Author(s)

Shogo Hatanaka^1*, Yoshito Kawada¹, Kana Washizu¹, Nobuko Utsumi^1,2, Takafumi Yamano¹, Keiichiro Nishimura¹, Tetsuya Watanabe¹, Katsuhito Hosaka¹, Keisuke Todoroki¹, Go Nakajima¹, Munefumi Shimbo¹, Takeo Takahashi¹

¹Department of Radiation Oncology, Saitama Medical Center, Saitama Medical University, Kawagoe City, Japan.
²Department of Radiology, JCHO Tokyo Shinjuku Medical Center, Tokyo, Japan.

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 < 0.05). We found that variation in bladder volume [cm³] predicted deviations in the bladder V_70Gy, V_50Gy, and V_30Gy [%]; 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.

Bladder Volume, Localized Prostate Cancer, Intensity-Modulated Radiation Therapy, Dose to Organs at Risk, Computed Tomography

Hatanaka, S. , Kawada, Y. , Washizu, K. , Utsumi, N. , Yamano, T. , Nishimura, K. , Watanabe, T. , Hosaka, K. , Todoroki, K. , Nakajima, G. , Shimbo, M. and Takahashi, T. (2016) 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. Journal of Cancer Therapy, 7, 741-751. doi: 10.4236/jct.2016.710075.