Cost-effectiveness of computed tomographic colonography screening for colorectal cancer in the medicare population

Abstract

Background: The Centers for Medicare and Medicaid Services (CMS) considered whether to reimburse computed tomographic colonography (CTC) for colorectal cancer screening of Medicare enrollees. To help inform its decision, we evaluated the reimbursement rate at which CTC screening could be cost-effective compared with the colorectal cancer screening tests that are currently reimbursed by CMS and are included in most colorectal cancer screening guidelines, namely annual fecal occult blood test (FOBT), flexible sigmoidoscopy every 5 years, flexible sigmoidoscopy every 5 years in conjunction with annual FOBT, and colonoscopy every 10 years.

Methods: We used three independently developed microsimulation models to assess the health outcomes and costs associated with CTC screening and with currently reimbursed colorectal cancer screening tests among the average-risk Medicare population. We assumed that CTC was performed every 5 years (using test characteristics from either a Department of Defense CTC study or the National CTC Trial) and that individuals with findings of 6 mm or larger were referred to colonoscopy. We computed incremental cost-effectiveness ratios for the currently reimbursed screening tests and calculated the maximum cost per scan (ie, the threshold cost) for the CTC strategy to lie on the efficient frontier. Sensitivity analyses were performed on key parameters and assumptions.

Results: Assuming perfect adherence with all tests, the undiscounted number life-years gained from CTC screening ranged from 143 to 178 per 1000 65-year-olds, which was slightly less than the number of life-years gained from 10-yearly colonoscopy (152-185 per 1000 65-year-olds) and comparable to that from 5-yearly sigmoidoscopy with annual FOBT (149-177 per 1000 65-year-olds). If CTC screening was reimbursed at $488 per scan (slightly less than the reimbursement for a colonoscopy without polypectomy), it would be the most costly strategy. CTC screening could be cost-effective at $108-$205 per scan, depending on the microsimulation model used. Sensitivity analyses showed that if relative adherence to CTC screening was 25% higher than adherence to other tests, it could be cost-effective if reimbursed at $488 per scan.

Conclusions: CTC could be a cost-effective option for colorectal cancer screening among Medicare enrollees if the reimbursement rate per scan is substantially less than that for colonoscopy or if a large proportion of otherwise unscreened persons were to undergo screening by CTC.

Figure 1

The natural history of colorectal cancer as simulated by the Microsimulation Screening Analysis (MISCAN), Simulation Model of Colorectal Cancer (SimCRC), and Colorectal Cancer Simulated Population model for Incidence and Natural History (CRC-SPIN) models. The opportunity to intervene in the natural history through screening is indicated by the dotted lines. Screening can remove a precancerous lesion (ie, adenoma), thus preventing it from progressing to cancer, or it can detect a preclinical cancer at a potentially earlier stage of disease when it is more amenable to treatment.

Figure 2

Discounted costs and discounted life-years gained per 1000 65-year-olds screened for 14 colorectal cancer screening strategies and the efficient frontier connecting the efficient strategies. The two computed tomographic colonography (CTC) strategies are not competing options; they represent a range of CTC test characteristics. They are shown together for comparison purposes only. A) Microsimulation Screening Analysis (MISCAN). B) Simulation Model of Colorectal Cancer (SimCRC). C) Colorectal Cancer Simulated Population model for Incidence and Natural History (CRC-SPIN). COL = colonoscopy; DoD = Department of Defense study parameters; HII = Hemoccult II; HS = Hemoccult SENSA; IFOBT = immunochemical fecal occult blood test; NCTC = National CT Colonography Trial parameters; SIG = sigmoidoscopy without biopsy; SIGB = sigmoidoscopy with biopsy; y = years.

Figure 3

Computed tomographic (CT) colonography unit cost thresholds at which the base-case CT colonography strategies are efficient screening options compared with other reimbursed colorectal cancer screening strategies for different values for the unit cost of a colonoscopy without polypectomy. The CT colonography cost thresholds for unit colonoscopy costs as high as $4000 were calculated and used to fit the lines. The data points shown illustrate the colonoscopy cost below which the incremental cost-effectiveness ratio is less than reference values ($50 000, $100 000, and $150 000). CRC-SPIN = Colorectal Cancer Simulated Population model for Incidence and Natural History; DoD = Department of Defense study parameters; ICER = incremental cost-effectiveness ratio; LYG = discounted life-year gained; MISCAN = Microsimulation Screening Analysis; NCTC = National CT Colonography Trial parameters; SimCRC = Simulation Model of Colorectal Cancer.