title: 11C-methionine-PET for evaluation of carbon ion radiotherapy in patients with pelvic recurrence of rectal cancer.
abstract: OBJECTIVE
  Progress of the novel carbon ion radiotherapy (CIRT) in the treatment of cancers has created the need for a method to accurately evaluate the response. We investigated whether L-[11C]methyl-methionine (11C-methionine) uptake at pre- and post-CIRT could be an early response predictor in patients with pelvic recurrence of rectal cancer.
  
  
  METHODS
  11C-Methionine-positron emission tomography (PET) was performed prospectively in 53 patients with pelvic recurrence of rectal cancer before CIRT, and 48 patients were performed 11C-methionine PET at 1 month after CIRT. 11C-Methionine tumor uptake was measured by the tumor to muscle ratio (T/M ratio). The T/M ratios were evaluated in relation to clinical outcomes such as local re-recurrence, distant metastasis, and survival. The response to CIRT was also judged by computed tomography (CT) and magnetic resonance imaging (MRI). 11C-Methionine PET judgment was compared with CT/MRI judgment regarding the relevance to clinical outcome.
  
  
  RESULTS
  Baseline T/M ratio was 5.27+/-1.90 (mean+/-SD) in patients without developing local re-recurrence and 7.66+/-3.17 in patients with local re-recurrence (p=0.023, Mann-Whitney U test). Post-CIRT T/M ratios were 3.10+/-1.28 in patients without local re-recurrence and 6.15+/-2.98 in patients with local re-recurrence (p=0.006, Mann-Whitney U test). By Kaplan-Meier analysis with log-rank test, patients with a baseline T/M ratio of <or=7.6 or a post-CIRT T/M ratio of <or=5.0 had significant lower pelvic re-recurrence rate. However, the percent change (reduction rate) from baseline to post-CIRT T/M ratio did not have significant relation to pelvic re-recurrence. There were no significant differences between 11C-methionine results (baseline T/M ratio, post-CIRT T/M ratio and percent change) and other clinical parameters (distant metastasis and survival).
  
  
  CONCLUSIONS
  11C-methionine-PET can be used for early prediction of local re-recurrence after CIRT. Because CIRT is local therapy, (11)C-methionine-PET cannot predict distant metastasis or survival after CIRT.
authors.affiliation: Diagnostic Imaging, Molecular Imaging Center, National Institute of Radiological Sciences, Anagawa 4-9-1, Inageku, Chiba, Japan. mitsuru@nirs.go.jp
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Koizumi
authors.forename: Tsuneo
authors.initials: T
authors.lastname: Saga
authors.forename: Kyosan
authors.initials: K
authors.lastname: Yoshikawa
authors.forename: Kazutoshi
authors.initials: K
authors.lastname: Suzuki
authors.forename: Shigeru
authors.initials: S
authors.lastname: Yamada
authors.forename: Mitsuhiko
authors.initials: M
authors.lastname: Hasebe
authors.forename: Seiya
authors.initials: S
authors.lastname: Ohashi
authors.forename: Sherif
authors.initials: S
authors.lastname: Abd-Elrazek
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ishikawa
authors.forename: Kenji
authors.initials: K
authors.lastname: Sagou
authors.forename: Katsumi
authors.initials: K
authors.lastname: Tamura
authors.forename: Ryusuke
authors.initials: R
authors.lastname: Hara
authors.forename: Hirotoshi
authors.initials: H
authors.lastname: Kato
authors.forename: Shigeo
authors.initials: S
authors.lastname: Yasuda
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yanagi
authors.forename: Hirohiko
authors.initials: H
authors.lastname: Tsujii
mesh_terms: D000230:Adenocarcinoma / Q000000981:diagnostic imaging / Q000532:radiotherapy / Q000556:secondary; D000328:Adult; D000368:Aged; D002250:Carbon Radioisotopes / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D008297:Male; D008715:Methionine; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000000981:diagnostic imaging*; D010386:Pelvic Neoplasms / Q000000981:diagnostic imaging; D049268:Positron-Emission Tomography / Q000379:methods*; D011379:Prognosis; D011446:Prospective Studies; D019275:Radiopharmaceuticals; D012004:Rectal Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*
chemical_list: D002250:Carbon Radioisotopes; D019275:Radiopharmaceuticals; D008715:Methionine