Kashihara Tairo, Urago Yuka, Okamoto Hiroyuki, Takemori Mihiro, Nakayama Hiroki, Mikasa Shohei, Nakaichi Tetsu, Iijima Kotaro, Chiba Takahito, Kuwahara Junichi, Nakamura Satoshi, Chang Weishan, Matsui Yoshiyuki, Igaki Hiroshi
Department of Radiation Oncology, National Cancer Center Hospital, 5-1-1 Tsukiji, Chuo-ku, Tokyo, Japan.
Radiation Safety and Quality Assurance Division, National Cancer Center Hospital, 5-1-1 Tsukiji, Chuo-ku, Tokyo, Japan.
Asian J Urol. 2024 Apr;11(2):286-293. doi: 10.1016/j.ajur.2022.08.006. Epub 2023 Feb 4.
Hydrogel spacer (HS) was developed to reduce rectal toxicities caused by radiotherapy, but has been reported to cause major adverse events. Our institute has attempted to introduce a hyaluronic acid (HA) as an alternative spacer. This study aimed to compare rectal doses and geometric distributions between the HS and HA implantation in prostate cancer.
HS and HA were inserted in 20 and 18 patients undergoing high-dose brachytherapy, respectively. The rectum spacer volumes injected were 10 mL and 22 mL, respectively. In the treatment planning system, 13.5 Gy was administered with common catheter positions. The rectal dose indices were assessed between the spacer groups for dosimetry evaluation. Distances between the prostate and rectum and configurations of the spacers were compared.
The mean doses irradiated to 0.1 and 2 mL of the rectum were 10.45 Gy and 6.71 Gy for HS, and 6.73 Gy and 4.90 Gy for HA (<0.001). The mean minimum distances between the prostate and rectum were 1.23 cm and 1.79 cm for HS and HA, respectively (<0.05). Geometrical configuration comparisons revealed that HA has a higher ability to expand the space than HS.
The rectal dose reduction ability of HA is significantly greater than that of HS, suggesting its potential as a new spacer.
水凝胶间隔物（HS）被开发用于降低放疗引起的直肠毒性，但据报道会导致严重不良事件。我们研究所尝试引入透明质酸（HA）作为替代间隔物。本研究旨在比较前列腺癌中HS和HA植入后的直肠剂量及几何分布。
分别在20例和18例接受高剂量近距离放疗的患者中插入HS和HA。注入的直肠间隔物体积分别为10 mL和22 mL。在治疗计划系统中，通过常见的导管位置给予13.5 Gy的剂量。在间隔物组之间评估直肠剂量指数以进行剂量学评估。比较前列腺与直肠之间的距离以及间隔物的形态。
HS组直肠0.1 mL和2 mL受照的平均剂量分别为10.45 Gy和6.71 Gy，HA组分别为6.73 Gy和4.90 Gy（<0.001）。HS组和HA组前列腺与直肠之间的平均最小距离分别为1.23 cm和1.79 cm（<0.05）。几何形态比较显示，HA比HS具有更强的扩张空间能力。
HA降低直肠剂量的能力明显强于HS，表明其作为新型间隔物的潜力。
