Peritumoral contrast enhancement helps diagnose high-grade soft-tissue sarcomas

The presence of peritumoral contrast enhancement is a MRI feature that may be solely used to diagnose high-grade soft-tissue sarcomas (STS), according to a study published in the July issue of Radiology.

Establishing tumor grade is vital when making a treatment plan for high-grade STS, yet the grade can sometimes be nondiagnostic or mischaracterized when being assigned through percutaneous biopsy.

“For a patient with STS, the histologic tumor grade is the most critical piece of information needed for treatment planning, as it is heavily tied to the patient’s risk of metastasis and overall survival,” wrote lead author Fang Zhao, MD, of Shandong University in China, and colleagues. “The pathologic grade of a sarcoma is the parameter used for selecting patients for whom chemotherapy should be considered, as high-grade STS may be treated with neoadjuvant chemotherapy, while low-grade STS is not.”

Although MRI is commonly used for the staging of STS, little is known about its features’ correlation to pathologic grade of STS. The researchers consequently investigated a variety of MRI features of STS and aimed to distinguish features that enabled differentiation between high-grade and low-grade STS.

The study retrospectively included 95 patients with STS who had undergone MRI with T1-weighted, T2-weighted and contrast material-enhanced sequences prior to neoadjuvant therapy and surgery. Tumor grades one through three were recorded from the histologic specimen for each STS and images were evaluated by two observers for tumor size and MR features from each sequence. These features encompassed signal intensity, heterogeneity, margin and perilesional characteristics.

Descriptive statistics for low-grade and high-grade STS were recorded and the accuracy of individual features was determined. A multivariate logistic regression model was then created to identify features that were independently predictive of a high-grade tumor.

Of the 95 patients with STS, 16 were categorized as grade one, 34 as grade two and 45 as grade three. The researchers discovered that high-grade STS differed from low-grade STS in size, tumor margin, internal signal intensity composition and peritumoral characteristics. High-grade STS tumors were more commonly at least five centimeters, more heterogeneous at T2-weighted imaging, more likely to have partly or poorly defined margins with all nonenhanced and contrast-enhanced T1-weighted sequences, more likely to have peritumoral high signal intensity and showcased peritumoral enhancedment more frequently.

The logistic regression model revealed peritumoral contrast enhancement is the strongest independent indicator of high-grade status.

“Since treatment decisions for STS depend heavily on the assignment of tumor grade, MR imaging features that can be used to predict a high tumor grade can serve to supplement biopsy results,” concluded Zhao and colleagues.