title: Dosimetric study of pelvic proton radiotherapy for high-risk prostate cancer.
abstract: OBJECTIVE
  To compare dose distributions in targeted tissues (prostate, seminal vesicles, pelvic regional nodes) and nontargeted tissues in the pelvis with intensity-modulated radiotherapy (IMRT) and forward-planned, double-scattered, three-dimensional proton radiotherapy (3D-PRT).
  
  
  METHODS
  IMRT, IMRT followed by a prostate 3D-PRT boost (IMRT/3D-PRT), and 3D-PRT plans were created for 5 high-risk prostate cancer patients (n = 15 plans). A 78-CGE/Gy dose was prescribed to the prostate and proximal seminal vesicles and a 46-CGE/Gy was prescribed to the pelvic nodes. Various dosimetric endpoints were compared.
  
  
  RESULTS
  Target coverage of the prostate and nodal planning target volumes was adequate for all three plans. Compared with the IMRT and IMRT/3D-PRT plans, the 3D-PRT plans reduced the mean dose to the rectum, rectal wall, bladder, bladder wall, small bowel, and pelvis. The relative benefit of 3D-PRT (vs IMRT) at reducing the rectum and rectal wall V5-V40 was 53% to 71% (p < 0.05). For the bladder and bladder wall, the relative benefit for V5 to V40 CGE/Gy was 40% to 63% (p < 0.05). The relative benefit for reducing the volume of small bowel irradiated from 5 to 30 CGE/Gy in the 3D-PRT ranged from 62% to 69% (p < 0.05). Use of 3D-PRT did not produce the typical low-dose "bath" of radiation to the pelvis seen with IMRT. Femoral head doses were higher for the 3D-PRT.
  
  
  CONCLUSIONS
  Use of 3D-PRT significantly reduced the dose to normal tissues in the pelvis while maintaining adequate target coverage compared with IMRT or IMRT/3D-PRT. When treating the prostate, seminal vesicles, and pelvic lymph nodes in prostate cancer, proton therapy may improve the therapeutic ratio beyond what is possible with IMRT.
authors.affiliation: University of Florida, Department of Radiation Oncology, Gainesville, FL 32206, USA.
authors.forename: Bhishamjit S
authors.initials: BS
authors.lastname: Chera
authors.forename: Carlos
authors.initials: C
authors.lastname: Vargas
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Morris
authors.forename: Debbie
authors.initials: D
authors.lastname: Louis
authors.forename: Stella
authors.initials: S
authors.lastname: Flampouri
authors.forename: Daniel
authors.initials: D
authors.lastname: Yeung
authors.forename: Srividya
authors.initials: S
authors.lastname: Duvvuri
authors.forename: Zuofeng
authors.initials: Z
authors.lastname: Li
authors.forename: Nancy Price
authors.initials: NP
authors.lastname: Mendenhall
mesh_terms: D005269:Femur / Q000528:radiation effects; D006801:Humans; D007421:Intestine, Small / Q000528:radiation effects; D008198:Lymph Nodes / Q000528:radiation effects; D008297:Male; D010388:Pelvis; D011467:Prostate / Q000528:radiation effects; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D061766:Proton Therapy; D011832:Radiation Injuries / Q000517:prevention & control*; D011859:Radiography; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods; D012007:Rectum / Q000528:radiation effects; D012669:Seminal Vesicles / Q000528:radiation effects; D001743:Urinary Bladder / Q000528:radiation effects; D011522:Protons
chemical_list: D011522:Protons