FDG PET and risk-adapted therapy in Hodgkin's and non-Hodgkin's lymphoma

PURPOSE OF REVIEW: The prognostic utility of midtreatment fluorine-18 fluorodeoxyglucose positron emission tomography (F-FDG PET) has become widely appreciated in aggressive B-cell non-Hodgkin's lymphoma and, more recently, in Hodgkin's lymphoma. Outcomes based on midtreatment FDG PET performed during primary and salvage therapy are reviewed and management strategies considered, with a focus on treatment intensification for poor-risk disease as identified by metabolic imaging. RECENT FINDINGS: PET, when performed after as few as two cycles of primary chemotherapy, is strongly prognostic in certain aggressive lymphomas and provides information independently from validated prognostic indices. What constitutes a positive or negative scan is not always clear, particularly if there is minimal tracer uptake, and the causes of false positive and false negative scans must be considered. How to tailor therapy based on the midtreatment PET result is the focus of current trials and is presently being defined for both Hodgkin's and non-Hodgkin's lymphoma. SUMMARY: Early PET has the strong potential to improve clinical outcomes by sparing good-risk patients from overly aggressive treatments, and by more accurately identifying poor-risk patients so as to guide changes in management. Treatment modifications on the basis of midtreatment PET are presently best made in clinical trial settings.