09 Aug Colonoscopy, Virtual and Real, Less Cost-Effective Than Stool Tests

AuntMinnie | Virtual and conventional colonoscopy were both beneficial but less cost-effective for preventing colorectal cancer than stool screening plus flexible sigmoidoscopy — though virtual colonoscopy may have benefits for screening laggards — according to a new model analysis in Radiology.

Using data from the National CT Colonography Trial (NCTCT), the authors found that in general, colonoscopy, fecal immunochemical test (FIT) plus flexible sigmoidoscopy, and fecal occult blood test (FOBT) plus flexible sigmoidoscopy all increased life expectancy and reduced lifetime risk of colorectal cancer more than screening every five or 10 years with virtual colonoscopy (also known at CT colonography or CTC).

In direct comparison, conventional colonoscopy was more cost-effective than virtual colonoscopy in most scenarios, the authors found. When screening compliance was reduced to 50%, however, CTC came out ahead in two of the three simulation models used in the analysis.

There were questions about the study’s methodology from a CTC practitioner, who said that the model’s 95% completion rate for optical colonoscopy seemed unrealistically high; that VC’s true cost was probably lower than that of conventional colonoscopy, thereby skewing the model; and that the study didn’t consider the high percentage of individuals who refuse to undergo other colon cancer screening tests.

“I think the results suggest that virtual colonoscopy has a role for people who are unwilling or unable to undergo other screening tests, and if there’s a segment of the population that is willing to try VC but not the others, my personal opinion is that this paper encourages them to do so because [VC] is clearly better than not screening,” responded lead author David Vanness, PhD, in an interview with AuntMinnie.com. Vanness is an assistant professor of population health sciences at the University of Wisconsin School of Medicine.

Based on results of multicenter CTC trial

The 2008 NCTCT trial — to date, the largest multicenter study to assess CTC’s effectiveness — was designed to address widely varying results from previously conducted CT colonography trials. Results of the NCTCT confirmed that CT colonography depicts colorectal adenomas and carcinomas (neoplasia) with sensitivities of 78% to 90% and specificities of 86% to 88%, depending on lesion size (New England Journal of Medicine, September 18, 2008, Vol. 359:12, pp. 1208-1217).

“It remains unclear whether, given these performance characteristics, screening with CT colonography is an efficient use of resources,” wrote Vanness, Amy Knudsen, PhD, and colleagues (Radiology, August 3, 2011).

Joint guidelines from the American Cancer Society and the U.S. Multisociety Task Force on Colorectal Cancer recommend various options for screening average-risk individuals ages 50 years and older for colorectal cancer (CRC), including CTC every five years. However, the U.S. Preventive Services Task Force excludes CT colonography from its guidelines due to a 2008 opinion that there was insufficient evidence to recommend it for widespread screening.

The study’s estimates of CTC performance from the NCTCT trial were incorporated into three previously validated Cancer Intervention and Surveillance Modeling Network (CISNET) CRC microsimulations: MISCAN-COLON, CRC-SPIN, and SimCRC. Each model uses common data and a unique model structure to simulate the natural history of CRC. The aim of the study was to estimate the cost-effectiveness of CT colonography for CRC screening in average-risk 50-year-old asymptomatic subjects.

Analyses of survival and lifetime costs for screening with CTC every five or 10 years were compared with conventional colonoscopy, flexible sigmoidoscopy plus either sensitive unrehydrated FOBT or FIT, and no screening based on the three models.

The researchers modeled perfect screening compliance, as well as reduced adherence (showing up for screening half as often as recommended, but always proceeding to colonoscopy if the test result was positive). They calculated both the incremental cost-effectiveness and estimated net health benefits from the U.S. provider perspective. Data regarding natural history and non-CRC deaths were gleaned from Surveillance, Epidemiology, and End Results (SEER) data from 1996 to 1999.

Medicare data (2007) were used to estimate screening costs. Because the U.S. Centers for Medicare and Medicaid Services has not assigned relative value units for screening CTC, however, the authors were left to estimate CTC costs by summing reimbursement-based cost estimates for noncontrast CT of the abdomen and pelvis, noncontrast pelvis, and 3D reconstruction, adjusted for resource savings associated with imaging contiguous anatomic regions.

Next, incremental cost-effectiveness ratios (ICERs) were calculated for each strategy as a ratio of the incremental cost versus life-years gained, compared with the next least-costly screening strategy.

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