532 Appendices Part II. Efficacy of [18F]FDG-PET/CT in indeterminate thyroid nodules Part II investigated the efficacy of [18F]FDG-PET/CT in the pre-operative diagnostic work-up of cytologically indeterminate thyroid nodules. This part of the thesis is built on the results of the Efficacy of [18F]FDG-PET in Evaluation of Cytological indeterminate Thyroid nodules prior to Surgery (EfFECTS) trial, a triple blinded, randomised controlled Dutch multicentre trial that investigated the implementation [18F]FDG-PET/CT as a rule-out test in the diagnostic workup of Bethesda III and IV thyroid nodules, aiming to reduce the number of futile diagnostic surgeries for benign nodules. The trial enrolled 132 patients with scheduled diagnostic surgery for a Bethesda III and IV thyroid nodule in 15 hospitals in the Netherlands. They all underwent one partial-body [18F]FDG-PET/CT of the neck, which was primarily visually assessed. Chapter 4 presented the main results of the EfFECTS trial, including the safety and impact of an [18F]FDG-PET/CT-driven diagnostic workup as compared to diagnostic surgery without additional preoperative diagnostics. [18F]FDG-PET/CT-driven management avoided 40% (95% CI, 28%-53%) diagnostic surgeries for benign nodules: 48% (33%-63%) in non-oncocytic and 13% (2%-40%) in oncocytic nodules (i.e., Bethesda IV cytology suspicious for an oncocytic follicular neoplasm, p=0.02). No malignant or borderline tumours were observed in patients undergoing active surveillance following an [18F]FDG negative scan. With 94.1% (95% CI, 80.3%-99.3%) sensitivity and 95.1% (83.5%-99.4%) negative predictive value, visual assessment of [18F]FDG-PET/CT was an accurate rule-out test. It was not useful as a rule-in test, with 39.8% (95% CI, 30.0%-50.2%) specificity and 35.2% (25.4%-45.9%) positive predictive value. As expected based on previous literature, [18F] FDG-PET/CT did not differentiate in nodules with oncocytic cytology: all but one of the 31 included oncocytic nodules were visually [18F]FDG positive; the benign call rate was merely 3% (95% CI, 0.1%-16.7%). In non-oncocytic nodules, the benign call rate was 39.6% (30.0%-49.8%): a clinically useful result in approximately four out of ten patients undergoing [18F]FDG-PET/CT for a Bethesda III/IV nodule. Secondary trial objectives were also discussed in Chapter 4. Cost-effectiveness and health-related quality of life (HRQoL) are discussed in more detail in Chapters 5 and 6. In addition, diagnostic confidence in [18F]FDG-PET/CT was high in both patients and physicians. With regard to the surgical complication rate, a trend towards fewer medication-dependent hypothyroidism following diagnostic hemithyroidectomy was seen in the [18F]FDG-PET/CT-driven group (6% versus 17% in the diagnostic surgery group, p=0.07). Incidental [18F]FDG-PET/CT findings were reported in 22 of 132 (17%) of patients, of which 3 (2%) had therapeutic consequences for detected disease (two thyroid malignancies and one possible de novo diabetes mellitus), 4 (3%) underwent unbeneficial extension of their planned diagnostic surgery to total thyroidectomy for a benign contralateral thyroid nodules, and 15 (11%) only had minor consequences (i.e., overdiagnosis by additional FNAC or overtreatment by additional nodulectomy of benign nodules). Providing the highest level of evidence on the matter for the first time, Chapter 4 concluded that [18F]FDG-PET/CT is an accurate, oncologically safe and
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