Analysis of dosimetric improvements using hydrogel spacer in high-dose-rate brachytherapy for prostate cancer

Moe Honda; Tomoya Oshikane; Motoki Kaidu; Eisuke Abe; Takahiro Komiya; Shumpei Yamako; Yukiyo Goto; Hisashi Nakano; Toshimichi Nakano; Satoshi Tanabe; Atsushi Ohta; Satoru Utsunomiya; Nobuko Yamana; Fumio Ishizaki; Hiroyuki Ishikawa

doi:10.5114/jcb.2025.155737

eISSN: 2081-2841
ISSN: 1689-832X

Journal of Contemporary Brachytherapy

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5/2025
vol. 17

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abstract:

Original paper

Analysis of dosimetric improvements using hydrogel spacer in high-dose-rate brachytherapy for prostate cancer

Moe Honda

^{1, 2}

,

Tomoya Oshikane

¹

,

Motoki Kaidu

³

,

Eisuke Abe

^{2, 3}

,

Takahiro Komiya

³

,

Shumpei Yamako

³

,

Yukiyo Goto

³

,

Hisashi Nakano

³

,

Toshimichi Nakano

¹

,

Satoshi Tanabe

³

,

Atsushi Ohta

³

,

Satoru Utsunomiya

⁴

,

Nobuko Yamana

⁵

,

Fumio Ishizaki

⁶

,

Hiroyuki Ishikawa

¹

Department of Radiology and Radiation Oncology, Niigata University Graduate School of Medical and Dental Sciences, Chuo-ku, Niigata 951-8510, Japan
Division of Radiation Oncology, Nagaoka Chuo General Hospital, Nagaoka 940-8653, Japan
Division of Radiation Oncology, Niigata University Medical and Dental Hospital, Chuo-ku, Niigata 951-8510, Japan
Department of Radiological Technology, Niigata University Graduate School of Health Sciences, Chuo-ku, Niigata 951-8518, Japan
Department of Radiology, Niigata Prefectural Shibata Hospital, Shibata, Niigata 957-8588, Japan
Department of Urology, Niigata University Graduate School of Medical and Dental Sciences, Chuo-ku, Niigata 951-8510, Japan

J Contemp Brachytherapy 2025; 17, 5: 315–321

DOI: https://doi.org/10.5114/jcb.2025.155737

Online publish date: 2025/10/31

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Purpose
This study primarily aimed to evaluate the effects of a hydrogel spacer (HS) on dosimetric distribution in the planning target volume as well as on rectal and urethral doses in high-dose-rate brachytherapy (HDR-BT) for prostate cancer, and to identify prostate sub-regions with improved dosimetric parameters and patient conditions that particularly benefit from the use of HS.

Material and methods
This study included 28 patients, who underwent HDR-BT using HS. Treatment plans with HS and simulated plans without HS were compared. The prostate was divided into six regions: ventral and dorsal in the dorsoventral direction, and apex, mid-gland, and base in the craniocaudal direction. V100% and D90% were evaluated in each region, along with dose assessments for the rectum and urethra. Paired t-tests were performed to analyze significance, and effect sizes were calculated using Cohen’s d.

Results
S significantly improved V100% in the dorsal regions (p < 0.05), particularly in the dorsal apex and dorsal mid regions (median V100% with and without HS: apex, 100.00 vs. 97.10; mid, 100.00 vs. 97.22). D90% showed improvement across all regions (p < 0.05), with greater effects observed in the dorsal apex and dorsal mid regions (median D90% with and without HS: apex, 110.15 vs. 103.56; mid, 113.31 vs. 106.21; d ≥ 0.8). Rectal dose parameters improved significantly (p < 0.05), whereas urethral dose changes were not significant (p = 0.14).

Conclusions
HS effectively reduced rectal doses and improved V100% and D90% in the dorsal apex and dorsal mid regions of the prostate. These regions are anatomically closer to the rectum and are often subject to dose constraints as well as critical areas for sufficient dose delivery because of the frequent localization of prostate cancer lesions. Therefore, HS is particularly beneficial for patients with dominant lesions in these regions.

keywords:

Analysis of dosimetric improvements using hydrogel spacer in high-dose-rate brachytherapy for prostate cancer

Moe Honda 1, 2 , Tomoya Oshikane 1 , Motoki Kaidu 3 , Eisuke Abe 2, 3 , Takahiro Komiya 3 , Shumpei Yamako 3 , Yukiyo Goto 3 , Hisashi Nakano 3 , Toshimichi Nakano 1 , Satoshi Tanabe 3 , Atsushi Ohta 3 , Satoru Utsunomiya 4 , Nobuko Yamana 5 , Fumio Ishizaki 6 , Hiroyuki Ishikawa 1

prostate cancer, hydrogel spacer, high-dose-rate, brachytherapy, dosimetry