Oncologic outcomes and renal function preservation after stereotactic ablative body radiotherapy versus radiofrequency ablation in stage I renal cell carcinoma

Abstract Purpose This study compared stereotactic ablative body radiotherapy (SABR) and radiofrequency ablation (RFA) in patients with biopsy-proven stage I renal cell carcinoma (RCC), focusing on oncologic outcomes and renal function outcomes. Methods Patients with stage I RCC treated with CyberKnife-based SABR or percutaneous RFA between 2009 and 2024 were retrospectively analyzed. Renal function was assessed using serial changes in estimated glomerular filtration rate (eGFR). Inverse probability of treatment weighting (IPTW) was applied to adjust for baseline imbalances. Results With a median follow-up of 46.3 months, 123 patients (SABR, n = 54; RFA, n = 69) were analyzed. Patients treated with SABR were significantly older (p = 0.002), and had larger tumors (p < 0.001), lower baseline eGFR (p = 0.002), and tumors more frequently located anteriorly (p = 0.008) and in close proximity to the renal sinus (p = 0.012). After IPTW, SABR demonstrated oncologic outcomes comparable to RFA, with 3-year freedom from local recurrence (98.8% vs. 91.6%; p = 0.733), disease-free survival (78.5% vs. 79.3%; p = 0.965), and overall survival (82.4% vs. 87.9%; p = 0.724). The annual rate of eGFR decline was similar between groups (–2.1 vs. –1.3 mL/min/1.73 m²; p = 0.364). Sustained eGFR < 15 mL/min/1.73 m² or dialysis occurred in 2 and 3 patients in the SABR and RFA groups, respectively. Except for one grade 3 bleeding event related to fiducial marker insertion in the SABR group, no grade ≥ 3 non-renal toxicities were observed. Conclusion In patients with stage I RCC, SABR may be considered a local treatment option with oncologic and renal outcomes comparable to those of RFA.