ESTRO 2024 - Abstract Book

S428

Brachytherapy - Urology

ESTRO 2024

[4]. The purpose of this study was to determine if the dose received by prostate sectors was associated with risk of biochemical recurrence or PSA bounce.

Material/Methods:

Dosimetric data from post-implant CTs performed approximately 30 days after radioactive seed insertion were obtained for the 606 men treated with LDR prostate brachytherapy 2009-2020 inclusive at our institution. Median follow up was 5.8 years. Prostate sectors were created by dividing the prostate into three equal thirds (base/mid gland/apex), then each third into four axial sectors in a cross-shape (X). As the D'Agostino-Pearson normality test indicated data were not normally distributed, non-parametric statistical tests were performed. Three comparisons were made: 1. The Mann Whitney U test compared the D90% for each sector among those patients who experienced biochemical recurrence, to the D90% for the same sector among those who did not experience biochemical recurrence. 2. The Mann Whitney U test compared the D90% for each sector among those patients who experienced PSA bounce, to the D90% for the same sector for those who did not experience PSA bounce. 3. The Kruskal-Wallis test was used to compare D90% for each sector according to outcomes of biochemical recurrence, PSA bounce and no PSA bounce/biochemical recurrence. The anterior base sector and posterior mid-gland sector received the lowest (85.9%, IQR 76.6-95.6%) and highest (141.8%, IQR 128.3-155.5%) median D90% respectively. There was no association between the D90% to any sector and risk of biochemical recurrence versus no biochemical recurrence, or risk of PSA bounce versus no PSA bounce (Table 1). There was also no association between the D90% to any sector and risk of outcomes of biochemical recurrence, PSA bounce or no PSA bounce/biochemical recurrence (Table 1). Further analyses were performed evaluating the dose to the anterior base sector, as this sector consistently received the lowest D90%, and risk of outcomes. When the D90% to the anterior base sector was stratified by the median global prostate D90% levels, there were no significant differences in outcomes of PSA bounce (p=0.9077) or biochemical recurrence (p=0.6676). Five year biochemical progression free survival (bPFS) rates were 89.7% for those with median D90% ≤ global prostate D90% and 87.9% for those with median D90% > global prostate D90% (Fig. 1). Similarly, when the D90% to the anterior base sector was stratified by the first and third quartile global prostate D90% levels, there were no statistically significant differences in outcomes of PSA bounce (p=0.8830 and p=0.4262) or biochemical recurrence (p=0.3394 and p=0.4350 respectively) (Fig. 1). Results: