FDG-PET/CT in lymphoma

Molecular Imaging has played a prominent role in the assessment of lymphoma for now almost three decades since the introduction of (67)Ga-citrate imaging for staging and restaging of both Hodgkin's and non-Hodgkin's lymphoma (HL and NHL). Since then other molecular probes have been investigated for more accurate pre- and posttreatment assessment of lymphomas but none of these probes was widely accepted and utilized until the emergence of (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET). FDG-PET or FDG-PET/CT, which combines FDG-PET with CT scanning, is now widely utilized for response assessment of lymphoma after completion of therapy, for pretreatment staging, and, increasingly, also for assessment of response during therapy (therapy monitoring). Particularly for response assessment at therapy conclusion, FDG-PET has been shown to be considerably more accurate than CT or conventional MRI because of its ability to distinguish between viable tumor and necrosis or fibrosis in posttherapy residual mass (es) that are frequently present in patients with lymphoma without any other clinical or biochemical evidence of disease. FDG-PET/CT is therefore the noninvasive modality of choice for response classifications of HL and aggressive NHLs consistent with the recently revised, primarily FDG-PET/CT-based, response criteria for lymphoma. This review will highlight the most important applications of FDG-PET (FDG-PET/CT) in lymphoma emphasizing the strengths and pitfalls of this imaging approach, past and ongoing efforts to standardize the use of FDG-PET, particularly in response assessment and therapy monitoring. Other promising molecular probes for lymphoma imaging will also be briefly discussed.