Abstract
10056 Background: Few prognostic factors had been described for pediatric high-grade osteosarcoma (HGO). Primary tumor necrosis percentage after neoadjuvant chemotherapy, analyzed by pathologists, remains as an important prognostic factor. Magnetic resonance imaging (MRI) has been postulated to predict necrosis in adults. Our aim was therefore to calculate the diagnostic utility of MRI in children. Methods: Prospective, longitudinal and clinical study was performed from September 2011 to January 2012. Twenty two patients (< 18 years), with extremity HGO and no prior chemotherapy treatment were included. All had MRI from diagnosis and just before surgery. We performed a sensibility-specificity analysis comparing percentage of necrosis by MRI vs histological Rosen grades (grades I and II were classified as bad responders; III and IV as good responders). Cut off value for MRI was 90%. Agreement between radiologists was calculated by Cohen´s Kappa coefficient. Results: Average age was 11.7 ± 3.04 (SD), 54.5% were women. All patients received neoadyuvant chemotherapy (cisplatin 120mg/m2 and adriamicin 75mg/m2). Nine patients had limb-sparing surgery, 8 limb disarticulation and 5 amputations; 72.8% were classified as bad responders by histology. MRI sensibility was 25%, specificity 86.6%, positive predictive value 50% and negative predictive value 68.4%. Kappa correlation coefficient between radiologists was 0,229. Conclusions: Diagnostic utility values in this study were lower than those reported previously. Torricelli, Dyke and Guo reported MRI sensibility of over 70% and specificity ranging from 37% to 87% (similar number of patients). Predictive values were also higher (> 80%). Differences are likely explained by the lack of correlation between radiologists. Our results support the need to establish systematized criteria to measure necrosis by MRI. In order to predict clinical response to chemotherapy in HGO, it is necessary to establish areas and cut off percentages of necrosis for appropriate clinical decision making.
Published Version
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