Radhakrishna Nikhila, Palled Siddanna Rudrappa, Pasha Tanvir, Buchapudi Rekha Reddy, Govardhan H B, Thimmaiah Naveen, Viswanath Lokesh
Department of Radiation Oncology, Kidwai Memorial Institute of Oncology, Bengaluru, Karnataka, India.
Department of Radiation Physics, Kidwai Memorial Institute of Oncology, Bengaluru, Karnataka, India.
J Contemp Brachytherapy. 2021 Oct;13(5):519-525. doi: 10.5114/jcb.2021.109788. Epub 2021 Oct 7.
Interstitial brachytherapy (ISBT) is often used as post-external beam radiotherapy (EBRT) to treat locally advanced gynecological malignancies. Female urethra is in close proximity to the target during ISBT. However, it has not been evaluated as an organ-at-risk (OAR). Overlapping symptoms caused by radiation-induced bladder toxicity vs. urethral toxicity make it difficult to identify and report urethral toxicities separately. This was a retrospective study to estimate dose-volume parameters of female urethra during high-dose-rate ISBT.
Data of 24 patients with gynecological malignancies treated by ISBT were selected. Urethra and periurethral regions were retrospectively contoured. Mean volume, D, D, D, D, D, D, and D were documented. Unpaired -test was used for comparison of means.
20/24 Ca. cervix, 1/24 Ca. vagina, and 3/24 Ca. vaginal vault received 6-6.5 Gy in 4 ISBT fractions. Mean urethral length was 3.54 0.55 cm. Mean doses received by urethra per BT fraction were D = 4.23 1.32 Gy, D = 2.71 1.01 Gy, D = 3.31 1.07, and D = 3.54 1.09 Gy. Comparison of total BT 2 Gy equivalent dose (EQD) with 4 fractions for urethra between patients with (9/24) and without anterior vaginal wall (15/24) involvement included D = 18.79 ±7.49 Gy vs. 11.14 ±6.15 Gy*, D = 10.90 ±10.03 Gy vs. 4.54 ±3.93 Gy*, D = 19.50 ±8.69 Gy vs. 11.97 ±6.54 Gy*, D = 23.78 ±8.94 Gy vs. 15.51 ±7.39 Gy*, and D = 25.88 ±9.37 Gy vs. 17.39 ±8.03 Gy*, respectively (* < 0.05).
Female urethra receives significant doses during ISBT for gynecological malignancies, especially when the anterior vaginal wall is within the target volume. Reporting doses to urethra would enable to develop clinical correlation and dose-volume constraints for urethra as organ-at-risk in future.
组织间近距离放射治疗（ISBT）常用于外照射放疗（EBRT）后治疗局部晚期妇科恶性肿瘤。ISBT治疗期间女性尿道紧邻靶区。然而，它尚未被评估为危及器官（OAR）。放射性膀胱毒性与尿道毒性引起的重叠症状使得难以分别识别和报告尿道毒性。这是一项回顾性研究，旨在评估高剂量率ISBT期间女性尿道的剂量体积参数。
选取24例接受ISBT治疗的妇科恶性肿瘤患者的数据。对尿道和尿道周围区域进行回顾性勾画。记录平均体积、D、D、D、D、D、D和D。采用非配对t检验比较均值。
24例患者中，20例为子宫颈癌，1例为阴道癌，3例为阴道穹窿癌，均接受4次ISBT分割，每次剂量6 - 6.5 Gy。平均尿道长度为3.54±0.55 cm。每次BT分割尿道接受的平均剂量为：D = 4.23±1.32 Gy，D = 2.71±1.01 Gy，D = 3.31±1.07 Gy，D = 3.54±1.09 Gy。比较有（9/24）和无（15/24）阴道前壁受累患者尿道的总BT 2 Gy等效剂量（EQD）与4次分割剂量，结果分别为：D = 18.79±7.49 Gy对11.14±6.15 Gy*，D = 10.90±10.03 Gy对4.54±3.93 Gy*，D = 19.50±8.69 Gy对11.97±6.54 Gy*，D = 23.78±8.94 Gy对15.51±7.39 Gy*，D = 25.88±9.37 Gy对17.39±8.03 Gy*（*P<0.05）。
妇科恶性肿瘤ISBT治疗期间女性尿道接受显著剂量，尤其是当阴道前壁在靶区内时。报告尿道剂量将有助于建立临床相关性，并为未来将尿道作为危及器官制定剂量体积限制。
