Evaluation of chemotherapy response in osteosarcoma with FDG-PET

Objective  The objective of this study is to evaluate the utility of positron emission tomography (PET) with 2-deoxy-¹⁸F] fl uoro-D-glucose (FDG) in the assessment of the chemotherapy response of osteosarcoma when compared with the degree of necrosis determined histologically. Methods  Whole-body FDG-PET scan was performed on 11 patients with osteosarcoma. All patients received neoadjuvant chemotherapy. The tumor size changes on magnetic resonance imaging; FDG-PET standardized uptake values prior to (SUV₁) and following (SUV₂) chemotherapy were analyzed and correlated with response to chemotherapy as assessed using histopathology in surgically excised tumors. Nine patients underwent FDG-PET scan both prior to and following neoadjuvant chemotherapy. The remaining two patients were examined only prior to surgery. Results  Histologically, five patients had a good histologic response to chemotherapy (≧90% necrosis). The changes in tumor size did not correlate with histologic response (P > 0.05). SUV₂ with good response was significantly lower than that with poor response (1.93 ± 0.50, 5.86 ± 2.55, respectively). Both the positive and negative predictive values of the SUV₂ of less than 2.5 for a good response were 100%. Patients with good response showed a significantly higher ratio of SUV2 to SUV1 (SUV_2:1) than patients with poor response (0.74 ± 0.11, 0.26 ± 0.39, respectively, P < 0.05). The positive and negative predictive values of SUV_2:1 ≤ 0.5 for good and poor responses were 80% and 100%, respectively. Conclusions  FDG-PET imaging of osteosarcoma correlates positively with histologic response to neoadjuvant chemotherapy. SUV₂ and SUV_2:1 could be feasible as non-invasive surrogate predictors of response in osteosarcoma patients.