S1271
Clinical - Urology
ESTRO 2026
2 Department of Biomedical Sciences, Humanitas University, Pieve Emanuele, Italy
Purpose/Objective: SBRT is increasingly used for oligoprogressive metastatic renal cell carcinoma (mRCC), targeting resistant disease sites and potentially prolonging the benefit of ongoing systemic therapy. However, evidence on optimal integration of SBRT in this setting is still evolving. This study aimed to evaluate systemic treatment duration and clinical outcomes following SBRT for oligoprogressive mRCC. Material/Methods: We retrospectively reviewed patients with mRCC who received SBRT for oligoprogressive disease at a single institution between 2010 and 2021. Eligible patients had ≤ 5 new or progressing lesions in ≤ 3 organs while on systemic therapy, without present or prior brain metastases. All active lesions were treated with SBRT to an EQD2 dose ≥ 50 Gy ( α / β = 3 Gy), without escalation of systemic therapy after radiotherapy. Subsequent SBRT courses were allowed within the same systemic therapy line if new oligoprogression occurred. The primary endpoint was time to next systemic therapy (TTNT). Secondary endpoints included overall survival (OS), time to progression (TTP), duration of subsequent systemic therapy, and SBRT-related adverse events (AE), graded per CTCAE v5.0. Time-to-event outcomes were estimated using Kaplan–Meier analysis, while baseline characteristics were summarized descriptively. Results: A total of 42 lesions were treated across 29 SBRT courses in 20 patients. Median age was 72 years, 75% were male and 95% had clear-cell histology. SBRT was delivered during treatment with TKIs (75.9%), immunotherapy (17.2%), or other agents (6.9%). Each course targeted a median of one lesion (range 1–4) to a median minimum EQD2 of 129.6 Gy, most commonly in the lungs (47.6%) and liver (19%). Four patients received >1 SBRT course, accounting for 11 courses across 5 systemic therapy lines (median 2 courses per line). Median follow-up was 20.6 months. Median TTNT was 27.0 months, with 76.3% (95% CI 51.9–89.4) and 65.4% (95% CI 40.5–81.9) of patients maintaining their systemic therapy line at 12 and 24 months. Median OS was 48.9 months, with a 3-year rate of 66.2% (95% CI 39.6–83.2). Median TTP was 10.5 months, with 1- and 2-year rates of 44.8% (95% CI 25.1–62.6) and 15.1% (95% CI 3.9–33.1). Subsequent systemic therapy median duration was 10.3 months (IQR 1.7–16.8). No grade ≥ 3 acute or late AE were observed.
Conclusion: SBRT for oligoprogressive mRCC was associated with prolonged continuation of ongoing systemic therapy and effective disease control, with minimal AE. These findings add to the growing body of evidence supporting SBRT integration in the management of oligoprogressive mRCC. References: 1. Guckenberger M et al. Characterisation and classification of oligometastatic disease: ESTRO-EORTC consensus recommendation. The Lancet Oncology. 2020 Jan 1;21(1):e18-282. Vandaele S et al. Stereotactic Body Radiotherapy for Extracranial Oligometastatic Renal Cell Carcinoma: State of the Art and Future Perspectives. Technology in Cancer Research & Treatment. 2025 Jul;24:153303382513573443. Franzese C et al. The impact of stereotactic ablative radiotherapy on oligoprogressive metastases from renal cell carcinoma. Journal of Cancer Research and Clinical Oncology. 2023 Jul;149(8):4411-74. EORTC research project 1822 - E2-RADIatE-OligoCare. Keywords: SBRT, oligoprogressive mRCC Prospective randomized controlled trial of hyaluronic acid spacer for hypofractionated prostate radiation therapy: 3-year results (NCT04189913) Martin T King 1 , Michael Chao 2 , Michelle Svatos 3 , Leavitt Morisson 4 , Daniel Low 5 , Erik Chell 6 , Peter F Orio 7 1 Radiation Oncology, Brigham and Women's Hospital, Boston, USA. 2 Radiation Oncology, Genesis Care Victoria, Melbourne, Australia. 3 NA, Teleflex, Pleasanton, USA. 4 NA, Biostatistical Consulting, Boston, USA. 5 Radiation Oncology, UCLA, Los Angeles, USA. 6 NA, Chell Scientific Consulting, Oakland, USA. Proffered Paper 3623
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