Dosimetric comparison of rectal dose-reductive techniques in intra-cavitary brachytherapy for cervical cancer: A retrospective analysis

Masafumi Sawada; Yutaka Shiraishi; Hirofumi Toyama; Tomoki Tanaka; Ryuichi Kota; Naoyuki Shigematsu

doi:10.5114/jcb.2023.130842

Dosimetric comparison of rectal dose-reductive techniques in intra-cavitary brachytherapy for cervical cancer: A retrospective analysis

J Contemp Brachytherapy. 2023 Aug;15(4):269-274. doi: 10.5114/jcb.2023.130842. Epub 2023 Aug 30.

Authors

Masafumi Sawada^{1

2}, Yutaka Shiraishi^{1

2}, Hirofumi Toyama^{1

2}, Tomoki Tanaka^{1

2}, Ryuichi Kota^{1

2}, Naoyuki Shigematsu^{1

2}

Affiliations

¹ Department of Radiology, Keio University School of Medicine, Shinjuku-ku, Tokyo, Japan.
² Department and institution address where the research was conducted: Department of Radiology, Keio University School of Medicine, 35, Shinano-machi, Shinjuku-ku, Tokyo, Japan.

Abstract

Purpose: Rectal complications in radiotherapy for cervical cancer can highly affect quality of life and correlate with rectal dose. Vaginal gauze packing (VP) and rectal retraction (RR) are widely used for rectal dose reduction in high-dose-rate brachytherapy. We aimed to perform a dosimetric comparison of these two methods for three-dimensional image-guided adaptive brachytherapy.

Material and methods: We retrospectively examined 50 patients with cervical cancer treated with definitive radiotherapy, including intra-cavitary brachytherapy, performed with VP and RR. We extracted two fractions for each patient: one fraction with VP and the next fraction with RR, and then compared dose-volume parameters. In total, 50 fractions each were analyzed in VP and RR groups. Dose to 90% (D₉₀) of high-risk clinical target volume (HR-CTV), and minimum dose to most exposed 2.0 cm³ of other organs at risk (D_2cm³) for the rectum and bladder were determined from planning computed tomography.

Results: There were no significant differences between VP and RR in D₉₀ of HR-CTV (mean: 7.479 Gy and 7.652 Gy, respectively, p = 0.172). The D_2cm³ values for the rectum (mean: 4.234 Gy vs. 4.627 Gy, p = 0.008) and bladder (mean: 5.959 Gy vs. 6.690 Gy, p < 0.001) were significantly lower with VP compared with RR.

Conclusions: VP reduced the dose to the rectum and bladder when compared with RR without impairing the dose to CTV.

Keywords: high-dose-rate intra-cavitary brachytherapy; rectal dose; rectal retractor; uterine cervical cancer; vaginal gauze packing.