Role of early PET in the management of diffuse large B-cell lymphoma

This article reviews the role of interim fluorine-18-fluorodeoxyglucose (FDG)-PET in the management of aggressive non-Hodgkin lymphoma.

In the diagnosis of diffuse large B-cell lymphoma, FDG-PET has proved to be a highly sensitive imaging modality.

The specificity of 18FDG-PET is improved with the addition of computed tomography (CT) and combined PET/CT is now considered a standard staging procedure for aggressive lymphoma. In addition, residual FDG positivity at the end of therapy is strongly predictive for inferior survival and has been incorporated into revised response criteria for aggressive lymphoma. With the established prognostic value of PET/CT both before and after therapy, interest has now turned to whether interim FDG-PET could be an early indicator of tumor sensitivity. Current clinical trials are now focused on clarifying the role of PET/CT in the early distinction between good and poor responders to standard immunochemotherapy. The interest in such early patient selection assumes that a rapid metabolic response to standard immunochemotherapy predicts a better therapeutic response and survival, and that nonresponders may benefit from an early change in therapy. Preliminary data suggested that interim PET could identify the early presence of such residual disease. However, recent publications are hindered by important variances in patient populations and treatment protocols, the timing and methodology of scans, the reporting criteria used to assess response, and the reproducibility of reporting in accordance with these criteria. Questions remain on the utility of FDG-PET in this indication.