ESTRO 2025 - Abstract Book

S1988

Clinical - Urology

ESTRO 2025

2206

Digital Poster Simultaneous integrated boost versus sequential boost in hypofractionated VMAT prostate cancer radiotherapy: Implications for rectal sparing Zeineb Naimi, Siwar Abdessaied, Raja Oueslati, Roua Toumi, Raouia Ben Amor, Awatef Hamdoun, Ghada Bouguerra, Rihab Haddad, Lotfi Kochbati Radiation Oncology Department, Abderrahmen Mami Hospital, Ariana, Tunisia Purpose/Objective: The aim of this study was to compare the dosimetric outcomes of simultaneous integrated boost versus sequential boost in hypofractionated VMAT prostate cancer radiotherapy, with a particular focus on OAR sparing. Material/Methods: Data of localized prostate cancer patients who underwent hypofractionated VMAT as part of definitive androgen deprivation therapy (ADT)-RT was analysed. The prescription dose was 60 Gy/20 fractions to the prostate and 48 Gy/20 fractions to the seminal vesicles. For each patient, two treatment plans were generated using simultaneous integrated boost (SIB) and sequential boost (SeqB) techniques. Dose-volume histograms (DVHs) were generated for planning target volumes (PTVs), bladder, rectum, femoral heads, and bowel bag. Doses to OARs, conformity index (CI) and homogeneity index (HI) were assessed and statistically compared between the two techniques using the t student test. Results: A total of 40 treatment plans were generated. Both SIB and SeqB plans achieved adequate target volume coverage (V95% > 95% and V98% > 98%), with no statistically significant difference between the two techniques. Although both planning techniques met the OAR dose constraints, SIB plans showed higher rectum sparing against high doses. Specifically, V52.8Gy, V57Gy, and V60Gy for the rectum were significantly lower in SIB plans with a mean reduction of 17.9% (p=0.017), 23% (p=0.00) and 80% (p=0.00), respectively. No significant difference was found for low-dose volumes to the rectum (V5Gy, V10Gy, V20Gy) between both techniques. The V60Gy, V48.6Gy and V40.8Gy to the bladder did not statistically differ between SIB and SeqB plans. SIB plans resulted in better CI (0.99 versus 0.89, p=0.02) and HI (0.01 versus 0.04), p=0.04) than SeqB plans. Conclusion: Simultaneous integrated boost in hypofractionated prostate cancer RT showed higher efficiency in reducing high doses to the rectum over SeqB, potentially minimizing the risk of rectal toxicity. Further studies are needed to compare clinical outcomes and toxicity between both techniques.

Keywords: Prostate cancer; Hypofractionated radiotherapy

2230

Digital Poster SBRT in high-risk localized prostate cancer (HRPCa): a mono-institutional experience Gianluca Vullo 1 , Giuseppe Facondo 1 , Marco Andrea Signor 1 , Francesca Titone 1 , Eugenia Moretti 2 , Marika Guernieri 2 , Marco Trovò 1 1 Radioterapia Oncologica, ASUFC, Udine, Italy. 2 Fisica Saniaria, ASUFC, Udine, Italy

Purpose/Objective: To report oncological outcomes and toxicities from a series of high-risk prostate cancer (HRPCa) treated with SBRT