FDG-PET imaging in hematological malignancies

The majority of aggressive lymphomas is characterized by an up regulated glycolytic activity, which enables the visualization by F-18 FDG-PET/CT. One-stop hybrid FDG-PET/CT combines the functional and morphologic information, outperforming both, CT and FDG-PET as separate imaging modalities. This has resulted in several recommendations using FDG-PET/CT for staging, restaging, monitoring during therapy, and assessment of treatment response as well as identification of malignant transformation. FDG-PET/CT may obviate the need for a bone marrow biopsy in patients with Hodgkin's lymphoma and diffuse large B cell lymphoma. FDG-PET/CT response assessment is recommended for FDG-avid lymphomas, whereas CT-based response evaluation remains important in lymphomas with low or variable FDG avidity. The treatment induced change in metabolic activity allows for assessment of response after completion of therapy as well as prediction of outcome early during therapy. The five-point scale Deauville Criteria allows the assessment of treatment response based on visual FDG-PET analysis. Although the use of FDG-PET/CT for prediction of therapeutic response is promising it should only be conducted in the context of clinical trials. Surveillance FDG-PET/CT after complete remission is discouraged due to the relative high number of false-positive findings, which in turn may result in further unnecessary investigations. Future directions include the use of new PET tracers such as F-18 fluorothymidine (FLT), a surrogate biomarker of cellular proliferation and Ga-68 CXCR4, a chemokine receptor imaging biomarker as well as innovative digital PET/CT and PET/MRI techniques.