18FDG PET versus high-dose 67Ga scintigraphy for restaging and treatment follow-up of lymphoma patients

Abstract

To date, only one published study has directly compared 67Ga scintigraphy (low dose, planar) with planar dual-head gamma camera 18F-fluorodeoxyglucose (18FDG) imaging for the purpose of treatment follow-up monitoring in lymphoma patients, and no data on restaging are available. The present study reports the direct comparison of high-dose (297-370 MBq) 67Ga planar and single photon emission computed tomography (SPECT) imaging and conventional 18FDG positron emission tomography (PET) for restaging and treatment follow-up of lymphoma patients versus a gold standard consisting of morphological imaging, including plain radiography and computed tomography (CT) scanning, bone marrow examination and long-term follow-up (<12 months). Sixteen patients, 10 with non-Hodgkin's lymphoma and six with Hodgkin's disease, were included (10 men, six women; median age, 43 years; range, 16-64 years). The median follow-up time was 27 months (range, 12-34 months). In two patients, 67Ga and 18FDG PET (370 MBq) were performed twice, resulting in 18 cross-sectional episodes. In 11 episodes, the results obtained by both imaging modalities were in agreement with regard to the presence or absence of disease when compared with the gold standard. However, the abnormalities found on 18FDG PET were always more extensive. In two episodes, 67Ga imaging normalized after treatment, whereas PET showed significant regression followed by subsequent normalization. In four additional episodes, 67Ga images were negative, whereas 18FDG PET visualized non-tumour-related pathology, such as lung infection, rib fracture or dense thymic tissue. In one gold standard-negative patient, the underlying cause of sternal FDG uptake remained undetermined. The data presented, although limited in number, suggest that 18FDG PET performs better than Ga imaging in monitoring lymphoma disease status. However, a correlation with clinical history and a knowledge of the characteristics of benign lesions are mandatory. Further studies are recommended.