Colorectal cancer is the third most common cancer worldwide. Colorectal cancer starts as a polyp which mostly remains silent with symptoms appearing late in the stage. Life time risk of polyps is significant with about one in three people developing polyps and cancer occurring in 5 in 100 people. Colon polyps and cancer may inconsistently bleed and cause a positive stool test for blood, however it takes more than 3 to 5 years to develop symptomatic cancer. A positive family history in the immediate family increases the risk of colon cancer further. Lifestyle changes can be made like smoking cessation, healthy diet and weight loss to reduce the risk. Early detection holds the key to prevention. There are several ways to detect polyps or cancer in early stages. Polyps are removed to prevent cancer and surgery for early cancer can be curative.
The most commonly used procedure to detect and prevent colon cancer is colonoscopy as it examines the entire colon under deep sedation and polyps can be removed during the procedure. Over 15 to 25 years follow up of patients after their first colonoscopy and polyp removal have shown a 50% reduction in colon cancer related death. Thus despite the need for laxative colon prep, a small miss rate of polyps and some risks (perforation in less than 1:1000), colonoscopy remains the most useful test. Careful attention to individual patients background diseases, their medications e.g., blood thinners has allowed gastroenterologists to select appropriate laxative prep and take other steps to make this a safe and mostly painless procedure.
Alternative tests include stool test for blood which is a simple but less reliable method to detect polyps and can be negative in presence of cancer. CAT scan of the colon has significantly improved over years but is not yet approved for screening as it misses small polyps, has radiation risk and polyps when found cannot be removed.
Screening colonoscopy is recommended starting at age 50 years unless indicated at younger age for a positive family history. The first colonoscopy is the most important colonoscopy. If normal, it is repeated after 10 years. Unfortunately full benefit from screening colonoscopy has not yet been achieved in the US due to inadequate participation at age 50 years. Moreover the benefit from the procedure can be maximized with improved quality of colonoscopy (higher polyp detection and complete polyp resection) as provided by gastroenterologists well trained specifically in spending enough time to detect and remove as many polyps as completely as possible.
Public awareness of healthy diet, smoking cessation, maintenance of ideal weight are useful to reduce the risk. Getting the first colonoscopy by a well trained gastroenterologist at appropriate age remains the most important intervention to reduce colon cancer. It helps to discuss colonoscopy with your primary care physician or gastroenterologist when approaching 50 for individualizing your care.