Kiriyama Tetsukazu, Fukui Akira, Ishikawa Hirohumi, Doi Misako, Nishimoto Yuki, Cyosei Kenta, Kishimoto Koji, Yoshinori Tanabe
Department of Radiology, Uwajima City Hospital, Ehime 798-8510 Japan.
Department of Radiological Technology, Graduate School of Health Sciences, Okayama University, Okayama, 700-8558, Japan.
Med Dosim. 2025;50(3):203-208. doi: 10.1016/j.meddos.2025.01.005. Epub 2025 Feb 1.
One major adverse effect of prostate radiotherapy is associated with the rectum. The SpaceOAR system has been developed to address this problem, as it enables treatment planning with a reduced dose to the rectum. This study aimed to evaluate and compare the treatment plans between three-dimensional conformal radiotherapy (3D-CRT) and volumetric modulated arc therapy (VMAT) for prostate cancer using the SpaceOAR system. Thirty-five patients treated with prostate cancer radiation using the SpaceOAR system received a total radiation dose of 60 Gy/20 fractions. The dose constraints and robustness of the plan for VMAT and 3D-CRT were compared. For 3D-CRT, 6-field conformal method and 2-arc conformal method were created and compared in 3 treatment plans together with VMAT. The dose-constraint evaluation was performed using the planning target volume (PTV), rectum (mean dose), bladder (mean dose), and femoral head (mean dose). One issue associated with prostate radiotherapy is the physiological movement of the target prostate gland, which reduces the accuracy of irradiation. The prostate moves several millimeters during irradiation due to physiological movements, and there are reports of a decrease in the PTV index due to this effect. This has a significant impact on the cure rate of prostate cancer. A comparative study of the 3 irradiation methods was conducted to investigate this issue. Each study item was analyzed using the Friedman test to determine the significance of the 3 irradiation methods. Our analysis showed that the dose constraint was statistically significant for VMAT, but 3D-CRT was also sufficient in achieving dose constraints. The hydrogel spacer reduced the rectal dose and improved the dose-constrained fulfillment rate in VMAT and 3D-CRT. In a study of prostate motion during irradiation, 3D-CRT, a robust plan, was superior in the PTV mean evaluation over VMAT, where the multileaf collimator moved in fine increments. VMAT is currently the standard treatment for prostate cancer; however, with the introduction of the SpaceOAR system using hydrogel spacers, 3D-CRT may also be a viable option for prostate cancer treatment.
前列腺放疗的一个主要不良反应与直肠有关。SpaceOAR系统的研发就是为了解决这一问题，因为它能够在治疗计划中降低对直肠的剂量。本研究旨在评估和比较使用SpaceOAR系统的前列腺癌三维适形放疗（3D-CRT）和容积调强弧形放疗（VMAT）的治疗计划。35例使用SpaceOAR系统进行前列腺癌放疗的患者接受了60 Gy/20次分割的总辐射剂量。比较了VMAT和3D-CRT计划的剂量限制和稳健性。对于3D-CRT，创建了6野适形方法和2弧适形方法，并在3个治疗计划中与VMAT一起进行比较。使用计划靶区（PTV）、直肠（平均剂量）、膀胱（平均剂量）和股骨头（平均剂量）进行剂量限制评估。与前列腺放疗相关的一个问题是靶器官前列腺的生理运动，这会降低照射的准确性。由于生理运动，前列腺在照射过程中会移动几毫米，并且有报道称由于这种影响PTV指数会降低。这对前列腺癌的治愈率有重大影响。进行了三种照射方法的对比研究以调查此问题。使用Friedman检验对每个研究项目进行分析，以确定三种照射方法的显著性。我们的分析表明，VMAT的剂量限制具有统计学意义，但3D-CRT在实现剂量限制方面也足够。水凝胶间隔物降低了VMAT和3D-CRT中的直肠剂量，并提高了剂量限制的达成率。在一项关于照射过程中前列腺运动的研究中，3D-CRT作为一种稳健的计划，在PTV平均评估方面优于VMAT，VMAT中多叶准直器以精细增量移动。VMAT目前是前列腺癌的标准治疗方法；然而，随着使用水凝胶间隔物的SpaceOAR系统的引入，3D-CRT也可能是前列腺癌治疗的一个可行选择。
