Novel MRI scoring system to assess osseous malignancy in patients with soft tissue sarcoma following radiotherapy.

Abstract

11561 Background: Although radiotherapy is an important component of STS management, radiation induced changes such as radiation osteitis are commonly identified on magnetic resonance imaging (MRI). These imaging findings may be concerning for malignancy and sometimes require biopsy for investigation. This study proposes a novel MRI scoring system to assess osseous lesions and predict potential for malignancy based on MRI score in STS patients who received radiotherapy. Methods: The MRI score consisted of 3 parameters: morphology, signal intensity, and progression. Interobserver reliability between the total score of MRI examinations scored by two senior musculoskeletal radiologists were analyzed with Cohen’s kappa coefficient. Receiver operating curve (ROC) analysis was performed to determine a predictive MRI score for malignancy. Results: 156 MRI’s from 30 STS patients who received radiotherapy were retrospectively reviewed. Two (6.7%) patients developed regional osseous metastasis identified on MRI. The kappa coefficient of the scoring system was 0.785 demonstrating substantial interobserver agreement (p<0.001). ROC analysis demonstrated that the optimal cut-off value for malignant lesion on MRI was 5.5 (area under the curve 0.998 (95% CI 0.993-1.000) p<0.001). Conclusions: This novel MRI scoring system recommends lesions with a score of six and above to be biopsied to distinguish if malignancy is present. We believe this scoring system can be utilized by multidisciplinary care teams to guide clinical recommendations for patients with STS and MRI findings concerning for malignancy versus radiation induced changes.[Table: see text]