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. 2017 Dec 1;12(1):192.
doi: 10.1186/s13014-017-0932-7.

Analysis of the relationship between prescribed dose and dosimetric advantage of real-time intraoperatively built custom-linked seeds in iodine-125 prostate brachytherapy

Katsumi Hirose  1   2 , Masahiko Aoki  3 , Mariko Sato  1 , Hiroyoshi Akimoto  1 , Yasuhiro Hashimoto  4 , Atsushi Imai  4 , Noritaka Kamimura  4 , Hideo Kawaguchi  1 , Yoshiomi Hatayama  1 , Ichitaro Fujioka  1 , Mitsuki Tanaka  1 , Chikara Ohyama  4 , Yoshihiro Takai  1   2
Affiliations

Analysis of the relationship between prescribed dose and dosimetric advantage of real-time intraoperatively built custom-linked seeds in iodine-125 prostate brachytherapy

Katsumi Hirose et al. Radiat Oncol. .

Abstract

Background: The purpose of this study was to investigate the differences in the dosimetric advantage of using intraoperatively built custom-linked (IBCL) seeds between permanent iodine-125 (I-125) seed implantation (PI) alone and PI followed by external-beam radiation therapy (EBRT) for prostate cancer.

Methods: We reviewed the records of 62 patients with localized prostate cancer who received transperineal interstitial brachytherapy with I-125 using free seeds or IBCL seeds. Twenty-four low- and intermediate-risk patients underwent PI alone with the prescribed dose of 160 Gy, and 39 high-risk patients underwent PI with 110 Gy, followed by EBRT with 45 Gy (PI + EBRT). Intraoperative and post-implant dosimetric parameters 1 month after implantation were collected and analyzed.

Results: The numbers of patients implanted with free seeds and IBCL seeds were 14 (58.3%) and 10 (41.7%), respectively, in the PI group and 25 (65.8%) and 13 (34.2%), respectively, in the PI + EBRT group. In the PI group, although there were significant differences in prostate V100 (p = 0.003) and D90 (p = 0.009) and rectum V100 (p = 0.026) on intraoperative dosimetry, these differences were not found on post-implant dosimetry. In the PI + EBRT group, the dosimetric parameters of IBCL seeds, such as prostate V200 (p = 0.013) and V250 (p = 0.010) and urethra D30 (p = 0.038), were better than those of free seeds on intraoperative dosimetry. Furthermore, even on post-implant dosimetry, prostate D90 (p = 0.004), V150 (p = 0.001), and homogeneity index (HI, p = 0.001), as well as V200 (p = 0.001) and V250 (p = 0.020), and urethra D5 (p = 0.008) as well as D30 (p = 0.003) had a better dosimetric quality in IBCL seeds than in free seeds. There was no significant difference in the operation time between free seeds and IBCL seeds in each PI and PI + EBRT group.

Conclusions: Our results reveal that greater dosimetric benefits could be obtained using IBCL seeds in the case of permanent implantation with a lower prescribed dose, such as PI + EBRT, rather than PI alone.

Keywords: Brachytherapy; IBCL seed; Prostate cancer; Seed migration.

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Conflict of interest statement

Ethics approval and consent to participate

All study participants provided informed consent, and we obtained general consent to the research.

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1
Fig. 1
Changes in dosimetric parameters for the PI group with 160-Gy PI. a The percentages of the prostate volume receiving each percentage of the prescribed dose. b The intraoperative and post-implant D90 prostate values. c The homogeneity index for free and IBCL seed groups. The spread of the data is denoted by a box and whiskers plot: box limits represent the 25th and 75th percentiles; the line within the box represents the median; whisker ends represent the 1st and 99th percentiles. *p < 0.05, **p < 0.01, in comparison with free seed and IBCL seed in each I.O. and P.I. Abbreviations: I.O. = intraoperative dosimetry; P.I. = postimplant dosimetry
Fig. 2
Fig. 2
Changes in dosimetric parameters for the PI + EBRT group with 110-Gy PI. a The percentages of the prostate volume receiving each percentage of the prescribed dose. b The intraoperative and post-implant D90 prostate values. c The homogeneity index for free and IBCL seed groups. The spread of the data is denoted by a box and whiskers plot: box limits represent the 25th and 75th percentiles; the line within the box represents the median; whisker ends represent the 1st and 99th percentiles. **p < 0.01, in comparison with free seed and IBCL seed in each I.O. and P.I. Abbreviations: I.O. = intraoperative dosimetry; P.I. = postimplant dosimetry
Fig. 3
Fig. 3
Comparison of operation times (min). The box indicates the 25th and 75th percentiles; the horizontal line in the box represents the median. Whisker ends represent the 1st and 99th percentiles
See this image and copyright information in PMC

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