Comparison of post-implant dosimetrics between intraoperatively built custom-linked seeds and loose seeds by sector analysis at 24 hours and 1 month for localized prostate cancer

Abstract

Purpose: To compare post-implant dosimetrics between intraoperatively built custom-linked (IBCL) seeds and loose seeds (LS) at 24 hours and 1 month by sector analysis, and to evaluate the effect of IBCL seeds with regard to change in dosimetric parameters, in patients with prostate cancer treated with brachytherapy. Material and methods: Consecutive patients treated for localized prostate cancer who received definitive brachytherapy between March 2013 and October 2017 were retrospectively analyzed. Prostate V 100 (PV 100), prostate D 90 (PD 90), prostate V 150 (PV 150), urethral D 30 (UD 30), urethral V 150 (UV 150), and rectal V 100 (RV 100) were assessed. Results: Thirty-two patients were treated with LS and 32 patients were treated with IBCL seeds. The median follow-up time was 49.9 months in the LS group and 27.1 months in the IBCL group. PV 150 , UV 150 , and UD 30 at 24 hours and UD 30 at 1 month showed significant difference (F-test), and standard deviation (SD) tended to be lower in the IBCL group. Analysis of change in the variables revealed significance for ΔPV 100 and ΔPD 90 (F-test, p = 0.014 and < 0.001, respectively), and ΔPV 150 and ΔUD 30 showed marginal significance (p = 0.084 and 0.097, respectively). PV 150 , UV 150 , and UD 30 at 24 hours and 1 month were significantly lower in the IBCL group, and there was no significant difference in PV 100 , PD 90 , and RV 100 compared with the LS group (t-test). The homogeneity index (HI) was significantly higher in the IBCL group (p < 0.001). Conclusions: In this retrospective single institutional study, there was a decrease in the SD of the dosimetric parameters in the IBCL group, and it was statistically significant in change in the variables between 24 hours and 1 month (F-test). The use of IBCL seeds significantly decreased PV 150 , UV 150 , and UD 30 , and significantly improved HI, without lowering PD 90 or PD 100 .

Long-term results with custom-linked iodine-125 seeds and real-time brachytherapy in low- and intermediate-risk prostate cancer

“…However, they worsen over time and it is important to know the long-term efficacy. In addition, there are different techniques with seeds, with prior planning or with real-time, and various seed construction systems, with variable implant dosimetry quality, including loose, linked, and intra-operatively built custom-linked seeds [ 4 ]. A good technique and optimized dosimetry are able to improve the results at five years, while comparing two groups of similar patients [ 5 ].…”

Commentary: “Long-Term Outcomes and Prognostic Analysis of Computed Tomography-Guided Radioactive 125 I Seed Implantation for Locally Recurrent Rectal Cancer After External Beam Radiotherapy or Surgery”: Letter to the Editor

“…Such results may be more favorable to the formulation of a preoperative implantation plan to control post-implantation radiation damage. In addition, it is also necessary to include D100, V150, and V200, because D100 can reflect the dose in the peripheral area of the tumor, and V150 and V200 can reflect the volume of the high dose within the tumor target ( 5 , 6 ). In our recent study ( 6 ), we found that the faster the tumor shrank, the more likely the 125 I seeds were to gather centrally, which might lead to the local ultra-high dose region, thereby causing radiation damage to surrounding normal tissues.…”