title: Tryptophan PET in pretreatment delineation of newly-diagnosed gliomas: MRI and histopathologic correlates.
abstract: Pretreatment delineation of infiltrating glioma volume remains suboptimal with current neuroimaging techniques. Gadolinium-enhanced T1-weighted (T1-Gad) MR images often underestimate the true extent of the tumor, while T2-weighted images preferentially highlight peritumoral edema. Accumulation of α-[(11)C]methyl-L-tryptophan (AMT) on positron emission tomography (PET) has been shown in gliomas. To determine whether increased uptake on AMT-PET would detect tumor-infiltrated brain tissue outside the contrast-enhancing region and differentiate it from peritumoral vasogenic edema, volumes and spatial concordance of T1-Gad and T2 MRI abnormalities as well as AMT-PET abnormalities were analyzed in 28 patients with newly-diagnosed WHO grade II-IV gliomas. AMT-accumulating grade I meningiomas were used to define an AMT uptake cutoff threshold that detects the tumor but excludes peri-meningioma vasogenic edema. Tumor infiltration in AMT-accumulating areas was studied in stereotactically-resected specimens from patients with glioblastoma. In the 28 gliomas, mean AMT-PET-defined tumor volumes were greater than the contrast-enhancing volume, but smaller than T2 abnormalities. Volume of AMT-accumulating tissue outside MRI abnormalities increased with higher tumor proliferative index and was the largest in glioblastomas. Tumor infiltration was confirmed by histopathology from AMT-positive regions outside contrast-enhancing glioblastoma mass, while no or minimal tumor cells were found in AMT-negative specimens. These results demonstrate that increased AMT accumulation on PET detects glioma-infiltrated brain tissue extending beyond the contrast-enhanced tumor mass. While tryptophan uptake is low in peritumoral vasogenic edema, AMT-PET can detect tumor-infiltrated brain outside T2-lesions. Thus, AMT-PET may assist pretreatment delineation of tumor infiltration, particularly in high-grade gliomas.
authors.affiliation: PET Center and Translational Imaging Laboratory, Children's Hospital of Michigan, Detroit, MI, USA.
authors.forename: David O
authors.initials: DO
authors.lastname: Kamson
authors.forename: Csaba
authors.initials: C
authors.lastname: Juhász
authors.forename: Amy
authors.initials: A
authors.lastname: Buth
authors.forename: William J
authors.initials: WJ
authors.lastname: Kupsky
authors.forename: Geoffrey R
authors.initials: GR
authors.lastname: Barger
authors.forename: Pulak K
authors.initials: PK
authors.lastname: Chakraborty
authors.forename: Otto
authors.initials: O
authors.lastname: Muzik
authors.forename: Sandeep
authors.initials: S
authors.lastname: Mittal
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000000981:diagnostic imaging* / Q000473:pathology*; D001932:Brain Neoplasms / Q000175:diagnosis*; D002247:Carbon Isotopes; D005260:Female; D005682:Gadolinium; D005910:Glioma / Q000175:diagnosis*; D006801:Humans; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D018709:Statistics, Nonparametric; D014364:Tryptophan; D055815:Young Adult
chemical_list: D002247:Carbon Isotopes; D014364:Tryptophan; D005682:Gadolinium