The relationship between the bladder volume and optimal treatment planning in definitive radiotherapy for XXXX .

@entity1 @entity263 @entity343
BACKGROUND: There is no current consensus regarding the optimal bladder volumes in definitive radiotherapy for @entity263 . The aim of this study was to clarify the relationship between the bladder volume and optimal treatment planning in radiotherapy for @entity263 . MATERIAL AND METHODS: Two hundred and forty-three @entity1 underwent definitive radiotherapy with helical tomotherapy for intermediate- and high-risk @entity263 . The prescribed dose defined as 95% of the planning target volume ( @entity343 ) 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 @entity343 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 @entity343 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 @entity1 (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 @entity1 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.
