title: Endorectal balloons in the post prostatectomy setting: do gains in stability lead to more predictable dosimetry?
abstract: OBJECTIVE
  To perform a comparative study assessing potential benefits of endorectal-balloons (ERB) in post-prostatectomy patients.
  
  
  METHODS
  Ten retrospective post-prostatectomy patients treated without ERB and ten prospective patients treated with the ERB in situ were recruited. All patients received IMRT and IGRT using kilovoltage cone-beam computed tomography (kVCBCT). kVCBCT datasets were registered to the planning dataset, recontoured and the original plan recalculated on the kVCBCTs to recreate anatomical conditions during treatment. The imaging, structure and dose data were imported into in-house software for the assessment of geometric variation and cumulative equivalent uniform dose (EUD) in the two groups.
  
  
  RESULTS
  The difference in location (ΔCOV) for the bladder between planning and each CBCT was similar for each group. The range of mean ΔCOV for the rectum was 0.15-0.58 cm and 0.15-0.59 cm for the non-ERB and ERB groups. For superior-CTV and inferior-CTV the difference between planned and delivered D95% (mean ± SD) for the non-ERB group was 2.1 ± 6.0 Gy and -0.04 ± 0.20 Gy. While for the ERB group the difference in D95% was 8.7 ± 12.6 Gy and 0.003 ± 0.104 Gy.
  
  
  CONCLUSIONS
  The use of ERBs in the post-prostatectomy setting did improve geometric reproducibility of the target and surrounding normal tissues, however no improvement in dosimetric stability was observed for the margins employed.
authors.affiliation: Liverpool and Macarthur Cancer Therapy Centres, Australia; Centre for Medical Radiation Physics, University of Wollongong, Australia; Ingham Institute, Australia. Electronic address: michael.jameson@sswahs.nsw.gov.au.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Jameson
authors.forename: Jeremiah
authors.initials: J
authors.lastname: De Leon
authors.forename: Apsara A
authors.initials: AA
authors.lastname: Windsor
authors.forename: Kirrily
authors.initials: K
authors.lastname: Cloak
authors.forename: Sarah
authors.initials: S
authors.lastname: Keats
authors.forename: Jason A
authors.initials: JA
authors.lastname: Dowling
authors.forename: Shekhar S
authors.initials: SS
authors.lastname: Chandra
authors.forename: Philip
authors.initials: P
authors.lastname: Vial
authors.forename: Mark
authors.initials: M
authors.lastname: Sidhom
authors.forename: Lois
authors.initials: L
authors.lastname: Holloway
authors.forename: Peter
authors.initials: P
authors.lastname: Metcalfe
mesh_terms: D054893:Cone-Beam Computed Tomography; D006801:Humans; D008297:Male; D011446:Prospective Studies; D011468:Prostatectomy / Q000379:methods; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy* / Q000601:surgery; D011832:Radiation Injuries / Q000517:prevention & control; D011835:Radiation Protection; D011874:Radiometry; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D018714:Radiotherapy, Adjuvant; D012007:Rectum / Q000000981:diagnostic imaging / Q000528:radiation effects*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D001743:Urinary Bladder / Q000000981:diagnostic imaging / Q000528:radiation effects
keywords: EUD; Endorectal balloon; IMRT; Inter-fraction motion; Post prostatectomy