Lu Yanfei, Chen Jianhong, Wang Fangfang, Zhou Qiong, Zhang Xiang
Zhejiang Cancer Hospital, Hangzhou, Zhejiang, China.
Hangzhou Institute of Medicine (HIM), Chinese Academy of Sciences, Hangzhou, Zhejiang, China.
J Appl Clin Med Phys. 2024 Dec;25(12):e14521. doi: 10.1002/acm2.14521. Epub 2024 Sep 11.
Endometrial cancer is one of the most common gynecological malignancies in the world. Vaginal brachytherapy is an important postoperative adjuvant treatment for endometrial cancer. However, a common problem with existing applicators is insufficient dose at the vaginal apex.
This study describes the Hangzhou (HZ) cylinder, a novel 3D printed vaginal intracavity brachytherapy applicator, detailing its characteristics, dose distribution, and clinical applications.
The HZ cylinder is distinguished by its unique structure: a U-shaped channel with a 2 mm diameter, a straight central axis channel of the same diameter, and 10 parallel straight channels. For comparison, standard plans were employed, designed to ensure that a minimum of 95% of the prescribed dose reached 5 mm beneath the mucosal surface. We conducted comparative analyses of mucosal surface doses and doses at a 5 mm depth below the mucosa between the HZ cylinder and a conventional single-channel cylinder across various treatment schemes. Additionally, the study examined dose differences in target volume and organs at risk (OARs) between actual HZ cylinder plans and hypothetical single-channel plans.
In the standard plans, mucosal surface doses at the apex of the vagina were 209.32% and 200.61% of the prescribed dose with the HZ and single-channel cylinders, respectively. The doses on the left and right wall mucosal surfaces varied from 149.26% to 178.13% and 142.98% to 180.75% of the prescribed dose, and on the anterior and posterior wall mucosal surfaces varied from 128.87% to 138.50% and 142.98% to 180.75% of the prescribed dose. Analysis of 24 actual treatment plans revealed that when the vaginal tissue volume dose covering 98% (vaginal D98%) was comparable between the HZ cylinder and virtual single-channel plans (6.74 ± 0.07 Gy vs. 6.69 ± 0.10 Gy, p = 0.24), rectum doses of HZ cylinder plans were significantly lower than those of single-channel plans (D1cc, 5.96 ± 0.56 Gy vs. 6.26 ± 0.71 Gy, p = 0.02 and D2cc, 5.26 ± 0.52 Gy vs. 5.56 ± 0.62 Gy, p = 0.02).
The HZ cylinder demonstrates a reduction in dose to the rectum and bladder while maintaining adequate target volume coverage. Its mucosal surface dose is comparable to that of the traditional single-channel cylinder. These findings suggest that the HZ cylinder is a viable and potentially safer alternative for vaginal brachytherapy, warranting further investigation with larger sample sizes.
子宫内膜癌是全球最常见的妇科恶性肿瘤之一。阴道近距离放射治疗是子宫内膜癌重要的术后辅助治疗方法。然而，现有施源器的一个常见问题是阴道顶端剂量不足。
本研究描述了杭州（HZ）施源器，一种新型的3D打印阴道腔内近距离放射治疗施源器，详细介绍其特点、剂量分布和临床应用。
HZ施源器的独特结构使其与众不同：有一个直径2毫米的U形通道、一个相同直径的直的中心轴通道以及10个平行的直通道。为作比较，采用了标准计划，以确保至少95%的处方剂量能到达黏膜表面下方5毫米处。我们对HZ施源器和传统单通道施源器在各种治疗方案下的黏膜表面剂量以及黏膜下方5毫米深度处的剂量进行了对比分析。此外，该研究还检查了实际的HZ施源器计划与假设的单通道计划在靶区体积和危及器官（OARs）方面的剂量差异。
在标准计划中，使用HZ施源器和单通道施源器时，阴道顶端的黏膜表面剂量分别为处方剂量的209.32%和200.61%。左右壁黏膜表面的剂量分别为处方剂量的149.26%至178.13%和142.98%至180.75%，前后壁黏膜表面的剂量分别为处方剂量的128.87%至138.50%和142.98%至180.75%。对24个实际治疗计划的分析表明，当HZ施源器计划和虚拟单通道计划覆盖98%阴道组织体积的剂量（阴道D98%）可比时（6.74±0.07 Gy对6.69±0.10 Gy，p = 0.24），HZ施源器计划的直肠剂量显著低于单通道计划（D1cc，5.96±0.56 Gy对6.26±0.71 Gy，p = 0.02；D2cc，5.26±0.52 Gy对5.56±0.62 Gy，p = 0.02）。
HZ施源器在保持对靶区体积足够覆盖的同时，能降低直肠和膀胱的剂量。其黏膜表面剂量与传统单通道施源器相当。这些发现表明，HZ施源器是阴道近距离放射治疗一种可行且可能更安全的替代方案，值得用更大样本量作进一步研究。
