Interim FDG-PET Imaging in Lymphoma

In the present article, the authors reviewed the rationale of FDG-PET/CT performed at an interim time point during therapy (iPET), focusing on the transition from standard, anatomical assessment of tumor shrinkage with CT to document a chemotherapy response, to the use of functional imaging with PET to assess chemosensitivity of the individual tumor. The prognostic or predictive role of iPET in different lymphoma subsets has been reviewed, with particular emphasis on early and advanced-stage Hodgkin lymphoma, diffuse large B-cell lymphoma, peripheral T-cell lymphoma, extranodal natural killer/T-cell lymphoma, and primary mediastinal B-cell lymphoma. A large body of evidence exists in most lymphoma subtypes stressing the role of iPET for early chemotherapy response during first-line chemotherapy treatment, but an increased number of reports have recently been published focusing on the role of iPET in relapsed or refractory lymphoma to predict treatment outcome. Varying patterns of FDG uptake was observed across various lymphoma entities; hence, interpretation of FDG-PET scans should be in the context of the tumor architecture and the prevalence of cellular population, in particular, neoplastic vs non-neoplastic inflammatory cells present in tissue microenvironment. In the second part of the article, the authors reviewed the iPET-response adapted clinical trials and the clinical benefits of this strategy compared to standard non-PET adapted therapy. In particular, the authors extrapolated the reproducibility of FDG-PET image interpretation and the feasibility of a timely treatment adaptation based on FDG-PET results in daily clinical practice. This is essential for the reader, as the iPET-adapted strategy has become the standard of care in both early- and advanced-stage Hodgkin lymphoma, and, in the future, probably this strategy will be expanded to primary mediastinal B-cell lymphoma, follicular lymphoma, and peripheral T-cell lymphoma.