Evaluation of chemotherapy response in osteosarcoma with FDG-PET

The objective of this study is to evaluate the utility of positron emission tomography (PET) with 2-deoxy-[(18)F] fluoro-D-glucose (FDG) in the assessment of the chemotherapy response of osteosarcoma when compared with the degree of necrosis determined histologically.

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 (SUV(1)) and following (SUV(2)) 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.

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). SUV(2) 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 SUV(2) 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)

FDG-PET imaging of osteosarcoma correlates positively with histologic response to neoadjuvant chemotherapy. SUV(2) and SUV(2:1) could be feasible as non-invasive surrogate predictors of response in osteosarcoma patients.