title: Clinical implementation of dynamic and step-and-shoot IMRT to treat prostate cancer with high risk of pelvic lymph node involvement.
abstract: OBJECTIVE
  Two systems have been developed for treating patients with locally advanced prostate cancer using intensity-modulated radiotherapy (IMRT): one using dynamic multi-leaf collimator delivery and the other using step-and-shoot. This paper describes the clinical implementation of these two techniques, and presents results from the first 14 patients treated in a clinical setting (nine dynamic, five step-and-shoot).
  
  
  METHODS
  Dynamic treatments were planned using Corvus, and step-and-shoot using Helax-TMS; all were delivered using Elekta accelerators. Prior to the first clinical treatments, validation measurements were carried out for each system, including measurements for a complete IMRT treatment. The reproducibility of dynamic delivery and the characteristics of the accelerator for low-monitor-unit (MU) deliveries were also assessed. An extensive quality assurance (QA) program was performed for each of the patients. Additionally, timing measurements were carried out to assess the practicalities of the technique.
  
  
  RESULTS
  The planning objectives were met in most cases. Absolute doses for complete IMRT treatments were within 2%, on average, with dose distributions generally showing agreement within 3% or 3 mm. Beam modulation measurements made throughout each patient's treatment indicated that both delivery methods were reproducible. The dynamic plans required an average of 765 MU per beam, with a treatment delivery time of 14 min; corresponding results for step-and-shoot plans were 105 MU and 10 min.
  
  
  CONCLUSIONS
  Two IMRT techniques for this group of patients have been successfully implemented in the clinic. The more complex dynamic treatments showed no advantages over the step-and-shoot approach. QA results have shown accurate and reproducible delivery for both techniques, giving increased confidence in the techniques and allowing a reduction in the QA program.
authors.affiliation: Joint Department of Physics, The Royal Marsden NHS Trust, Downs Road, Sutton, Surrey SM2 5PT, UK.
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Adams
authors.forename: David J
authors.initials: DJ
authors.lastname: Convery
authors.forename: Vivian P
authors.initials: VP
authors.lastname: Cosgrove
authors.forename: Helen A
authors.initials: HA
authors.lastname: McNair
authors.forename: John N
authors.initials: JN
authors.lastname: Staffurth
authors.forename: Jaap
authors.initials: J
authors.lastname: Vaarkamp
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Nutting
authors.forename: Alan P
authors.initials: AP
authors.lastname: Warrington
authors.forename: Steve
authors.initials: S
authors.lastname: Webb
authors.forename: Jan
authors.initials: J
authors.lastname: Balyckyi
authors.forename: David P
authors.initials: DP
authors.lastname: Dearnaley
mesh_terms: D006801:Humans; D008198:Lymph Nodes / Q000473:pathology*; D008297:Male; D010388:Pelvis; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011785:Quality Assurance, Health Care; D011878:Radiotherapy / Q000379:methods; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D016896:Treatment Outcome