Despite the fact that colon cancer screening saves lives, the majority of US adults age 50 and over who are eligible for such screening fail to take advantage of it. Consider the numbers: In 2000, only 16.3 million of 80 million eligible adults (about 20%) received colon cancer screening such as the faecal occult blood test (the most popular choice), sigmoidoscopy or colonoscopy.
Colorectal cancer, gross appearance of an opened colectomy specimen. (Image: Emmanuelm at en.wikipedia)
While each form of colon cancer screening has its advantages and disadvantages, people are often squeamish about anything having do with the subject,
"The important thing is to do at least one of the tests once you reach age 50," said William Grady, M.D., a colorectal cancer specialist at Seattle Cancer Care Alliance and member of the Clinical Research Division at Fred Hutchinson Cancer Research Centre.
While diet and exercise may play a role in preventing colon cancer, the most important way to prevent death from the disease is through early detection, Grady said. "This means regular colorectal cancer screening tests beginning at age 50 - earlier if you are at higher risk. If all colon-cancer cases were detected at their earliest stages, five-year overall survival rates would jump from 65% to 90%."
End colon cancer campaign
In honour of the US National Colorectal Cancer Awareness Month, this month the Hutchinson Centre is reprising its "End Colon Cancer Now" awareness campaign that features a website containing information about screening and a quick test to assess your risk of colon cancer.
Grady and other screening advocates are adamant about colon cancer screening because even though it is preventable, it remains the second-leading cause of cancer death in the US It is also one of the most commonly diagnosed cancers in the US, occurring more than 90% of the time in people age 50 and older.
Following is a summary of the currently available colon cancer screening tests:
- Faecal Occult Blood Test (FOBT): This is a safe and simple test and is most effective if done annually. It involves a take-home kit available from the doctor's office that tests for the presence of blood in the stool. The downside to FOBT is it is not specific to detecting cancer, just blood, which can be a symptom of colon cancer. FOBT has a high false-positive rate. If blood is detected in the stool, the patient will be referred for a sigmoidoscopy or colonoscopy.
- Flexible sigmoidoscopy: Similar to a colonoscopy in that a flexible tube is inserted into the colon via the rectum. A scope looks for growths called polyps on the membrane wall; polyps can be precursors to cancer. Although this test only needs to be done once every five years, it does not examine the entire colon and does not have the ability to remove any polyps that are found.
- Colonoscopy: The current "gold standard" of screening tools, according to Grady, because it only needs to be done once every 10 years in people of normal risk. The scope examines the entire colon and contains a tool to remove polyps instantly and painlessly. The downside is mostly the perception that preparing for the test and the exam itself are uncomfortable. However, the process of emptying the colon in advance of the test - taking a special laxative - can be done at home in two parts prior to coming to the clinic for the exam. Patients are usually sedated for the 15-30-minute colonoscopy itself and usually feel nothing.
- Newer, non-invasive high-tech tests are available, such as virtual colonoscopy and CT colonography, however, these radiological exams still require colon-cleansing preparations and cannot remove any polyps that are found.
- In the future, simple blood tests that can detect molecular markers for colon cancer will be available. Grady is a leading researcher in this area. Developing an effective blood test is important because it will greatly increase the rate of screening.
Persons with hereditary risk factors for colon cancer, such as first-degree relatives who had colon cancer, need to be screened earlier and perhaps more often, said Grady, who recommends that such patients talk to their doctor for screening recommendations.
Washington is among 27 states that mandate health insurance coverage of colon cancer screening, which helps to eliminate the financial obstacle to testing.
Source: Fred Hutchinson Cancer Research Centre
