18FDG positron emission tomography versus 67Ga scintigraphy as prognostic test during chemotherapy for non-Hodgkin's lymphoma

A prospective study was performed, comparing gallium scintigraphy (Ga-67) and positron emission tomography (PET) using fluorine-18 fluorodeoxyglucose ((18)FDG), to monitor the response of aggressive non-Hodgkin's lymphoma during treatment. Ga-67 and (18)FDG scans were performed in 26 patients after two cycles of CHOP (cyclophosphamide, doxorubicin, vincristine, prednisone) therapy. The scans were reviewed independently by four experienced nuclear physicians, who were blinded for the alternative scan technique and follow-up. Eleven out of 26 patients remained free from progression with a mean follow up of 25 +/- 5 months, whereas 14 patients relapsed, and one died of lung cancer. Interobserver variation was significantly greater for Ga-67 than for (18)FDG PET. Some 64% of patients who had a negative early restaging (18)FDG PET remained free from progression versus 50% of patients with negative Ga-67 scans. Only 25% of patients with a positive PET remained disease free versus 42% of Ga-67-positive patients. Time to progression was associated with (18)FDG PET results, but not with those by Ga-67. (18)FDG PET had better test characteristics than Ga-67 for the evaluation of early response in aggressive non-Hodgkin's lymphoma patients.