title: NTCP modeling analysis of acute hematologic toxicity in whole pelvic radiation therapy for gynecologic malignancies - A dosimetric comparison of IMRT and spot-scanning proton therapy (SSPT).
abstract: OBJECTIVE
  This treatment planning study was conducted to determine whether spot scanning proton beam therapy (SSPT) reduces the risk of grade ⩾3 hematologic toxicity (HT3+) compared with intensity modulated radiation therapy (IMRT) for postoperative whole pelvic radiation therapy (WPRT).
  
  
  METHODS
  The normal tissue complication probability (NTCP) of the risk of HT3+ was used as an in silico surrogate marker in this analysis. IMRT and SSPT plans were created for 13 gynecologic malignancy patients who had received hysterectomies. The IMRT plans were generated using the 7-fields step and shoot technique. The SSPT plans were generated using anterior-posterior field with single field optimization. Using the relative biological effectives (RBE) value of 1.0 for IMRT and 1.1 for SSPT, the prescribed dose was 45Gy(RBE) in 1.8Gy(RBE) per fractions for 95% of the planning target volume (PTV). The homogeneity index (HI) and the conformity index (CI) of the PTV were also compared.
  
  
  RESULTS
  The bone marrow (BM) and femoral head doses using SSPT were significantly lower than with IMRT. The NTCP modeling analysis showed that the risk of HT3+ using SSPT was significantly lower than with IMRT (NTCP=0.04±0.01 and 0.19±0.03, p=0.0002, respectively). There were no significant differences in the CI and HI of the PTV between IMRT and SSPT (CI=0.97±0.01 and 0.96±0.02, p=0.3177, and HI=1.24±0.11 and 1.27±0.05, p=0.8473, respectively).
  
  
  CONCLUSIONS
  The SSPT achieves significant reductions in the dose to BM without compromising target coverage, compared with IMRT. The NTCP value for HT3+ in SSPT was significantly lower than in IMRT.
authors: Proton Beam Therapy Center, Hokkaido University Hospital, Sapporo, Japan; Department of Radiation Medicine, Graduate School of Medicine, Hokkaido University, Sapporo, Japan.
authors: Takaaki
authors: T
authors: Yoshimura
authors: Department of Radiation Oncology, Hokkaido University Hospital, Sapporo, Japan. Electronic address: rumiko0220@pop.med.hokudai.ac.jp.
authors: Rumiko
authors: R
authors: Kinoshita
authors: Department of Radiation Medicine, Graduate School of Medicine, Hokkaido University, Sapporo, Japan.
authors: Shunsuke
authors: S
authors: Onodera
authors: Proton Beam Therapy Center, Hokkaido University Hospital, Sapporo, Japan.
authors: Chie
authors: C
authors: Toramatsu
authors: Department of Medical Physics, Hokkaido University Hospital, Sapporo, Japan.
authors: Ryusuke
authors: R
authors: Suzuki
authors: Department of Biostatistics, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
authors: Yoichi M
authors: YM
authors: Ito
authors: Proton Beam Therapy Center, Hokkaido University Hospital, Sapporo, Japan.
authors: Seishin
authors: S
authors: Takao
authors: Proton Beam Therapy Center, Hokkaido University Hospital, Sapporo, Japan; Global Station for Quantum Medical Science and Engineering, Global Institution for Collaborative Research and Education (GI-CoRE), Hokkaido University, Sapporo, Japan; Division of Quantum Science and Engineering, Faculty of Engineering, Hokkaido University, Sapporo, Japan.
authors: Taeko
authors: T
authors: Matsuura
authors: Proton Beam Therapy Center, Hokkaido University Hospital, Sapporo, Japan.
authors: Yuka
authors: Y
authors: Matsuzaki
authors: Proton Beam Therapy Center, Hokkaido University Hospital, Sapporo, Japan; Division of Quantum Science and Engineering, Faculty of Engineering, Hokkaido University, Sapporo, Japan.
authors: Kikuo
authors: K
authors: Umegaki
authors: Department of Radiation Medicine, Graduate School of Medicine, Hokkaido University, Sapporo, Japan; Global Station for Quantum Medical Science and Engineering, Global Institution for Collaborative Research and Education (GI-CoRE), Hokkaido University, Sapporo, Japan.
authors: Hiroki
authors: H
authors: Shirato
authors: Global Station for Quantum Medical Science and Engineering, Global Institution for Collaborative Research and Education (GI-CoRE), Hokkaido University, Sapporo, Japan; Department of Radiation Oncology, Graduate School of Medicine, Hokkaido University, Sapporo, Japan.
authors: Shinichi
authors: S
authors: Shimizu
mesh_terms: D001853:Bone Marrow / Q000528:radiation effects; D005260:Female; D005270:Femur Head / Q000528:radiation effects; D005833:Genital Neoplasms, Female / Q000150:complications / Q000532:radiotherapy*; D006402:Hematologic Diseases / Q000209:etiology*; D006801:Humans; D008962:Models, Theoretical; D009364:Neoplasm Recurrence, Local; D058958:Organs at Risk; D010388:Pelvis / Q000528:radiation effects*; D011336:Probability; D061766:Proton Therapy / Q000009:adverse effects* / Q000379:methods*; D011832:Radiation Injuries; D011874:Radiometry / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects* / Q000379:methods*; D014057:Tomography, X-Ray Computed
keywords: LKB-NTCP model analysis; Spot-scanning proton therapy; Treatment planning study; Whole pelvic radiation therapy