Evaluation of chemotherapy response in primary bone tumors with F-18FDG positron emission tomography compared with histologically assessed tumor necrosis

Purpose: The purpose of this study was to evaluate the potential of positro n emission tomography using F-18-fluoro-2-deoxy-D-glucose (FDG PET) to asse ss the chemotherapy response of primary osseous tumors compared with the de gree of necrosis determined histologically. Patients and Methods: Seventeen patients with primary bone tumors (11 osteo sarcomas, 6 Ewing's sarcomas) were examined using FDG PET and planar bone s cintigraphy before neoadjuvant chemotherapy and before surgery. Tumor respo nse was classified histologically according to Salzer-Kuntschik (grades I-I II: good response; grades IV-VI: poor response). In both imaging methods, q uantification was performed using tumor to nontumor ratios (T:NT). Results: Histologically, 15 patients were classified as having good respons es (grade I, n = 1; grade II, n = 6; grade III, n = 8) and two as having po or responses (grades IV and V). FDG PET showed more than a 30% decrease in T:NT ratios in all patients who had good responses. However, three of these patients had increasing bone scintigraphy T:NT ratios, and another five ha d decreasing ratios of less than 30%. The patients with poor responses had increasing T:NT ratios and decreasing ratios of less than 30%, respectively , using both imaging methods. Conclusions: FDG PET seems to be a promising tool for evaluating the respon se of primary osseous tumors to chemotherapy. In this preliminary study, FD G PET was superior to planar bone scintigraphy.