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

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).