Prognostic significance of positron emission tomography using fluorine-18-fluorodeoxyglucose in patients treated for malignant lymphoma

Aim: To evaluate the prognostic significance of positron emission tomograph y (PET) using fluorine-18-[2]-fluoro-2-deoxyglucose (FDG) in patients treat ed for Hodgkin's disease (HD) or non-Hodgkin's lymphoma (NHL) compared to c onventional restaging (CRS). Methods: Fifty-six patients with either HD (n = 22), high-grade NHL (n = 26) or centrocytic-centroblastic NHL (n = 8) wer e included. PET was performed in 41 patients for treatment reevaluation up to three months after therapy and in patients with persisting residual moss es (n = 10) or suspected relapse (n = 5) four to twelve months after treatm ent. The scans were evaluated qualitatively and quantitatively using standa rdised uptake values (SUV). Progression-free survival (PFS) was estimated t o assess the prognostic value of FDG PET and clinical follow-up was token a s gold standard. Results: PET was positive in nineteen of 41 patients studi ed for treatment reevaluation. Progression was observed after a median inte rval of two months (range 0-15) in sixteen of 19 patients after a positive PET scan and in three of 22 patients after a negative scan (p <.001). Media n duration of follow-up in progression-free patients was 21 months (range 6 -72). In patients with a partial remission in CRS progression was more comm on in PET-positive than in PET-negative patients (5 of 7 vs. 1 of 14; p <.0 1) and positivity with PET was associated with poorer PFS (p <.0025). PET s tudies performed four to twelve months after treatment were true negative i n seven, true positive in five and false-positive in three patients. SUV >1 1.35 of lymphoma lesions was associated with poorer PFS than SUV <11.35 (p <0.025). Conclusion: We conclude that FDG PET after treatment of malignant lymphoma has a high prognostic value ond should be recommended in patients with persistence of residual mosses.