Prognostic value of pre-treatment 18F-FDG PET/CT in pediatric bone sarcomas

Objectives The aim is to prospectively assess the prognostic value of pre-treatment FDG PET/CT in pediatric bone sarcomas.

Methods Twenty-seven consecutive patients (16M/11F) aged 3.8 to 17.9 y.o (mean 12.6, SD ± 3.4) presenting with primitive malignant bone sarcoma (n=18 Osteosarcoma and n=9 Ewing Sarcoma), were followed over more than 5 years. All patients underwent pre-treatment FDG PET/CT scan, bone scintigraphy, chest CT and MRI; followed by a post-neo-adjuvant-chemotherapy PET/CT scan before surgery (n=24). Histological response was assessed using Huvos classification.

Results Primary tumor uptake was significantly higher in Osteosarcoma (mean SUVmax 9.4) than in Ewing sarcoma (mean SUVmax 6.0)(p=0.05). Twelve patients had distant metastasis: 7 pts had solely lung metastasis, 2 pts had solely bone metastasis, 2 pts had bone and lung metastasis and 1 pt had lung and lymph node metastasis. Skip metastasis was found in 2 pts with Osteosarcoma. After surgery, based on Huvos histological response (>90% necrosis), 7/18 pts with Osteosarcoma and 6/9 pts with Ewing Sarcoma were classified as good responders. Overall survival at 5 years was higher for Osteosarcoma (72% of pts) than Ewing Sarcoma (44% of pts) (p=ns). For the whole pediatric group, initial FDG uptake in primary site was correlated with overall survival (OS) (p=0.035) and progression free survival (PFS) (p=0.06). Similar data were found in the Osteosarcoma sub-group for OS (p=0.012) and PFS (p=0.078); no correlation was found for the Ewing group. Post-chemotherapy residual uptake in primary site did not show any significant correlation with OS, PFS or histology. Although certain trend suggest higher SUVmax cut-off for Osteosarcoma, and lower for Ewing sarcoma, when correlated with pathology.

Conclusions Pre-treatment PET/CT appears to be an interesting tool for the prognostic value of pediatric bone sarcomas, in light with histological response and follow up. Promising correlations with post-chemotherapy data need to be confirmed in larger studies.