Response of osteogenic sarcoma to neoadjuvant therapy: evaluated by 18F-FDG-PET

The aim of this study was to evaluate the potential role of F-18-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) in assessing the chemotherapy response of osteosarcoma when compared with histologically assessed tumor necrosis.

Fifteen patients were examined with whole-body FDG-PET prior to and following neoadjuvant therapy. The maximum standard uptake value (SUV max) of tumor and tumor to background ratio (TBR) prior to and following chemotherapy was used for semiquantitative PET imaging analysis. The SUV max of prechemotherapy and post-chemotherapy was recorded as SUV1 and SUV2. TBR1 and TBR2 represented prechemotherapy and post-chemotherapy TBR. TBR was calculated by drawing an identical region of interest over the tumor and the contralateral normal limb or pelvis. Tumor necrosis was classified according to Salzer-Kuntschik's criteria.

Eight patients with more than 90% tumor necrosis were classified as showing good responses and seven patients with less than 90% tumor necrosis as showing poor responses. SUV2/SUV1, TBR2/TBR1, and TBR2 were significantly correlated with the tumor necrosis degree (P < 0.01, P < 0.001, P < 0.001). TBR2/TBR1 were below 0.46 in all the patients with favorable responses, and higher than 0.49 in all the patients with unfavorable responses. However, it was difficult to distinguish good responses from poor responses by SUV2/SUV1.

FDG-PET is a promising tool to assess the chemotherapy response of osteosarcoma noninvasively. The TBR was better than SUV max in evaluating the chemotherapy response in this study.