Wong Andrew T, Schreiber David, Agarwal Manuj, Polubarov Aleksey, Schwartz David
Department of Veterans Affairs, New York Harbor Healthcare System, Brooklyn, New York; SUNY Downstate Medical Center, Brooklyn, New York.
Department of Veterans Affairs, New York Harbor Healthcare System, Brooklyn, New York; SUNY Downstate Medical Center, Brooklyn, New York.
Pract Radiat Oncol. 2016 Jul-Aug;6(4):262-267. doi: 10.1016/j.prro.2015.10.019. Epub 2015 Nov 9.
Endorectal balloons may be of benefit during stereotactic body radiation therapy of the prostate to limit intrafraction prostatic motion and potentially minimize rectal toxicity. We evaluated the effect of the endorectal balloon (ERB) on rectal dosimetry, specifically the absolute volume of rectum receiving high dose.
Eleven patients with localized prostate cancer underwent stereotactic body radiation therapy planning with computed tomography simulation with and without a RadiaDyne ERB inflated with 60 mL of water. Prescription dose was 3625 cGy in 5 fractions of 725 cGy. The V3600 (volume receiving 3600 cGy), V3440 (volume receiving 3440 cGy), and volume receiving 50% of the prescription dose were calculated for both the rectum and rectal wall. Repeat plans were generated using smaller planning target volume margins (reduced to 1 mm from 3 mm posteriorly) and after virtually replacing the water-filled ERB with air equivalent density. Comparisons were made using the Wilcoxon signed-rank test.
The rectal V3600 and V3440 were significantly lower without ERB than with water-filled ERB using standard 3-mm posterior margin (P = .003 for both V3600/V3440), water-filled ERB using reduced 1-mm posterior margin (P = .016 and .003), or air-filled ERB (P = .003 and .004). Regarding the rectal wall, V3600 and V3440 were also significantly lower without ERB than with any ERB, except when using the water-filled ERB with reduced posterior margin (P = .328). The volumes of rectum and rectal wall receiving lower dose (volume receiving 50% of the prescription dose) were not significantly greater without the ERB.
We found an increase in the volume of rectum and rectal wall receiving high dose radiation utilizing an ERB. Consideration in using an ERB should account for potential increased rectal dose and subsequent toxicity.
在前列腺立体定向体部放射治疗期间，直肠内气囊可能有助于限制分次治疗期间前列腺的运动，并有可能将直肠毒性降至最低。我们评估了直肠内气囊（ERB）对直肠剂量测定的影响，特别是接受高剂量照射的直肠绝对体积。
11例局限性前列腺癌患者在有和没有用60毫升水充盈的RadiaDyne ERB的情况下，通过计算机断层扫描模拟进行立体定向体部放射治疗计划。处方剂量为3625 cGy，分5次给予，每次725 cGy。计算直肠和直肠壁的V3600（接受3600 cGy的体积）、V3440（接受3440 cGy的体积）以及接受50%处方剂量的体积。使用较小的计划靶体积边界（从后方的3毫米减少到1毫米）并在将充满水的ERB虚拟替换为空气等效密度后生成重复计划。使用Wilcoxon符号秩检验进行比较。
使用标准的3毫米后缘时，无ERB组的直肠V3600和V3440显著低于充满水的ERB组（V3600/V3440均为P = 0.003）；使用减少至1毫米后缘的充满水的ERB时（P = 0.016和0.003）以及使用充满空气的ERB时（P = 0.003和0.004）也是如此。关于直肠壁，无ERB组的V3600和V3440也显著低于任何有ERB的情况，但使用后缘减少的充满水的ERB时除外（P = 0.328）。没有ERB时，接受较低剂量（接受50%处方剂量的体积）的直肠和直肠壁体积没有显著增加。
我们发现使用ERB会使接受高剂量辐射的直肠和直肠壁体积增加。在考虑使用ERB时应考虑到直肠剂量可能增加以及随后的毒性。
