title: Comparing two strategies of dynamic intensity modulated radiation therapy (dIMRT) with 3-dimensional conformal radiation therapy (3DCRT) in the hypofractionated treatment of high-risk prostate cancer.
abstract: BACKGROUND
  To compare two strategies of dynamic intensity modulated radiation therapy (dIMRT) with 3-dimensional conformal radiation therapy (3DCRT) in the setting of hypofractionated high-risk prostate cancer treatment.
  
  
  METHODS
  3DCRT and dIMRT/Helical Tomotherapy(HT) planning with 10 CT datasets was undertaken to deliver 68 Gy in 25 fractions (prostate) and simultaneously delivering 45 Gy in 25 fractions (pelvic lymph node targets) in a single phase. The paradigms of pelvic vessel targeting (iliac vessels with margin are used to target pelvic nodes) and conformal normal tissue avoidance (treated soft tissues of the pelvis while limiting dose to identified pelvic critical structures) were assessed compared to 3DCRT controls. Both dIMRT/HT and 3DCRT solutions were compared to each other using repeated measures ANOVA and post-hoc paired t-tests.
  
  
  RESULTS
  When compared to conformal pelvic vessel targeting, conformal normal tissue avoidance delivered more homogenous PTV delivery (2/2 t-test comparisons; p < 0.001), similar nodal coverage (8/8 t-test comparisons; p = ns), higher and more homogenous pelvic tissue dose (6/6 t-test comparisons; p < 0.03), at the cost of slightly higher critical structure dose (Ddose, 1-3 Gy over 5/10 dose points; p < 0.03). The dIMRT/HT approaches were superior to 3DCRT in sparing organs at risk (22/24 t-test comparisons; p < 0.05).
  
  
  CONCLUSIONS
  dIMRT/HT nodal and pelvic targeting is superior to 3DCRT in dose delivery and critical structure sparing in the setting of hypofractionation for high-risk prostate cancer. The pelvic targeting paradigm is a potential solution to deliver highly conformal pelvic radiation treatment in the setting of nodal location uncertainty in prostate cancer and other pelvic malignancies.
authors.affiliation: Department of Radiation Oncology, London Regional Cancer Program, London, Ontario, Canada. jasper.yuen@lhsc.on.ca
authors.forename: Jasper
authors.initials: J
authors.lastname: Yuen
authors.forename: George
authors.initials: G
authors.lastname: Rodrigues
authors.forename: Kristina
authors.initials: K
authors.lastname: Trenka
authors.forename: Terry
authors.initials: T
authors.lastname: Coad
authors.forename: Slav
authors.initials: S
authors.lastname: Yartsev
authors.forename: David
authors.initials: D
authors.lastname: D'Souza
authors.forename: Michael
authors.initials: M
authors.lastname: Lock
authors.forename: Glenn
authors.initials: G
authors.lastname: Bauman
mesh_terms: D004307:Dose-Response Relationship, Radiation; D006801:Humans; D008297:Male; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D014057:Tomography, X-Ray Computed