title: Impact of bladder volume on radiation dose to the rectum in the definitive treatment of prostate cancer.
abstract: OBJECTIVE
  Our group created and routinely reviewed a dedicated prostate intensity-modulated radiation therapy (IMRT) delivery program. Previously, a retrospective review of our experience demonstrated that a larger bladder volume reduced radiation dose to the rectum. We conducted an observational study to confirm this relationship.
  
  
  METHODS
  Men receiving definitive radiation for prostate cancer were eligible for the study. Eligible patients received 2 computed axial tomography (CT) scans on the day of their planning CT scan: 1 with a full bladder and 1 with an empty bladder. On each CT data set, the prostate, rectum, bladder, penile bulb, and femoral heads were contoured. 2 IMRT plans were completed on each dataset: 1 by a medical dosimetrist and 1 by a medical physicist. The study plans targeted the prostate to 79.2 Gray (Gy) while respecting predefined dose tolerances to the other contoured structures. Rectal doses were compared on empty and full bladder CT data sets.
  
  
  RESULTS
  From June 29, 2010 to December 14, 2011, 17 full bladder data sets and 15 empty bladder data sets were available for analysis. Median change in bladder volume was 63 ml. Full vs empty bladder set-up was associated with a statistically significant reduction in the mean rectal dose of 25.41 Gy vs 27.6 Gy (𝑃 = .031).
  
  
  CONCLUSIONS
  Small sample size and small variations in bladder volumes.
  
  
  CONCLUSIONS
  A greater bladder volume resulted in a reduced mean dose to the rectum irrespective of planning method.
authors: Department of Radiation Oncology, Wake Forest University, Winston-Salem, North Carolina, USA. BFrizzel@wakehealth.edu.
authors: Bart
authors: B
authors: Frizzell
authors: Department of Biostatistics, Wake Forest University, Winston-Salem, North Carolina, USA.
authors: James
authors: J
authors: Lovato
authors: Department of Radiation Oncology, High Point Cancer Center, High Point, North Carolina, USA.
authors: Jennifer
authors: J
authors: Foster
authors: Department of Radiation Oncology, High Point Cancer Center, High Point, North Carolina, USA.
authors: Ashley
authors: A
authors: Towers
authors: Department of Radiation Oncology, Wake Forest University, Winston-Salem, North Carolina, USA.
authors: John
authors: J
authors: Lucas
authors: Department of Radiation Oncology, Wake Forest University, Winston-Salem, North Carolina, USA.
authors: Charles
authors: C
authors: Able
keywords: bladder; prostate; radiation; rectum