@misc{oai:repo.qst.go.jp:00071145,
 author = {Fukahori, Mai and Himukai, Takeshi and Matsufuji, Naruhiro and Kanematsu, Nobuyuki and Tsuji, Hiroshi and Kamada, Tadashi and 深堀 麻衣 and 日向 猛 and 松藤 成弘 and 兼松 伸幸 and 辻 比呂志 and 鎌田 正},
 month = {Jun},
 note = {Aim:
The radiation injury of the rectum is the major concern in radiotherapy for prostate cancer because it often threatens a patient's QOL. There are many references available for the dose constraints in conventional radiotherapy, however, no clear index has been established for carbon ion therapy. At NIRS, rectal DVH [cc] based on clinical outcomes in 20 fractions in 5 weeks has been used as the dose constraint (reference line) in evaluating treatment plans. Since 2008, new clinical protocol has been performed for prostate cancer to reveal the efficacy of hypofractionation from the 20 fractions to 16 fractions in 4 weeks. Furthermore, dose calculation algorithm has been updated from broad beam calculation (HIPLAN) to pencil beam calculation (XiO-N) in 2012. The aim of this study is to update reference line of the rectal DVH for prostate cancer to be applicable for the new fractionation protocol and treatment planning system (TPS).
Method:
The new reference line was derived based on 36 patients developed rectum injury treated with 57.6 Gy (RBE) in 16 fractions between May 2003 and May 2010. After transferring the plans of the patients from HIPLAN to XiO-N, these plans were recalculated and made dose-volume histograms (DVHs) of rectum were evaluated. The new rectum reference line was set as the average of all the DVH curves. In order to assess the appropriateness of the new reference line, DVHs of 3 patients who did not develop the rectum injury were derived and compared. 
Results:
The new reference line for 16 fractions gives reduced dose than the old one. It was also found that DVH [%] showed more significant relation to the occurrence of rectum injury than DVH [cc]. 
Conclusions:
Our new reference line of the rectal DVH for carbon ion radiotherapy of prostate cancer is derived and confirmed adequate for the new fraction protocol. It has been installed in the new TPS in terms of DVH [cc] as well as DVH [%] in order to support for doctors checking the treatment plans since September 2012., 52nd Annual Conference of the Particle Therapy Co-Operative Group（PTCOG52）},
 title = {Renewal of reference line for the rectal dose constraints in carbon therapy for prostate cancer},
 year = {2013}
}