title: Radiobiologically based treatment plan evaluation for prostate seed implants.
abstract: OBJECTIVE
  Accurate prostate low dose-rate brachytherapy treatment plan evaluation is important for future care decisions. Presently, an evaluation is based on dosimetric quantifiers for the tumor and organs at risk. However, these do not account for effects of varying dose-rate, tumor repopulation and other biological effects. In this work, incorporation of the biological response is used to obtain more clinically relevant treatment plan evaluation.
  
  
  METHODS
  Eleven patients were evaluated. Each patient received a 145 Gy implant. Iodine-125 seeds were used and the treatment plans were created on the Prowess system. Based on CT images the post-implant plan was created. In the post-plan, the tumor, urethra, bladder and rectum were contoured. The biologically effective dose was used to determine the tumor control probability and the normal tissue complication probabilities for the urethra, bladder, rectum and surrounding tissue.
  
  
  RESULTS
  The average tumor control probability and complication probabilities for the urethra, bladder, rectum and surrounding tissue were 99%, 29%, 0%, 12% and 6%, respectively. These measures provide a simpler means for evaluation and since they include radiobiological factors, they provide more reliable estimation of the treatment outcome.
  
  
  CONCLUSIONS
  The goal of this work was to create more clinically relevant prostate seed-implant evaluation by incorporating radiobiological measures. This resulted in a simpler descriptor of treatment plan quality and was consistent with patient outcomes.
authors.affiliation: Department of Radiation Oncology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.
authors.forename: Courtney
authors.initials: C
authors.lastname: Knaup
authors.affiliation: Department of Medical Radiation Physics, Karolinska Institutet & Stockholm University, Stockholm, Sweden.
authors.forename: Panayiotis
authors.initials: P
authors.lastname: Mavroidis
authors.affiliation: Department of Radiation Oncology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.
authors.forename: Carlos
authors.initials: C
authors.lastname: Esquivel
authors.affiliation: Department of Medical Physics & Engineering, Strahlenklinik, Klinikum Offenbach GmbH, Germany.
authors.forename: Dimos
authors.initials: D
authors.lastname: Baltas
authors.affiliation: Department of Radiation Oncology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.
authors.forename: Sotirios
authors.initials: S
authors.lastname: Stathakis
authors.affiliation: Department of Radiation Oncology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.
authors.forename: Gregory
authors.initials: G
authors.lastname: Swanson
authors.affiliation: Department of Radiation Oncology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.
authors.forename: Nikos
authors.initials: N
authors.lastname: Papanikolaou
keywords: LDR; prostate; radiobiology; treatment plan