ESTRO 2024 - Abstract Book

S2453

Clinical - Urology

ESTRO 2024

Conclusion:

UHRT to the prostate using a once-weekly schedule results in satisfactory biochemical control and low rates of distant metastases in a contemporary cohort of patients in India. There was a lack of dose-volume correlations in this cohort for late GU toxicities. Dose-volume correlations were found at the high-dose range for late GI toxicities.

Keywords: SBRT, Ultra-hypofractionation, Late toxicities

1769

Mini-Oral

Intraprostatic recurrence in prostate cancer patients in the FLAME trial

Karolína Menne Guricová 1 , Ivo G Schoots 2,3 , Wouter Vogel 1 , Linda GW Kerkmeijer 4,5 , Floris Pos 1 , Hans CJ de Boer 5 , Jochem van der Voort van Zyp 5 , Martina Kunze-Busch 4 , Robert J Smeenk 4 , Cédric Draulans 6 , Karin Haustermans 6 , Petra J van Houdt 1 , Uulke A van der Heide 1 1 The Netherlands Cancer Institute, Radiation Oncology, Amsterdam, Netherlands. 2 The Netherlands Cancer Institute, Diagnostic Oncology, Amsterdam, Netherlands. 3 Erasmus University Medical Center, Radiology & Nuclear Medicine, Rotterdam, Netherlands. 4 Radboud University Medical Center, Radiation Oncology, Nijmegen, Netherlands. 5 University Medical Center Utrecht, Radiation Oncology, Utrecht, Netherlands. 6 University Hospitals Leuven, Radiation Oncology, Leuven, Belgium The FLAME trial demonstrated that dose escalation to the gross tumor volume (GTV) improves outcome in patients with intermediate and high-risk prostate cancer, resulting in 92% biochemical disease-free survival (bDFS) at 5 years (Kerkmeijer et al., 2021). A potential next step that would allow to maintain such a high bDFS while reducing toxicity might be the use of isotoxic focal boosting to the GTV(s) accompanied by a de-escalation of dose to the remaining prostate gland (clinical target volume; CTV). However, in order to safely do so, it is critical to ensure that intraprostatic recurrences do not originate from outside the GTV. Prior studies (Pucar et al., 2007; Arrayeh et al., 2012; Gorovets et al., 2023) reported that local recurrence was mostly located within the primary GTV. In this study, we investigated if intraprostatic recurrences in the FLAME trial also occurred inside the GTV and the corresponding dose delivered to the GTV. Purpose/Objective:

Material/Methods:

The study included all patients from the FLAME trial, who exhibited an intraprostatic recurrence. We used pre treatment images including GTV and CTV delineations, and the radiotherapy dose distribution. The pre-treatment images consisted of planning CT, T2-weighted MRI, diffusion weighted MRI and Dynamic Contrast-Enhanced MRI. In case GTV delineations were not available, they were delineated by an experienced uroradiologist based on the available pre-treatment images. To analyze recurrence location, images from the time of recurrence were collected (PSMA-PET images and/or multiparametric MRI scans).