MP 5 Sleep: from symptoms to substrate

Abstract

<b>1684</b> <b>Objectives</b>: The 18F-FDG uptake in lymphoma patients is correlated with histologic grade and proliferative activity. Only limited and conflicting data have been published about the role of FDG PET in low-grade lymphoma. Low-grade lymphoma could be missed by PET alone due to low FDG avidity and could be missed by CT alone due to malignancy involving normal size lymph nodes. The aim of this study was to compare accuracies of unenhanced CT vs. FDG-PET, vs. PET/CT in patients with low-grade lymphoma. <b>Methods</b>: True Whole-Body FDG-PET/CT scans, covering from the top of skull to the bottom of the feet, of 10 patients with biopsy proven low-grade lymphoma were retrospectively reviewed. Images were acquired on a Gemini PET/CT scanner (Phillips Medical Systems) 60 minutes after an intravenous injection of a weight-adjusted dose of 0.14 mCi/kg FDG with a maximum dose of 14 mCi. Unenhanced CT, FDG-PET and PET/CT images were independently and separately interpreted by qualified readers (a board-certified CT radiologist and a board-certified Nuclear Medicine physician) who were unaware of the clinical history. Certainty of lesion characterization was scored on a 5-point scale (0 = definitely benign, 1 = probably benign, 2 = equivocal, 3 = probably malignant, 4 = definitely malignant). The presence or absence of low-grade lymphoma was subsequently assessed using all available clinical, pathologic, and follow-up information. <b>Results</b>: Of these 10 patients (4 F, 6 M; mean age: 55 yr), 7 were diagnosed with follicular lymphoma (3-Grade 3, 1- Grade 2, 2-Grade 1 and 1-unknown grade) and 3 with marginal zone lymphoma.).The frequency of equivocal and probable lesion characterization was reduced by 10% with PET/CT in comparison with CT and by 10% in comparison with PET. The frequency of definite lesion characterization increased by 40% for PET/CT compared to CT and by 30% compared to PET. <b>Conclusions</b>: We continue to accrue data; however, our initial experience showed that FDG-PET/CT is superior in staging/restaging patients with low-grade lymphoma compared to unenhanced CT or PET alone. More definitely normal and definitely abnormal lesions (and fewer probable and equivocal lesions) were identified by PET/CT than with unenhanced CT or PET alone. In low-grade lymphoma, combined PET/CT reading correctly identified low FDG avid lesions (potentially missed by PET alone) as well as malignancy involving normal size lymph nodes (potentially missed by CT alone). Therefore, we conclude that PET/CT should be the standard of care imaging modality in patients with low-grade lymphoma.