title: The relationship between the bladder volume and optimal treatment planning in definitive radiotherapy for localized prostate cancer.
abstract: BACKGROUND
  There is no current consensus regarding the optimal bladder volumes in definitive radiotherapy for localized prostate cancer. The aim of this study was to clarify the relationship between the bladder volume and optimal treatment planning in radiotherapy for localized prostate cancer.
  
  
  METHODS
  Two hundred and forty-three patients underwent definitive radiotherapy with helical tomotherapy for intermediate- and high-risk localized prostate cancer. The prescribed dose defined as 95% of the planning target volume (PTV) receiving ≧ 100% of the prescription dose was 76 Gy in 38 fractions. The clinical target volume (CTV) was defined as the prostate with a 5-mm margin and 2 cm of the proximal seminal vesicle. The PTV was defined as the CTV with a 5-mm margin. Treatment plans were optimized to satisfy the dose constraints defined by in-house protocols for PTV and organs at risk (rectum wall, bladder wall, sigmoid colon and small intestine). If all dose constraints were satisfied, the plan was defined as an optimal plan (OP).
  
  
  RESULTS
  An OP was achieved with 203 patients (84%). Mean bladder volume (± 1 SD) was 266 ml (± 130 ml) among those with an OP and 214 ml (±130 ml) among those without an OP (p = 0.02). Logistic regression analysis also showed that bladder volumes below 150 ml decreased the possibility of achieving an OP. However, the percentage of patients with an OP showed a plateau effect at bladder volumes above 150 ml.
  
  
  CONCLUSIONS
  Bladder volume is a significant factor affecting OP rates. However, our results suggest that bladder volumes exceeding 150 ml may not help meet planning dose constraints.
authors: Department of Radiation Oncology, St. Luke's International Hospital, Tokyo, Japan. nnakamur-tky@umin.ac.jp
authors: Naoki
authors: N
authors: Nakamura
authors: Naoto
authors: N
authors: Shikama
authors: Osamu
authors: O
authors: Takahashi
authors: Kenji
authors: K
authors: Sekiguchi
authors: Yukihiro
authors: Y
authors: Hama
authors: Keiko
authors: K
authors: Akahane
authors: Keiichi
authors: K
authors: Nakagawa
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D006801:Humans; D008297:Male; D008875:Middle Aged; D009929:Organ Size; D011379:Prognosis; D011471:Prostatic Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D011880:Radiotherapy Planning, Computer-Assisted; D001743:Urinary Bladder / Q000473:pathology*