Men Favor CTC Over Flexible Sigmoidoscopy for CRC Screening

Pam Harrison

March 04, 2015

VIENNA — When men are offered colorectal cancer (CRC) screening with CT colonography, often described as a virtual colonoscopy, instead of flexible sigmoidoscopy, participation rates improve, according to the Italian PROTEUS study.

For women, however, participation rates were the same with the two strategies.

"Our CRC screening programs in Italy are sponsored by the government, so the government puts money into these programs and they want to make sure that they get something back," said Daniele Regge, MD, assistant professor of radiology at the University of Turin and chief of the radiology unit at the Cancer Institute in Turin, Italy.

"Results from this study are pretty good," he told Medscape Medical News. "We had higher participation rates for CT colonography than for flexible sigmoidoscopy, so if government decides they want to substitute sigmoidoscopy with colonography, they can do that," he said.

Dr Regge presented the PROTEUS results here at the European Congress of Radiology 2015.

Screening participation and rates of detection of advanced adenomas were assessed in people undergoing CRC screening with CT colonography or the more traditional flexible sigmoidoscopy.

The study cohort consisted of asymptomatic people at average risk for CRC who were 58 to 60 years of age and who were sent an invitation to undergo screening.

The response rate was slightly better for those randomly assigned to colonography than to sigmoidoscopy (30.4% vs 27.0%; odds ratio [OR], P = .07).

For men, the response to colonography screening was 60% higher than the response to sigmoidoscopy screening (OR, 1.6; P = .01).

In contrast, for women, there was no difference in response rates for the two options.

To assess the acceptability of each of the screening strategies, the investigators conducted a phone survey of participants.

Rates of moderate to severe adverse events related to bowel preparation were higher in the colonography group than in the sigmoidoscopy group (18% vs 7%).

This is likely because colonography participants were required to use a bowel preparation product, although one with low cathartic activity, for several days before the procedure. Those in the sigmoidoscopy group only had to self-administer an enema 2 hours before screening, which "appears to be slightly more acceptable to patients," Dr Regge reported. However, he said, "we still don't really understand why CT colonography is not as well accepted."

Rates of fear and anxiety expressed by participants were minimal for both procedures, Dr Regge added. The most common reasons for refusing to participate in CT colonography screening were organizational problems (28%), embarrassment (19%), and an absence of symptoms (13%).

Men were more likely to agree to CT colonography screening if they were retired, had had some counseling from their general practitioner, or had a friend or relative with CRC.

PROTEUS was not powered to detect the difference in rates of advanced adenoma identified with the two strategies, he noted. That question will be answered in a larger study.

Nevertheless, preliminary results indicate that CT colonography detected more advanced adenomas, including three CRCs, than flexible sigmoidoscopy (4.4% vs 2.3%; P = .05).

In addition, detection rates of advanced adenomas were significantly higher in men than women (OR, 3.3; P = .017).

Not surprisingly, the detection of advanced adenomas located proximally was significantly higher with CT colonography than with flexible sigmoidoscopy (3.0% vs 0.3%; P = .023).

"This is the first randomized controlled trial comparing the uptake of CT colonography with flexible sigmoidoscopy in a population-based screening program," Dr Regge said. "Since there are significant potential clinical implications, we will go on to estimate the net benefit of CT colonography to improve male uptake of CRC screening," he added.

Participation Rates Important

Participation rates in any screening test are not a minor end point, said study discussant Andrea Laghi, MD, associate professor of radiology at the University of Rome La Sapienza, who was one of the authors of the European guidelines on CT colonography.

For example, he explained, the rate of cancer detection even with a test that does not have a really high accuracy rate can still be high if participation rates are high. "This is an important concept," Dr Laghi said, "which is why this study is so important."

He added that he thinks the reasons the men gave for declining CT colonography screening were merely "excuses."

"The real reason participation results did not meet our expectations is poor awareness of CRC in general," he said.

"We must promote CRC screening in general, which is what we have done through a website that recommends screening for bowel cancer for the general population in Europe," he said. "And we need to promote CT colonography more among primary care providers and the general population in order to increase awareness of it."

Dr Laghi pointed out that comparing CT colonography with flexible sigmoidoscopy was an "unfair comparison" because sigmoidoscopy is a well-established test in the regions of Italy where it was offered. Because it is highly regarded, it is very difficult for CT colonographers to overcome regional preference for sigmoidoscopy.

"It's my view that CRC screening cannot be done by visualizing half the colon," Dr Laghi said, referring to the fact that flexible sigmoidoscopy examines only the left side of the colon (the distal colon).

Dr Regge pointed out that it is not completely true that the majority of advanced adenomas are in the distil colon. The majority of CRCs are accessible with flexible sigmoidoscopy, which means that about two-thirds of advanced adenomas are accessible with flexible sigmoidoscopy," he explained.

Studies indicate that a single flexible sigmoidoscopy done around the age of 60 can prevent about one-third of CRCs overall.

However, both Dr Regge and Dr Laghi acknowledge that flexible sigmoidoscopy has a limited impact on the risk for proximal CRCs.

Dr Regge and Dr Laghi has disclosed no relevant financial relationships.

European Congress of Radiology (ECR) 2015. Presented March 4, 2015.

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