Comparative effectiveness and cost-effectiveness of screening colonoscopy vs. sigmoidoscopy and alternative strategies.

OBJECTIVES: Fecal occult blood testing (FOBT) and sigmoidoscopy are proven to decrease colorectal cancer (CRC) incidence and mortality. Sigmoidoscopy's benefit is limited to the distal colon. Observational data are conflicting regarding the degree to which colonoscopy affords protection against proximal CRC. Our aim was to explore the comparative effectiveness and cost-effectiveness of colonoscopy vs. sigmoidoscopy and alternative CRC screening strategies in light of the latest published data.

METHODS: We performed a contemporary cost-utility analysis using a Markov model validated against data from randomized controlled trials of FOBT and sigmoidoscopy. Persons at average CRC risk within the general US population were modeled. Screening strategies included those recommended by the United States (US) Preventive Services Task Force, including colonoscopy every 10 years (COLO), flexible sigmoidoscopy every 5 years (FS), annual fecal occult blood testing, annual fecal immunochemical testing (FIT), and the combination FS/FIT. The main outcome measures were quality-adjusted life-years (QALYs) and costs.

RESULTS: In the base case, FIT dominated other strategies. The advantage of FIT over FS and COLO was contingent on rates of uptake and adherence that are well above current US rates. Compared with FIT, FS and COLO both cost <$50,000/QALY gained when FIT per-cycle adherence was <50%. COLO cost $56,800/QALY gained vs. FS in the base case. COLO cost <$100,000/QALY gained vs. FS when COLO yielded a relative risk of proximal CRC of <0.5 vs. no screening. In probabilistic analyses, COLO was cost-effective vs. FS at a willingness-to-pay threshold of $100,000/QALY gained in 84% of iterations.

CONCLUSIONS: Screening colonoscopy may be cost-effective compared with FIT and sigmoidoscopy, depending on the relative rates of screening uptake and adherence and the protective benefit of colonoscopy in the proximal colon. Colonoscopy's cost-effectiveness compared with sigmoidoscopy is contingent on the ability to deliver ~50% protection against CRC in the proximal colon.