Introduction
Brachytherapy is a major tool for dose escalation in gynecological cancer treatment. Control of rectal repletion is particularly challenging; it can impact dose received by this organ at risk and there are reported toxicities. The use of methods, such as enema and bowel preparation, to reduce rectal volume is a difficult process for patients, and its repeatability requires patients’ cooperation. Due to the effect of antibiotics on reducing intestinal gases, this study was conducted to measure the effect of adding rifaximin to bowel preparation on rectal dose-volume histogram (DVH) parameters.

Material and methods
In this prospective interventional study, 24 patients with cervical and endometrial cancer were treated with adjuvant high-dose-rate (HDR) brachytherapy. Both first and second sessions of brachytherapy were performed with bowel preparation, before and after the administration of rifaximin, respectively. The rectum was contoured as an organ at risk, and DVH parameters were recorded and compared in both sessions using magnetic resonance imaging (MRI)-based 3D treatment planning system.

Results
Rifaximin consumption reduced the rectal volume (p = 0.01), but had no significant correlation with other DVH parameters, especially D2cc (p = 0.599). Moreover, rectal volume had no significant correlation with DVH parameters (all p-values ≤ 0.05).

Conclusions
Even though the addition of rifaximin to bowel preparation significantly reduced rectal volume, no significant difference was observed in DVH parameters. Therefore, it is recommended that adjuvant vaginal cuff HDR brachytherapy should be performed without the use of rifaximin, until further researches’ validate its effects.



中文翻译：

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不可吸收口服抗生素在腔内近距离放射治疗肠道准备中的作用：利福昔明对阴道袖带近距离放射治疗期间直肠剂量学参数的影响

简介
近距离放射治疗是妇科癌症治疗中剂量递增的主要工具。控制直肠充盈尤其具有挑战性。它会影响这个处于危险中的器官接受的剂量，并且据报道有毒性。使用灌肠和肠道准备等方法减少直肠体积对患者来说是一个困难的过程，其可重复性需要患者的配合。由于抗生素对减少肠道气体的作用，本研究旨在测量在肠道准备中添加利福昔明对直肠剂量-体积直方图 (DVH) 参数的影响。

材料与方法
在这项前瞻性介入研究中，24 名宫颈癌和子宫内膜癌患者接受了辅助高剂量率 (HDR) 近距离放射治疗。第一次和第二次近距离放射治疗分别在给予利福昔明之前和之后进行肠道准备。直肠被描绘为一个有风险的器官，并使用基于磁共振成像 (MRI) 的 3D 治疗计划系统在两个疗程中记录和比较 DVH 参数。

结果
服用利福昔明减少了直肠体积（p = 0.01），但与其他 DVH 参数没有显着相关性，尤其是 D2cc（p = 0.599）。此外，直肠体积与 DVH 参数没有显着相关性（所有 p 值 ≤ 0.05）。

结论
尽管在肠道准备中添加利福昔明显着减少了直肠体积，但在 DVH 参数中没有观察到显着差异。因此，建议在不使用利福昔明的情况下进行辅助阴道袖带 HDR 近距离放射治疗，直到进一步研究验证其效果。