Androgen Deprivation Benefits in Low-Dose-Rate Brachytherapy With Hydrogel Spacer

We aim to investigate the impact of rectal dose reduction of both androgen deprivation therapy (ADT) and concurrent hydrogel spacer placement (HSP) in patients treated with low-dose-rate (LDR) brachytherapy for prostate cancer and to determine whether there are variations in the degree of efficacy of dose reduction across different segments of the rectum.

This study involved 130 consecutive patients treated with I-125 LDR brachytherapy, with (ADT: n = 66) or without (nADT: n = 64) prior ADT, from June 2017 to April 2021. Among these, 13 ADT and 17 nADT patients underwent HSP following induction in May 2020, whereas the remaining patients (nHSP) included 53 ADT and 47 nADT individuals. In the post plan, a rectal dose assessment was made using the rectal volume (RV), divided by horizontal sections into three equal-length subparts (sRVs), such as high-, mid-, and low-RV. The mean sRV₁₀₀ values were compared between the nADT and ADT patient groups, both with and without HSP. Similarly, mean sRV₁₀₀ was compared between the nHSP and HSP patient groups, both with and without ADT.

In nADT patients, HSP significantly reduced the mean RV₁₀₀ of the high-RV (0.002 cc versus 0.086 cc, p < 0.05) and mid-RV (0.127 cc versus 0.377 cc, p < 0.05), but not of the low-RV (0.060 cc versus 0.150 cc, p = 0.06). In contrast, in ADT patients, HSP significantly reduced the RV₁₀₀ at all three sites (0.002 cc versus 0.031 cc, p < 0.05; 0.034 cc versus 0.269 cc, p < 0.05; and 0.015 cc versus 0.151 cc, p < 0.05, respectively). No significant difference was observed when comparing mean sRV₁₀₀ with or without ADT in both HSP and nHSP patients.

The combination of ADT and HSP for LDR prostate brachytherapy showed the potential to significantly reduce RV₁₀₀, especially in the lower rectum.