Quantitative classification and radiomics of [18F]FDG-PET/CT in indeterminate thyroid nodules
Elizabeth J. de Koster, Wyanne A. Noortman, Jacob M. Mostert, Jan Booij, Catherine B. Brouwer, Bart de Keizer, John M. H. de Klerk, Wim J.G. Oyen, Floris H. P. van Velden, Lioe‐Fee de Geus‐Oei, Dennis Vriens, for the EfFECTS trial study group
Abstract
Abstract Purpose To evaluate whether quantitative [ 18 F]FDG-PET/CT assessment, including radiomic analysis of [ 18 F]FDG-positive thyroid nodules, improved the preoperative differentiation of indeterminate thyroid nodules of non-Hürthle cell and Hürthle cell cytology. Methods Prospectively included patients with a Bethesda III or IV thyroid nodule underwent [ 18 F]FDG-PET/CT imaging. Receiver operating characteristic (ROC) curve analysis was performed for standardised uptake values (SUV) and SUV-ratios, including assessment of SUV cut-offs at which a malignant/borderline neoplasm was reliably ruled out (≥ 95% sensitivity). [ 18 F]FDG-positive scans were included in radiomic analysis. After segmentation at 50% of SUV peak , 107 radiomic features were extracted from [ 18 F]FDG-PET and low-dose CT images. Elastic net regression classifiers were trained in a 20-times repeated random split. Dimensionality reduction was incorporated into the splits. Predictive performance of radiomics was presented as mean area under the ROC curve (AUC) across the test sets. Results Of 123 included patients, 84 (68%) index nodules were visually [ 18 F]FDG-positive. The malignant/borderline rate was 27% (33/123). SUV-metrices showed AUCs ranging from 0.705 (95% CI, 0.601–0.810) to 0.729 (0.633–0.824), 0.708 (0.580–0.835) to 0.757 (0.650–0.864), and 0.533 (0.320–0.747) to 0.700 (0.502–0.898) in all ( n = 123), non-Hürthle ( n = 94), and Hürthle cell ( n = 29) nodules, respectively. At SUV max , SUV peak , SUV max -ratio, and SUV peak -ratio cut-offs of 2.1 g/mL, 1.6 g/mL, 1.2, and 0.9, respectively, sensitivity of [ 18 F]FDG-PET/CT was 95.8% (95% CI, 78.9–99.9%) in non-Hürthle cell nodules. In Hürthle cell nodules, cut-offs of 5.2 g/mL, 4.7 g/mL, 3.4, and 2.8, respectively, resulted in 100% sensitivity (95% CI, 66.4–100%). Radiomic analysis of 84 (68%) [ 18 F]FDG-positive nodules showed a mean test set AUC of 0.445 (95% CI, 0.290–0.600) for the PET model. Conclusion Quantitative [ 18 F]FDG-PET/CT assessment ruled out malignancy in indeterminate thyroid nodules. Distinctive, higher SUV cut-offs should be applied in Hürthle cell nodules to optimize rule-out ability. Radiomic analysis did not contribute to the additional differentiation of [ 18 F]FDG-positive nodules. Trial registration number This trial is registered with ClinicalTrials.gov: NCT02208544 (5 August 2014), https://clinicaltrials.gov/ct2/show/NCT02208544 .