Aims

Interstitial brachytherapy (ISBT) plays an important role in the management of locally advanced gynaecological malignancies. However, the relationship between urinary toxicity and dose to the urethra is not well understood. We sought to evaluate the correlation between urethral dose and the incidence of genitourinary complications among patients undergoing vaginal high dose rate ISBT.

Materials and methods

Eighty-three patients treated with ISBT between August 2014 and April 2018 were retrospectively reviewed. CTCAE version 5.0 was used to grade toxicity. Individual treatment plans were evaluated to collect dose parameters. Urethral contours were added to the structure sets using a uniform 1 cm diameter brush and minimum doses to the hottest 0.1, 0.2 and 0.5 cm³ (D0.1cm³, D0.2cm³ and D0.5cm³) of the urethra were obtained. Total (ISBT ± external beam radiotherapy) equivalent doses in 2 Gy fractions (EQD2) received by the targets and organs at risk were calculated. Numerical counts (%) and medians (interquartile range) were used to characterise the data. Fisher's exact and the Mann–Whitney–Wilcox tests were used as appropriate. Receiver operator curve analysis was used to define the urethral threshold dose that correlated to genitourinary toxicity.

Results

The median age and follow-up times were 67 years (59–75) and 25 months (16–37), respectively. Patients had predominantly primary endometrial (49%) and vaginal (37%) cancer, with four (5%) patients with metastatic rectal cancer to the vagina. Twenty-four of 79 (30%) patients experienced acute genitourinary toxicity and 34 of 71 (48%) experienced late genitourinary toxicity. In both analyses, the median urethral dose was significantly higher among those with toxicity. Receiver operator curve analysis indicated that D0.1cm³, D0.2cm³ and D0.5cm³ of the urethra were associated with the development of toxicity at doses >78, >71 and >62 Gy, respectively.

Conclusion

Urethral dose seems to predict genitourinary toxicity in ISBT of vaginal tumours. Further study with an expanded cohort and longer follow-up is warranted.

中文翻译：

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阴道高剂量率间质近距离放射治疗患者尿道剂量与泌尿生殖系统毒性的关系

宗旨

间质近距离放射治疗（ISBT）在局部晚期妇科恶性肿瘤的治疗中发挥着重要作用。然而，尿毒性与尿道剂量之间的关系尚不清楚。我们试图在接受阴道高剂量率 ISBT 的患者中评估尿道剂量与泌尿生殖系统并发症发生率之间的相关性。

材料和方法

对 2014 年 8 月至 2018 年 4 月期间接受 ISBT 治疗的 83 名患者进行了回顾性研究。CTCAE 5.0 版用于对毒性进行分级。评估个体治疗计划以收集剂量参数。使用直径为 1 cm 的均匀刷子和对最热的 0.1、0.2 和 0.5 cm ³（D0.1cm ³、D0.2cm ³和 D0.5cm ³) 的尿道。计算目标和风险器官接受的 2 Gy 部分 (EQD2) 中的总 (ISBT ± 外照射放疗) 等效剂量。数字计数 (%) 和中位数 (四分位距) 用于表征数据。适当地使用了 Fisher 精确检验和 Mann-Whitney-Wilcox 检验。接受者操作曲线分析用于定义与泌尿生殖毒性相关的尿道阈值剂量。

结果

中位年龄和随访时间分别为 67 岁 (59-75) 和 25 个月 (16-37)。患者主要患有原发性子宫内膜癌 (49%) 和阴道癌 (37%)，其中四名 (5%) 患者患有转移到阴道的直肠癌。79 名患者中有 24 名 (30%) 出现急性泌尿生殖系统毒性，71 名患者中有 34 名 (48%) 出现晚期泌尿生殖系统毒性。在这两项分析中，毒性患者的中位尿道剂量显着更高。接受者操作曲线分析表明，尿道的 D0.1cm ³、D0.2cm ³和 D0.5cm ³分别与>78、>71 和>62 Gy 剂量下的毒性发展相关。

结论

尿道剂量似乎可以预测阴道肿瘤 ISBT 中的泌尿生殖系统毒性。有必要扩大队列并进行更长时间的后续研究。