title: Urethra sparing - potential of combined Nickel-Titanium stent and intensity modulated radiation therapy in prostate cancer.
abstract: OBJECTIVE
  To investigate a novel method for sparing urethra in external beam radiotherapy of prostate cancer and to evaluate the efficacy of such a treatment in terms of tumour control using a mathematical model.
  
  
  METHODS
  This theoretical study includes 20 patients previously treated for prostate cancer using external beam radiotherapy. All patients had a Nickel-Titanium (Ni-Ti) stent inserted into the prostate part of urethra. The stent has been used during the treatment course as an internal marker for patient positioning prior to treatment. In this study the stent is used for delineating urethra while intensity modulated radiotherapy was used for lowering dose to urethra. Evaluation of the dose plans were performed using a tumour control probability model based on the concept of uniform equivalent dose.
  
  
  RESULTS
  The feasibility of the urethra dose reduction method is validated and a reduction of about 17% is shown to be possible. Calculations suggest a nearly preserved tumour control probability.
  
  
  CONCLUSIONS
  A new concept for urethra dose reduction is presented. The method relies on the use of a Ni-Ti stent as a fiducial marker combined with intensity modulated radiotherapy. Theoretical calculations suggest preserved tumour control.
authors.affiliation: Department of Medical Physics, Oncology, Aalborg Sygehus, Aarhus University Hospital, Denmark. jabot@rn.dk
authors.forename: Jakob Borup
authors.initials: JB
authors.lastname: Thomsen
authors.forename: Dennis Tideman
authors.initials: DT
authors.lastname: Arp
authors.forename: Jesper
authors.initials: J
authors.lastname: Carl
mesh_terms: D006801:Humans; D008297:Male; D008962:Models, Theoretical; D009532:Nickel; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011829:Radiation Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects*; D015607:Stents; D014025:Titanium; D014521:Urethra / Q000528:radiation effects*
chemical_list: C040654:titanium nickelide; D009532:Nickel; D014025:Titanium