Assessment of Chemotherapy Response Using FDG-PET in Pediatric Bone Tumors: A Single Institution Experience

Response to neo-adjuvant chemotherapy is an important prognostic factor for osteosarcoma (OS) and the Ewing sarcoma family of tumors (ESFT). [F-18]-fluorodeoxy-D-glucose (FDG)-positron emission tomography (PET) is a non-invasive imaging modality that predicts histologic response to chemotherapy of various malignancies; however, limited data exist about the usefulness of FDG-PET in predicting the histologic response of pediatric bone tumors to chemotherapy. We analyzed the FDG-PET imaging characteristics of pediatric bone tumors and determined the association with response to chemotherapy.

Pediatric patients with OS (n=19) or ESFT (n=17) were evaluated for FDG-PET standard uptake values before (SUV1) and after (SUV2) chemotherapy. The relationship to the chemotherapy response was assessed by histopathology in surgically-excised tumors. A complete data set (SUV1, SUV2, and histologic response) was available in 23 patients.

While the mean SUV1s were not different between patients with OSs and ESFTs (9.44 vs. 6.07, p=0.24), the SUV2s were greater in the patients with OSs than ESFTs (4.55 vs. 1.66, p=0.01). The ratios of SUV2-to-SUV1 (SUV2 : SUV1) were 0.65 and 0.35 for OS and ESFT, respectively (p=0.08). All of the patients with ESFTs and 47% of the patients with OS had a favorable histologic response to chemotherapy. The SUV(2 : 1) [(SUV1-SUV2)/SUV1]≥0.5 and SUV2≤2.5 were related to favorable histologic responses to chemotherapy; the sensitivity and specificity of SUV(2 : 1) at 0.5 and SUV2 at 2.5 were 93% and 88%, and 88% and 78%, respectively.

FDG-PET can be used as a non-invasive surrogate to predict response to chemotherapy in children with bone tumors.