E. J. Kuo1, J. X. Wu1, K. A. Zanocco1 1David Geffen School Of Medicine,Section Of Endocrine Surgery,Los Angeles, CA, USA
Introduction:
In an effort to reduce the overdiagnosis and overtreatment of low-risk thyroid cancer, recent American Thyroid Association guidelines increased the size-based biopsy thresholds for some sonographic categories of thyroid nodules. However, fine-needle aspiration (FNA) biopsy continues to be recommended for intermediate-suspicion nodules greater than 1cm in diameter. We hypothesize that the quality-adjusted life expectancy of patients with sonographically intermediate suspicion thyroid nodules would be improved and costs would be decreased by raising the size threshold for biopsy from 1.0 cm to 1.5 cm.
Methods:
A Markov transition-state model was constructed to compare the cost-effectiveness of immediate FNA versus ultrasound surveillance of an incidentally detected 1.5 cm thyroid nodule with intermediate-suspicion sonographic features (hypoechoic, smooth-margined solid nodule without microcalcifications, extrathyroidal extension, or taller than wide shape). Treatment outcome probabilities and their corresponding utilities were estimated based on literature review. Nonlinear growth modeling techniques were used to predict changes in the observed nodule size over time. Effectiveness was measured in quality-adjusted life years (QALYs). Costs were estimated using Medicare reimbursement data. A 3% annual discount rate was applied to all future costs and QALYs. The threshold for cost-effectiveness was defined as an incremental cost-effectiveness ratio of less than $100,000/QALY. Univariate and multivariate sensitivity analyses were used to examine the uncertainty of cost, probability, and utility estimates in the model.
Results:
The expected cost of routine ultrasound surveillance was $3,024 with an effectiveness of 23.8 QALYs. Ultrasound surveillance was $1,053 less costly and 0.01 QALY more effective than immediate FNA, making ultrasound surveillance the dominant strategy. Ultrasound surveillance decreased the lifetime rate of surgery from 26.5% to 23.7%. Immediate FNA became cost-effective during one-way sensitivity analysis when the pretest probability of malignancy increased from 15% to 71% or the cost of ultrasound examination increased from $130 to $570. Two-way sensitivity analysis demonstrated that routine FNA was cost effective if the quality adjustment factor for observation following a benign biopsy result exceeded the quality adjustment factor for observation without a biopsy. The model was not sensitive to the cost or complication rates of surgical therapy.
Conclusion:
Ultrasound surveillance is more cost-effective than immediate FNA for small thyroid nodules with intermediate-suspicion sonographic imaging characteristics, unless the probability of malignancy exceeds 71%. This model is highly sensitive to the utility differences between patients undergoing sonographic surveillance and patients with benign biopsy results. Therefore, additional primary investigation of health-related quality of life in these groups is necessary.