S1162
Clinical - Urology
ESTRO 2026
was given at the physician’s discretion. EEndpoints were biochemical recurrence-free survival (bRFS), distant metastasis-free survival (DMFS), and prostate cancer–specific mortality (PCSM). Kaplan–Meier and Fine–Gray regression were used, and the generalized competing-risk parameter ( ω ) quantified the proportion of total mortality due to PCa at 60 and 96
Midgland and apex measurements are most predictive of rectum D0.03cc ≥ 36Gy; D1cc ≥ 32Gy and D3cc ≥ 29Gy. Adequate spacer thickness at prostatic midgland and apex is crucial for radiation dose savings to the rectum for Prostate SBRT. Future directions include refining the SMScore to account for only midgland and apex spacer thickness measurements. Cut-off values of spacer thickness can be predicted to provide guidelines to facilitate rectal sparing. References: 1.Fischer-Valuck BW, Chundury A, Gay H, Bosch W, Michalski J. Hydrogel spacer distribution within the perirectal space in patients undergoing radiotherapy for prostate cancer: Impact of spacer symmetry on rectal dose reduction and the clinical consequences of hydrogel infiltration into the rectal wall. Pract. Radiat. Oncol. 2017;7(3):195–202. https://doi.org/10.1016/j.prro.2016.10.0042.Grossman CE, Folkert MR, Lobaugh S, Desai NB, Kollmeier MA, Gorovets D, et al. Quality Metric to Assess Adequacy of Hydrogel Rectal Spacer Placement for Prostate Radiation Therapy and Association of Metric Score with Rectal Toxicity Outcomes. Adv. Radiat. Oncol. 2023;8(4):101070. https://doi.org/10.1016/j.adro.2022.101070  Keywords: Thickness, Scoring, Positioning Precision radiotherapy in intermediate-risk prostate cancer: role of dose escalation and androgen deprivation therapy Cem Onal 1,2 , Aysenur Elmali 2 , Ertugrul Senturk 3 , Birhan Demirhan 4 , Petek Erpolat 3 , Ozan Cem Guler 1 1 Department of Radiation Oncology, Baskent University Faculty of Medicine Adana Dr. Turgut Noyan Research and Treatment Center, Adana, Turkey. 2 Department of Radiation Oncology, Baskent University Faculty of Medicine, Ankara, Turkey. 3 Department of Radiation Oncology, Gazi University Faculty of Medicine, Ankara, Turkey. 4 Department of Radiation Oncology, Iskenderun Gelisim Hospital, Hatay, Turkey Purpose/Objective: To assess the impact of simultaneous integrated boost (SIB) and androgen-deprivation therapy (ADT) duration on long-term oncologic outcomes in favorable (FIR) and unfavorable (UIR) intermediate-risk prostate cancer (IR-PCa) treated with image-guided radiotherapy (RT). Material/Methods: Digital Poster Highlight 977 Between 2009 and 2023, 531 patients with biopsy- proven IR-PCa from two academic institutions received definitive image-guided IMRT or VMAT (median 78 Gy), with or without an MRI-guided SIB up to 86 Gy. ADT
months.. Results:
After a median follow-up of 96.1 months, 8-year bRFS and DMFS for the entire cohort were 92.2% and 94.9%, respectively. Disease progression occurred in 7.4% of patients, and PCSM accounted for 2.5% of deaths. Patients with UIR disease exhibited significantly inferior outcomes versus FIR (8-year bRFS 89.8% vs 98.1%, p=0.003; DMFS 93.3% vs 98.7%, p=0.006). ADT use improved long-term outcomes overall (bRFS 95.8% vs 87.1%, p = 0.005; DMFS 97.2% vs 91.7%, p=0.01). Stratified analysis revealed that ADT conferred no measurable advantage in FIR (bRFS 100% vs 96.2%, p=0.55; DMFS 100% vs 97.3%, p=0.29) but yielded major gains in UIR (bRFS 94.5% vs 81.9%, p=0.001; DMFS 96.3% vs 88.4%, p=0.003). Longer ADT duration (>6 months) offered no additional improvement beyond short-term therapy. SIB did not significantly influence bRFS (90.6% vs 93.9%, p=0.30) or DMFS (92.7% vs 97.2%, p=0.04 overall; nonsignificant within FIR/UIR subgroups), confirming excellent tumor control across dose levels. On Fine–Gray analysis, ≥ 50% positive biopsy cores independently predicted PCSM (sHR 2.86, p = 0.02), whereas ADT use reduced disease-specific mortality risk (sHR 0.41, p = 0.04). Competing-risk modeling showed ω ≈ 0 throughout follow-up in FIR, indicating minimal prostate-cancer mortality, while UIR displayed a progressive ω rise from 0.04 at 60 months to 0.13 at 96 months, reflecting increasing proportional mortality burden from prostate cancer. Conclusion: In the modern image-guided RT era, ADT benefits are confined to UIR disease, while FIR patients achieve excellent control with RT alone. SIB ensures durable local control without increasing PCSM. ω -based competing-risk modeling highlights the minimal disease-specific mortality in FIR, supporting a precision-intensity approach: de-escalation for FIR to avoid overtreatment and intensification for UIR to
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