Background Managing soft-tissue sarcoma (STS) relies on histologic grade, which is the strongest prognostic factor and a routine assessment at biopsy. However, underestimation of histologic grade may occur because of tumor heterogeneity. Purpose To identify MRI features that are associated with high-grade STS (grade III) and to determine the relationship between MRI features and patient survival. Materials and Methods In this retrospective single-center study, patients (age ≥16 years) were included if they presented with STS diagnosed between 2008 and 2015, had a baseline contrast material-enhanced MRI study, had a pathologic grade assessed on the whole surgical specimen, and had no history of neoadjuvant treatment. Visceral sarcomas, well-differentiated liposarcomas, and angiosarcomas were excluded. Images were evaluated for size, heterogeneity, architecture, margins, and surrounding tissue at T2-weighted, T1-weighted precontrast, and T1-weighted postcontrast MRI. χ² tests, Fisher tests, and multivariable binary logistic regression were performed to identify features associated with a final grade of III. The associations between combinations of these features and overall survival and metastasis-free survival were investigated with Kaplan-Meier curves and multivariable Cox models. Results A total of 130 patients were included (53 women [mean age ± standard deviation, 60.7 years ± 19.2]); 72 of the 130 (55.4%) STSs were grade III. At multivariable analysis, three MRI features were associated with grade III STS: peritumoral enhancement (odds ratio [OR], 3.4; P = .003), presence of an area compatible with necrosis (OR, 2.4; P = .03), and heterogeneous signal intensities greater than or equal to 50% at T2-weighted imaging (OR, 2.3; P = .04). The presence of at least two of these three features was an independent predictor of metastasis-free survival (hazard ratio, 4.5; P = .01) and overall survival (hazard ratio, 4.2; P = .04). Conclusion MRI features including necrosis, heterogeneity, and peritumoral enhancement of soft-tissue sarcomas were associated with grade III tumors, metastasis-free survival, and overall survival. © RSNA, 2019 Online supplemental material is available for this article.

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