Whole-body positron emission tomography using F-18-fluorodeoxyglucose for posttreatment evaluation in Hodgkin's disease and non-Hodgkin's lymphoma has higher diagnostic and prognostic value than classical computed tomographyscan imaging

A residual mass after treatment of lymphoma is a clinical challenge, becaus e it may represent vital tumor as well as tissue fibrosis. Metabolic imagin g by F-18-fluorodeoxyglucose (F-18-FDG) positron emission tomography (PET) offers the advantage of functional tissue characterization that is largely independent of morphologic criteria. We compared F-18-FDG PET to computed t omography (CT) in the posttreatment evaluation of 54 patients with Hodgkin' s disease (HD) or intermediate/high-grade non-Hodgkin's lymphoma (NHL). Res idual masses on CT were observed in 13 of 19 patients with HD and 11 of 35 patients with NHL. Five of 24 patients with residual masses on CT versus 1 of 30 patients without residual masses presented a positive F-18-FDG PET st udy. Relapse occurred in all 6 patients (100%) with a positive F-18-FDG PET , 5 of 19 patients (26%) with residual masses on CT but negative F-18-FDG P ET, and 3 of 29 patients (10%) with negative CT scan and F-18-FDG PET studi es (P less than or equal to .0001). We observed a higher relapse and death rate in patients with residual masses at CT compared with patients without residual masses at CT (progression-free survival at 1 year: 62 +/- 10 v 88 +/- 7%, P = .0045; overall survival at 1 year: 77 +/- 5 v 95 +/- 5%, P = .0 038), A positive F-18-FDG PET study was even more consistently associated w ith poorer survival: compared with patients with a negative F-18-FDG PET st udy, the 1-year progression-free survival was 0% versus 86% +/- 5% (P < .00 01) and the 1-year overall survival was 50% +/- 20% versus 92% +/- 4% (P < .0001), The detection of vital tumor by F-18-FDG PET after the end of treat ment has a higher predictive value for relapse than classical CT scan imagi ng (positive predictive value: 100% v 42%). This could help identify patien ts requiring intensification immediately after completion of chemotherapy. However, F-18-FDG PET mainly predicts for early progression but cannot excl ude the presence of minimal residual disease, possibly leading to a later r elapse. (C) 1999 by The American Society of Hematology.