ESTRO 2025 - Abstract Book

S4350

RTT - Treatment planning, OAR and target definitions

ESTRO 2025

2171

Proffered Paper Erectile function preservation after external beam radiotherapy using a dose-optimization approach on sexual structures for localized prostate cancer Antoine Ailloud 1 , Corina Udrescu 1 , Samy Horn 1 , Nicolas Vial 2 , Sébastien Crouzet 3 , Lionel Badet 3 , Ariane Lapierre 1 , Olivier Chapet 1 1 Radiotherapy, HCL, Lyon, France. 2 Radiotherapy, CHUSE, Saint-etienne, France. 3 Urology, HCL, Lyon, France Purpose/Objective: Erectile dysfunction (ED) is a common side effect of external beam radiotherapy (RT) for localized prostate cancer. The primary aim of this study was to evaluate an optimization approach targeting sexual structures to reduce the incidence of ED following RT. Material/Methods: Twenty-seven patients with localized prostate cancer, without erectile dysfunction (ED) (IIEF-5 ≥ 20) and not undergoing androgen deprivation therapy, were treated with doses ranging from 76 to 78 Gy in 2 Gy per fraction or 60 Gy in 3 Gy per fraction. CT/MRI fusion imaging was used to delineate the prostate volume and sexual structures, including the internal pudendal arteries (IPA), penile bulb (PB), and corpora cavernosa (CC). The dose delivered to erectile structures was optimized according to the ALARA (As Low As Reasonably Achievable) principle. Doses were extracted from the dose-volume histogram (DVHs). Erectile function was assessed using the IIEF-5 score. No ED, mild ED, and severe ED were defined by IIEF-5 scores of 20-25, 17-19, and <17, respectively. Statistical analyses were performed using the Mann-Whitney test, with the biostatTGV® software. Results: The mean follow-up duration was 3.9 years, and the mean age of the patients was 67.7 years. At 2 years, 69.2% of patients had no erectile dysfunction (ED), 7.7% mild ED, and 23.1% severe ED. Including the prescription of tadalafil, 84.6% of patients had no ED or mild ED at 2 years. A significant difference was observed between patients without ED (IIEF-5 ≥ 20) and those with ED (IIEF-5 < 20) in relation to various dosimetric parameters on the CC: mean dose (6.6Gy vs 14.9Gy; p=0.02), D5% (19.9Gy vs 45.1Gy; p=0.03), D10% (13.9Gy vs 34.3Gy; p=0.02), D50% (4.1Gy vs 10.1Gy; p=0.02), D90% (2.0Gy vs 4.1Gy; p=0.006), D95% (1.8Gy vs 3.6Gy; p=0.007) and D100% (1.2Gy vs 2.6Gy; p=0.004), respectively. No significant differences were observed for the dosimetric parameters on the IPA and PB, even if a trend was observed. The biochemical relapse-free survival rate was 100% at 2 years. Conclusion: The dose optimization of sexual structures in localized prostate cancer shows promising results in preserving erectile function after RT. The dose to the CC appears to be significantly correlated with the risk of ED at 2 years. Prospective studies are needed to assess the impact of optimizing sexual structures on ED.

Keywords: Erectile function, radiotherapy, prostate cancer

2178

Digital Poster Humeral heads radiation exposure in breast cancer radiotherapy: How does VMAT compare to 3D conformal radiotherapy? Zeineb Naimi, Mouna El Bakkali, Syrine Lahiouel, Raouia Ben Amor, Awatef Hamdoun, Rihab Haddad, Ghada Bouguerra, Lotfi Kochbati Radiation Oncology Department, Abderrahmen Mami Hospital, Ariana, Tunisia