S1153
Clinical - Urology
ESTRO 2026
Digital Poster 803 Single-fraction stereotactic ablative body radiotherapy for T1b-T2a primary kidney cancer Itamar Averbuch 1 , Dimitri Bragilovski 1 , Shay Golan 2 , Dror Limon 1 , Elisha Fredman 1 1 Radiation Oncology, Davidoff Cancer Center, Petah Tikvah, Israel. 2 Urology, Rabin Medical Center, Petah Tikvah, Israel Purpose/Objective: Single-fraction stereotactic ablative body radiotherapy (SF-SABR) is an emerging non-invasive alternative for non-operative patients with primary kidney cancer, however thus far limited to T1a tumors measuring <4cm. We examined the safety and efficacy of SF-SABR in larger T1b-T2a (4-10cm) tumors. Material/Methods: Patients with newly diagnosed stage cT1b-2a kidney tumors were treated with SF-SABR at a single academic medical center. The primary endpoint was one-year local and distant control, defined as the absence of local progression or development of secondary sites of disease, with a secondary endpoint of acute and late toxicity. Median follow-up was calculated using the reverse Kaplan-Meier method. Results: Between 4/2022 – 4/2025, 20 patients were treated with SF-SABR (three with biopsy proven clear cell (2) and chromophobe (1) RCC), 17 based on radiographic diagnosis), to doses of 26 Gy (85%) or 25 Gy (15%). The median age was 79 years (range: 62–97), and 13/20 (65%) were male. The median Charlson comorbidity index was 6 (range, 5–12). 12 (60%) were left-sided tumors while eight (40%) were in the right kidney. The median maximal tumor diameter and volume were 5.7±1.0 cm (range: 4.5–7.8) and 76.6 cc (range: 41.7– 233.0), respectively. 12 (60%) patients had documented lesion growth of at least 20% on previous imaging prior to treatment. At a median follow-up of 19 months, nine (65%) had a radiographic partial response while 11 (55%) had stable disease. One-year local and distant control was 100%. The toxicity profile was available for 18 (90%) patients, of whom five (25%) and three (15%) experienced grade 1 and 2 toxicity, respectively (Table 1). One patient developed grade 3 flank pain and nausea one month after SABR, treated with oral steroids. No grade 4 or 5 toxicity were observed. Median decrease in GFR (CKD-EPI) at 6- months, 1-year, and 2-years post-treatment was 3, 5.5, and 12.5 ml/min/173m2, respectively.VomitingAbdominal painFlank painNauseaFatigueGrade 11 (5%)0 (0%)3 (15%)0 (0%)1 (5%)Grade 20 (0%)1 (5%)0 (0%)1 (5%)1 (5%)Grade 3 0 (0%)0 (0%)1 (5%)1 (5%)0 (0%) Conclusion: To the best of our knowledge, this is the first study
radiotherapy (WPRT) to eradicate subclinical nodal disease remains debated [1, 2, 3], particularly in intermediate-risk PCa. This study assessed the impact of WPRT in this population. Material/Methods: We conducted a multicenter retrospective study across all five radiotherapy departments of AP-HP (Assistance Publique – Hôpitaux de Paris), as part of the GRRAP (AP-HP Radiotherapy Research Group) program. Biopsy-proven intermediate-risk PCa (d’Amico classification) treated with conformational external beam radiotherapy between 2010 and 2019 were included. The primary endpoint was recurrence- free survival (RFS), defined as time from diagnosis to biochemical, local, metastatic recurrence, or death. Secondary endpoints were overall survival (OS) and acute (<6 months) or late ( ≥ 6 months) genitourinary (GU), gastrointestinal (GI), and sexual toxicities (CTCAE v4.03/v5.0). Survival outcomes were assessed using univariate and multivariate Cox models. Results: Three hundred patients (60 per center) were included; 94% received IMRT and 6% 3D-RT. After a median follow-up of 77 months, univariate analysis showed no significant association between WPRT and RFS (HR; 0.61; 95% CI, 0.26–1.42; p=0.25). Multivariable analysis adjusted for clinical and treatment factors yielded similar results (HR, 0.70; 95% CI, 0.27 to 1.81; p = 0.46). OS results were also comparable. Rates of grade 2 acute or late toxicities were similar, but grade ≥ 3 late GI toxicity was higher with WPRT (14.3% vs. 5.4%; p=0.045; OR 2.90). Conclusion: In intermediate-risk PCa, WPRT did not improve RFS or OS compared with prostate-only RT but was associated with an increased risk of severe GI toxicity. References: 1 Roach M et al. Sequence of hormonal therapy and radiotherapy field size in unfavourable, localised prostate cancer (NRG/RTOG 9413): long-term results of a randomised, phase 3 trial. Lancet Oncol 2018;19:1504–15.2 Pommier P et al. Is There a Role for Pelvic Irradiation in Localized Prostate Adenocarcinoma? Update of the Long-Term Survival Results of the GETUG-01 Randomized Study. Int J Radiat Oncol Biol Phys 2016;96:759–69.3 Murthy V et al. Prostate-Only Versus Whole-Pelvic Radiation Therapy in High-Risk and Very High-Risk Prostate Cancer (POP-RT): Outcomes From Phase III Randomized Controlled Trial. J Clin Oncol Off J Am Soc Clin Oncol 2021;39:1234–42. Keywords: Prostate, Pelvic Radiotherapy, Intermediate risk
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