Comparison of ^99mTc-MDP Bone Scintigraphy and ¹⁸F-FDG PET/CT to predict histologic response to neoadjuvant chemotherapy in patients with osteosarcoma

Objectives We compared the usefulness of ^99mTc-MDP bone scintigraphy and ¹⁸F-FDG PET/CT in predicting histologic response in patients with osteosarcoma receiving neoadjuvant chemotherapy.

Methods We retrospectively enrolled 62 patients with high-grade osteosarcoma treated with two cycles of neoadjuvant chemotherapy (NAC) and surgery. All patients underwent ^99mTc-MDP bone scintigraphy and ¹⁸F-FDG PET/CT before and after NAC. ^99mTc-MDP uptake of primary tumor was measured quantitatively as the maximum tumor-to-nontumor ratio (T/NT) and ¹⁸F-FDG uptake was measured as the maximum SUV (SUV) before and after NAC. The percent changes of T/NT (%T/NT) and SUV (%SUV) after NAC were calculated respectively, and the correlations between these parameters were evaluated. After surgery, the effects of NAC were graded histopathologically (good vs. poor) and the optimum cut-off values of %T/NT and %SUV for predicting histologic response were assessed by ROC curve analysis respectively.

Results %T/NT and %SUV positively correlated with each other (r = 0.549, p < 0.001). Based on ROC curve analysis, both %T/NT (AUC = 0.768, p < 0.001) and %SUV (AUC = 0.829, p < 0.001) predicted good histologic response. However, there was no significant difference between the AUCs of %T/NT and %SUV (p = 0.373). The sensitivity and specificity for predicting good histologic response were 83.3% and 75.0%, for the criterion of %T/NT < -10% and 80.0% and 81.2%, for the criterion of %SUV < -45%.

Conclusions Both ^99mTc-MDP bone scintigraphy and ¹⁸F-FDG PET/CT are useful for predicting histologic response after NAC in osteosarcoma.

Research Support This work was supported by Establishment of Center for PET Application Technology Development, Korea Institute of Radiological and Medical Sciences (KIRAMS), and by grants from the Ministry of Education, Science and Technology (50441-2015).