ESTRO 2025 - Abstract Book

S1916

Clinical - Urology

ESTRO 2025

1022

Poster Discussion The EREctile function preservation for prostate Cancer radiation Therapy (ERECT) trial (NCT04861194): preliminary results up to 18 months Tariq A Lalmahomed 1 , Frederik R Teunissen 1,2 , Johannes CJ de Boer 1 , Harm HE van Melick 3 , Helena M Verkooijen 4,5 , Richard P Meijer 6 , Ruud C Wortel 7 , Jochem RN van der Voort van Zyp 1 1 Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, Netherlands. 2 Department of Radiation Oncology, Radboud University Medical Center, Nijmegen, Netherlands. 3 Department of Urology, Sint Antoniusziekenhuis, Utrecht-Nieuwegein, Netherlands. 4 Division of Imaging and Oncology, University Medical Center Utrecht, Utrecht, Netherlands. 5 Division of Imaging, Netherlands Cancer Institute, Amsterdam, Netherlands. 6 Department of Oncological Urology, University Medical Center Utrecht, Utrecht, Netherlands. 7 Department of Urology, University Medical Center Utrecht, Utrecht, Netherlands Purpose/Objective: Erectile dysfunction (ED) is a frequent side effect of external beam radiotherapy (EBRT) for prostate cancer (PCa). The introduction of the magnetic resonance-guided linear accelerator (MR-Linac) has improved treatment precision and enables neurovascular-sparing treatments. The prospective phase 2 EREctile function preservation for prostate Cancer radiation Therapy (ERECT) trial (NCT04861194) aims to investigate the benefit of neurovascular-sparing radiotherapy in reducing ED for localized PCa. Material/Methods: ERECT is a prospective, single-center, single-arm phase 2 study. 70 patients were treated with a 1.5 Tesla MR-Linac, receiving 36.25 Gy in five fractions, with sparing of key erectile structures (internal pudendal arteries, neurovascular bundles, corpora cavernosa and penile bulb). The endpoint of this preliminary analysis was the incidence of patient reported ED at 6, 12 and 18 months post-treatment in ERECT patients, compared to a conventional group receiving the same dosage without neurovascular sparing. A Chi-square test was performed to test for between-group differences (α=0.05). ED was defined as a score on the International Index of Erectile Function -5 (IIEF- 5) of ≤ 11. Mean scores were compared using a Wilcoxon rank- sum test (α=0.05). Only patients with good erectile function at baseline, defined as an International Index of Erectile Function-5 (IIEF- 5) score ≥ 17, were analyzed (1). Patients using androgen deprivation therapy were excluded. All ERECT and conventional patients were also included in the prospective Utrecht Prostate Cohort (NCT04228211). Results: 59 ERECT patients and 132 conventional patients had baseline IIEF- 5 scores of ≥ 17. ERECT patients were younger (median age 63 vs. 68, p<.001) and included more ISUP grade 1 (26% vs. 12%), while the conventional group had more ISUP grade 3 (25% vs. 8.8%). Similar rates of diabetes (3.1% vs. 3.4%) and cardiovascular disease (16% vs. 17%) were observed in both groups. ED incidence was significantly lower in ERECT patients at all time points (6 months: 6% vs. 21%, p=.015; 12 months: 8.5% vs. 38%, p<.001; 18 months: 16% vs. 36%, p=.019). ERECT patients consistently reported significantly higher mean IIEF-5 scores (6 months: 21 vs. 18, p=.007; 12 months: 20 vs. 15, p<.001; 18 months: 20 vs. 14, p<.001).