New study examines the effectiveness of colonoscopies

New study examines the effectiveness of colonoscopies   Colonoscopies are a dreaded rite of passage for many middle-age adults. The promise has been that if you endure the awkwardness and invasiveness of having a camera travel the length of your large intestine once every decade after age 45, you have the best chance of catching – and perhaps preventing – colorectal cancer. It’s the second most common cause of cancer death in the United States. About 15 million colonoscopies are performed in the US each year.   Now, a landmark study is looking at the effectiveness of offering colonoscopies. The study marks the first time colonoscopies have been compared head-to-head to no cancer screening in a randomized trial. It found only meager benefits for the group of people invited to get the procedure: an 18% lower risk of getting colorectal cancer and no significant reduction in the risk of cancer death.   But many experts say that as good as this study was, it has important limitations, and these results shouldn’t deter people from getting colonoscopies.   “I think it’s just hard to know the value of a screening test when the majority of people in the screening didn’t get it done,” said Dr. William Dahut, chief scientific officer at the American Cancer Society, who was not involved in the study.   Less than half of people invited to get a colonoscopy in the study – just 42% – actually got one.   When the study authors restricted the results to the people who actually received colonoscopies – about 12,000 out of the more than 28,000 who were invited to do so – the procedure was found to be more effective. It reduced the risk of colorectal cancer by 31% and cut the risk of dying of that cancer by 50%.   Based on the results, then, study researcher Dr. Michael Bretthauer, a gastroenterologist who leads the clinical effectiveness group at the University of Oslo in Norway, expects that screening colonoscopy probably reduces a person’s chances of colorectal cancer by 18% to 31% and their risk of death from 0% to as much as 50%.   But, he said, even 50% is “on the low end of what I think everybody thought it would be.”   Other studies have estimated larger benefits for colonoscopies, reporting that these procedures could reduce the risk of dying of colorectal cancer by as much as 68%.