title: Optimal bladder volume at treatment planning for prostate cancer patients receiving volumetric modulated arc therapy.
abstract: OBJECTIVE
  To investigate optimal bladder volumes at treatment planning (TP) in prostate cancer patients who undergo volumetric modulated arc therapy (VMAT).
  
  
  METHODS
  To determine the minimum value, 122 patients were classified into 6 groups according to the bladder volume at TP: <100 mL (group 1), 100-149 mL (group 2), 150-199 mL (group 3), 200-249 mL (group 4), 250-299 mL (group 5), and ≥300 mL (group 6). Bladder volumes receiving more than 70 Gy (V70Gy) and V50Gywere calculated in each subgroup and compared with the bladder dose-volume constraints specified in our institution. To determine the maximum value, 64 patients who underwent uniform nursing interventions were classified into the same 6 groups. Bladder volumes on cone beam computed tomography (CBCT) images were measured once weekly during treatment, for a total of 8 measurements. Relative bladder volumes (bladder volume on CBCT image [mL]/bladder volume at TP [mL] × 100%) were evaluated in each of the 6 subgroups.
  
  
  RESULTS
  The upper bounds of the 95% confidence intervals of the mean V70Gyand V50Gyvalues in group 1 exceeded the dose constraints at our institution. The mean relative bladder volumes were 104%, 91%, 77%, 81%, 63%, and 59% in groups 1, 2, 3, 4, 5, and 6, respectively. The institutional criterion of 70% for the mean relative bladder volume was achieved in groups 1-4, but it could not be achieved in groups 5-6. Therefore, the patients in groups 2-4 met both institutional dose constraints for the bladder at TP and the institutional criterion for the mean relative bladder volume during treatment.
  
  
  CONCLUSIONS
  The optimal bladder volumes at TP were between 100 and 250 mL in this setting. Nursing intervention needs to be implemented before treatment planning to ensure that patients achieve the optimal bladder volume range.
authors.affiliation: Department of Radiation Oncology, Tane General Hospital, Osaka, Japan. Electronic address: c.fujioka@tane.or.jp.
authors.forename: Chiaki
authors.initials: C
authors.lastname: Fujioka
authors.affiliation: Department of Radiation Oncology, Tane General Hospital, Osaka, Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Ishii
authors.affiliation: Department of Radiation Oncology, Tane General Hospital, Osaka, Japan.
authors.forename: Toshiko
authors.initials: T
authors.lastname: Yamanaga
authors.affiliation: Department of Radiation Oncology, Tane General Hospital, Osaka, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Ogino
authors.affiliation: Department of Radiation Oncology, Tane General Hospital, Osaka, Japan.
authors.forename: Shun
authors.initials: S
authors.lastname: Kishimoto
authors.affiliation: Department of Radiation Oncology, Tane General Hospital, Osaka, Japan.
authors.forename: Ryu
authors.initials: R
authors.lastname: Kawamorita
authors.affiliation: Department of Radiology, Izumi Municipal Hospital, Osaka, Japan.
authors.forename: Takuhito
authors.initials: T
authors.lastname: Tada
authors.affiliation: Department of Radiation Oncology, Tane General Hospital, Osaka, Japan.
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Nakajima
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D054893:Cone-Beam Computed Tomography; D006801:Humans; D008297:Male; D008875:Middle Aged; D009929:Organ Size; D058958:Organs at Risk / Q000000981:diagnostic imaging*; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D001743:Urinary Bladder / Q000000981:diagnostic imaging*