Department of Radiation Physics and Technology, Southern Tohoku Proton Therapy Center, Fukushima, Japan.
Preparing Section for New Faculty of Medical Science, Fukushima Medical University, Fukushima, Japan.
J Radiat Res. 2021 Mar 10;62(2):294-299. doi: 10.1093/jrr/rraa115.
In recent years, a novel technique has been employed to maintain a distance between the prostate and the rectum by transperineally injecting a hydrogel spacer (HS). However, the effect of HS on the prostate positional displacement is poorly understood, despite its stability with HS in place. In this study, we investigated the effect of HS insertion on the interfraction prostate motion during the course of proton therapy (PT) for Japanese prostate cancer patients. The study population consisted of 22 cases of intermediate-risk prostate cancer with 11 cases with HS insertion and 11 cases without HS insertion. The irradiation position and preparation were similar for both groups. To test for reproducibility, regular confirmation computed tomography (RCCT) was done four times during the treatment period, and five times overall [including treatment planning CT (TPCT)] in each patient. Considering the prostate position of the TPCT as the reference, the change in the center of gravity of the prostate relative to the bony anatomy in the RCCTs of each patient was determined in the left-right (LR), superior-inferior (SI) and anterior-posterior (AP) directions. As a result, no significant difference was observed across the groups in the LR and SI directions. Conversely, a significant difference was observed in the AP direction (P < 0.05). The proportion of the 3D vector length ≤5 mm was 95% in the inserted group, but 55% in the non-inserted group. Therefore, HS is not only effective in reducing rectal dose, but may also contribute to the positional reproducibility of the prostate.
近年来，一种新的技术被采用，通过经会阴向前列腺和直肠之间注射水凝胶间隔物（HS）来保持两者之间的距离。然而，尽管 HS 能够稳定地保持在原位，但人们对其在前列腺位置位移方面的影响知之甚少。在这项研究中，我们研究了 HS 插入对质子治疗（PT）过程中日本前列腺癌患者前列腺分次间运动的影响。研究人群包括 22 例中危前列腺癌患者，其中 11 例插入了 HS，11 例未插入 HS。两组的照射位置和准备相似。为了测试重复性，在治疗期间进行了 4 次常规确认计算机断层扫描（RCCT），在每位患者中总共进行了 5 次（包括治疗计划 CT（TPCT））。考虑到 TPCT 中的前列腺位置，确定了每位患者 RCCT 中相对于骨骼解剖结构的前列腺重心在左右（LR）、上下（SI）和前后（AP）方向上的变化。结果显示，LR 和 SI 方向上两组之间没有显著差异。然而，在 AP 方向上观察到显著差异（P < 0.05）。插入组的 3D 向量长度≤5mm 的比例为 95%，而非插入组的比例为 55%。因此，HS 不仅能有效降低直肠剂量，还可能有助于前列腺的位置重复性。
