A hybrid colorectal cancer screening strategy that incorporates annual fecal immunological testing beginning at age 50 years and a single colonoscopy at age 66 years proved both clinically effective and cost-effective in a simulation model.
Using the Archimedes Model – a "large-scale integrated simulation of human physiology, diseases, and health care systems" – Tuan Dinh, Ph.D., of Archimedes Inc., San Francisco, and colleagues found that compared with no screening, the hybrid strategy with annual fecal immunological testing (FIT) reduced colorectal cancer incidence by 73%, gained 11,200 quality-adjusted life years (QALYs), and saved $126.8 million for every 100,000 people screened during a 30-year period.
Source: American Gastroenterological Association
Without screening, a cohort of 100,000 members of Kaiser Permanente Northern California who were included in the virtual study experienced 6,004 colorectal cancers and 1,837 colorectal cancer deaths. All methods of screening that were evaluated in the model – including annual FIT, colonoscopy at 10-year intervals, sigmoidoscopy at 5-year intervals, both FIT and sigmoidoscopy, and both FIT and colonoscopy – substantially reduced the colorectal cancer incidence, by 53%-76%, and added a significant number of QALYs, compared with no screening, the investigators reported online March 28 in Clinical Gastroenterology and Hepatology.
Colonoscopy as a single-modality screening strategy was most effective for colorectal cancer reduction (76%), and FIT alone was the least costly approach (with savings of $142.6 million per 100,000 persons, compared with no screening), but FIT plus colonoscopy came close: The hybrid strategy reduced colorectal cancer by 73%, and compared with FIT alone, gained 1,400 QALYs/100,000 at an incremental cost of $9,700 per QALY gained. Colonoscopy gained 500 QALY/100,000 more than the hybrid strategy at an incremental cost of $35,100 per QALY gained.
Furthermore, the hybrid strategy required 55% fewer FITs and 41% more colonoscopies than FIT alone, and required 2.1-2.3 fewer colonoscopies per person during 30 years than screening by colonoscopy alone, they reported (Clin. Gastroenterol. Hepatol. 2013 March 28 [doi: 10.1016/j.cgh.2013.03.013]).
On sensitivity analysis, a hybrid approach using biennial FIT was also cost-effective, compared with either FIT or colonoscopy alone.
The core of the Archimedes Model is "a set of equations that represent physiological pathways at the clinical level (i.e., at the level of detail of basic medical tests, clinical trials, and patient charts)." The colorectal cancer submodel, which was derived from public databases, published epidemiologic studies, and clinical trials, was developed in collaboration with the American Cancer Society, the authors explained.
The simulated population included a cross section of 2008 Kaiser Permanente members who were aged 50-75 years at the start of the virtual trial comparing the screening strategies.
The findings are important, given that colorectal cancer is the second-leading cause of cancer deaths among adults in the United States, and although colonoscopy is the recommended approach for primary screening in most U.S. guidelines, it is the most invasive, risky, and costly screening modality, the investigators noted.
Conversely, stool tests with follow-up colonoscopy for positive results are the least expensive. In the past, stool test strategies have been hampered by low sensitivity for adenomas and low specificity, but recent improvements in sensitivity and specificity of FIT has renewed interest in the use of stool tests, they said.
Though the hybrid FIT/colonoscopy strategy is limited by several factors – for example, the accuracy of any simulation model is dependent on assumptions about test performance and adherence, which may vary – the findings of this study suggest the hybrid strategy could improve outcomes while lowering costs.
"The simulation results indicated that [the hybrid strategy] required 37% fewer colonoscopies than [colonoscopy alone], while delivering only slightly inferior health benefits," the investigators said. These results demonstrate that "it is possible to design hybrid colorectal cancer screening strategies that can deliver health benefits and cost-effectiveness that are comparable to those of single-modality strategies, with a favorable impact on resource demand," they noted.
Future clinical studies should address whether hybrid strategies have the additional advantage of increasing screening adherence, they concluded.
This study was carried out by Archimedes under a contract with The Permanente Medical Group (TPMG). One author, Dr. Theodore R. Levin, is a TPMG shareholder, and another, Cindy Caldwell, is a TPMG employee. The authors reported having no other conflicts of interest.