time before the test. Then, on three separate occasions, the patient places a small stool sample on a special card and returns it to the doctor or a laboratory. Studies show that a fecal occult blood test given every one to two years to people between the ages of 50 and 80 decreases the number of deaths due to colorectal cancer. [Top]
Barium enema • Test lets the doctor use an enhanced form of x-ray to evaluate the large intestine. Liquid containing barium, a contrast dye that helps show the intestine on the x-ray,
is injected into the rectum through the anus. Sometimes air may also be added. The test may be effective in detecting large polyps, and is usually given to a patient about once every five years. Small polyps, however, may be missed with this technique.
Flexible Sigmoidoscopy • This examina- tion allows the doctor to insert a slender, flexible tube with a light called a sigmoid- oscope inside the rectum to look for polyps, tumors, or abnormal areas. The sigmoidoscope reaches 60 cm, allowing the doctor to examine the rectum and part of left colon including the sigmoid colon. These areas have a higher rate of colon cancers than other parts of the colon. If the doctor sees abnormal tissue, he or she can remove it and have it examined more closely under a microscope. If a polyp or tumor is detected, patients are often given a follow up test called a colonoscopy (see below), which allows the doctor a more complete look at the colon. Fewer people may die of colorectal cancer if they have regular sigmoidoscopy after the age of 50. The test is usually given about once every five years.
Colonoscopy • Examination of the inside of the entire colon and rectum using a long, thin tube called a colonoscope. The colon- o scope is attached to a video camera and monitor. If colonoscopy reveals any unusual condition such as inflammation, an ulcer, a tumor, or a polyp, the doctor may photo- graph it. With the advent of video colono-scopy, it is now also possible to record the examination on a video cassette for later review when necessary. Furthermore, if the doctor sees abnormal tissue, he or she can remove it and have it examined under a microscope. Read an excellent, easy-to-understand article with respect to the entire colonoscopy procedure at GI Health.com
If, based on the results of one or more screening tests, your doctor thinks you may have colorectal cancer, he or she will order a diagnostic test called a biopsy. Biopsies allow doctors to remove tissue so that it can be examined under a microscope.
Some common types of biopsies are:
Endoscopic biopsy • In an endoscopic biopsy, a doctor uses a slender illuminated tube, like the sigmoidoscope and colono- scope previously described, to look inside the body and remove tissue.
Needle biopsy • During a needle biopsy, a doctor inserts a needle from the outside into the abnormal area and extracts a tissue sample.
Surgical biopsy • In a surgical biopsy, a surgeon makes an incision and removes a part or all of the abnormal tissue.
How Does Colorectal Cancer Progress?
Once cancer has been diagnosed, health care professionals use a process called "staging" to characterize the cancer based on whether the disease has spread to other parts of the body, and if so, to define how far the cancer has advanced. In colorectal cancer, there are five stages.
Stage 0 • Called carcinoma in situ, this stage of colorectal cancer is confined to the innermost lining of the colon or rectum only. Surgery is the standard treatment, and the cure rate is high.
Stage I • Cancer has spread to the second and third layers of the lining and penetrated the inside wall of the colon or rectum, but has not spread to the outer wall or outside of the colon or rectum. This stage is also called "Dukes' A" colon or rectal cancer. In this stage, patients may hear their doctors say the cancer is localized. Surgery is standard treatment, and the cure rate is high.
Stage II • Cancer has spread outside the colon or rectum to nearby tissue, but has not invaded the lymph nodes. This is sometimes called "Dukes' B" colon or rectal cancer. Surgery is standard treatment, although in some individual patients chemotherapy, radiation therapy, or a combination of the two may be appropriate. There are also clinical trials in which researchers are studying various treatment regimens – chemotherapy, radiation therapy, or biologic therapy – alone or in combination.
Stage III • Cancer has advanced into nearby lymph nodes, but has not spread to other parts of the body. Sometimes this is called "Dukes' C" colon or rectal cancer. The standard treatment is surgery followed by six months of chemotherapy. In some indivi- dual patients, radiation therapy may be appropriate. There are also clinical trials in which researchers are studying various treatment regimens – chemotherapy, radiation therapy, or biolo- gical therapies – alone or in combination.
Stage IV • Cancer has spread to other parts of the body. This stage is also called "Dukes' D" colon or rectal cancer. Treatment options are complex, but most likely will include surgery and chemotherapy, perhaps combined with radiation therapy and participation in clinical trials evaluating new drugs and biologic therapy. [Top]
Treatment for Colorectal Cancer
Treatment for any disease always depends on the individual patient's condition. But in general, there are three types of standard treatment for colorectal cancer: surgery, chemotherapy, and radiation therapy. Depending on the stage of the cancer, doctors may use two or three types of treatment at the same time or following one another.
Surgery • Removing the cancer is the primary treatment for all stages of colon and rectal cancer. In very early stages of both colon and rectal cancer, doctors may remove cancers without cutting through the skin using instruments inserted through the anus. If the cancer is larger, surgeons may cut through the abdominal wall to remove the cancer along with a small amount of healthy tissue surrounding it, and usually some nearby lymph nodes. The surgeon then sews the colon or rectum back together. In rare cases, the surgeon is unable to sew the healthy tissues back together and the patient will need a colostomy, an opening in the abdominal wall used for elimination of body waste. In some cases, the colostomy is needed only until the rectum or colon heals and then can be reversed.
Chemotherapy • Using drugs to kill cancer cells is called chemotherapy. The drugs may be administered by mouth or delivered into a vein or muscle by a needle or a small flexible tube called a catheter. Because the drugs enter the bloodstream and travel throughout the body, chemotherapy is a systemic treatment – it affects all of the body's cells and can help fight cancers that have spread to other organs. A colorectal cancer patient whose cancer has deeply perforated the wall of the intestine or has spread to the lymph nodes will often receive chemotherapy, sometimes in combination with radiation therapy. Patients sometimes receive chemotherapy after surgery to reduce the chance that cancer will come back. The treatment can increase the survival rate for some patients, and it can also help relieve symptoms of advanced cancer.
Radiation Therapy • X-rays and other types of radiation are used to kill cancer cells and shrink tumors. The radiation may come from outside the body - external radiation – or from radioactive materials implanted near the cancer cells inside the body - internal radiation. In both rectal and colon cancer, external radiation is used most often, especially when the cancer involves the rectum or has spread to other internal organs or tissues and it's not certain that surgery has removed all of the cancer. [Top]
Other treatments for colorectal cancers are being tested in clinical trials. They include:
Biological Therapy • Biological therapy attempts to stimulate the body's immune system to fight cancer by using natural therapy (manufactured by the body) or artificial therapy (manufactured in the laboratory) to strengthen or direct the body's natural defenses against disease. This treatment is sometimes called immuno- therapy or biological response modifier (BRM) therapy.
Colorectal cancer is the second most deadly form of cancer after lung cancer. In 2003, an estimated 18,000 Cana- dians will be diagnosed with colorectal cancer and 8,300 will die of it (according to the Canadian Cancer Society). The good news is that colorectal cancer is one of the most preventable cancers and, if found early, is 90% curable.
Sources and Credits
This article was reprinted according to the copyright terms of Health Talk • Colorectal Cancer Information Network
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