S1167
Clinical - Urology
ESTRO 2026
stabilization. After the nadir, PSA remained stable in both groups, with post-nadir slopes near zero (LDR-BT 0.09 vs SBRT 0.06 ng/mL/month). PSA bounce occurred in 21.6% of LDR-BT and 41.3% of SBRT patients (p = 0.048). The median time to bounce was earlier for LDR-BT (28 months) than for SBRT (53 months, p = 0.037). None of the patients experiencing bounce developed biochemical recurrence, while 17 of 67 patients without bounce did (p = 0.002). Overall, LDR-BT demonstrated a more homogeneous long- term PSA decline with less interpatient variability, whereas SBRT showed greater dispersion across individual trajectories, findings that persisted throughout long-term follow-up. Conclusion: LDR brachytherapy results in a slower but more sustained PSA decline and lower nadir, reflecting more stable long-term biochemical control compared with SBRT. SBRT induces a faster initial decline and higher PSA variability, with a greater incidence of benign PSA bounce not associated with recurrence. These distinct PSA kinetic profiles support the prognostic relevance of early PSA slopes and nadir levels for long-term biochemical outcomes. References: Caloglu M, Ciezki JP, Reddy CA, Angermeier K, Ulchaker J, Chehade N, et al. PSA bounce and biochemical failure after permanent seed prostate brachytherapy. Int J Radiat Oncol Biol Phys. 2011;80(3):735–41.Crook J, Gillan C, Yeung I, Austen L, McLean M, Catton C, et al. PSA kinetics and PSA bounce following permanent seed prostate brachytherapy. Int J Radiat Oncol Biol Phys. 2007;69(2):426–33. Keywords: LDR, brachytherapy, SBRT Digital Poster 1080 Radiomics analysis of MRI Guided Adaptive Radiation Therapy as predictors of PSA kinetics in prostate cancer patients treated on MRLinac Rimoun R Boutrus 1 , Zeinab Ibrahim 1 , Saud Alkhlofi 1 , Mohammed Bayomy 2 , Ali Eid 1 1 Radiation Oncology Department, Bahrain Oncology Center, Muharraq, Bahrain. 2 Hematology Oncology Department, Salmanya Medical Complex, Manama, Bahrain Purpose/Objective: to examine the correlation between the changes in radiomics features (delta radiomics) over the course of treatment and the PSA nadir and time to nadir in prostate cancer patients treated with MRgRT Material/Methods: The medical records of 19 patients with low/favourable intermediate risk prostate cancer were reviewed. All patients were treated with MRgRT to a
with RT and ADT, our study confirms the usefulness of the NCCN classification in discriminating clinical outcomes between IRPCa and HRPCa. Keywords: Prostate cancer, NCCN classification, Outcomes Digital Poster Highlight 1060 Long-term PSA kinetics after SBRT and LDR brachytherapy in low- and favorable-intermediate risk prostate cancer María Cerrolaza 1 , Agustina Mendez 1 , Cristina Garcia 1 , Maria del Mar Puertas 1 , Victoria Navarro 2 , Claudia Colom 1 , Ana Galan 1 , Claudia Laborda 1 , Andrea Ochoa 1 , Javier Diez 3 , Pablo Alares 4 , Reyes Ibañez 1 1 Radiation Oncology, Miguel Servet University Hospital, zaragoza, Spain. 2 Radiation Oncology, Lozano Blesa University Clinical Hospital, zaragoza, Spain. 3 Department of Physics, Miguel Servet University Hospital, zaragoza, Spain. 4 External Consultant, in collaboration with the Department of Radiation Oncology, Miguel Servet University Hospital, zaragoza, Spain Purpose/Objective: Stereotactic body radiotherapy (SBRT) and low-dose- rate brachytherapy (LDR-BT) are established curative options for low- and favorable-intermediate-risk prostate cancer. Differences in dose delivery and fractionation may influence post-treatment PSA kinetics. This study compared long-term PSA kinetics following SBRT and LDR-BT. Material/Methods: A total of 97 patients with low- or favorable- intermediate-risk prostate cancer who did not receive androgen deprivation therapy were included in this retrospective analysis. All were treated using LDR-BT (n=51) or SBRT (n=46). PSA was measured every six months for up to 10 years. Endpoints included PSA nadir, time to nadir, PSA slopes (0–3, 6, 12 months), and PSA bounce—defined as a temporary PSA rise followed by spontaneous decline ( ≥ 0.2 ng/mL for LDR- BT, ≥ 0.5 ng/mL for SBRT). Group comparisons used t- test, Mann–Whitney U, or Fisher’s exact test, with p < 0.05 considered significant. Results: After a median follow-up of 115 months, median baseline PSA was significantly lower in the LDR-BT group (6.97 ng/mL) than in the SBRT group (7.60 ng/mL, p = 0.017). LDR-BT achieved a lower PSA nadir (median 0.02 ng/mL vs 0.36 ng/mL, p = 0.036) but reached it later (72 vs 36 months, p = 0.004). During the first 3 months, SBRT induced a steeper PSA decline (median slope − 1.48 ng/mL/month vs − 0.66 ng/mL/month, p = 0.031), while beyond 6 months, PSA slopes converged, reflecting biochemical
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