Usefulness of Quantitative Bone Single Photon Emission Computed Tomography/Computed Tomography for Evaluating Response to Neoadjuvant Chemotherapy in a Patient with Periosteal Osteosarcoma

We report here a case of periosteal sarcoma in a 10-year-old female, along with quantitative values obtained with bone single photon emission computed tomography/computed tomography (SPECT/CT), which were useful to evaluate treatment response to preoperative chemotherapy. Pretreatment radiograph images of the lower leg showed cortical thickening eroded by a broad-based soft-tissue mass without the involvement of the underlying cortex, while computed tomography (CT) revealed a small juxtacortical mass with thick calcification and periosteal reaction. In magnetic resonance imaging (MRI), the mass showed hypointensity in the inner part and isointensity in the outer part in T1-weighted images, while the inner part showed hypointensity and the outer part hyperintensity in T2-weighted images. Bone SPECT/CT results indicated the focal and intense uptake of the mass. Following neoadjuvant chemotherapy (NAC), radiograph and MRI results revealed a slight increase in size, with growing calcification. Although visual inspection of the bone SPECT/CT findings showed nearly the same amount of focal uptake, quantitative parameters determined with those findings were decreased, with maximum standardized uptake value (SUV), peak SUV, mean SUV, metabolic bone volume (MBV), and total bone uptake (TBU) reduced by -20.7%, -22.0%, -12.6%, -33.5%, and -41.9%, respectively. The excision biopsy at the surgery showed a pathological grade 1 (non-complete response) after NAC, including a more than 20% of cell necrosis part. The quantitative bone SPECT/CT was considered to reflect treatment response in this case.