title: Clinical value of ¹¹C-methionine PET/CT in patients with plasma cell malignancy: comparison with ¹⁸F-FDG PET/CT.
abstract: OBJECTIVE
  PET/CT using FDG has been widely used for the imaging of various malignant tumours, including plasma cell malignancy (PCM), but (11)C-methionine (MET), as a radiolabelled amino acid tracer, may also be useful because PCM is able to activate protein synthesis. The purpose of this study was to evaluate the clinical value of PET/CT imaging using MET in PCM, including multiple myeloma, compared with that of FDG PET/CT.
  
  
  METHODS
  The study group comprised 20 patients with histologically proven PCM who underwent FDG PET/CT and MET PET/CT scans before (n = 6) or after (n = 14) treatment. Semiquantitative analysis was performed on a lesion basis. We also visually evaluated the scans qualitatively using a five-point scale (0, negative; 1, probably negative; 2, equivocal; 3, probably positive; 4, positive) on a lesion and a patient basis. The results were compared between the two scans.
  
  
  RESULTS
  Active PCM was confirmed in 15 patients, including two patients with extramedullary lesions. Uptake of MET tended to be higher (maximum standardized uptake value 10.3 ± 5.6, mean ± SD) than that of FDG (3.4 ± 2.7, p < 0.001), and more lesions of grade 3 or 4 were depicted by MET (MET 156 lesions vs. FDG 58 lesions). On a patient basis, two patients were accurately diagnosed only by MET. In the remaining 18 patients, consistent results were obtained, but potential upgrade of staging or restaging was necessary in 6 of 11 positive patients because more abnormal lesions were demonstrated by MET. The patient-based sensitivity, specificity and accuracy of MET for restaging were 89 %, 100 % and 93 %, respectively, while those of FDG were 78 %, 100 % and 86 %, respectively.
  
  
  CONCLUSIONS
  MET revealed an equal or greater number of lesions in PCM than FDG. MET may be especially useful when negative or inconclusive findings are obtained by FDG despite highly suspicious indications of recurrence.
authors: Department of Diagnostic Imaging and Nuclear Medicine, Kyoto University Graduate School of Medicine, 54 Shogoinkawahara-cho, Sakyo-Ku, Kyoto 606-8507, Japan. ynakamo1@kuhp.kyoto-u.ac.jp
authors: Yuji
authors: Y
authors: Nakamoto
authors: Kensuke
authors: K
authors: Kurihara
authors: Masatoshi
authors: M
authors: Nishizawa
authors: Kouhei
authors: K
authors: Yamashita
authors: Koya
authors: K
authors: Nakatani
authors: Tadakazu
authors: T
authors: Kondo
authors: Akifumi
authors: A
authors: Takaori-Kondo
authors: Kaori
authors: K
authors: Togashi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008715:Methionine; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods*; D054219:Neoplasms, Plasma Cell / Q000000981:diagnostic imaging*; D049268:Positron-Emission Tomography; D014057:Tomography, X-Ray Computed
chemical_list: D019788:Fluorodeoxyglucose F18; C086242:carbon-11 methionine; D008715:Methionine