title: Radiobiological impact of dose calculation algorithms on biologically optimized IMRT lung stereotactic body radiation therapy plans.
abstract: BACKGROUND
  The aim of this study is to evaluate the radiobiological impact of Acuros XB (AXB) vs. Anisotropic Analytic Algorithm (AAA) dose calculation algorithms in combined dose-volume and biological optimized IMRT plans of SBRT treatments for non-small-cell lung cancer (NSCLC) patients.
  
  
  METHODS
  Twenty eight patients with NSCLC previously treated SBRT were re-planned using Varian Eclipse (V11) with combined dose-volume and biological optimization IMRT sliding window technique. The total dose prescribed to the PTV was 60 Gy with 12 Gy per fraction. The plans were initially optimized using AAA algorithm, and then were recomputed using AXB using the same MUs and MLC files to compare with the dose distribution of the original plans and assess the radiobiological as well as dosimetric impact of the two different dose algorithms. The Poisson Linear-Quadatric (PLQ) and Lyman-Kutcher-Burman (LKB) models were used for estimating the tumor control probability (TCP) and normal tissue complication probability (NTCP), respectively. The influence of the model parameter uncertainties on the TCP differences and the NTCP differences between AAA and AXB plans were studied by applying different sets of published model parameters. Patients were grouped into peripheral and centrally-located tumors to evaluate the impact of tumor location.
  
  
  RESULTS
  PTV dose was lower in the re-calculated AXB plans, as compared to AAA plans. The median differences of PTV(D95%) were 1.7 Gy (range: 0.3, 6.5 Gy) and 1.0 Gy (range: 0.6, 4.4 Gy) for peripheral tumors and centrally-located tumors, respectively. The median differences of PTV(mean) were 0.4 Gy (range: 0.0, 1.9 Gy) and 0.9 Gy (range: 0.0, 4.3 Gy) for peripheral tumors and centrally-located tumors, respectively. TCP was also found lower in AXB-recalculated plans compared with the AAA plans. The median (range) of the TCP differences for 30 month local control were 1.6 % (0.3 %, 5.8 %) for peripheral tumors and 1.3 % (0.5 %, 3.4 %) for centrally located tumors. The lower TCP is associated with the lower PTV coverage in AXB-recalculated plans. No obvious trend was observed between the calculation-resulted TCP differences and tumor size or location. AAA and AXB yield very similar NTCP on lung pneumonitis according to the LKB model estimation in the present study.
  
  
  CONCLUSIONS
  AAA apparently overestimates the PTV dose; the magnitude of resulting difference in calculated TCP was up to 5.8 % in our study. AAA and AXB yield very similar NTCP on lung pneumonitis based on the LKB model parameter sets we used in the present study.
authors.affiliation: Department of Radiation Oncology, University of Arkansas for Medical Sciences, 4301 W. Markham St., #771, Little Rock, AR, USA. liang184@gmail.com.
authors.forename: X
authors.initials: X
authors.lastname: Liang
authors.affiliation: Department of Radiation Oncology, University of Arkansas for Medical Sciences, 4301 W. Markham St., #771, Little Rock, AR, USA. PenagaricanoJoseA@uams.edu.
authors.forename: J
authors.initials: J
authors.lastname: Penagaricano
authors.affiliation: Department of Radiation Oncology, University of Nebraska Medical Center, 42nd and Emile, Omaha, NE, USA. sabrinadan@gmail.com.
authors.forename: D
authors.initials: D
authors.lastname: Zheng
authors.affiliation: Department of Radiation Oncology, University of Arkansas for Medical Sciences, 4301 W. Markham St., #771, Little Rock, AR, USA. SMMorrill@uams.edu.
authors.forename: S
authors.initials: S
authors.lastname: Morrill
authors.affiliation: Department of Radiation Oncology, University of Arkansas for Medical Sciences, 4301 W. Markham St., #771, Little Rock, AR, USA. xzhang2@uams.edu.
authors.forename: X
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of Radiation Oncology, University of Arkansas for Medical Sciences, 4301 W. Markham St., #771, Little Rock, AR, USA. PCorry@uams.edu.
authors.forename: P
authors.initials: P
authors.lastname: Corry
authors.affiliation: Department of Radiation Oncology, University of Arkansas for Medical Sciences, 4301 W. Markham St., #771, Little Rock, AR, USA. RJGriffin@uams.edu.
authors.forename: R J
authors.initials: RJ
authors.lastname: Griffin
authors.affiliation: Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, TX, USA. ehan@mdanderson.org.
authors.forename: E Y
authors.initials: EY
authors.lastname: Han
authors.affiliation: Department of Radiation Oncology, University of Arkansas for Medical Sciences, 4301 W. Markham St., #771, Little Rock, AR, USA. MEHardee@uams.edu.
authors.forename: M
authors.initials: M
authors.lastname: Hardee
authors.affiliation: Department of Radiation Oncology, University of Arkansas for Medical Sciences, 4301 W. Markham St., #771, Little Rock, AR, USA. RatanatharathornVan@uams.edu.
authors.forename: V
authors.initials: V
authors.lastname: Ratanatharathom
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D002289:Carcinoma, Non-Small-Cell Lung / Q000532:radiotherapy*; D019583:Dose Fractionation, Radiation; D005260:Female; D006801:Humans; D016014:Linear Models; D008175:Lung Neoplasms / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D016012:Poisson Distribution; D011336:Probability; D017564:Radiation Pneumonitis / Q000503:physiopathology; D011874:Radiometry; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D014057:Tomography, X-Ray Computed