IN-111 PENTETREOTIDE SCINTIGRAPHY IN MALIGNANT-LYMPHOMAS

Somatostatin receptor imaging (SRI) was car carried out as part of the initial staging of 26 patients with histologically proven Hodgkin's ( 3) and non-Hodgkin's (23) lymphoma, and in the assessment of the first treatment's efficacy in seven of these patients. Static acquisitions over the whole body were performed 4 and 24 h after intravenous admini stration of 150 MBq of indium-111 pentetreotide. SRI data were compare d with the re suits of conventional methods (clinical data, abdominal and thoracic computed tomography, bone marrow biopsy). Only 50 of the 86 (58%) confirmed extra-medullary tumour sites were detected by SRI. Twelve previously unknown localizations were visualized in seven patie nts. The Am Arbor clinical stage was modified in only one of them. Whe n tumoral tracer uptake was present, a tumour uptake index (TUI) was c alculated using two regions of interest (one over the tumoral hot spot and one over the shoulder) on 24-h planar images. The patients were c lassified into three groups: high tumour uptake (TUI>2.5 in all tumour sites, group A, six patients), low tumour uptake (1.5<TUI<2.5 in all tumour sites, group B, 18 patients), and no tumour uptake (group C, tw o patients). The sensitivity of SRI detection was higher in group A (9 0%) than in group B (52%) (P<0.001). Six weeks after the fourth chemot herapy cycle, conventional methods and SRI were concordant in five of seven investigated cases (four complete remissions and one residual ac tive thoracic mass showing tracer uptake), and discordant in two. SRI demonstrated residual tumoral tracer uptake in these two patients, who had previously been considered to be in complete remission. In conclu sion, SRI does not seem to be reliable for the initial staging of lymp homas because of the highly variable and usually low tumoral tracer up take. It may be more useful in the diagnosis of residual masses after treatment. However, further studies are needed to assess its specifici ty.