title: Clinical value of [¹¹C]methionine PET for stereotactic radiation therapy with intensity modulated radiation therapy to metastatic brain tumors.
abstract: OBJECTIVE
  This study investigated the clinical impact of (11)C-labeled methionine-positron emission tomography (MET-PET) for stereotactic radiation therapy with intensity modulated radiation therapy (SRT-IMRT) in metastatic brain tumors.
  
  
  METHODS
  Forty-two metastatic brain tumors were examined. All tumors were treated with SRT-IMRT using a helical tomotherapy system. Gross tumor volume (GTV) was defined and drawn on the stereotactic magnetic resonance (MR) image, taking into account the respective contributions of MR imaging and MET-PET. Planning target volume (PTV) encompassed the GTV-PET plus a 2-mm margin. SRT-IMRT was performed, keeping the dose for PTV at 25-35 Gy in 5 fractions. The ratio of the mean value of MET uptake to the contralateral normal brain (L/N ratio) was plotted for the PTV prior to SRT-IMRT, at 3 months following SRT-IMRT, and at 6 months following SRT-IMRT. Tumor characteristic changes of MET uptake before and after SRT-IMRT were evaluated quantitatively, comparing them with MRI examination.
  
  
  RESULTS
  Mean ± SD L/N ratios were 1.95 ± 0.83, 1.18 ± 0.21, and 1.12 ± 0.25 in the pre-SRT-IMRT group, in the 3 months post-SRT-IMRT group, and in the 6 months post-SRT-IMRT group, respectively. Differences in the mean L/N ratio between the pre-SRT-IMRT group and the 3-month post-SRT-IMRT group and between the pre-SRT-IMRT group and the 6 month post-SRT-IMRT group were statistically significant, irrespective of MRI examination.
  
  
  CONCLUSIONS
  We showed examples of metastatic lesions demonstrating significant decreases in MET uptake following SRT-IMRT. MET-PET seems to have a potential role in providing additional information, although MRI remains the gold standard for diagnosis and follow-up after SRT-IMRT. The present study is a preliminary approach, but to more clearly define the impact of PET-based radiosurgical assessment, further experimental and clinical analyses are required.
authors.affiliation: Chubu Medical Center for Prolonged Traumatic Brain Dysfunction, Kizawa Memorial Hospital, Minokamo, Gifu, Japan. doctor.3@jasmine.ocn.ne.jp
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Miwa
authors.forename: Masayuki
authors.initials: M
authors.lastname: Matsuo
authors.forename: Jun
authors.initials: J
authors.lastname: Shinoda
authors.forename: Tatsuki
authors.initials: T
authors.lastname: Aki
authors.forename: Shingo
authors.initials: S
authors.lastname: Yonezawa
authors.forename: Takeshi
authors.initials: T
authors.lastname: Ito
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Asano
authors.forename: Mikito
authors.initials: M
authors.lastname: Yamada
authors.forename: Kazutoshi
authors.initials: K
authors.lastname: Yokoyama
authors.forename: Jitsuhiro
authors.initials: J
authors.lastname: Yamada
authors.forename: Hirohito
authors.initials: H
authors.lastname: Yano
authors.forename: Toru
authors.initials: T
authors.lastname: Iwama
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000000981:diagnostic imaging / Q000378:metabolism; D001932:Brain Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology / Q000556:secondary* / Q000628:therapy; D002250:Carbon Radioisotopes / Q000493:pharmacokinetics; D003131:Combined Modality Therapy / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008715:Methionine / Q000493:pharmacokinetics; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods*; D016634:Radiosurgery / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D047368:Tumor Burden
chemical_list: D002250:Carbon Radioisotopes; D008715:Methionine