Assessment of Sorafenib and AntiVEGF Combination Therapy Response which Added to Neoadjuvant Therapy in two Pediatric Metastatic Ewing Sarcoma Patients by Fluorine-18 Fluorodeoxyglucose Positron Emission Tomography (18F-PET) Method: It may Determine the Prognosis

Background: The prognosis is still poor in metastatic Ewing sarcoma (ES) patients. We aimed to assess importance of 18F-PET/CT in 2 pediatric local invasive/ metastatic Ewing sarcoma patients which have been performed antiVEGF and Sorafenib besides their neo-adjuvant and adjuvant chemotherapies (ChT) to improve their prognosis. Response to therapy has been followed by 18F-PET/CT in addition to MR imaging. Patients: First patient was a 12 year-old-girl who was suffering from right leg pain and diagnosed with Ewing sarcoma (ES). 18F-PET/CT showed a locally invasive mass with 14x5 cm dimensions located on one third of proximal tibia with a 5,1 SUVmax value was observed . After 4 cycles of conventional ChT beside antiVEGFSorafenib, SUVmax: 2,1 and tumor necrosis was 80%. Patient received local Radiotherapy (RT) and still in remission after 18 months. Second patient was a 13 year-old-girl who admitted with swelling and pain on right scapula. MR imaging revealed a mass causing deterioration on right scapula and surrounding soft tissue. Diagnosed as ES. PET/CT showed that: primary lesion SUV max 12,4 value, beside another metastatic lesion on left fifth rib with 3,4 SUVmax,confirmed by MRI and biopsi. In addition to conventional neo-adjuvant ChT regimen for ES, antiVEGF and sorafenib were added. There was no 18F-PET/CT involvement during pre-surgical evaluation. Tumor necrosis was %98 and surgical border was tumor negative. Postoperative adjuvant chemotherapy with antiVEGF and sorafenib continued untill end of the treatment protocol. Besides, local RT. Primary region of the tumor and metastatic lesion were still 18F-PET/CT imaging negative, by the enf of the therapy. Patient is still well after 15 months. Conclusion: 18F-PET/CT imaging can predict tumor response to neoadjuvant/adjuvant ChT which includes promising antiVEGF and sorafenib therapies in pediatric ES patients in the manner of the primary tumor necrosis ratio and metastatic evaluations.