5-Year Renal Function Outcomes after SABR for Primary Renal Cell Carcinoma: A Report from the International Radiosurgery Oncology Consortium of the Kidney (IROCK)

PURPOSE/OBJECTIVE(S)

Renal cell carcinoma (RCC) presents uncommonly in patients with a congenital solitary kidney or prior contralateral nephrectomy. The objective of this study was to compare renal function outcomes of stereotactic ablative body radiotherapy (SABR) in patients with solitary vs. bilateral kidneys.

MATERIALS/METHODS

Patients with primary RCC with ≥2 years of follow-up at 12 participating International Radiosurgery Consortium for Kidney (IROCK) institutions were included. Patients with upper tract urothelial carcinoma or metastatic disease were excluded. Renal function was measured by estimated glomerular filtration rate (eGFR). For patients where eGFR was not recorded, Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation was used to estimate eGFR based on known creatinine. Baseline characteristics and renal function outcomes were compared between solitary vs. bilateral kidneys. Multivariable logistic regression was used to identify factors predictive of eGFR decline ≥ 15 mL/min and any eGFR increase evaluated at 1-year post-SABR.

RESULTS

One hundred and ninety patients with solitary (n = 56) or bilateral kidneys (n = 134) underwent SABR and were followed for a median of 5.0 years (IQR: 3.4-6.8). Pre-SABR eGFR (mean ± SD) was similar in patients with solitary (61.1 ± 23.2 mL/min) vs. bilateral kidneys (58.0 ± 22.3 mL/min, p = 0.324). Mean tumor size was 3.70 ± 1.40 cm in solitary and 4.35 ± 2.50 cm in bilateral kidneys (p = 0.026). After SABR, an initial compensatory increase in eGFR was observed in both cohorts (22.7% solitary and 17.7% bilateral at 1 year). This compensatory increase persisted in patients with bilateral but not a solitary kidney (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 and -13.3 ± 15.9 mL/min in bilateral kidneys (p = 0.665). At all timepoints assessed, there were no significant differences in eGFR decline between solitary vs. bilateral cohorts (all p > 0.05). There were also no significant differences in post-SABR end-stage renal disease (7.1% vs. 6.7%) or dialysis (3.6% vs. 3.7%) in solitary vs. bilateral, respectively. Multivariable analysis demonstrated that increasing tumor size (OR per 1 cm: 1.57; 95% CI: 1.14-2.16, p = 0.006) and baseline eGFR (OR per 10 mL/min: 1.30; 95% CI: 1.02-1.66, p = 0.034) was more likely to be associated with eGFR decline ≥ 15 mL/min. There was no significant association between solitary vs. bilateral kidney and eGFR decline (OR: 1.22; 95% CI: 0.45-3.34, p = 0.693).

CONCLUSION

There was no observed difference between renal function outcomes in patients with a solitary vs. bilateral kidneys. 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.

Found in translation: a medical student's reflection on the emotional realities of translational cancer research

The packed snow yielded its familiar crunch with every step I took. Behind me, the winter daylight faded as darkness crept through the cloudless sky. With each step forward, the brick walls of the cancer centre loomed larger ahead. This was my destination for the evening. Despite my fatigue after a day of classes and clinical sessions, I believed these hours—and many more like them—were justified, for they were spent in pursuit of worthwhile scientific goals and were ultimately in service to patients [...]