Response assessment using dynamic MR imaging in non-metastatic osteosarcoma

Abstract

10018 Background: Conventional static imaging methods are of limited utility in assessing osteosarcoma (OS) response to neoadjuvant chemotherapy primarily due to the lack of significant change in tumor size. Methods: We prospectively evaluated the utility of dynamic contrast-enhanced MR imaging (DEMRI) in assessing tumor response as part of a phase II trial of multiagent chemotherapy for treatment of OS from 1999 to 2006. Forty-two subjects (median age, 13.5 years) with non-metastatic OS of the extremity (27 femur, 10 tibia, 3 humerus, 1 fibula, and 1 ulna) underwent one or more DEMRI examinations and had histological assessment of tumor response. DEMRI was performed at baseline (before course 1 of chemotherapy [week 0]), at week 9 (after 3 courses of chemotherapy), and at week 12 (after 4 courses of chemotherapy before definitive surgery). Quantitative DEMRI measures reflecting rate and intensity of enhancement (dynamic vector magnitude [DVM]) and regional contrast transfer between the plasma and extracellular/extravascular spaces (kep) were analyzed in relation to histological response. Nonparametric Wilcoxon signed-rank test was used to compare DEMRI parameters during preoperative chemotherapy with baseline. Logistic regression was used to examine the association between DEMRI parameters and histological response at each time point. Results: Both DEMRI parameters at week 9 and at week 12 of preoperative chemotherapy were significantly decreased from baseline (p<0.001). Patients with lower DVM or lower kep at week 9 or at week 12 ( Table ) were significantly more likely to have good histological response (>90% tumor necrosis). Conclusions: DEMRI is a non-invasive method that can be used to assess tumor response to neoadjuvant chemotherapy in OS. A slower rate of contrast accumulation in the extracellular/extravascular space corresponds to increased tumor necrosis. [Table: see text] No significant financial relationships to disclose.