Prevention and early detection are key factors in controlling and curing colorectal cancer. Indeed, colorectal cancer is the second most preventable cancer, after lung cancer. When the cancer is found early, initial treatment can often lead to an excellent outcome. Colorectal cancer is cancer that occurs in the large intestine and rectum. The colon is a muscular tube that is about five feet long. It absorbs water and nutrients from food. The rectum, the lower six inches of the digestive tract, serves as a holding place for stool, which then passes out of the body through the anus. This year, about 148,000 people in the United States will be diagnosed with colorectal cancer. Although many people think of colorectal cancer as a disease that primarily affects men, it is slightly more common in women. Today, the average person has about a 1 in 20 chance of developing colorectal cancer during his or her life.
How Colorectal Cancer Develops?
The colon is divided into four sections: the ascending colon, transverse colon, descending colon, and sigmoid colon. Most colorectal cancers arise in the sigmoid colon -- the portion just above the rectum. They usually start in the innermost layer and can grow through some or all of the several tissue layers that make up the colon and rectum. The extent to which a cancer penetrates the various tissue layers determines the stage of the disease. Most colorectal cancers grow slowly over a period of several years, often beginning as small benign growths called polyps. Removing these polyps early, before they become malignant, is an effective means of preventing colorectal cancer.
Colorectal cancer sometimes arises without any symptoms. For this reason, screening tests (such as colonoscopy and a test for blood in the stool) are recommended to detect the cancer early, when it is more curable.
When symptoms do occur, however, they may include the following:
rectal bleeding or blood in the stool
a change in bowel habits (such as diarrhea, constipation, and narrowing of the stool) that lasts for more than a few days
a continuous feeling that you need to have a bowel movement, which does not resolve after passing stool
Some of these symptoms may be caused by other conditions. But you should see your doctor if they persist. Any incidence of rectal bleeding or blood in the stool should be brought to your doctor's attention.
Screening and Diagnosis
The best way to cure colorectal cancer is to prevent it from occurring in the first place. A regular program of screening examinations is the best way to ensure an early diagnosis, and an early diagnosis offers the best chance for a cure.
Screening & Diagnostic Tests
Colorectal cancer screening and diagnosis may involve one or more of a number of procedures:
This examination allows the doctor to inspect the rectum and colon, using a thin tube that has a light on the end. It is inserted into the rectum while the patient lies on his or her side. Patients often receive a mild sedative during this procedure to ensure their comfort. Any polyps or other growths that are found during these examinations are usually removed at the time and sent to a laboratory for examination.
A ten-year study by Tata Memorial Centre investigators showed that colonoscopy was more effective than another screening technique called double-contrast barium enema for detecting precancerous colon polyps. The findings of this study were the first to show that the various surveillance tools used to follow patients who have had colon polyps removed are not equally reliable. Moreover, unlike barium enema, colonoscopy allows the doctor to remove any polyps at the time of the examination.
Fecal Occult Blood Test
Also known as a stool blood test, this laboratory test looks for blood in the stool. The patient is asked to follow a special diet and then bring in stool specimens (usually applied to small, folded cards) from three successive days.
This examination is similar to the colonoscopy exam, but it uses a shorter tube to inspect the lower colon.
Virtual colonoscopy is a new technique that uses CT scans to create a 3-D image that can be used to evaluate the bowel. At this time, it is still a research tool and is not generally available. It is also important to note that, while this is a promising technique, it does not allow for a biopsy or polyp removal at the same time an abnormality is found.
For more information about diagnostic tests, see Staging.
If you do not have an increased risk of colorectal cancer because of your personal or family medical history, we recommend the following screening tests, beginning at age 50:
colonoscopy every 10 years
a yearly test for blood in the stool, preferably combined with flexible sigmoidoscopy every five years
If you have an increased risk of colorectal cancer because of your personal or family medical history, you should have a colonoscopy every 5 years beginning at age 40, or younger if hereditary non-polyposis colorectal cancer (HNPCC) is suspected. For first-degree, direct relatives of patients with colorectal cancer that has presented before age 50, screening should begin 10 to 20 years before the age of the diagnosed patient. For example, if your father is diagnosed with colorectal cancer at age 48, then you should begin your own colorectal cancer screening between ages 28 and 38.
If tests show that you have colorectal cancer, additional examinations may be performed to determine its extent -- a process called staging. Knowing how far your cancer has progressed is important when deciding what regimen of treatment might be most appropriate for you. The following tests are routinely used to stage colorectal cancer:
computed tomography (CT) and magnetic resonance imaging (MRI) scans, which may be used to see if the cancer has spread to other organs, such as the liver and lungs
chest x-ray, which may be performed to see if the cancer has spread to the lungs
blood tests for CEA, a protein that acts as a marker for colorectal cancer
Depending on your specific clinical situation, these additional tests may be ordered:
positron-emission tomography (PET) scanning, which may be conducted to find other places where cancer may be lurking
angiography, which may be done to find blood vessels next to cancer that has spread to the liver, allowing doctors to plan surgery to minimize blood loss
endorectal ultrasound probe, which uses sound waves to produce an image of the tumor; it may be placed in the rectum to see how far a cancer has invaded the rectal wall. This procedure is used for staging rectal cancer only.
The choice of treatment for colorectal cancer depends on the stage of the disease -- that is, how large the tumor has grown, how deeply it has invaded the layers of the colon or rectum, and whether it has spread to other organs (most commonly the liver), lymph nodes, or other parts of the body.
Treatment options include surgery, radiation therapy, chemotherapy, and combinations of these approaches.