Yamada Yuki, Tomita Natsuo, Kitagawa Yuto, Imai Mikiko, Ito Mitsuaki
Radiation Oncology, Kasugai Municipal Hospital, Kasugai, JPN.
Radiology, Nagoya City University Graduate School of Medical Sciences, Nagoya, JPN.
Cureus. 2020 Nov 17;12(11):e11537. doi: 10.7759/cureus.11537.
Image-guided brachytherapy (IGBT) is commonly used for patients with cervical cancer, but two-dimensional intracavitary brachytherapy (2D-ICBT) is also still utilized for certain patients. We report a patient with cervical cancer who developed vaginal fistulas of the bladder and small bowel after chemoradiotherapy with 2D-ICBT. A 61-year-old woman with stage IIB cervical cancer underwent a combination of external beam radiotherapy (EBRT) at a dose of 50.4 Gy in 28 fractions and 2D-ICBT at a dose of 22 Gy in four fractions. As packs were well inserted around the uterus in all fractions of 2D-ICBT, the doses to the surrounding organs at risk (OAR) could be likely to be kept at low levels. She developed a huge fistula between the vagina and bladder approximately 2.5 years after radiotherapy (RT). She also developed a fistula between the vagina and small bowel approximately seven years after RT and underwent bypass from the small bowel to the transverse colon. The OAR were delineated using computed tomography for EBRT planning, and the cumulative dose of 2D-ICBT plus EBRT was evaluated as the source of toxicity. The cumulative dose converted to the equivalent dose in 2-Gy fractions (EQD2) was calculated using the linear-quadratic model with α/β = 3 for the OAR. The cumulative EQD2 values of the minimum dose to the most irradiated 2 cc (D2cc) of the bladder and small bowel were 90.2 Gy and 79.5 Gy, respectively. These values exceeded the upper limits of the dosimetric criteria of the OAR, suggesting an association with both vaginal fistulas. As the adoption of IGBT is too slow in some countries, it is noteworthy that a reduced bladder volume may result in a significant increase in the dose to the small bowel and bladder in 2D-ICBT.
图像引导近距离放射治疗（IGBT）常用于宫颈癌患者，但二维腔内近距离放射治疗（2D-ICBT）仍在某些患者中使用。我们报告了一名宫颈癌患者，在接受2D-ICBT放化疗后出现膀胱和小肠阴道瘘。一名61岁的IIB期宫颈癌女性接受了外照射放疗（EBRT），剂量为50.4 Gy，分28次进行，以及2D-ICBT，剂量为22 Gy，分4次进行。由于在2D-ICBT的所有分次中，施源器在子宫周围插入良好，周围危及器官（OAR）的剂量可能保持在较低水平。放疗（RT）后约2.5年，她出现了阴道与膀胱之间的巨大瘘管。RT后约7年，她还出现了阴道与小肠之间的瘘管，并接受了小肠至横结肠的旁路手术。使用计算机断层扫描进行EBRT计划时勾勒出OAR，并将2D-ICBT加EBRT的累积剂量评估为毒性来源。使用线性二次模型，α/β = 3，计算OAR转换为2 Gy分次等效剂量（EQD2）的累积剂量。膀胱和小肠最受照射的2 cc（D2cc）最小剂量的累积EQD2值分别为90.2 Gy和79.5 Gy。这些值超过了OAR剂量学标准的上限，提示与两个阴道瘘均有关联。由于在一些国家IGBT的采用速度过慢，值得注意的是，膀胱体积减小可能导致2D-ICBT中对小肠和膀胱的剂量显著增加。
