IROCK Report: 5-Year Renal Function Outcomes After SABR for Primary RCC

New data presented at the American Society for Radiation Oncology 2023 Annual Meeting compared renal function outcomes of stereotactic ablative body radiotherapy (SABR) in patients with solitary versus bilateral kidneys.

Renal cell carcinoma (RCC) is not a common presentation in patients with a congenital solitary kidney or prior contralateral nephrectomy.

Vivian Tan, MD, of the London Health Sciences Centre, and colleagues assessed renal function in patients with primary RCC from 12 participating International Radiosurgery Consortium for Kidney (IROCK) institutions. One hundred and ninety patients with solitary (n=56) or bilateral kidneys (n=134) who underwent SABR were included, and renal function was measured by estimated glomerular filtration rate (eGFR). In the event that eGFR was not recorded, the Chronic Kidney Disease Epidemiology Collaboration equation was used to estimate eGFR based on known creatinine.

Baseline characteristics and renal function outcomes were compared between solitary and bilateral kidneys. Dr. Tan and colleagues utilized multivariable logistic regression to identify factors predictive of eGFR decline and any eGFR increase evaluated at 1 year post-SABR.

After following the patients for a median of 5.0 years, pre-SABR eGFR (mean ± SD) was similar in patients with solitary (61.1 ± 23.2 mL/min) and bilateral kidneys (58.0 ± 22.3 mL/min; P=.324). Mean tumor size was 3.70 ± 1.40 cm in solitary kidneys and 4.35 ± 2.50 cm in bilateral kidneys (P=.026).

After SABR, researchers observed an initial compensatory increase in eGFR in both cohorts (22.7% and 17.7%, respectively, at 1 year), though this compensatory increase persisted only in patients with bilateral kidneys (10.3% vs 0% at 3 years and 21.1% vs 0% at 5 years, respectively).

At 5 years post-SABR, eGFR decreased by −14.5 ± 7.6 in solitary kidneys and —13.3 ± 15.9 mL/min in bilateral kidneys (P=.665). Notably, researchers added that there were no significant differences in eGFR decline at all time points assessed (P>.05).

Furthermore, there were no reported significant differences in post-SABR end-stage renal disease (7.1% vs 6.7%) or dialysis (3.6% vs 3.7%) in solitary versus bilateral kidneys.

Multivariable analysis showed that increasing tumor size as well as baseline eGFR was more likely to be associated with eGFR decline. There was no significant association between solitary versus bilateral kidneys and eGFR decline (odds ratio, 1.22; 95% CI, 0.45-3.34; P=.693).

“There was no observed difference between renal function outcomes in patients with solitary versus bilateral kidneys,” Dr. Tan and colleagues concluded. “While larger tumor size may increase the risk of eGFR decline post-SABR, treatment of a solitary kidney does not appear to increase the risk of renal dysfunction long term.”