Aim: To evaluate the role of 18F-FDG-positron emission tomography (PET) in the staging and restaging of follicular lymphoma (FL). PET appears to be highly sensitive and specific in the high-grade lymphoma, by contrast its usefulness in FL has not been clearly defined. Methods: 127 PET scans were performed in 100 patients with FL in a retrospective study. Pathological PET-activity and standard computer tomography (CT) staging were compared in 56 patients before treatment. In the frame of restaging PET was performed in 71 patients (87 % treated by conventional therapy). Progression free survivals (PFS) of PET-positive and PET-negative patients were compared. Results: in comparison with CT and clinical examination, PET identified larger involvement in 30/56 patients, smaller in 7/56 and the same extension of FL was found in 15/56 patients. 4 patients revealed discordant foci visible only on PET and simultaneous lymphadenopathy on CT without PET activity (p<0,001). 15 patients with larger involvement by PET were essentially upstaged (from stage 0-2 to 3-4). Including the results of trephine biopsy the stage was substantially changed in 13/56 (23 %) patients. 56/71 patients were PET-negative after the treatment, 9 (16%) relapsed in median 10 months, 47 remained in remission at median follow-up of 19 months. 11/71 patients were PET-positive after the treatment, 9 (82 %) relapsed in median of 6 months. All of 4/71 patients with undetermined PET-positivity (SUV ±2,0) are in long-term remission at median follow-up of 39 months. PFS of the PET-negative patients was significantly longer in comparison with the PET-positive patients (p<0,001). Conclusion: PET may contribute to the management of follicular lymphoma patients. PET in the staging can substantially change the treatment strategy. PET-positivity after the treatment predicts high risk of early relapse and can identify patients with poor prognosis

        Key words: 18F-FDG-PET, follicular lymphoma, grading, staging, prognosis