Positron emission tomography with fluorine-18-2-fluoro-2-deoxy-D-glucose (F18-FDG) does not visualize extranodal B-cell lymphoma of the mucosa-associated lymphoid tissue (MALT)-type

Background: On the basis of promising data on the use of fluorine-18-2-fluo ro-2-deoxy-D-glucose (F18-FDG) whole body positron emission tomography (WB- FDG-PET) in the staging of patients with lymphoma, we initiated a pilot ser ies to evaluate the role of WB-FDG-PET in the staging of extranodal B-cell lymphoma of the mucosa-associated lymphoid tissue (MALT) type. Patients and methods: We examined ten consecutive patients with histologica lly-verified MALT-type lymphomas of various origin before initiation of the rapy. Nine patients had low-grade lymphomas (five cases of gastric lymphoma , two patients with lymphoma arising in the lung, one parotid and one lacri mal gland lymphoma), while one patient had a high-grade gastric lymphoma ar ising from a low-grade background. Two patients had stage EI, seven had sta ge EII disease, and one presented with stage EIII. WB-FDG-PET scans were pe rformed 40 min following the injection of 300-380 MBq of F18-FDG. The PET s cans were correlated with extensive conventional staging including ophthalm ologic investigation, otolaryngologic examination, gastroscopy, endosonogra phy, enteroclysis, colonoscopy, CT of thorax and abdomen, and bone marrow b iopsy. Results: WB-FDG-PET documented no lymphoma in any of the 10 patients studie d, as no focal tracer uptake was demonstrated in either gastric or extragas tric lesions or in involved lymph nodes, irrespective of histologic grading . In three patients the scan showed a false negative result with respect to the MALT lesions but showed focal tracer uptake indicating tumor spread, w hich, however, was ruled out by further follow-up and biopsy, respectively, and was thus rated false positive. Due to these results, the study was dis continued prematurely after the first ten patients. Conclusions: These discouraging results indicated that WB-FDG-PET is not us eful for staging and follow-up of MALT-type lymphoma, and should therefore not be included in the clinical decision making process.