Open Access

Naoya Murakami, Satoshi Shima, Tairo Kashihara, Nikolaos Tselis, Tomoyasu Kato, Yoshiaki Takagawa, Koji Masui, Ken Yoshida, Kana Takahashi, Koji Inaba, Kae Okuma, Hiroshi Igaki, Yuko Nakayama, Jun Itami

• Purpose: The purpose of this study was to report our initial experience of hyaluronic acid gel injection (HGI) in the vesicovaginal septum (VVS) for bladder dose reduction in brachytherapy (BT) for uterine cervical carcinoma. Material and methods: Between September 2016 and May 2018, 15 uterine cervical cancer patients received HGI in the VVS as a part of their definitive radiotherapy (RT) treatment consisting of external beam radiation therapy (EBRT) with additional BT. Of those, 9 patients received BT both with and without HGI, and remaining 6 patients were excluded because these 6 patients received HGI in the VVS for all BT fractions. All 9 patients received HGI in the rectovaginal septum. For these patients, the dosimetric parameters bladder D2cc, HR-CTV D90, and rectum D2cc were selected, and two groups were generated (BT with vs. without HGI in the VVS) for dosimetric comparison. Results: The median cumulative EQD2 for HR-CTV, rectum D2cc, and bladder D2cc for the 9 patients were 73.3, 52.8, and 67.1, respectively. While no statistical difference could be detected for rectal dose reduction, bladder dose was significantly less in the group with HGI in the VVS compared to that without (449 cGy [range, 416-566, 1SD = 66.1] vs. 569 cGy [range, 449-647, 1SD = 59.5], p = 0.033), with no compromising of target coverage. Although it did not reach statistically significance, there was a trend toward better HR-CTV D90 in the group with HGI compared to that without HGI in the VVS (713 cGy vs. 706 cGy, p = 0.085). No severe bleeding, hematuria, bladder wall injury, or urethral injury requiring hospitalization was experienced in association with HGI in the VVS. Conclusions: HGI in the VVS can be performed safely and can effectively reduce the bladder dose in BT for uterine cervical cancer patients.