Clinical relevance of gallium-67 scintigraphy in lymphoma before and aftertherapy

The clinical impact of gallium-67 scintigraphy before and after therapy for lymphoma remains controversial. The aims of this study were: (1) to compar e the staging of lymphoma by Ga-67 scintigraphy only with staging by clinic al examination and conventional imaging (CI), and (2) to analyse the clinic al relevance of both Ga-67 imaging and CT after treatment. From March 1995 to November 1998, 86 Ga-67 scintigraphy studies were performed in 62 patien ts with Hodgkin's disease (n=52) or non-Hodgkin's lymphoma (n=10). Ga-67 sc intigraphy was performed at diagnosis (n=44) or after therapy (n=42) using 185-220 MBq Ga-67 citrate and planar and single-photon emission tomography (SPET) studies. Treatment comprised radiotherapy, chemotherapy or combined modalities. CI included plain chest radiography, computed tomography (CT) o f the chest and abdomen/pelvis, ultrasound of the abdomen, lymphography. bo ne marrow biopsy and, when necessary, magnetic resonance imaging (MRI) and bone scintigraphy. For individual suspected sites of disease before treatme nt, complete agreement between clinical examination and CI on the one hand and Ga-67 scintigraphy on the other hand was observed in 25/44 patients (57 %: 95% confidence interval 41%-72%). Clinical examination and CI showed mor e sites than did Ga-67 scintigraphy in 12/44 patients (27%) and Ga-67 imagi ng demonstrated more sites than CI in 6/44 patients (11%). The clinical sta ge of the dis ease as assessed using Ga-67 scintigraphy only was in agreeme nt with that using all diagnostic procedures in 34/44 patients (77%, 95% co nfidence interval 62%-89%). Compared with CI staging, Ga-67 scintigraphy do wnstaged seven patients (16%) and upstaged three (7%). Ga-67 scintigraphy d ownstaged mainly because of the limited value of the technique below the di aphragm and upstaged owing to the good sensitivity in the lung. Alter thera py, both CI and Ga-67 scintigraphy were normal in 11 patients. All but one of these patients were in complete remission after a median follow-up of 31 months. In contrast, radiological residual mass was observed in 31/42 pati ents, Ga-67 imaging was normal in 22/31 (71%); 17 of these 22 patients, inc luding nine with a large residual mass (greater than or equal to 2 cm), wer e in complete remission after a median follow-up of 32 months, while four s uffered relapses 8-45 months later. The cause of death remained unknown in one patient. Ga-67 scintigraphy showed abnormal uptake in 9 of the 31 patie nts with a large residual mass, Active disease was demonstrated in eight pa tients and one patient was in complete remission 30 months thereafter. Our data show that Ga-67 imaging cannot replace CI in initial staging but can d emonstrate additional individual sites of disease in more than 10% of patie nts and can lead to clinical upstaging with potential prognostic and therap eutic consequences. After therapy, Ga-67 scintigraphy has a clinical impact when radiological abnormalities persist because it can either avoid unnece ssary complementary treatment or confirm the need to change treatment modal ities.