by John Gever

Easy access to CT colonoscopy may not reduce the number of conventional colonoscopies performed.

After the University of Wisconsin’s (UW) health system persuaded local insurers to cover the imaging-based screens in 2004, there was little sign that patients preferred them to standard endoscopic exams, according to Patrick Pfau, MD, the university’s director of clinical gastroenterology.

Mean quarterly counts of optical colonoscopies performed at UW rose from 1,104 in 2003 to 1,976 in 2008 (P<0.001), he reported here at Digestive Disease Week.

For CT colonography, the highest quarterly number was 307 in the third quarter of 2005. By the end of 2008, the number had declined to 203 per quarter, Pfau said.

In 2009, he added, 86.6% of all colorectal screening exams were performed with optical colonoscopy. Only 8.5% were screened with CT colonography. The rest were screened with fecal occult blood or immunochemical tests.

He said the university’s experience defied predictions that patients would abandon optical colonoscopy in droves if their health plans would pay for the less invasive “virtual colonoscopy,” as CT colonography is often called.

But Pfau cautioned that the results may not be generalizable to the rest of the country, as UW serves a community — the Madison, Wis., metro area — that is disproportionately well educated and affluent.

Other research has suggested that about 70% of the over-50 population there has been screened for colorectal lesions, far above the national average, he said.

Pfau explained that, in 2004, leaders of the UW health system reached agreements with several health insurers, serving large numbers of area residents, that CT colonography-based screening would be covered on the same basis as optical colonoscopy.

Modeling studies had suggested that endorsement of CT colonography by the medical community and insurers would lead to reductions in optical colonoscopy procedures by as much as 25%, Pfau said.

To test these predictions, Pfau and colleagues pulled records on colorectal screening and therapeutic exams performed in patients 50 to 75 years old in the UW system from 2003, the year before CT colonography became eligible for insurance coverage, to 2009.

The increase in optical colonoscopies over that interval did not appear attributable to therapeutic procedures triggered by abnormal CT colonography results, they wrote.

The number of therapeutic colonoscopies remained relatively level, with a quarterly mean of 463 in 2003, compared with 490 in 2009 (P=0.36).

Screening-only colonoscopies, on the other hand, rose from 555 per quarter on average in 2003 to 995 per quarter (P<0.001).

Pfau and colleagues had no data on the reasons behind patients’ choices. But at a press conference here, Pfau speculated that patients may not perceive an advantage for CT colonography when the details are explained to them.

When doctors tell patients about the undiminished need for bowel preparation with CT colonography, as well as its lower sensitivity for certain lesions and the requirement that patients undergo a regular colonoscopy to confirm and treat positive findings, their enthusiasm for initial CT colonoscopy often wanes, he suggested.

Pfau said it also may be that individual clinicians are continuing to recommend conventional colonoscopy. His experience is that most patients in Madison go along with their doctors’ advice, he said.

John Gever is a MedPage Today Senior Editor.

Originally published in MedPage Today. Visit MedPageToday.com for more colon cancer news.