CT Colonography May be Most Cost-Effective for Colon Cancer Screening

Laurie Barclay, MD

April 23, 2007

April 23, 2007 — Computed tomography colonography (CTC) with nonreporting of diminutive lesions, which have a low malignancy rate, was more cost-effective than optical colonoscopy for colon cancer screening, according to the results of a study published online in the April 23 Early View of the June 1 print issue of Cancer.

"Prior cost-effectiveness models analyzing...CTC screening have assumed that patients with diminutive lesions (≤5 mm) will be referred to optical colonoscopy (OC) for polypectomy," write Perry J. Pickhardt, MD, from the University of Wisconsin, in Madison, and colleagues. "However, consensus guidelines for CTC recommend reporting only polyps measuring ≥6 mm. The purpose of the current study was to assess the potential harms, benefits, and cost-effectiveness of CTC screening without the reporting of diminutive lesions compared with other screening strategies."

Despite the availability of effective screening tests for colon cancer, screening rates remain low and deaths remain high; colorectal cancer is the third leading cause of cancer death in both men and women. OC and flexible sigmoidscopy, which have been the primary screening tools for the past few decades, can give rise to complications ranging from abdominal pain to bowel perforation and bleeding.

CTC, also known as virtual colonoscopy, uses x-rays and imaging software to create 2- and 3-dimensional images of the gastrointestinal tract, with higher tolerability and fewer adverse effects than OC and flexible sigmoidscopy.

Using a Markov model applied to a hypothetical cohort of 100,000 people aged 50 years, the investigators determined the cost-effectiveness of screening with CTC (with and without a 6-mm reporting threshold), OC, and flexible sigmoidoscopy.

Compared with no screening, the model predicted an overall cost per life-year gained of $4361, $7138, $7407, and $9180, respectively, for CTC with a 6-mm reporting threshold, CTC with no threshold, flexible sigmoidscopy, and OC. Although the additional costs associated with the reporting of diminutive lesions at the time of CTC amounted to $118,440 per additional life-year gained, the incidence of colorectal cancer was reduced by only 1.3% (from 36.5% to 37.8%).

CTC with a 6-mm threshold yielded a 77.6% reduction in invasive endoscopic procedures (39,374 vs. 175,911) and 1112 fewer reported OC-related complications from perforation or bleeding than with primary OC screening.

"CTC with nonreporting of diminutive lesions was found to be the most cost-effective and safest screening option evaluated, thereby providing further support for this approach," the authors write. "Overall, the removal of diminutive lesions appears to carry an unjustified burden of costs and complications relative to the minimal gain in clinical efficacy."

Study limitations include failure to consider the need for recovery time after OC, the need for a second person to drive the patient home after OC, pathology costs related to the histologic evaluation of polyps, and costs of additional workups related to extracolonic abnormalities detected with CTC.

"These results provide further support for the practice of a 6-mm polyp size reporting threshold at CTC screening," the authors conclude. "The use of primary CTC screening as a selective filter for OC polypectomy for lesions measuring ≥6 mm represents a potentially powerful new approach to CRC screening."

Cancer. Published online April 23, 2007.

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