Magnetic Resonance Imaging Features for Distinguishing High-Grade From Low-Grade Soft Tissue Sarcoma: A Systematic Review and Meta-Analysis

Soft tissue sarcomas are malignant tumors characterized by heterogeneity and are associated with a high mortality rate. Histopathological grading is considered a pivotal factor in prognostication and treatment planning. While core needle biopsy exhibits high accuracy in determining tumor histology, it fails in some cases, potentially misclassifying high-grade tumors as low-grade. Magnetic resonance imaging (MRI) has been evaluated as an adjunctive tool for predicting histopathological tumor grade. This systematic review and meta-analysis evaluated MRI features capable of distinguishing high-grade from low-grade tumors in patients with soft tissue sarcoma. A literature search was carried out in PubMed, Embase, and Cochrane Central in May 2024. The following features were evaluated for both low-grade and high-grade tumors: tumor size, heterogeneity on T2, presence of necrotic areas, margin definition on T1, and post-contrast peritumoral enhancement. Statistical analysis was conducted using the OpenMeta[Analyst] software (Providence, RI: Brown University), applying random effects models for pooled analyses with a 95% confidence interval (CI) based on the inverse variance method. A total of four studies, involving 343 patients categorized by tumor grade (high-grade or low-grade), who underwent MRI, were included in the analysis. The meta-analysis found similar incidences of tumor sizes less than 5 cm in both high-grade and low-grade tumors (22.7%; 95% CI: 10.3-25% vs. 27%; 95% CI: 2.7-51.2%) and tumor sizes greater than 5 cm (71.3%; 95% CI: 64-78.6% vs. 52%; 95% CI: 23.6-80.5%). High-grade tumors showed a higher incidence of post-contrast peritumoral enhancement compared to low-grade tumors (66%; 95% CI: 43-89% vs. 26%; 95% CI: 4.6-47.4%) as well as heterogeneity on T2 greater than 50% (72.4%; 95% CI: 49.3-95.4% vs. 25.4%; 95% CI: 5.2-56%). Additionally, high-grade tumors had a lower incidence of the absence of necrotic signal compared to low-grade tumors (28.8%; 95% CI: 8.5-49.1% vs. 68%; 95% CI: 57.5-78.6%). Our findings suggest that post-contrast peritumoral enhancement, presence of necrotic areas, and heterogeneity on T2 greater than 50% are MRI features associated with high-grade tumors in soft tissue sarcoma. Tumor size, however, does not appear to be a reliable indicator for differentiating tumor grade.