Comparison of the diagnostic accuracy of contrast-enhanced MRI and diffusion-weighted MRI in the differentiation between uterine leiomyosarcoma / smooth muscle tumor with uncertain malignant potential and benign leiomyoma

Purpose To compare the diagnostic accuracy of contrast-enhanced (CE) magnetic resonance imaging (MRI) and diffusion-weighted MRI (DWI) in the differentiation between uterine leiomyosarcoma (LMS) / smooth muscle tumor with uncertain malignant potential (STUMP) and benign leiomyoma. Materials and Methods A consecutive cohort of 8 LMS/STUMP and 25 benign leiomyomas underwent pelvic MRI exam at 3T. Two radiologists independently evaluated images based on CE-MRI (central nonenhancement at equilibrial phase) and DWI (hyperintensity on b = 1000 s/mm² and hypointensity on apparent diffusion coefficients [ADC] map). The ADC values were calculated from b = 0 and 1000 s/mm². Results CE-MRI yielded a significantly superior diagnostic accuracy (0.94 vs. 0.52) and a significantly higher specificity (0.96 vs. 0.36) than DWI (P < 0.05 for both), and remained a comparably high sensitivity as DWI (0.88 vs. 1.00). A combination of DWI and ADC value <1.08 × 10^-3 mm²/s (determined by receiver operating characteristic analysis) improved diagnostic accuracy, sensitivity, and specificity of DWI to 0.88, 0.88, and 0.88, respectively, by post-hoc analysis based on the same study cohort. Conclusion For prospective differentiation between uterine LMS/STUMP and benign leiomyoma, CE-MRI can provide accurate information and is preferable to DWI. Combination of DWI and ADC values can achieve a comparable diagnostic accuracy to CE-MRI. J. Magn. Reson. Imaging 2016;43:333-342.