Integrated FDG-PET/CT for detection, therapy monitoring and follow-up of granulocytic sarcoma. Initial results.

AIM

Granulocytic sarcomas (GS) are rare extramedullary manifestations of myeloid or lymphoblastic leukaemia. Laboratory examinations are of limited use for diagnosis of extramedullary disease. Radiological imaging based on morphology is challenging. To date, the possible role of FDG-PET/CT as a method for combined metabolic and morphologic imaging is unclear. We present a series of 10 patients to evaluate the potential role of FDG-PET/CT in the management of GS.

PATIENTS, MATERIALS, METHODS: A retrospective evaluation of 18 FDG-PET/CT exams in 10 patients with histologically proven GS was performed. All scans included a contrast enhanced CT. The FDG uptake of GS was analyzed and the sensitivity of lesion detection was compared to PET and CT alone. The changes in FDG uptake after therapy were compared to morphological changes detected by CT and follow-up / clinical outcome.

RESULTS

52 untreated or recurrent GS lesions were detected by FDG-PET/CT and all showed an increased FDG uptake with a mean SUVmax and SUVavg of 5.1 and 3.4, respectively. GS was multifocal in 8/10 patients. Combined PET/CT avoided 5 false positive findings compared to PET alone and 13 false negative findings and 1 false positive compared to CT alone. Changes in FDG uptake after therapy correlated with clinical outcome and were more reliable than CT assessment alone. PET/CT identified recurrent GS in 3 patients.

CONCLUSION

Viable GS are FDG-avid. Using this metabolic information and morphologic CT criteria, combined FDG-PET/CT was more accurate in lesion detection than FDG-PET or CT alone. Changes in FDG uptake after therapy might be a useful additional parameter for therapy monitoring. Therefore, FDG-PET/CT appears to be a promising diagnostic and monitoring tool in the management of patients with GS.