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Mathematical model suggests one-time colonoscopy at age 55 can reduce mortality
Screening for colorectal cancer is as cost effective as other forms of cancer screening, and deaths from colorectal cancer can be significantly reduced with even a single colonoscopy at age 55, according to an article in the October 18, 2000, issue of The Journal of the American Medical Association.
A. Lindsay Frazier, M.D., M.Sc., and colleagues from the Harvard Medical School and the Harvard School of Public Health in Boston, constructed a mathematical model of hypothetical persons to evaluate the cost effectiveness of colorectal cancer (CRC) screening in average-risk individuals. Discounted lifetime costs, life expectancy, and incremental cost-effectiveness (CE) ratio were compared, using 22 different CRC screening strategies, including those recommended by an expert panel.
According to background information cited in the study, CRC is the second leading cause of cancer-related mortality in the United States, resulting in approximately 56,600 deaths in 1999. Screening for CRC reduces mortality through detection of malignancy at an earlier, more treatable stage, as well as by identification and removal of the precursor lesion, the adrenomatous polyp. A recent panel recommended that average-risk individuals begin screening at the age of 50 years with one of the following strategies: annual fecal occult blood testing (FOBT), flexible sigmoidoscopy (SIG) every five years, annual FOBT plus SIG every five years, double-contrast barium enema (DCBE) every five to 10 years, or colonoscopy (COL) every 10 years.
The researchers obtained test costs and the costs of CRC treatment, by stage and time period (initial, continuing, and terminal care) from a cost study from a large health maintenance organization. They obtained clinical data to estimate the prevalence of adrenomatous polyps, the probability of transformation from low-risk to high-risk polyp, and CRC prevalence at 50 years of age. They calculated incremental cost-effectiveness (CE) ratio for each screening strategy (additional cost divided by additional benefit) compared with the next least expensive strategies.
In a base-case analysis of all 22 strategies for white men at average risk, the authors assumed 60 percent compliance with the initial screen and 80 percent with follow-up or surveillance colonoscopy. "The most effective strategy for white men was annual rehydrated FOBT plus sigmoidoscopy (followed by colonoscopy if either a low- or high-risk polyp was found) every 5 years from age 50 to 85 years, which resulted in a 60 percent reduction in cancer incidence and an 80 percent reduction in CRC mortality compared with no screening, and an incremental CE ratio of $92,900 per year of life gained compared with annual unrehydrated FOBT plus sigmoidoscopy every five years," they write.
Because of increased life expectancy among white women and increased cancer mortality among blacks, CRC screening was even more cost-effective in these groups than in white men.
The authors point out that compliance for CRC screening is currently quite low in the United States. "Given the low proportion of Americans who currently comply with the recommended screening schedule, advising all Americans to be screened at least once may be a reasonable starting point for national policy," they write. "Among the 1-time screening alternatives, COL was the most effective option with a lifetime reduction in CRC mortality of 31 percent and an incremental CE ratio of $22,400 per life-year saved compared with 1-time SIG, assuming 60 percent compliance."
The authors conclude that among the screening strategies they considered, rehydrated FOBT plus SIG every 5 years was the most effective screening strategy. However, they note that "the choice of screening strategy in clinical practice should be determined not just by cost-effectiveness but also by provider competence and patient preferences. A 1-time screen at 55 years of age with COL can achieve a 30 percent to 50 percent reduction in CRC mortality, depending on the level of compliance. Although further reductions in mortality can be accomplished with repeated screening, significant progress in reducing CRC mortality can be achieved with a single screen," they conclude.