Sigmoidoscopy screening can reduce colorectal cancer rates, deaths

Tim Church

The use of flexible sigmoidoscopy screening reduces deaths from colorectal cancer cases by more than 25 percent. That’s according to results from the first randomized clinical trial in the United States that looked at the effectiveness of sigmoidoscopy. The article was published in the New England Journal of Medicine.

Tim Church a University of Minnesota cancer prevention expert, said 155,000 people were involved in the study, including more than 29,000 people in Minnesota.

“There was a 21 percent reduction in the incidence of colorectal cancer in the screened group when we compared to the usual care group,” he said. “And that’s a big reduction – more than 1 out of 5 cancers were prevented. And, then, [there was] a 26 percent reduction in the deaths from colorectal cancer. “

Freedom of choice

Church says it’s important to be screened because colorectal cancer is the second-leading cause of cancer-related death in the United States. He said the results from this most recent study provide patients with freedom of choice when it comes to screening options for colorectal cancer. That’s important for public health because, he said, the options should should result in more people being screened.  

The options include fecal occult blood tests, colonoscopy, and flexible sigmoidoscopy. 

According to Church, of all the screening options, flexible sigmoidoscopy and colonoscopy are the most sensitive for detecting polyps that may lead to colorectal cancer. Removal of pre-cancerous polyps – which can be done during sigmoidoscopy or colonoscopy – reduces colorectal cancer risk.

A sigmoidoscopy, however, examines the lower colon using a thin, flexible tube-like instrument. The procedure has fewer side effects, requires less bowel preparation and poses a lower risk of bowel perforation than colonoscopy, which uses a similar but longer tube to view the entire colon.

“Each of the screening methods has its own strengths and weaknesses. And people have different preferences,” Church said. “So, the bottom line is: If you want to get screened for colorectal cancer, you have a wide variety of choices. You need to figure out what’s best for you, but you have no excuse not to be screened.”

Study results more than a decade in the making

To arrive at their results, researchers from 10 institutions worked for nearly two decades to track the health of more than 154,000 patients, as part of the Prostate Lung Colorectal and Ovarian (PLCO) cancer screening trial.

“The University of Minnesota saw almost a fifth of the trial participants,” said Church. “We worked closely with the nine other institutes to help promote and enroll patients within the other communities across the country.” 

Participants in the trial were randomly assigned to a flexible sigmoidoscopy screening group or a usual care group that only received screening if they asked for it or when their physician recommended it. The flexible sigmoidoscopy group participants were screened once when they entered the study and again three to five years later. 

The researchers compared overall colorectal cancer cases and deaths in the two groups, and analyzed incidence and mortality according to where the cancers developed. Although flexible sigmoidoscopy examines only the rectum and sigmoid colon, participants with a suspicious finding were referred for a follow-up colonoscopy, in which both the distal and proximal regions of the colon would be examined.

At the end of the 12 year trial, participants in the screening group had a 21 percent lower incidence of colorectal cancer overall as a result of catching precancerous trouble spots earlier and a 26 percent lower rate of colorectal cancer mortality than participants in the usual care group. 

The findings showed that over the course of 10 years, if 1,000 people had two sigmoidoscopy screenings, there would be approximately three fewer new cases and one less death from colorectal cancer than in a group the same size not receiving regular screenings.