In a large trial of more than 150,000 older U.S. adults, those who were randomly assigned to get screened using so-called flexible sigmoidoscopy on two different occasions were 21 percent less likely to get colon cancer than those not offered the screening.

They were also 26 percent less likely to die of cancer, probably because screening picked up pre-cancerous lesions and early-stage cancers before they could cause serious harm, researchers reported Monday in the New England Journal of Medicine.

Colonoscopy "is a very unpleasant thing," said Dr. Alfred Neugut, an epidemiologist and oncologist from Columbia University in New York, who wasn't part of the study team.

"Sigmoidoscopy is a much less elaborate procedure, so you can basically walk into the doctor's office and get it on the spot… and it's much less invasive," he said.

Flexible sigmoidoscopy is one of three colon cancer screening methods recommended by the U.S. Preventive Services Task Force, a government-backed body that sets screening guidelines.

The Task Force says that annual fecal occult blood testing, flexible sigmoidoscopy every five years with fecal testing every three years or colonoscopy every 10 years are all options for adults aged 50 to 75 at average risk of cancer.

But many Americans in that age group still don't get screened -- and one of the reasons may be the discomfort of preparing to get a colonoscopy, including taking laxatives, and the inconvenience and invasiveness of the procedure itself.

The new findings provide more evidence that sigmoidoscopy as an initial test -- followed by colonoscopy only in the case of positive findings -- may be a valid alternative, researchers said.

The data come from the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial, which compared new cases of cancer and cancer-related deaths in adults who did or didn't get different types of screening.

This analysis, led by Dr. Robert Schoen from the University of Pittsburgh Medical Center, involved 154,900 adults age 55 to 74 who were offered either two sigmoidoscopies, three or five years apart, or no colon cancer screening.

Over the next 12 years, there were 1,012 new cases of colon cancer in the screening group and 1,287 in the unscreened group. In addition, there were 252 related deaths among people offered sigmoidoscopy, compared to 341 in the unscreened group.

The lower mortality in the screening group seemed to be attributable entirely to fewer deaths from so-called distal colon cancer, which occurs in the part of the intestines closer to the rectum. There was no difference between the two groups in deaths from proximal colon cancer, which is cancer higher up in the intestines and beyond the reach of the sigmoidoscopy scope.

FALSE POSITIVES COMMON

The screening tests were not without their limitations. One in five men and one in eight women had a false-positive sigmoidoscopy, which resulted in more invasive testing that ultimately found no pre-cancers or cancers. In addition, 22 people suffered a bowel perforation either from the initial sigmoidoscopy or a follow-up colonoscopy.

A limitation of the trial itself is that the two study groups weren't as different as the researchers initially intended: almost half of people in the group assigned to no screening ended up getting a sigmoidoscopy or colonoscopy on their own during the study.

Trials in the UK and Italy have also suggested screening with sigmoidoscopy can reduce deaths from colon cancer.

Because of that, the UK plans to offer sigmoidoscopies free of charge to all adults in their mid-50s within the next five years, according to Wendy Atkin, a professor of gastrointestinal epidemiology at Imperial College London, who worked on the UK study.

"We need to revisit sigmoidoscopy in the United States," Atkin told Reuters Health.

Research suggests nurses can do the less-invasive test, she said. It's also significantly cheaper than colonoscopy -- at roughly $150, compared to about $1,000 for a colonoscopy.

Schoen doesn't expect colonoscopy to go out of style as the most popular method for colon cancer screening in the U.S. But, he added, flexible sigmoidoscopy as an initial test is a good choice for some people who want to avoid a colonoscopy unless it's completely necessary.

"Absolutely it's an option on the table," he told Reuters Health.

"If someone, for example, was afraid of anesthesia, if they want a test where the prep is not so aggressive -- they just take enemas as opposed to drinking laxatives, if they cannot spare a day… all those are good reasons if you want to go and have a (sigmoidoscopy)," Schoen said.

Neugut told Reuters Health many U.S. doctors don't do the less-invasive procedures anymore. But data are lacking to prove colonoscopy is any better than initially going for sigmoidoscopy, he said.

"Anyone who doesn't want to have a colonoscopy, they should consider sigmoidoscopy as certainly… a valid form of screening for colon cancer," Neugut said.

SOURCE: bit.ly/cZYeY6 New England Journal of Medicine, online May 21, 2012.

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