TITLE:
The Impact of Variation in Bladder Volume on the Doses of Target and Organ-at-Risk in Intensity-Modulated Radiation Therapy for Localized Prostate Cancer
AUTHORS:
Shogo Hatanaka, Yoshito Kawada, Kana Washizu, Nobuko Utsumi, Takafumi Yamano, Keiichiro Nishimura, Tetsuya Watanabe, Katsuhito Hosaka, Keisuke Todoroki, Go Nakajima, Munefumi Shimbo, Takeo Takahashi
KEYWORDS:
Bladder Volume, Localized Prostate Cancer, Intensity-Modulated Radiation Therapy, Dose to Organs at Risk, Computed Tomography
JOURNAL NAME:
Journal of Cancer Therapy,
Vol.7 No.10,
October
7,
2016
ABSTRACT: Intensity-modulated
radiation therapy (IMRT) has become
the mainstay of treatment for localized prostate cancer. In IMRT, minimizing differences between the conditions
used during planning CT and daily treatment is important to prevent adverse
events in normal tissues. In the present study, we evaluated the impact of
variation in bladder volume on the doses to various organs. A total of 35
patients underwent definitive radiotherapy at Saitama Medical Center. A Light Speed RT16 (GE Healthcare) was used for planning and
to obtain examination CT images. Such images were acquired after 4 - 6 days of planning CT image acquisition. The IMRT
plans were optimized using the planning CT data to satisfy the dose constraints
set by our in-house protocols for the PTV and the OARs. The dose distributions were then re-calculated using the
same IMRT beams, and checked on examination
CT images. It was clear that bladder volume affected the doses to certain
organs. We focused on the prostate, bladder, rectum, small bowel, and large
bowel. Regression coefficients were calculated for variables that correlated strongly with bladder
volume (p 3] predicted deviations in the
bladder V70Gy, V50Gy, and V30Gy [%]; the maximum dose
to the small bowel [cGy]; and the maximum dose to the large bowel [cGy]. The
regression coefficients were -0.065, -0.125, -0.180, -10.22, and -9.831,
respectively. We evaluated the impacts of such variation on organ doses. These
may be helpful when checking a
patient’s bladder volume before daily IMRT for localized prostate cancer.