Cost-Effectiveness of Follow-Up Ultrasound for Incidental Thyroid Nodules on CT.

Thyroid nodules are common incidental findings on CT. Existing professional society recommendations, based primarily on expert opinion, advise follow-up ultrasound for nodules above size cutoffs in patients of all ages. The purpose of this study was to use a simulation model to evaluate the cost-effectiveness of current recommendations and of other age- and size-based follow-up strategies for thyroid nodules incidentally detected on CT. By using a simulation model with 1,000,000 adults with nodules measuring 40 mm or less that have no suspicious features, we evaluated size cutoffs from 5 to 25 mm in patients younger than an age maximum from 25 to 65 years, as well as follow-up versus no follow-up for patients above the age maximum. For each strategy, patient survival was determined by disease-specific and baseline mortality rates and surgical mortality. Costs and quality-adjusted life years (QALYs) were tabulated. A probabilistic sensitivity analysis was performed with varying model parameters. All cost-effective strategies recommended no follow-up for patients above the age cutoffs (which varied from 25 to 65 years). In the base-case simulation, 10 strategies were cost-effective at a willingness-to-pay threshold of $100,000/QALY. Of these, the strategy yielding the highest QALYs was follow-up for patients under 60 years old with nodules 10 mm or larger and no follow-up for patients 60 years old or older, with an incremental cost-effectiveness ratio of $50,196/QALY (95% CI, $39,233-67,479). In the probabilistic sensitivity analysis, if the 10-year disease-specific survival of patients with untreated cancer was more than 94% of patients with treated cancer, then no follow-up for any nodules was optimal. Follow-up ultrasound for thyroid nodules incidentally detected on CT is likely not cost-effective in older patients. Follow-up for most thyroid nodules in younger patients may be cost-effective. Future societal recommendations may account for the limited benefit of obtaining follow-up for incidental thyroid nodules on CT in older patients.