Regular Colonoscopy can Prevent 40 Percent of Colorectal Cancers, Harvard Study Finds

Regular colonoscopy can prevent about 40 percent of all colorectal cancers, according to a study from Harvard School of Public Health (HSPH). Researchers said that people with the cancer risk should follow doctor's advice and get a colonoscopy every ten years.

Colonoscopy is a kind of screening test where doctors examine the rectum and the entire colon using a light instrument called a colonoscope. The advantage of this test is that the doctor can view the rectum and the entire colon. An additional advantage of using this test is that the doctor can remove any abnormal tissue for further testing.  This is the most sensitive test available today.

"Colonoscopy is the most commonly used screening test in the U.S. but there was insufficient evidence on how much it reduces the risk of proximal colon cancer and how often people should undergo the procedure. Our study provides strong evidence that colonoscopy is an effective technique for preventing cancers of both distal and proximal regions of the colorectum, while sigmoidoscopy alone is insufficient for preventing proximal cancer,"  said Shuji Ogino, author and associate professor in the Department of Epidemiology at HSPH and co-senior author of the study.

The study was based on data from 88,902 participants who had participated in the Nurses' Health Study and the Health Professionals Follow-up Study. From this data, researchers found the number of times people underwent colorectal cancer screening tests such as colonoscopy or sigmoidoscopy and the incidence of colorectal cancer.

In the study, about 1815 people were diagnosed with the cancer while 474 had died from the cancer.

Researchers found that both the cancer screening tests were linked with lower risk of colorectal cancer. Colonoscopy particularly reduced the chances of cancer that occurs in the prximal or the upper part of the colon.

The study also showed that 40 percent of the cancers could have been prevented if all the study participants had undergone recommended colon cancer screening tests.

The study is published in the New England Journal of Medicine.

Cancers that affect the colon and rectum are called colorectal cancers. Almost all colon cancers begin with benign 'polyps' that develop into cancer.

Colorectal cancer is the fourth most common cancer in both men and women in the U.S. According to estimates by the National Cancer Institute, some 102,480 new cancers of colon and 50,830 cancers of rectum will be diagnosed in the year 2013.