Renal cell carcinoma (RCC) ranks as the eighth most common malignancy in Spain and remains among the top ten globally. Surgical resection—partial or radical nephrectomy—continues to be the curative gold standard.
However, an increasing proportion of elderly or medically fragile patients are deemed unsuitable for surgery due to comorbidities or high perioperative risk.For this population, minimally invasive ablative approaches such as radiofrequency ablation (RFA), cryoablation, and microwave ablation (MWA) have been proposed, though their efficacy and reproducibility are limited by anatomical and operator-related factors.In recent years, stereotactic body radiation therapy (SBRT) has emerged as a non-invasive, nephron-sparing, and well-tolerated treatment alternative capable of achieving high local control rates in localized RCC.
Study Overview
A narrative review by A. Ocanto et al., published in Actas Urológicas Españolas (2025), summarizes two decades of evidence on ablative techniques for inoperable renal tumors, emphasizing the evolution and clinical outcomes of SBRT.The authors reviewed English-language studies from 2010 to 2025 using PubMed, Scopus, Cochrane, and other major databases, focusing on prospective and high-quality retrospective series assessing local control, renal function preservation, and treatment-related toxicity.
Key Evidence: High Local Control and Favorable Toxicity Profile
Across the literature, local control rates after SBRT range from 80% to 100%, with most prospective studies and meta-analyses reporting outcomes above 95%.
SBRT has demonstrated:
- 2-year local control: 97–98% (IROCK data)
- 5-year cancer-specific survival (CSS): up to 92%
- Minimal renal impact: eGFR decline between 10–13 mL/min
- Low toxicity: predominantly Grade 1–2, with Grade ≥3 events in <5%
The FASTRACK II Trial: Establishing Modern SBRT Standards
The landmark FASTRACK II (TROG 15.03) phase II trial led by Siva et al. validated SBRT as a safe and effective primary therapy for clinically inoperable RCC:
- 70 patients, median tumor size 4.6 cm
- Dose regimens: 26 Gy ×1 (≤4 cm) or 42 Gy ×3 (4–10 cm)
- Outcomes:
- 100% local control
- 86% overall survival at 3 years
- 10% Grade 3 toxicity (mostly gastrointestinal)
- T1–T2a tumors (≤7 cm)
- eGFR ≥30 mL/min/1.73 m²
- ECOG 0–1 or Karnofsky ≥70%
- Non-metastatic disease (M0)
- Patients unfit or unwilling for surgery
Common regimens include:
- 25–26 Gy in 1 fraction (≤4 cm lesions)
- 42–48 Gy in 3 fractions or 40–50 Gy in 5 fractions for larger tumors
Emerging data suggest that SBRT may potentiate immune checkpoint blockade by inducing tumor antigen release and immune activation—the so-called abscopal effect. Building on the success of KEYNOTE-564 (pembrolizumab after nephrectomy), clinical trials are anticipated to test adjuvant or concurrent SBRT–IO combinations in RCC.
Clinical Implications
SBRT now stands as a mature, evidence-based alternative for patients with localized, inoperable RCC.
It offers:
- Non-invasive, outpatient treatment
- Excellent tumor control and renal preservation
- Minimal toxicity
- Feasibility for both peripheral and hilar tumors
Take-Home Message
Stereotactic body radiotherapy has transformed the therapeutic landscape of localized renal cancer—providing curative potential without surgery, anesthesia, or hospitalization. As clinical experience and trial data expand, SBRT may soon redefine standard care for inoperable RCC.
Written by: Abrahams Ocanto, Servicio de Oncología Radioterápica, Hospital Universitario San Francisco de Asís, GenesisCare, Madrid, Spain; Servicio de Oncología Radioterápica, Hospital Universitario Vithas La Milagrosa, GenesisCare, Madrid, Spain
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