Purpose: The existing literature of 18 F-FDG PET/CT in Ewing sarcoma investigates populations of patients with both soft tissue and bone primary tumors. The aim of our study was to evaluate whether 18 F-FDG PET/CT using the maximum standardized uptake value (SUV (max)) before and after initiation of chemotherapy, can be used as an indicator of survival in patients with Ewing sarcoma originating only in bone.
Materials and Methods: A retrospective database search was conducted from 2004 - 2011 and 178 patients with pathologically proven bone primary Ewing sarcoma were identified. Patients who received treatment before the initial PET/CT or underwent PET/CT at other institutions were excluded. Twenty-nine patients underwent 18 F-FDG PET/CT before and after starting chemotherapy at our institution. The study included 10 females and 19 males, with a median age of 18 years. One patient was excluded from the analysis due to partial tumor resection before the initial PET/CT. Median follow up time for patients alive was 6.2 years (range: 2.6-9.8 years). Univariate Cox proportional hazard model was used to assess effects of baseline SUV (max), post-chemo SUV (max), and the change of SUV (max) on overall survival (OS) and progression-free survival (PFS).
Results: Median SUV (max) was 8.9 for baseline and 3.2 post chemotherapy. A high SUV (max) before (HR = 1.05, 95% CI: 1.0-1.1, P = 0.01) and after (HR =1.2, 95% CI: 1.0-1.4, P = 0.01) chemotherapy was associated with worse overall survival. Optimal cut points SUVmax higher than 11.55 before chemotherapy was associated with worse overall survival and progression free survival. Baseline SUVmax higher than 11.55 had significantly worse OS (HR = 5.71, 95% CI: 1.85 – 17.61, p-value = 0.003) and PFS (HR = 3.16, 95% CI: 1.13 – 8.79, p-value = 0.03) compared to those with lower SUVmax. No significant post chemotherapy cut points for SUV (max) were identified.
Conclusion: Baseline and post chemotherapy SUV (max) can be used as a prognostic indicator for overall survival in bone primary Ewing sarcoma.