title: In vivo radiobiological characterization of proton beam at the National Cancer Center in Korea: effect of the Chk2 mutation.
abstract: OBJECTIVE
  The relative biological effectiveness (RBE) in the presence or absence of CHK2 was estimated at the Korean National Cancer Center Proton Therapy Center (NCCPTC).
  
  
  METHODS
  The proton beam was fixed at 210 MeV with 6-cm spread-out Bragg peaks (SOBPs) because this is expected to be the most frequently used clinical setting. X-rays were obtained using a 6-MV conventional linear accelerator. The RBE was estimated from the survival of jejunal crypt in C3H/He and Chk2(-/-) mice.
  
  
  RESULTS
  The estimated RBEs of the NCCPTC at the middle of the SOBP were 1.10 and 1.05 in the presence and absence of CHK2, respectively. The doses that reduced the number of regenerated crypt per jejunal circumference to 20 (D(20)) in C3H/He mice were 14.8 Gy (95% confidence interval [CI], 13.7-15.9) for X-rays and 13.5 Gy (95% CI, 14.5-15.5) for protons. By contrast, the doses of D(20) in Chk2(-/-) mice were 15.7 Gy (95% CI, 15.0-16.4) and 14.9 Gy (95% CI, 14.0-15.8) for X-rays and protons, respectively.
  
  
  CONCLUSIONS
  The RBE of the NCCPTC is clearly within the range of RBEs determined at other facilities and is consistent with the generic RBE value of 1.10 for 150- to 250-MeV beams. The mutation of Chk2 gave rise to radioresistance but exhibited similar RBE.
authors.affiliation: Radiation Medicine Branch, National Cancer Center, Goyang, Korea.
authors.forename: Sang Soo
authors.initials: SS
authors.lastname: Kim
authors.forename: Dong Wan
authors.initials: DW
authors.lastname: Choo
authors.forename: Dongho
authors.initials: D
authors.lastname: Shin
authors.forename: Hye Jung
authors.initials: HJ
authors.lastname: Baek
authors.forename: Tae Hyun
authors.initials: TH
authors.lastname: Kim
authors.forename: Noboru
authors.initials: N
authors.lastname: Motoyama
authors.forename: Blanche M
authors.initials: BM
authors.lastname: De Coster
authors.forename: John
authors.initials: J
authors.lastname: Gueulette
authors.forename: Yoshiya
authors.initials: Y
authors.lastname: Furusawa
authors.forename: Koichi
authors.initials: K
authors.lastname: Ando
authors.forename: Kwan Ho
authors.initials: KH
authors.lastname: Cho
mesh_terms: D058739:Aberrant Crypt Foci / Q000235:genetics / Q000532:radiotherapy; D000818:Animals; D002173:Cancer Care Facilities; D064447:Checkpoint Kinase 2; D016001:Confidence Intervals; D004307:Dose-Response Relationship, Radiation; D005260:Female; D007583:Jejunum / Q000502:physiology / Q000528:radiation effects*; D051379:Mice; D008809:Mice, Inbred C3H; D009154:Mutation; D010315:Particle Accelerators; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism; D061766:Proton Therapy; D011829:Radiation Dosage; D011836:Radiation Tolerance / Q000235:genetics; D012038:Regeneration; D012062:Relative Biological Effectiveness; D056910:Republic of Korea; D014916:Whole-Body Irradiation / Q000379:methods
chemical_list: D064447:Checkpoint Kinase 2; C578633:Chek2 protein, mouse; D017346:Protein Serine-Threonine Kinases