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

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

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.

MeSH terms

  • Aged
  • Brachytherapy*
  • Humans
  • Iodine Radioisotopes / therapeutic use*
  • Male
  • Neoplasm Seeding*
  • Prognosis
  • Prostatic Neoplasms / pathology
  • Prostatic Neoplasms / radiotherapy*
  • Prostatic Neoplasms / surgery
  • Radiotherapy Dosage
  • Radiotherapy Planning, Computer-Assisted / methods*
  • Radiotherapy, Intensity-Modulated / methods
  • Rectum / radiation effects
  • Urethra / radiation effects

Substances

  • Iodine Radioisotopes
  • Iodine-125