Colon cancer is a potentially curable disease if caught early. Cure rates are up to 95 percent and 85 percent for stage I and stage II disease respectively. The American Cancer Society, ACS, recommends screening for colon cancer at age 50 years for persons if you are at average risk for the disease. Persons who have a first degree family relative, that is, a parent or sibling, should begin screening at an age 10 years younger than the age of diagnosis of the relative. The several screening methods used to identify colon cancer are fecal occult blood, barium enema, sigmoidoscopy, colonoscopy.
Fecal Occult Blood
This is a non-invasive test in which the stool is examined for the presence of microscopic blood. Patients take a stool sample to a medical laboratory where it is tested with special chemicals for any traces of blood. This test is quick, relatively inexpensive and can be quite useful. However it is not specific for colon cancer as other conditions such as hemorrhoids and diverticular disease can give positive results. It is therefore never used on its own to make the diagnosis. Instead, it is used as an indicator for further testing.
Barium Enema
Prior to the use of endoscopes, this was the primary screening tool for colon cancer. Essentially, a radiopaque substance, which is barium, is introduced into the colon via the rectum then plain X-rays are taken of the abdomen. Colon cancer tends to give a distinct appearance resembling a bitten apple. Other conditions that may mimic the appearance of cancer on X-ray include complicated diverticular disease.
Flexible Sigmoidoscopy
This test involves the use of a special instrument called a flexible sigmoidoscope. A special camera is passed into the colon via the rectum to allow visualization of the interior of the left side of the colon, where approximately 60 percent of colon cancer occurs. This is an invasive procedure often requiring the use of some for of sedation to reduce patient discomfort
Colonoscopy
Colonoscopy is similar to a sigmoidoscopy except that it employs a longer camera which has the ability to visualize the entire colon. Thus it has the potential to pickup cancer anywhere in the colon. It also requires the patient to be sedated to undergo the procedure. The doctor may also perform a biopsy via this instrument which gives a definitive diagnosis.
Virtual Colonoscopy
This is a special CAT scan of the colon which mimics the traditional colonoscopy. It is not as favorable as other screening methods due to the inability to biopsy any tumors seen. The present recommendation by the ACS is that a virtual colonoscopy can be done every five years in place of a flexible sigmosidoscopy.
Recommendations
The ACS recommends that a flexible sigmoidoscopy be done every five years or a colonoscopy be done every 10 years. A fecal occult blood test can be done yearly and if positive, then a colonoscopy should be done. A virtual colonoscopy may also be done every five years.
References
- American Cancer Society
- "Washington Manual of Surgery"; Doherty, G.M. et al. 2002
