Role of F-18 FDG PET/CT in response assessment of Ewing's sarcoma family of tumors

Objectives To determine the role of F-18 FDG PET/CT in response assessment of Ewing`s sarcoma family of tumors (ESFT).

Methods 37 patients (30 males & 7 females,age range 3-45 years, median age 20 years) of histopathologically proven ESFT were assessed by serial PET/CT.Findings reveal 17 (45.9%) cases of stage II, 1(2%) of stage III & 19(51.3%) of stage IV tumors.Response was assessed by PERCIST criteria after therapy (surgery /chemotherapy and or radiotherapy). Data was interpreted by qualitative and semiquantitative (standardized uptake value-SUVmax) methods.PET/CT represents a non invasive means of estimating histological tumor grade and can be used to detect response prior to anatomical imaging. Resolution of metabolic activity was used as the marker of response.Correlative imaging, clinical follow up upto 1 year and/or biopsy results whenever available were used as the reference standard.

Results PET/CT showed response (CMR+PMR) in 21 cases.17/21 patients were considered to have true positive results based on the reference standard while false positive in 4.Total 16 patients were non-responders & PET/CT was considered false negative in 1 case.SUVmax of primary lesion ranged from 2.5 to 19.3 with mean SUVmax of 6.0.Sensitivity, specificity, positive predictive value, negative predictive value & accuracy of F-18FDG PET/CT were were 94.4%,78.9%,80.9%,93.7% and 86.4% respectively.

Conclusions F-18FDG PET/CT may be a strong valuable tool in response assessment of ESFT.This study suggest the need of a large prospective study with serial evaluations and pathological correlations

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Response assessment in ESFT

Table showing response assessed by PET/CT and comparison with reference standards