title: Generalizable class solutions for treatment planning of spinal stereotactic body radiation therapy.
abstract: OBJECTIVE
  Spinal stereotactic body radiation therapy (SBRT) continues to emerge as an effective therapeutic approach to spinal metastases; however, treatment planning and delivery remain resource intensive at many centers, which may hamper efficient implementation in clinical practice. We sought to develop a generalizable class solution approach for spinal SBRT treatment planning that would allow confidence that a given plan provides optimal target coverage, reduce integral dose, and maximize planning efficiency.
  
  
  METHODS
  We examined 91 patients treated with spinal SBRT at our institution. Treatment plans were categorized by lesion location, clinical target volume (CTV) configuration, and dose fractionation scheme, and then analyzed to determine the technically achievable dose gradient. A radial cord expansion was subtracted from the CTV to yield a planning CTV (pCTV) construct for plan evaluation. We reviewed the treatment plans with respect to target coverage, dose gradient, integral dose, conformality, and maximum cord dose to select the best plans and develop a set of class solutions.
  
  
  RESULTS
  The class solution technique generated plans that maintained target coverage and improved conformality (1.2-fold increase in the 95% van't Riet Conformation Number describing the conformality of a reference dose to the target) while reducing normal tissue integral dose (1.3-fold decrease in the volume receiving 4 Gy (V(4Gy)) and machine output (19% monitor unit (MU) reduction). In trials of planning efficiency, the class solution technique reduced treatment planning time by 30% to 60% and MUs required by ∼20%: an effect independent of prior planning experience.
  
  
  CONCLUSIONS
  We have developed a set of class solutions for spinal SBRT that incorporate a pCTV metric for plan evaluation while yielding dosimetrically superior treatment plans with increased planning efficiency. Our technique thus allows for efficient, reproducible, and high-quality spinal SBRT treatment planning.
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA.
authors.forename: David C
authors.initials: DC
authors.lastname: Weksberg
authors.forename: Matthew B
authors.initials: MB
authors.lastname: Palmer
authors.forename: Khoi N
authors.initials: KN
authors.lastname: Vu
authors.forename: Neal C
authors.initials: NC
authors.lastname: Rebueno
authors.forename: Hadley J
authors.initials: HJ
authors.lastname: Sharp
authors.forename: Dershan
authors.initials: D
authors.lastname: Luo
authors.forename: James N
authors.initials: JN
authors.lastname: Yang
authors.forename: Almon S
authors.initials: AS
authors.lastname: Shiu
authors.forename: Laurence D
authors.initials: LD
authors.lastname: Rhines
authors.forename: Mary Frances
authors.initials: MF
authors.lastname: McAleer
authors.forename: Paul D
authors.initials: PD
authors.lastname: Brown
authors.forename: Eric L
authors.initials: EL
authors.lastname: Chang
mesh_terms: D061888:Craniospinal Irradiation / Q000379:methods*; D004526:Efficiency; D006801:Humans; D058958:Organs at Risk; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D015203:Reproducibility of Results; D013125:Spinal Neoplasms / Q000145:classification / Q000473:pathology / Q000532:radiotherapy* / Q000556:secondary; D013131:Spine / Q000033:anatomy & histology; D047368:Tumor Burden