title: Optimizing the flattening filter free beam selection in RapidArc®-based stereotactic body radiotherapy for Stage I lung cancer.
abstract: OBJECTIVE
  To optimize the flattening filter-free (FFF) beam selection in stereotactic body radiotherapy (SBRT) treatment for Stage I lung cancer in different fraction schemes.
  
  
  METHODS
  Treatment plans from 12 patients suffering from Stage I lung cancer were designed using the 6XFFF and 10XFFF beams in different fraction schemes of 4 × 12, 3 × 18 and 1 × 34 Gy. Plans were evaluated mainly in terms of organs at risk (OARs) sparing, normal tissue complication probability (NTCP) estimation and treatment efficiency.
  
  
  RESULTS
  Compared with the 10XFFF beam, 6XFFF beam showed statistically significant lower dose to all the OARs investigated. The percentage of NTCP reduction for both lung and chest wall was about 10% in the fraction schemes of 4 × 12 and 3 × 18 Gy, whereas only 7.4% and 2.6% was obtained in the 1 × 34 Gy scheme. For oesophagus, heart and spinal cord, the reduction was greater with the 6XFFF beam, but their absolute estimates were <10(-6)%. The mean beam-on time for 6XFFF and 10XFFF beams at 4 × 12, 3 × 18 and 1 × 34 Gy schemes were 2.2 ± 0.2 vs 1.5 ± 0.1, 3.3 ± 0.9 vs 2.0 ± 0.5 and 6.3 ± 0.9 vs 3.5 ± 0.4 min, respectively.
  
  
  CONCLUSIONS
  The 6XFFF beam obtains better OARs sparing and lower incidence of NTCP in SBRT treatment of Stage I lung cancer, whereas the 10XFFF beam improves the treatment efficiency. To balance the OARs sparing and intrafractional variation owing to the prolonged treatment time, the authors recommend using the 6XFFF beam in the 4 × 12 and 3 × 18 Gy schemes but the 10XFFF beam in the 1 × 34 Gy scheme.
  
  
  CONCLUSIONS
  This study optimizes the FFF beam selection in different fraction schemes in SBRT treatment of Stage I lung cancer.
authors.affiliation: 1 Department of Radiation Oncology, Cancer Hospital of Shantou University Medical College, Shantou, China.
authors.forename: J-Y
authors.initials: JY
authors.lastname: Lu
authors.affiliation: 1 Department of Radiation Oncology, Cancer Hospital of Shantou University Medical College, Shantou, China.
authors.forename: Z
authors.initials: Z
authors.lastname: Lin
authors.affiliation: 2 Department of Nosocomial Infection Management, Second Affiliated Hospital of Shantou University Medical College, Shantou, China.
authors.forename: P-X
authors.initials: PX
authors.lastname: Lin
authors.affiliation: 1 Department of Radiation Oncology, Cancer Hospital of Shantou University Medical College, Shantou, China.
authors.forename: B-T
authors.initials: BT
authors.lastname: Huang
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D058958:Organs at Risk; D011832:Radiation Injuries / Q000517:prevention & control*; D016634:Radiosurgery / Q000009:adverse effects / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000009:adverse effects / Q000379:methods*; D016896:Treatment Outcome