ABSTRACT
PET enhances staging of lymphoma and is superior to CT scan. It consequently provides more accurate basis for treatment regimens. It provides a better assessment of response to therapy and is the most useful non-invasive modality to differentiate residual tumor from fibrosis/necrosis. Persistent uptake during and after chemotherapy appear to have a high sensitivity in predicting subsequent relapse although some patients may remain in prolonged remission. A negative finding after therapy indicates a very favorable prognosis. We still need better refinement to set off patients who could really benefit from the additional information and better definition of the optimal timing of imaging in clinical practice, The use of early PET response in determining choice of therapy should be utilized with caution until some critical questions are answered. These include: When is the best time to use PET for response assessment? what is the most suitable methodology, visual or quantitative? can early responders be cured with less intensive therapy? will survival be better for patients treated more intensively because they have a poor interim metabolic response?. Further evaluation of alternative PET radiotracers and whether they are superior to FDG and evaluation of the added value of dual FDG-PET acquisition are needed. When PET is not available, Ga-67 imaging of lymphoma can also provide information regarding the presence or absence of active lymphoma particularly in assessing the response to therapy and predicting the outcome.