POSITRON-EMISSION-TOMOGRAPHY IN NON-HODGKINS-LYMPHOMA - ASSESSMENT OFCHEMOTHERAPY WITH FLUORODEOXYGLUCOSE

Positron emission tomography (PET) using F-18 fluorodeoxyglucose (FDG) was performed in non-Hodgkin's lymphoma (NHL), which is known to be h ighly responsive to chemotherapy, but also yields variable treatment r esults to answer the following questions: (1) What is the extent and t ime course of changes in FDG utilization in response to chemotherapy? (2) Are the changes of FDG uptake at early time points of chemotherapy predictive for therapy outcome? (3) Which quantitative FDG parameter provides the most sensitive measures of initial tumor response? Dynami c PET scans were performed in 11 patients at baseline and 1 and 6 week s after initiation of chemotherapy. Based on attenuation corrected ima ges acquired 30 to 60 minutes postinjection, standardized uptake value s (SUV) were determined. Arterial input functions were estimated from vascular F-18 activity and the metabolic rates for FDG (MRFDG) were ca lculated using Patlak analysis. Before chemotherapy, high FDG uptake w as found in all lesions (SUV[max] 13.3 +/- 4.2). Seven days after init iation of chemotherapy, tumor FDG uptake decreased 60% (SUV[max]). A f urther decrease of 42% was seen at day 42 resulting in a total decreas e of 79% from baseline to day 42. During a follow up of 16.0 +/- 4.2 m onths, six of the 11 patients continued to show complete remission. Se ven days after initiation of chemotherapy, this group of patients disp layed significantly lower mean MRFDG than the group of patients with r elapse. At day 42, all parameters of FDG uptake showed a significant d ifference for both patient groups. The relative change of MRFDG from b aseline to day 42, as well as from day 7 to day 42, was significantly larger as compared with SUV parameters. Standard chemotherapy of patie nts with NHL causes rapid decrease of tumor FDG uptake as early as 7 d ays after treatment, which continues to decline during therapy, indica ting the sensitivity of metabolic signals to chemotherapeutic interven tions. FDG uptake at 42 days after therapy was superior in prediction of long-term outcome over day 7 parameters. Dynamic data acquisition c ombined with Patlak analysis of FDG kinetics may provide superior info rmation in therapy monitoring. (C) 1998 by The American Society of Hem atology.