303 [18F]FDG-PET/CT to prevent futile surgery: a blinded, randomised controlled multicentre trial 4 Blinding Patients, all local study site personnel, and all pathologists were blinded to [18F]FDG-PET/CT results and allocation. Central pathologists were additionally blinded to the local cyto- and histopathological diagnoses. Central nuclear medicine physicians were blinded to allocation and all clinicopathological data except for the ultrasonographic size and location of the index nodule. Other study investigators assessing outcomes were blinded to allocation. Patients allocated to the [18F] FDG-PET/CT-driven group with an [18F]FDG-negative nodule could inevitably deduce their allocation and [18F]FDG-PET/CT result from the surveillance advice. Outcomes The primary outcome was the fraction of patient management that was considered unbeneficial one year after the [18F]FDG-PET/CT scan. Unbeneficial management was defined as futile diagnostic surgery for histopathologically benign nodules (including hyperplastic nodules, follicular adenoma, and Hürthle cell adenoma) and/or unjustified surveillance for histopathological malignant or borderline tumours. According to novel insights arising during the trial, nodules diagnosed as noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) or follicular tumour of uncertain malignant potential (FT-UMP) are considered benign yet potentially premalignant (i.e., borderline) lesions, for which surgery is considered justified [19, 20]. Following broad acceptance of these insights, we added a refinement concerning these borderline tumours to the study protocol during the trial. As histopathology was not reviewed until trial completion, this modification did not in any way influence trial execution and primary end points. Results for the primary outcome for a strictly benign-malignant differentiation are reported. Secondary outcomes of the trial included the differences in surgical complication rates, one-year HRQoL expressed in quality-adjusted life years (QALYs), and societal costs (in €) between both strategies. The diagnostic accuracy of [18F]FDG-PET/CT (whole-group analysis) was estimated: [18F]FDG-positive or [18F]FDG-negative nodules confirmed as malignant or borderline tumours on histopathology were considered true-positive or false-negative, respectively; [18F]FDG-positive or [18F] FDG-negative nodules confirmed as benign on histopathology and those that remained unchanged on the one-year ultrasound were considered false-positive or true-negative, respectively. Finally, the number of incidental [18F]FDG-PET/CT findings with diagnostic and/or therapeutic consequences in the scanned area (descriptive whole-group analysis), implementability of [18F]FDG-PET/CT (i.e., diagnostic confidence) defined as the fraction of patients not reassured by a negative [18F]FDG-PET/ CT result, and survival were assessed. Per protocol, the follow-up for all endpoints was set at one year after [18F]FDG-PET/CT. Whenever available and relevant, data beyond one year of follow-up (censored 1 October 2021) are presented.
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