Definitive renal stereotactic ablative radiotherapy (SABR) is gaining momentum, with promising data showing excellent local control and short-term renal function comparable to surgery. However, data on late radiation-associated kidney injury and renal safety remain limited. We therefore assessed post-treatment renal outcomes and dose-response after kidney irradiation to inform nephron-sparing SABR for primary renal cell carcinoma (pRCC).
We conducted a retrospective cohort study of trunk radiotherapy patients at a tertiary university cancer center, with incidental kidney exposure (EQD2 ≥10 Gy) and longitudinal renal function follow-up. Of 731 screened patients, 232 met inclusion criteria. Chronic-kidney-disease (CKD) deterioration was analyzed against renal dose using multivariable Cox, cut-off, and spline analyses.
During median follow-up of 170 days (IQR 60-541), CKD worsening occurred in 46.98% of patients, at a median of 173 days (IQR 55-423). Mean and maximum kidney doses (EQD2) were 14.2 Gy (SD 4.68) and 14.6 Gy (SD 4.86), respectively. Higher renal dose independently predicted renal function decline (HR 1.04/Gy; p=0.028 for mean; p=0.014 for max). Female sex was a risk factor (HR 2.08; p<0.001). Cut-offs were 18.7 Gy (mean) and 19.0 Gy (max), with monotonic dose-response. Retrospective design limits causal inference; constraints remain exploratory; validation required.
Within low-to-moderate dose ranges to non-tumorous kidney tissue, irradiation was associated with a dose-dependent post-treatment decline in renal function, while severe toxicity was rare. Nephron-sparing SABR is a safe treatment option for pRCC, informing risk-adapted dose constraint refinement to minimize late injury.
Frontiers in oncology. 2026 Jun 23*** epublish ***
Marthe Sophie Kilian, Laura Anna Fischer, Jona Bensberg, Lisa-Antonia von Diest, Carla Marie Zwerenz, Mahalia Z Anczykowski, Stephanie Bendrich, Manuel Guhlich, Martin Leu, Leif Hendrik Dröge, Tibor I Kesztyüs, Annemarie Uhlig, Stefan Rieken, Rami A El Shafie
Department of Radiation Oncology, University Medical Center Göttingen, Göttingen, Germany., Medical Data Integration Center (MeDIC), University Medical Center Göttingen, Göttingen, Germany., Department of Urology, University Medical Center Göttingen, Göttingen, Germany.