Interobserver Variability of Quantitative and Qualitative Assessment Using MRI in Malignant Pleural Mesothelioma.

PURPOSE:To evaluate the interobserver variability associated with quantitative and qualitative MRI assessments of malignant pleural mesothelioma (MPM). MATERIALS AND METHODS:Patients with MPM who underwent uniform-protocol preoperative MRI between 2009 and 2014 were included. The MRI-derived tumor volume was estimated. Unidimensional measurements of maximal pleural thickness (P max) and average pleural thickness (P avg) on axial MR images; maximal fissural thickness (F max); maximal diaphragmatic thickness (D max); and average diaphragmatic thickness (D avg) on sagittal reconstructed images were acquired. Interobserver agreement regarding the American Joint Committee on Cancer (AJCC) tumor stage at each criterion level was assessed by using Cohen κ statistics. Agreement between quantitative measurements was assessed by using Bland-Altman plots and intraclass correlation coefficients (ICCs). RESULTS:The study cohort included 349 patients (median age, 68 years [age range, 30-90 years), 273 (78%) of whom were men and 203 (58%) of whom had epithelioid-subtype tumors. Qualitative assessment performed by using the AJCC staging criteria (eighth edition) was concordant in 31% of cases and yielded considerable disagreement (κ = 0.177). Inspection of the Bland-Altman plots led to decisive agreement between the two reviewers regarding MRI-derived tumor volume (ICC, 0.979). There was also a good degree of agreement between the two reviewers regarding unidimensional measurements of D max (ICC, 0.807), D avg (ICC, 0.823), P max (ICC, 0.787), P avg (ICC, 0.787), and F max (ICC, 0.659). CONCLUSION:Quantitative assessment can enhance the clinical staging of MPM. Compared with qualitative assessment, quantitative assessment has low interobserver variability and could yield a tumor size criterion that is currently lacking in the AJCC clinical staging of MPM.Supplemental material is available for this article.© RSNA, 2020.