What is colorectal cancer?
Colorectal cancer is a disease in which cells in the colon or rectum become abnormal and divide without normal control or order, forming a mass called a tumor. (The colon and rectum are parts of the body’s digestive system that remove water and nutrients from food and store solid waste until it passes out of the body.) Cancer cells invade and destroy the tissue around them. They can also break away from the tumor and spread to form new tumors in other parts of the body.
Colorectal cancer is the third most common type of non-skin cancer in men (after prostate cancer and lung cancer) and in women (after breast cancer and lung cancer). It is the second leading cause of cancer death in the United States after lung cancer. Fortunately, the rate of new cases and deaths resulting from this disease is decreasing. Still, over 147,000 new cases are diagnosed, and more than 57,000 people die from colorectal cancer each year.
Who is at risk for colorectal cancer?
The exact causes of colorectal cancer are not known. However, studies show that certain factors are linked to an increased chance of developing colorectal cancer:
What is screening, and why is it important?
Screening means checking for health problems before they cause symptoms. Screening can find polyps that may eventually become cancerous (precancerous polyps), as well as some cancers in an early stage, before they spread to other parts of the body.
Colorectal cancer screening is used to detect cancer, precancerous polyps, or other abnormal conditions. If screening detects an abnormality, diagnosis and treatment can occur promptly. In addition, finding and treating polyps may be one of the most effective ways to prevent the development of cancer altogether. Colorectal cancer is generally more treatable when it is found early.
What methods are used to screen people for colorectal cancer?
Health care providers may suggest one or more of the tests listed below for colorectal cancer screening.
Scientists are still studying colorectal cancer screening methods, both alone and in combination, to determine how effective they are. Studies are also under way to clarify the risks of each test.
See Question 5 for a table outlining some of the advantages and disadvantages of colorectal cancer screening tests. Additional information about these tests is available from the National Cancer Institute’s (NCI) Web site at http://www.cancer.gov/colon.
How can people and their health care providers decide which colorectal cancer screening test(s) to use and how often to be screened?
Several major organizations, including the U.S. Preventive Services Task Force (a group of experts convened by the U.S. Public Health Service), the American Cancer Society, and professional societies, have developed guidelines for colorectal cancer screening. Although some details of their recommendations vary regarding which screening tests to use and how often to be screened, all of these organizations support screening for colorectal cancer.
People should talk with their health care provider about when to begin screening for colorectal cancer, what tests to have, the benefits and risks of each test, and how often to schedule appointments.
The decision to have a certain test will take into account several factors:
The following table outlines some of the advantages and disadvantages of the colorectal cancer screening tests described in this fact sheet.
|Fecal Occult Blood Test (FOBT)|| || |
|Sigmoidoscopy|| || |
|Colonoscopy|| || |
|Double Contrast Barium Enema(DCBE)|| || |
|Digital Rectal Exam (DRE)|| || |
Do insurance companies pay for colorectal cancer screening?
Insurance coverage varies. People should check with their health insurance provider to determine their colorectal cancer screening benefits. Medicare covers several colorectal cancer screening tests for its beneficiaries.
What happens if a colorectal cancer screening test shows an abnormality?
If screening tests find an abnormality, the health care provider will perform a physical exam and evaluate the person’s personal and family medical history. Additional diagnostic tests may be ordered. These may include x-rays of the gastrointestinal tract, sigmoidoscopy, or most often, colonoscopy (see Question 4). The health care provider may also order a blood test called a CEA assay to measure carcinoembryonic antigen, a protein that is sometimes present in higher levels in patients with colorectal cancer.
If an abnormal area is found during a colonoscopy, a biopsy is performed to determine if cancer is present. If an abnormal area is found during a sigmoidoscopy, a biopsy may be performed during the test, and a colonoscopy may be recommended.
More information about colorectal cancer screening tests is available in Colorectal Cancer (PDQ®): Screening, part of the NCI’s comprehensive cancer information database.
The NCI booklet What You Need To Know About™ Cancer of the Colon and Rectum provides more information about the diagnosis and treatment of colorectal cancer. This publication and other resources are available from the NCI Publications Locator at http://www.cancer.gov/publications or by calling the Cancer Information Service (CIS) toll-free at 1–800–4–CANCER (1–800–422–6237). Additional information about colorectal cancer is available on the NCI’s Web site at http://www.cancer.gov/types/colorectal or http://www.cancer.gov/colon.
Are new tests under study for colorectal cancer screening?
New tests for colorectal cancer screening are under study. For example, virtual colonoscopy (also called computed tomographic colonography) is a procedure that uses special x-ray equipment to produce pictures of the colon. A computer then assembles these pictures into detailed images that can show polyps and other abnormalities. Because it is less invasive and does not require sedation, virtual colonoscopy may cause less discomfort and take less time than conventional colonoscopy. However, as with conventional colonoscopy and DCBE, thorough preparation of the colon is necessary before the test.
Unlike conventional colonoscopy, it is not possible to remove polyps or perform a biopsy during virtual colonoscopy. An additional procedure, such as conventional colonoscopy, is needed if the virtual procedure finds a potential problem. Clinical trials (research studies with people) are under way to compare the advantages and disadvantages of virtual colonoscopy with those of other colorectal cancer screening tests.
Genetic testing of stool samples is also under study as a possible way to screen for colorectal cancer. The lining of the colon is constantly shedding cells into the stool. Testing stool samples for genetic alterations that occur in colorectal cancer cells may help doctors find evidence of cancer or precancerous polyps. Research conducted thus far has shown that this test can detect colorectal cancer in people already diagnosed with this disease by other means. However, more studies are needed to determine whether the test can detect colorectal cancer or precancerous polyps in people who do not have symptoms.
Additional information about clinical trials to test new methods for colorectal cancer screening is available from the NCI’s Web site at http://www.cancer.gov/clinicaltrials/ or by calling the CIS at 1–800–4–CANCER (1–800–422–6237).