The use of FDG-PET/CT for detection and therapy monitoring of granulocytic sarcoma: Initial results

1686 Objectives Granulocytic sarcomas (GS) are rare extramedullary manifestations of myeloid leukemia. Diagnosis and monitoring of extramedullary disease is often impossible with routine clinical and laboratory examinations and imaging of GS based on morphology is challenging. The potential role of combined functional and morphologic imaging with FDG-PET/CT to date is unclear. We present first results of the use of FDG-PET/CT in the management of GS. Methods Retrospective analysis of 18 FDG-PET/CT studies in 10 patients with histologically proven GS. The results of FDG-PET/CT were compared with histology, additional imaging including the integrated contrast enhanced CT and clinical follow-up. Results FDG-PET/CT detected 52 GS. All GS showed an increased FDG-uptake with a mean SUVmax and SUVavg of 5.1 and 3.4. GS was multifocal in 8/10 patients. In 5 of 10 patients FDG-PET/CT detected previously unknown manifestations. These were interpreted as benign, did not have a pathologic correlation in CT or were located outside the field of view of prior examinations. The detection of additional manifestations of GS changed the therapeutic regimen from local irradiation to systemic chemotherapy in one patient. Changes in FDG-uptake after therapy correlated with the clinical outcome in all 5 patients with examinations before and after chemotherapy. In all 3 patients with follow-up examinations recurrent GS was detected by FDG-PET/CT. Conclusions FDG-PET/CT can detect untreated and recurrent GS by its increased FDG-uptake and had a higher detection rate than CT alone. Changes in FDG-uptake correlated with the response to treatment. Therefore FDG-PET/CT is a promising diagnostic tool for the management of patients with GS.