Colon Cancer - The Silent Killer
Imagine sleeping in your bed peacefully and waking up the next morning with a large boa constrictor wrapped around your neck. Even if it didn’t squeeze too hard, you would take precautions to ensure that an enormous snake never entered your home again!
Now envision a small polyp growing in your colon. You would not have a single symptom, and life would continue as usual. One day, you may have blood in your stool or a mild change in bowel habits. You go to your doctor and a colonoscopy is recommended. You then find a mass growing in your colon, and there are spots on your liver showing you have colon cancer with a poor prognosis.
Colon cancer is relatively common with 5% of the population in the U.S. developing this debilitating condition. It is the second leading cancer killer in men and women (after lung cancer). If detected early, treatment is very effective and frequently does not require a colostomy bag or chemotherapy. Studies suggest that it takes 10 years for most polyps to grow into cancers. Age 50 is the normal time recommended to begin screening in the absence of symptoms or family history. Even though it may be the most preventable cancer, about one third of adults aged 50-75 have never been screened.
There are several screening tests available. Stool cards checking for microscopic blood have been around for a long time and have been shown to reduce mortality. If the card shows traces of blood, your doctor will recommend a colonoscopy. The flexible sigmoidoscopy is a test where the last 18 inches of your colon is checked for polyps using a scope. This test is useful finding polyps and cancers, unfortunately cannot not identify polyps in over half of the colon. If a polyp is found then a colonoscopy will be recommended.
Newer tests such as stool DNA tests and CT colonography (CAT scan of colon) show promise. The stool DNA tests so far have not been very sensitive and one previously available test was withdrawn in 2012. CT colonography is noninvasive yet still requires a bowel preparation. Studies suggest that it can detect larger polyps almost as well as colonoscopy; however, there are limitations regarding flat polyps and radiation exposure. If a polyp is seen on CT, then an additional bowel preparation would be required prior to colonoscopy.
For this reason, colonoscopy has become the procedure of choice. Colon cancer can be reasonably excluded following a colonoscopy. Additionally, this test may prevent colon cancers, since precancerous polyps can be removed during the procedure. Studies such as the National Polyp Study suggest up to a 90% reduction in advanced lesions in those having colonoscopy compared to the general population. Because of higher rates of screening, colon cancer incidence has decreased 2-3% per year over the past 15 years.
Most of us are unconcerned or too busy to fret about colon cancer or boa constrictors. Make sure and talk to your doctor about being screened so colon cancer doesn’t slither into your life.
Steven Harrell, MD
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