Lisanne de Koster

437 Letter: what is the role of functional imaging and isotopic treatment? 10 after one year. We prospectively collected clinical data, healthcare usage, quality of life, direct and indirect costs of each of these patients. The [18F]FDG-PET/CT-driven approach indeed did reduce the number of futile surgeries by 40% (48% in nonHürthle cell nodules). No malignant or borderline tumours were observed in patients under surveillance. Sensitivity, specificity, negative and positive predictive value, and benign call rate of [18F]FDG-PET/CT were 94.1%, 39.8%, 95.1%, 35.2% and 31.1%, respectively, which was fully in line of our 2011 meta-analysis [304]. This observed high NPV fits the American Thyroid Association 2015-guideline statement that “one could surmise that […] an ideal ‘‘rule-out’’ test would have a NPV similar to a benign cytologic diagnosis (96.3%) (predictive value estimates based on a recent meta-analysis of performance of the Bethesda system), and these would hold true with a reasonable degree of precision and reproducibility.” [17]. None of the (few) patients crossing over in the study for fear of missed diagnosis or persistent obstructive complains of a nodule suffered from malignancy. Mean one-year societal costs, adjusted for imbalance in malignancy rate in both study arms despite successful stratification, were almost € 7000 lower in the [18F]FDG-PET/CT-driven approach. This included additional diagnostics and other costs due to incidental findings in the skull-base to aortic arch PET/CT-acquisition. Extending the oneyear window to a life-long horizon confirmed that this imaging-driven approach is cost-effective both for direct and societal costs with almost €10,000 lifetime reduction in costs [663]. The reassurance of a negative [18F]FDG-PET/CT resulted in sustained health-related quality of life throughout the first year of active surveillance. Diagnostic surgery for a nodule with benign histopathology resulted in more cognitive impairment and physical problems including cosmetic complaints, but improved goitre symptoms and anxiety. Anxiety was also reduced in patients with malignant histopathology [664]. Quantitative analyses confirmed that an [18F]FDG-PET/CT-driven approach is specifically effective in non-Hürthle nodules, although it suggested that using a different cut-off of the Standardised Uptake Value in Hürthle nodules, might improve the diagnostic value of [18F]FDG-PET/CT in this subcategory of patients [662]. We could not find image-based or immunohistochemical markers that explain the difference between true and false [18F]FDG-positive nodules [662, 665] and are currently preparing a manuscript on the comparative value of molecular imaging and molecular diagnostics in our cohort. Critics could dismiss our findings because of the relatively short follow-up of only one year, which was chosen due to rules set by the grant provider (Dutch Cancer Society). All patients are currently still in clinical follow-up (up to 5 years), and up-to-date no missed malignancies have been reported. Longterm analyses of our cohort are scheduled in 2025. Thus, we truly believe that that data from the Dutch EfFECTS trial confirm earlier publications by our group as well as others: the use of [18F]FDG-PET/CT in cytologically indeterminate thyroid nodules prevents unbeneficial diagnostic thyroid surgery, is oncologically safe, cost-effective and preserves quality of life. Its use is practice changing, should be offered to any patients scheduled for diagnostic surgery for indeterminate thyroid FNAC, and will be part of the updated Dutch national guideline (expected end of 2023).

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