Added Value of Magnetic Resonance Over Computed Tomography in Distinguishing Nonneoplastic Complex Thymic Cysts From Malignant Cystic Thymic Neoplasms.

PURPOSE: The aim of the study was to evaluate cystic thymic masses by using computed tomography (CT) and magnetic resonance (MR) scoring systems to differentiate nonneoplastic thymic cysts from cystic thymic neoplasms. METHODS: This retrospective multisite study included adult patients who underwent CT and MR imaging of the chest between 2007 and 2020 with any of the following impressions on cross-sectional imaging studies: "thymic mass with cystic component," "unilocular or multilocular cystic thymic lesion," "complex thymic cyst," "thymic cyst with hemorrhage." Two blinded radiologists reviewed and recorded specific imaging features as well as overall impressions on both CT and MR using a Likert scale scoring system. Data were analyzed, and diagnostic accuracy of CT and MR was compared using areas under the receiver operating characteristic curves (AUC). RESULTS: Fifty-six patients were included, of which 45 (80%) had benign masses. Total of 21 patients (38%) had indeterminate scores on CT of which 3 (14%) were malignant, while only 6 (11%) had indeterminate scores on MR and 1 was malignant. Magnetic resonance scoring system (AUC, 0.95) performed better than CT scoring system (AUC, 0.86) in distinguishing benign versus malignant lesions (P = 0.06). Lack of enhancement within the mass was completely predictive of benign etiology (P < 0.001). Wall thickness of an enhancing cyst was predictive of malignancy, with AUC 0.93. CONCLUSIONS: Magnetic resonance yielded higher specificity allowing a larger number of lesions to be confidently assigned a benign diagnosis. This could help in averting unnecessary follow-up, biopsies, or surgery. The authors recommend follow-up imaging with MR for prevascular masses, even those appearing "solid" on CT.

Cost-Effectiveness of Follow-Up for Subsolid Pulmonary Nodules in High-Risk Patients.

OBJECTIVE: To evaluate the cost-effectiveness of a number of follow-up guidelines and variants for subsolid pulmonary nodules. METHODS: We used a simulation model informed by data from the literature and the National Lung Screening Trial to simulate patients with ground-glass nodules (GGNs) detected at baseline computed tomography undergoing follow-up. The nodules were allowed to grow and develop solid components over time. We tested the guidelines generated by varying follow-up recommendations for low-risk nodules, that is, pure GGNs or those stable over time. For each guideline, we computed average US costs and quality-adjusted life-years (QALYs) gained per patient and identified the incremental cost-effectiveness ratios of those on the efficient frontier. In addition, we compared the costs and effects of the most recently released version of the Lung Computed Tomography Screening Reporting and Data System (Lung-RADS), version 1.1, with those of the previous version, 1.0. Finally, we performed sensitivity analyses of our results by varying several relevant parameters. RESULTS: Relative to the no follow-up scenario, the follow-up guideline system that was cost-effective at a willingness-to-pay of $100,000/QALY and had the greatest QALY assigned low-risk nodules a 2-year follow-up interval and stopped follow-up after 2 years for GGNs and after 5 years for part-solid nodules; this strategy yielded an incremental cost-effectiveness ratio of $99,970. Lung-RADS version 1.1 was found to be less costly but no less effective than Lung-RADS version 1.0. These findings were essentially stable under a range of sensitivity analyses. CONCLUSIONS: Ceasing follow-up for low-risk subsolid nodules after 2 to 5 years of stability is more cost-effective than perpetual follow-up. Lung-RADS version 1.1 was cheaper but similarly effective to version 1.0.