The Incremental Value of F-18 FDG PET and PET/CT in Malignant Lymphoma

F-18 FDG positron emission tomography (PET) is able to diagnose viable lymphoma tissue due to its elevated glucose metabolism, independent of the size of the lesions. For staging purposes, the value of FDG PET in Hodgkin’s (HL) and high-grade non-Hodgkin lymphoma (NHL) lies predominantly in a change of tumour stage with the consequence of a modification of therapeutic regimen and a more exact definition of radiotherapy (RTX) planning volume. In indolent lymphoma, a pre-therapeutic scan is mandatory for further therapy monitoring due to variable FDG-uptake. In restaging HL and NHL, discrimination between viable residual lymphoma and necrosis in case of a residual bulk is possible with FDG PET, which is limited by conventional methods. PET/CT combines the advantages of PET and CT and performs better than each method alone by further improving the accuracy of staging and response assessment over that of CT alone. There are a lower proportion of equivocal or benign findings because PET-CT specifies the nature of uptake. Some studies have demonstrated the possibility of therapy monitoring, but further prospective studies have to be performed before therapy may be avoided or modified according to the results of the PET/CT examination.