Promising Outcomes with SABR for Patients with Renal Cell Carcinoma

At the ASTRO 2025 Annual Meeting, new data highlighted stereotactic ablative body radiation (SABR) as a powerful treatment option for patients with renal cell carcinoma (RCC) who are not eligible for surgery. SABR, a non-invasive outpatient therapy, offers an incision-free approach with minimal hospitalization needs. Yet, its adoption for RCC has been slow.

A research team in Australia has led much of the work on SABR in RCC, publishing results from two major trials — FASTRACK I (Phase I) and FASTRACK II (Phase II). These studies suggested that SABR is both safe and effective. Analyses from the International Radiosurgery Oncology Consortium for Kidney (iROCK) had earlier shown that one- and three-fraction schedules may outperform five-fraction regimens.

The FASTRACK investigators pooled data from both trials, covering patients recruited between 2012 and 2020. Tumors smaller than 4 cm were treated with a single 26 Gy fraction, while larger tumors received 42 Gy in three fractions. The average tumor size was 4.7 cm.

Key results:

• Local control: 100% at two years, 99% at five years.
• Freedom from distant progression: 94.5% at two years, 83.9% at five years.
• Overall survival: 73.6% at five years.
• Renal function: Average decline in eGFR of 15.8 mL/min after five years; only one patient required dialysis.
• Toxicity: Grade 3 side effects occurred in eight patients (7.8%), including vomiting, pain, or bowel obstruction.

Lead author Dr. Shankar Siva of the Peter MacCallum Cancer Centre commented, “These studies were not designed to change urologists' minds! The data is compelling and should speak for itself, as robust prospective clinical trials investigating localized therapies in primary RCC are rare. Ultimately as patients and advocates become aware of the extraordinary efficacy of this totally non-invasive treatment, the community will demand access to SABR.”

Building on these outcomes, Dr. Siva’s team is preparing FASTRACK III, a randomized trial comparing SABR with partial nephrectomy in early-stage RCC (T1a and T1b).

“This needs to be a multinational effort and requires considerable funding, so there is a lot of work to be done,” Dr. Siva said.

If completed, FASTRACK III could be practice-changing — potentially making SABR a standard alternative to surgery for localized RCC worldwide.