title: Stereotactic ablative body radiation therapy with dynamic conformal multiple arc therapy for liver tumors: optimal isodose line fitting to the planning target volume.
abstract: OBJECTIVE
  To assess optimal relative prescribed dose values in stereotactic ablative body radiation therapy (SABR) using dynamic conformal multiple arc therapy (DCMAT) for liver tumors.
  
  
  METHODS
  We generated SABR plans for 8 typical liver tumors that received SABR with 50 Gy in 5 fractions. The prescribed dose had previously been defined as 80% of the maximal dose ("80% isodose plan"). Alternatively, 20%-90% isodose plans were created to compare dosimetric factors.
  
  
  RESULTS
  The mean liver volume values (%) that received >20 Gy (V20) and the mean liver dose were both the lowest with a 70% isodose plan and were the second lowest with a 60% isodose plan. The V20 dose was 5.19% lower (11.14%) with a 70% isodose plan and 4.51% lower (11.22%) with a 60% isodose plan compared with the value with an 80% isodose plan (11.75%). Mean planning target volume (PTV) dose increased as the % isodose decreased. The mean PTV dose was 10% higher (62.4 Gy) with a 70% isodose plan and 21% higher (68.9 Gy) with a 60% isodose plan compared with the value with an 80% isodose plan (56.8 Gy).
  
  
  CONCLUSIONS
  During SABR treatment planning using DCMAT for liver tumors, target doses increased as the percentage isodose value decreased, which could result in better outcomes. In contrast, a 70% isodose plan had the lowest normal liver dose and a 60% isodose plan had the second lowest. An optimal percentage isodose level might be adjusted depending on tumor radiation sensitivity and liver function reserve. Further investigation is warranted to determine whether these dosimetric advantages result in improved outcomes.
authors.affiliation: Radiation Oncology Center, Ofuna Chuo Hospital, Kanagawa, Japan.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Oku
authors.affiliation: Radiation Oncology Center, Ofuna Chuo Hospital, Kanagawa, Japan.
authors.forename: Atsuya
authors.initials: A
authors.lastname: Takeda
authors.affiliation: Radiation Oncology Center, Ofuna Chuo Hospital, Kanagawa, Japan.
authors.forename: Naoko
authors.initials: N
authors.lastname: Sanuki
authors.affiliation: Radiation Oncology Center, Ofuna Chuo Hospital, Kanagawa, Japan.
authors.forename: Yasunobu
authors.initials: Y
authors.lastname: Sudo
authors.affiliation: Radiation Oncology Center, Ofuna Chuo Hospital, Kanagawa, Japan.
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Oooka
authors.affiliation: Radiation Oncology Center, Ofuna Chuo Hospital, Kanagawa, Japan.
authors.forename: Yousuke
authors.initials: Y
authors.lastname: Aoki
authors.affiliation: Radiation Oncology Center, Ofuna Chuo Hospital, Kanagawa, Japan.
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Shimouchi
authors.affiliation: Radiation Oncology Center, Ofuna Chuo Hospital, Kanagawa, Japan.
authors.forename: Ryohei
authors.initials: R
authors.lastname: Nishina
authors.affiliation: Radiation Oncology Center, Ofuna Chuo Hospital, Kanagawa, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Nomura
authors.affiliation: Radiation Oncology Center, Ofuna Chuo Hospital, Kanagawa, Japan.
authors.forename: Takahisa
authors.initials: T
authors.lastname: Eriguchi
authors.affiliation: Department of Radiation Oncology, Tokai University, Kanawaga, Japan. Electronic address: kunieda-mi@umin.ac.jp.
authors.forename: Etsuo
authors.initials: E
authors.lastname: Kunieda
mesh_terms: D019583:Dose Fractionation, Radiation; D006801:Humans; D008113:Liver Neoplasms / Q000601:surgery*; D011874:Radiometry / Q000379:methods; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods; D012189:Retrospective Studies