Colorectal neoplasia screening with virtual colonoscopy: when, at what cost, and with what national impact?

doi:10.1016/S1542-3565(04)00247-2

Clinical Gastroenterology and Hepatology

Volume 2, Issue 7, July 2004, Pages 554-563

Presented in part at the American Gastrointestinal Association Presidential Plenary Session and the GI Oncology Plenary Session, Digestive Disease Week, New Orleans, Louisiana, May 15–20, 2004.

https://doi.org/10.1016/S1542-3565(04)00247-2 Get rights and content

Abstract

$Background & Aims :$ When optimized, virtual colonoscopy may be highly sensitive for colorectal neoplasia. We evaluated the effectiveness and cost-effectiveness of virtual colonoscopy screening (VC) vs. colonoscopy screening (COLO) and the potential impact at the national level. $Methods :$ Using a Markov model, we estimated the clinical and economic consequences of VC and COLO from ages 50 to 80 years. Using census data, we made projections to the national level. $Results :$ In the best case considered (95%, 94%, and 87% sensitivity for colorectal cancer [CRC], polyps ≥10 mm, and polyps <10 mm), VC was nearly as effective as COLO. However, if test costs were equal, total cost per person was 15% greater for VC than COLO, making COLO dominant. When test cost for VC was ≤60% of test cost for COLO, the small benefit of COLO vs. VC cost >$200,000/incremental life-year. The greater the likelihood of being referred for colonoscopy after VC, the greater the advantage of COLO. With 75% screening adherence in the United States, VC and COLO could decrease CRC incidence by 46%–54%, with COLO requiring 6.9 million colonoscopies/yr, and VC, 3.2 million colonoscopies/yr, plus 5.4 million virtual colonoscopies/yr with VC. $Conclusions :$ Even if screening test sensitivities were similar, COLO is likely to be preferred over VC unless virtual colonoscopy costs significantly less than colonoscopy. VC may be most appropriate in persons unlikely to need colonoscopy, such as those at low CRC risk. If VC were substituted for COLO, the demand on resources would shift from endoscopic to radiologic services, but would not diminish.

Section snippets

Decision analytic model

Key concepts in decision analysis have been reviewed recently, and a glossary of terms is provided in the Appendix.15 Our decision analytic Markov model, constructed in DataPro (TreeAge Software Inc., Williamston, MA) and the data sources that inform the inputs (Table 1) have been described in detail previously.7, 8, 16 In brief, the principal health states in the model are normal; small (<10 mm) adenomatous polyp; large (≥10 mm) adenomatous polyp; localized, regional, or distant CRC; and

Base case

Compared with no screening, VC-base decreased CRC incidence by 61% and shifted the stage distribution at diagnosis to earlier stages, resulting in 5,563 life-years gained/100,000 persons at a cost of $28,700/life-year gained (Table 2). COLO was more effective and less costly than VC-base, making it dominant (Table 2).

Sensitivity analyses: test performance characteristics

As expected, VC-Cotton was less effective and VC-Pickhardt was more effective than VC-base (Table 2). The progressive gains in life-years with improvements in VC test performance

Discussion

Our results help place in perspective the growing body of literature on virtual colonoscopy. We emphasize 5 major conclusions. First, the clinical benefit of VC with the test performance characteristics described by Pickhardt et al.12 may be similar to that of screening colonoscopy. Second, the effectiveness of a “sequential testing” strategy (radiology to select for colonoscopy) depends on the sensitivity of the confirmatory colonoscopy that follows a positive screening test result. Third,

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With optimal adherence, yearly FIT and colonoscopy every 10 years were dominant (more effective and less costly) than MT-sDNA every 3 years. Compared with successful organized FIT programs (50% consistent and 27% intermittent participation; patient support costs, $153/cycle), the patient support program for the MT-sDNA test would need 68% of subjects to participate consistently and 32% to participate intermittently every 3 years, or the MT-sDNA test would need to cost 60% less than in the base case ($260 commercial payment and $197 Medicare payment), for the MT-sDNA test to be preferred over FIT at a threshold of $100,000 per quality-adjusted life-year (QALY) gained. Compared with opportunistic yearly FIT screening (15% consistent and 30% intermittent participation), performing the MT-sDNA test every 3 years would cost less than $100,000 per QALY gained if the MT-sDNA test achieved a participation rate more than 1.7-fold that of FIT. The results were robust in sensitivity analyses. Assuming equal participation across strategies and a threshold of $100,000 per QALY gained, FIT was preferred in 99.3% of iterations in Monte Carlo simulation.
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Colorectal cancer (CRC) is notoriously hard to combat for its high incidence and mortality rates. However, with improved screening technology and better understanding of disease pathways, CRC is more likely to be detected at early stage and thus more likely to be cured. Among the available screening methods, colonoscopy is most commonly used in the U.S. because of its capability of visualizing the entire colon and removing the polyps it detected. The current national guideline for colonoscopy screening recommends an observation-based screening strategy. Nevertheless, there is scant research studying the cost-effectiveness of the recommended observation-based strategy and its variants. In this paper, we describe a partially observable Markov chain (POMC) model which allows us to assess the cost-effectiveness of both fixed-interval and observation-based colonoscopy screening strategies. In our model, we consider detailed adenomatous polyp states and estimate state transition probabilities based on longitudinal clinical data from a specific population cohort. We conduct a comprehensive numerical study which investigates several key factors in screening strategy design, including screening frequency, initial screening age, screening end age, and screening compliance rate. We also conduct sensitivity analyses on the cost and quality of life parameters. Our numerical result demonstrates the usability of our model in assessing colonoscopy screening strategies with consideration of partial observation of true health states. This research facilitates future design of better colonoscopy screening strategies.
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These reports suggest that when determining cost-effectiveness, assumptions about CTC accuracy to detect adenomas with high malignant potential are more important than assumptions about the overall accuracy or CTC, pointing to the importance of the underlying natural history model for colorectal cancer and, in particular, assumptions about the rate at which adenomas transition to cancer. Although eight of 10 models found CTC to be either dominated by colonoscopy or to have a less attractive incremental cost-effectiveness ratio than colonoscopy, several noted that CTC could be cost effective at a lower cost per exam (7,37–39). For example, the microsimulation models found that CTC could be cost effective compared to colonoscopy and other screening strategies if exams cost 22% to 41% of the cost of a colonoscopy (without polypectomy).
Computer disease simulation models are increasingly being used to evaluate and inform health care decisions across medical disciplines. The aim of researchers who develop these models is to integrate and synthesize short-term outcomes and results from multiple sources to predict the long-term clinical outcomes and costs of different health care strategies. Policy makers, in turn, can use the predictions generated by disease models together with other evidence to make decisions related to health care practices and resource utilization. Models are particularly useful when the existing evidence does not yield obvious answers or does not provide answers to the questions of greatest interest, such as questions about the relative cost-effectiveness of different practices. This review focuses on models used to inform decisions about imaging technology, discussing the role of disease models for health policy development and providing a foundation for understanding the basic principles of disease modeling. This manuscript draws from the collective computed tomographic colonography modeling experience, reviewing 10 published investigations of the clinical effectiveness and cost-effectiveness of computed tomographic colonography relative to colonoscopy. The discussion focuses on implications of different modeling assumptions and difficulties that may be encountered when evaluating the quality of models. This underscores the importance of forging stronger collaborations between researchers who develop disease models and radiologists, to ensure that policy-level models accurately represent the experience of everyday clinical practices.

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Original ArticleColorectal neoplasia screening with virtual colonoscopy: when, at what cost, and with what national impact?

Abstract

Section snippets

Decision analytic model

Base case

Sensitivity analyses: test performance characteristics

Discussion

Am J Med

Gastroenterology

Gastroenterology

Clin Gastroenterol Hepatol

Gastroenterology

Gastrointest Endosc

Gastroenterology

Gastroenterology

Gastroenterology

Gastroenterology

Gastroenterology

Am J Med

Gastroenterology

Am J Gastroenterol

Gastrointest Endosc

Cancer statistics, 2003

CA Cancer J Clin

A randomized trial of aspirin to prevent colorectal adenomas

N Engl J Med

A randomized trial of aspirin to prevent colorectal adenomas in patients with previous colorectal cancer

N Engl J Med

Clinical practice. Screening for colorectal cancer

N Engl J Med

Screening for colorectal cancer in adults at average riska summary of the evidence for the US Preventive Services Task Force

Ann Intern Med

Cost-effectiveness analyses of colorectal cancer screeninga systematic review for the US Preventive Services Task Force

Ann Intern Med

Aspirin as an adjunct to screening for prevention of sporadic colorectal cancer. A cost-effectiveness analysis

Ann Intern Med

Colorectal cancer test use among persons aged > or = 50 years—United States, 2001

MMWR Morbid Mortal Wkly Rep

Computed tomographic virtual colonoscopy to screen for colorectal neoplasia in asymptomatic adults

N Engl J Med

Computed tomographic colonography (virtual colonoscopy)a multicenter comparison with standard colonoscopy for detection of colorectal neoplasia

JAMA

Virtual colonoscopy—what it can do vs what it will do

JAMA

Polyps and cancer of the large bowela necropsy study in Liverpool

Gut

The National Polyp Study. Design, methods, and characteristics of patients with newly diagnosed polyps

Cancer

Use of colonoscopy to screen asymptomatic adults for colorectal cancer

N Engl J Med

The prevalence of polyps of the large intestine in Osloan autopsy study

Cancer

Prevalence of polyps in an autopsy series from areas with varying incidence of large-bowel cancer

Int J Cancer

Original Article
Colorectal neoplasia screening with virtual colonoscopy: when, at what cost, and with what national impact?