Prognostic value of positron emission tomography (PET) with fluorine-18 fluorodeoxyglucose ([F-18]FDG) after first-line chemotherapy in non-Hodgkin'slymphoma: Is [F-18]FDG-PET a valid alternative to conventional diagnostic methods?

Purpose: A complete remission (CR) after first-line therapy is associated w ick longer progression-tree survival (PFS). However, defining CR is not alw ays easy because of the presence of residual masses. Metabolic imaging with fluorine-ll fluorodeoxyglucose ([F-18]FDG) positron emission tomography (P ET) offers the ability to differentiate between viable and fibrotic inactiv e tissue. in this study we evaluated the value of PET in detecting residual disease and, hence, predicting relapse after first-line treatment in patie nts with non-Hodgkin's lymphoma (NHL). Patients and Methods: Ninety-three patients with histologically proven NHL, who underwent a whole-body [F-18]FDG-PET study after completion of first-l ine chemotherapy and who had follow-up of at least 1 year, were included. P ersistence or absence of residual disease on PET was related to PFS using K aplan-Meier survival analysis. Results: Sixty-seven patients showed a normal PET scan after first-line che motherapy; 56 of 67 remained in CR, with a median follow-up of 653 days. Ni ne of these patients with a residual mass considered as unconfirmed CR rece ived additional radiotherapy. Only 11 of 67 patients relapsed (median PFS, 404 days). persistent abnormal [F-18]FDG uptake was seen in 26 patients, an d all of them relapsed (median PFS, 73 days). Because standard restaging al so suggested residual disease, 12 patients received immediate secondary tre atment In 14 of 26 patients, only PET predicted persistent disease. From th ese patients, relapse was proven either by biopsy (n = 8) or by progressive disease on computed tomography or magnetic resonance imaging (n = 6). Conclusion: Persistent abnormal [F-18]FDG uptake after first-line chemother apy in NHL is highly predictive for residual or recurrent disease. In relap sing patients, PFS was significantly shorter after a Positive scan than aft er a negative scan. J Clin Oncol 19:414-419. (C) 2001 by American Society o f Clinical Oncology.