Annually about 140,000 new cases of colorectal cancer (CRC) are diagnosed in the United States; along with some 50,000 deaths. Both environmental and genetic factors can lead to these cancers (CRC). Most of these cancers occur after age 50 and develop in slowly growing noncancerous growths known as polyps in the colon. It takes about ten years for a polyp to develop into cancer. Removal of these precancerous polyps can prevent the development of cancer and removal of early cancer can prevent the risk of dying from it. In the US, the diagnosis of new cases and mortality rates from these cancers of the colon and rectum are steadily declining. Timely screening mostly with colonoscopy as per guidelines accounts for more than a 50% reduction in new case detection and mortality.
Apart from genetic reasons, there are potentially modifiable risk factors. These include physical inactivity, unhealthy diet, obesity, smoking, alcohol and lower rates of screening. A systematic review of several pooled studies has shown a relation between physical inactivity and an increased risk of colorectal cancers. Physically active individuals have a 27 percent lower risk of developing CRC as compared to those with a sedentary life style. Obesity also has been linked to increased risk of developing and dying from CRC. Convincing evidence exists regarding association between high body mass index (BMI) and risk of colorectal cancers. Excess abdominal fat, as measured by waist circumference, is more strongly associated with this risk than overall obesity.
Several studies have found an association between intake of diet high in fruits and vegetables and decreased colorectal cancers. A large meta-analytic study showed a reasonable protective effect of a balanced diet rich in fruit and vegetable in reducing risk of these cancers. High consumption of red and processed meat over a prolonged period has also been shown to increase colorectal cancer risk.
Research suggests a link between cigarette smoking and risk of developing colon polyps and cancer, with the relative risk being 18 percent higher for smokers as compared with those who have never smoked. According to Fedirko and his group, more than moderate alcohol use also significantly increases the risk of developing colorectal cancers. So it seems like lifestyle modification may reduce the development of colorectal cancers significantly.
Apart from the risk factors modification, screening for these cancers is the best way to prevent disease onset since most colon cancers arise gradually in adenomatous polyps and removal of polyps at the time of colonoscopy prevents the cancerous transformation. The adenoma-carcinoma sequence takes at least 10 years on average and removal of adenomatous polyps prevents cancer. March is National Colorectal Cancer awareness month. We must focus our efforts on the modifiable risk factors to prevent the risk of CRC by improving life style in terms of increased physical activity, healthy predominantly vegetarian diet, avoiding smoking and even moderate alcohol consumption while getting age appropriate screening.
(As it appeared on Dayton Daily News, March 19th, 2016)
Sangeeta Agrawal, MD, FASGE, FACG, AGAF
Chief of GI and Program Director of GI Fellowship,
Wright State University and VAMC,
Co-founder of Global Pragathi (NPO)