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The lifetime risk of colon cancer is 5 to 6%. The risk of colon cancer increases rapidly with older ages. The annual rate of colon cancer for people aged 80 and older is 450 per 100,000.
Certain people with genetic syndromes are at high risk for colon cancer. For instance, the probability of getting colon cancer by the age of 70 in people with the HNPCC gene is 70 to 80%. HNPCC stands for Hereditary Nonpolyposis Colorectal Cancer.
The average 5-year survival rate of colon cancer is 60 to 65%. The 5-year survival rate for patients with colon cancers detected at early stages is 80 to 90%. However, for patients with metastatic colon cancer, the 5-year survival rate is merely 25%. - The incidence of colon cancer varies from one countries to another. The incidence of colon cancer in developed countries like United States, and European countries is 10 to 20 times than that in developing countries. Therefore, colon cancer is also known as the disease of rich countries. However, the incidence of colon cancer in countries like China, India is on the rise as people in these countries start to adopt diets similar Western diet.
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The major symptoms of colon cancer are rectal bleeding, blood in the stool, or changes in bowel habit, abdominal pain, hematochezia or melena, weakness, anemia and weight loss. In the primary care setting, patients with rectal bleeding and blood in the stool are often ordered a colonoscopy to check whether they have colon cancer.
Ideally, individuals with symptoms of colon cancer should be examined without delay. In reality, there is often a significant delay between symptom and diagnosis. It takes about 4 to 6 months for a patient to be diagnosed with colon cancer after the initial onset of symptoms.
Early detection of colon cancer leads to a much better survival rate. Thus, it is very important to talk to your doctor if you have any of colon cancer symptoms, particularly if you are 50 years old and older. - It is believed that 90-95% of colon cancer cases arise from adenomatous polyps (also known as adenoma). This is referred to as the adenoma--carcinoma sequence. Although only a small proportion of adenomas progress to become cancer, it is still not possible to identify which one will become cancer. The adenoma--carcinoma theory is the corner stone of our understanding and management of colon cancer.
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Colon cancer can be detected early by regular screening. Early detection improves the chance of survival significantly. Studies show that your risk of colon cancer is reduced by 70 to 80%, just by complying to regular screening.
The most effective screening method is colonoscopy. The American Cancer Society recommends colonoscopy screening every 10 year, starting at age 50, for all adults. Any adenoma detected during colonoscopy will be removed by polypectomy. Several clinical trials show that colonoscopy is highly effective in reducing both incidence and mortality of colon cancer.
Other screening tests for colon cancer include stool-based tests such as fecal occult blood test (FOBT), fecal immunochemical test (FIT) and fecal DNA, and full-structural examination such as virtual colonoscopy and sigmoidoscopy.
