SABR (26Gy×1 or 42Gy/3fx) Delivers 100% 7-Year Local Control in Inoperable Primary RCC (FASTRACK II)

Stereotactic ablative body radiotherapy (SABR; high-dose, image-guided hypofractionated RT) was tested in FASTRACK II (TROG 15.03), a multicentre, non-randomised Phase 2 study in medically inoperable/high-risk or surgery-declining primary renal cell carcinoma (tumor ≤10cm; N0–N1), using 26Gy single fraction for tumors ≤4cm or 42Gy in 3 fractions for tumors >4cm. In the intention-to-treat population, 70 treated patients (median age 77; predominantly T1b or higher) had 100% freedom from local progression at 36, 60, and 84 months (median follow-up 62 months), with no grade 4 events or treatment-related deaths; within 9 months, 10% had SABR-related grade 3 AEs (notably pain 6%, nausea/vomiting 4%, colonic obstruction 3%, diarrhea 1%). For context, in non-surgical T1 renal masses, percutaneous ablation series typically report ~90–96% 5-year local control (often best in T1a; worse as tumors get larger), so 0 local failures out to 7 years—especially in a cohort enriched for >T1a disease—looks at least competitive, acknowledging cross-trial differences and the single-arm design.