ABSTRACT
Objective To investigate the influence of endorectal balloon on normal tissue dosimetry in prostate cancer patients treated with intensity-modulated radiation therapy (IMRT). Methods Ten patients with prostate cancer were included and each had two sets of planning CT-scans:one with and one without an air-filled endorectal balloon. Target volumes and organs at risk ( rectum, bladder,femoral heads)were contoured on the 20 CT scans and IMRT plannings were performed. The prescription dose was 78 Gy to 95％ of planning target volume. The percentage of volume of organs at risk ( without or with endorectal balloon) receiving more than 10 Gy, 20 Gy, 30 Gy, 40 Gy, 50 Gy, 60 Gy, 70 Gy and 75 Cy (V10 - V70 ,in increments of 10 Gy, and V75 ) were analyzed. Results The V1o - V60 0f rectum with endorectal balloon were 75. 5％ , 52. 6％ , 35. 3％ , 26. 1％, 19. 6％ , 14. 2％ , and those without endorectal balloon were 82. 2％ , 62. 8％ , 43. 9％ , 31. 4％ , 24. 0％ , 17. 1％ , respectively ( X2 = g. 46, P< 0. 01 ). Use of endorectal balloon significantly reduced the dose to the rectum ( v10 - V60 ) . The V70 and V75 of rectum with endorectal balloon were 9. 1％ and 8. 2％; and those without endorectal balloon were 9. 9％ and 6. 2％ respectively ( X2 = 1. 82,P＞0. 05) . The difference was not significant. There were no significant differences in the dose to bladder,left and right femoral head between patients with and without endorectal balloon.Conclusions Endorectal balloon can significantly decrease the medium and low dose volume of rectum for prostate cancer patients treated with IMRT, which may reduce the rectal toxicity.