title: Anatomic and metabolic evaluation of peripheral nerve sheath tumors in patients with neurofibromatosis 1 using whole-body MRI and (18)F-FDG PET fusion.
abstract: OBJECTIVE
  Malignant peripheral nerve sheath tumors (MPNSTs) are the leading cause of death for patients with neurofibromatosis type 1 (NF1). Identification of hypermetabolic lesions on PET may help identify patients at risk for MPNST. The objective of this study was to identify clinical and MRI-derived variables that predicted increased metabolic activity of neurofibromas in NF1 patients as determined by PET.
  
  
  METHODS
  This prospective study included NF1 patients with neurofibromas of 5 cm in diameter or greater. All patients underwent whole-body MRI and F-FDG PET imaging. Tumor volume was calculated from the MR scans using a semiautomated 3-dimensional segmentation method. SUVmax's were calculated to quantify metabolic activity. Logistic regression analyses were performed to determine the relationship among SUVmax, tumor volume, location (extremity vs trunk), type (plexiform vs circumscribed), depth (superficial vs deep), patient age, and whole-body tumor burden.
  
  
  RESULTS
  A total of 311 neurofibromas were identified in 19 NF1 patients (mean age, 38 years; range, 19-58 years). One extreme outlier was excluded from analysis. Whole-body tumor volumes ranged from 0.4 to 1182.4 mL. Fifty of 310 tumors were FDG-avid on PET (16%) with median SUVmax of 2.2 (range, 0.4-9.6). Metabolic activity (SUVmax >2.5) correlated with tumor location (deep > superficial, trunk > extremity) in tumors with PET avidity.
  
  
  CONCLUSIONS
  In NF1 patients with neurofibromas of 5 cm or greater, the majority of internal tumors are not metabolically active on PET. Tumors with increased metabolic activity as defined by SUVmax greater than 2.5 (ie, suggestive of MPNST) are more likely to be deep and located within the trunk.
authors.affiliation: From the *Department of Radiology, †Department of Neurology and Cancer Center, ‡Biostatistics Center, Massachusetts General Hospital, Boston, MA; and §Corades, S.L., Madrid, Spain.
authors.forename: Trinity
authors.initials: T
authors.lastname: Urban
authors.forename: Ruth
authors.initials: R
authors.lastname: Lim
authors.forename: Vanessa L
authors.initials: VL
authors.lastname: Merker
authors.forename: Alona
authors.initials: A
authors.lastname: Muzikansky
authors.forename: Gordon J
authors.initials: GJ
authors.lastname: Harris
authors.forename: Ara
authors.initials: A
authors.lastname: Kassarjian
authors.forename: Miriam A
authors.initials: MA
authors.lastname: Bredella
authors.forename: Scott R
authors.initials: SR
authors.lastname: Plotkin
mesh_terms: D000328:Adult; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D018317:Nerve Sheath Neoplasms / Q000150:complications / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000473:pathology*; D009456:Neurofibromatosis 1 / Q000150:complications / Q000000981:diagnostic imaging*; D049268:Positron-Emission Tomography; D051598:Whole Body Imaging; D055815:Young Adult
chemical_list: D019788:Fluorodeoxyglucose F18