title: The usefulness of (18)F-FDG PET/CT for assessing methotrexate-associated lymphoproliferative disorder (MTX-LPD).
abstract: Methotrexate-associated lymphoproliferative disorder (MTX-LPD) is a benign lymphoid proliferation or malignant lymphoma in patients who have been treated with MTX. MTX withdrawal and observation for a short period should be considered in the initial management of patients who develop LPD while on MTX therapy. Here we evaluated the diagnostic accuracy and predictive value of (18)F-fluorodeoxyglucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) for MTX-LPD.
  
  
  
  We retrospectively investigated the cases of 15 patients clinically suspected of having MTX-LPD. A total of 324 anatomic regions (207 nodal and 117 extranodal regions) were assessed by (18)F-FDG PET/CT and by multi-detector row CT (MDCT). Each anatomic region was classified as either malignant or benign. The uptake of (18)F-FDG was assessed semi-quantitatively with the standardized uptake value maximum (SUVmax), the whole-body metabolic tumor volume (WBMTV), and the whole-body total lesion glycolysis (WBTLG) in order to investigate predictive factors of spontaneous regression after the withdrawal of MTX.
  
  
  
  MTX-LPD lesions were observed in 92/324 (28.4 %) regions. (18)F-FDG PET/CT showed 90.2 % sensitivity, 97.4 % specificity, and 95.4 % accuracy, values which were significantly higher than those of MDCT (59.8, 94.8, and 84.9 %, respectively. p < 0.002). After the withdrawal of MTX, 9/15 patients (60.0 %) achieved complete response (CR). The SUVmax, WBMTV and WBTLG values of the CR patients were 9.2 (range 2.8-47.1), 44.3 (range 0-362.6) ml, 181.8 (range 0-2180.9) ml, respectively, which were not significantly different from those of the non-CR patients: 10.6 (range 0-24.9), 15.7 (range 0-250.1) ml, and 97.4 (range 0-1052.1) ml.
  
  
  
  Although (18)F-FDG PET/CT was a useful tool to detect MTX-LPD lesions, none of the (18)F-FDG PET parameters before the withdrawal of MTX could be used to predict CR after the withdrawal of MTX.
authors.affiliation: Department of Nuclear Medicine, Hokkaido University Graduate School of Medicine, N15 W7, Kita-Ku, Sapporo, 0608638, Hokkaido, Japan.
authors.forename: Shiro
authors.initials: S
authors.lastname: Watanabe
authors.affiliation: Department of Nuclear Medicine, Hokkaido University Graduate School of Medicine, N15 W7, Kita-Ku, Sapporo, 0608638, Hokkaido, Japan. osamumanabe817@med.hokudai.ac.jp.
authors.forename: Osamu
authors.initials: O
authors.lastname: Manabe
authors.affiliation: Department of Nuclear Medicine, Hokkaido University Graduate School of Medicine, N15 W7, Kita-Ku, Sapporo, 0608638, Hokkaido, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Hirata
authors.affiliation: Department of Diagnostic and Interventional Radiology, Hokkaido University Graduate School of Medicine, N15 W7, Kita-Ku, Sapporo, 0608638, Hokkaido, Japan.
authors.forename: Noriko
authors.initials: N
authors.lastname: Oyama-Manabe
authors.affiliation: Department of Nuclear Medicine, Hokkaido University Graduate School of Medicine, N15 W7, Kita-Ku, Sapporo, 0608638, Hokkaido, Japan.
authors.forename: Naoya
authors.initials: N
authors.lastname: Hattori
authors.affiliation: Department of Diagnostic and Interventional Radiology, Hokkaido University Graduate School of Medicine, N15 W7, Kita-Ku, Sapporo, 0608638, Hokkaido, Japan.
authors.forename: Yasuka
authors.initials: Y
authors.lastname: Kikuchi
authors.affiliation: Department of Nuclear Medicine, Hokkaido University Graduate School of Medicine, N15 W7, Kita-Ku, Sapporo, 0608638, Hokkaido, Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Kobayashi
authors.affiliation: Department of Nuclear Medicine, Hokkaido University Graduate School of Medicine, N15 W7, Kita-Ku, Sapporo, 0608638, Hokkaido, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Toyonaga
authors.affiliation: Department of Nuclear Medicine, Hokkaido University Graduate School of Medicine, N15 W7, Kita-Ku, Sapporo, 0608638, Hokkaido, Japan.
authors.forename: Nagara
authors.initials: N
authors.lastname: Tamaki
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000378:metabolism*; D006019:Glycolysis; D006801:Humans; D008232:Lymphoproliferative Disorders / Q000139:chemically induced / Q000000981:diagnostic imaging* / Q000378:metabolism; D008297:Male; D008727:Methotrexate / Q000009:adverse effects*; D008875:Middle Aged; D000072078:Positron Emission Tomography Computed Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000378:metabolism*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods; D047368:Tumor Burden
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D008727:Methotrexate
keywords: FDG; Metabolic tumor volume; Methotrexate-associated lymphoproliferative disorder; PET; Total lesion glycolysis