Thallium bone imaging as an indicator of response and outcome in nonmetastatic primary extremity osteosarcoma

Purpose. We investigated one 201Tl bone scintigraphy method as a predictor of histologic response and event-free survival (EFS) of nonmetastatic extremity osteosarcoma. Materials and methods. We evaluated images of the primary tumor to determine whether they exhibited a donut of avidity for 40 patients enrolled on a single institutional protocol. Participants underwent three serial 201Tl bone scintigraphy studies during preoperative neoadjuvant chemotherapy. Intra- and interobserver variability of the method was assessed, and the presence of the donut of avidity was examined as a predictor of EFS and histologic response. Results. Fifty-three percent of patients were female and 75 % were Caucasian; the median age at diagnosis was 13.5 years. Intraobserver agreement was moderate to very good, ranging from 0.595 to 0.865. Interobserver agreement was moderate to good for all time points, ranging from 0.576 to 0.708. There was a significant difference in EFS among patients with and without the donut-shape at any of the three time points (P = 0.049); patients whose tumors displayed a donutshape had inferior EFS. Conclusion. The pattern of donut avidity in extremity OS is a predictor of lower EFS, but does not correlate with histologic response to therapy