Interim- and posttreatment response to neoadjuvant chemotherapy assessed by F-18 FDG PET/CT can predict the outcome in osteosarcoma of the extremities

Purpose: We assessed whether sequential F-18 FDG PET/CT (PET/CT) could predict the outcome of patients with osteosarcoma of the extremities after one cycle and two cycles of neoadjevant chemotherapy. Methods: A total of 73 patients with American Joint Committee on Cancer (AJCC) stage II extremity osteosarcoma treated with two cycles of neoadjuvant chemotherapy, surgery and adjuvant chemotherapy were prospectively enrolled in this study. All patients underwent PET/CT before (PET1), after one cycle (PET2), and after the completion of neoadjuvant chemotherapy (PET2), respectively. PET parameters (maximum standardized uptake value [SUVmax], metabolic tumor volume [MTV], and total lesion glycolysis [TLG]) and their % changes were calculated, and histological responses were evaluated after surgery. ROC curve analyses and the Cox proportional hazards model were used to analyze whether imaging and clinicopathologic parameters could predict event (metastasis or local recurrence)-free survival. Results: A total of 36 patients (49%) exhibited a poor histologic response and 17 patients (23%) had experienced events (metastasis in 16 and local recurrence in 1). Both on PET2 and PET3, the % change of SUVmax most accurately predicted events by ROC curve analysis (area under the curve = 0.667 for PET1 and 0.685 for PET2, respectively). By multivariate analysis including the % changes of SUVmax on PET2, PET2, histologic response, age, sex and AJCC stage (A or B), only the % change of SUVmax on PET3 > -54% independently shortened event-free survival (relative risk, 6.39; 95% confidence interval, 1.45-28.10). Patients with the % change of SUVmax on PET3 > -54% had worse 3-y (72% vs. 93%) and 5-y (67% vs. 93%) metastasis-free survival rates than the others (P = 0.005). Conclusion: The % changes of SUVmax both on PET2 and PET3 could predict the outcome of patients with osteosarcoma of the extremities. The % changes of SUVmax on PET3 better predicted the outcome than histologic response.