Osteosarcoma after Preoperative Chemotherapy: Tissue Characterization with Specimen MR and the Role of Enhanced MR Imaging

Abstract

Preoperative intra-arterial chemotherapy and limbsalvage surgery for the treatment of osteosarcoma has led to marked improvement in long-term patient survival (1 3). The most accurate prognostic factor is the percentage of tumor necrosis after chemotherapy (4). Purpose : To evaluate the role of enhanced MR imaging in monitoring tumor response to preoperative chemotherapy for osteosarcomas. Materials and Methods : Fo r t y -s even patients (30 males and 17 females, with a mean age 17 years ; range 8 44 years) with osteosarcomas were included in this study. We obtained spin echo T1-, T2-, and enhanced T1-weighted images before and after preo p e r a t i ve chemotherapy and in all patients correlated changes in MR parameters with histopathologic response. We also obtained 19 specimen MR images, correlating these with histopathologic results in order to estimate tissue specific signals. Patients with more than 10% viable tumor in the resected specimen were considered poor responders (n=26), while those with 10% or less viable tumor were considered good responders (n=21).Results : Four distinct patterns of signal intensity corresponded, respectively to dead bone and dense fibrosis (low on T1-and T2-weighted images), viable tumor cells (intermediate on T1-and high on T2-weighted images), necrosis (low on T1-and high on T 2 -weighted images), and hemorrhage (high on T1-and T2-weighted images), but a wide range of overlap was noted. In all four groups, viable tumor cells remained. Increased tumor vo l u m e, stable or increased edema and enhancement were good predictors of poor response (predictive values of 83%, 77%, and 89%, respective l y ) . Decreased enhancement was the only reliable predictor of good response (predictive va l u e, 73%). Changes in tumor margin, homogeneity, signal intensity, and joint effusion did not correlate with histopathologic response. Conclusion : Signal intensities do not reflect histologic nature. Enhanced MR imaging is a useful predictor of tumor response to preoperative chemotherapy.

Evaluation of static and dynamic MRI for assessing response of bone sarcomas to preoperative chemotherapy: Correlation with histological necrosis

“…These findings are supported by other studies which also failed to find a significant correlation. [ 13 24 25 ]…”

“…Though few studies have reported its significant role in predicting histological response, many studies have given an equivocal report. [ 13 24 ] Although increase in tumor volume correlates well with the poor histological response, reduced or stable tumor volume does not guarantee a good response. [ 14 25 26 ]…”