Creatinine-based estimated glomerular filtration rate (eGFR) substantially underestimated the prevalence of chronic kidney disease (CKD) in patients with solid tumors compared with measured GFR (mGFR), according to findings presented at ASN Kidney Week 2026 in Denver, Colorado.1,2 Adding cystatin C narrowed the gap, but agreement with mGFR remained poor, particularly at thresholds guiding chemotherapy eligibility and dosing.
“The results suggest that errors in GFR estimation may contribute to exceeding toxicity in patients with cancer receiving anticancer therapy,” Veronica Torres Costa e Silva, MD, PhD, of the University of São Paulo Medical School, said in a statement.2 “I’ll give the example of cisplatin. Most recommendations state that patients with GFR of 45–60 ml/min/1.73m2 should have a dose reduction of 25–50%, and those with GFR below 45 ml/min/1.73m2 should not be considered eligible. This means that our patients are receiving exceedingly higher doses and having a higher frequency of toxicity because we are not capable of accurately assessing GFR and making accurate dose adjustments.”
GFR discrepancies are well recognized in the general population but have not been well characterized in patients with cancer.1 The 2024 KDIGO CKD guideline recommends estimating GFR using both creatinine and cystatin C when cystatin C is available.3
How Often Did eGFR Misclassify Kidney Function in Patients with Cancer?
This cross-sectional analysis evaluated a prospective cohort of 1200 patients with active solid tumors at a tertiary cancer center in São Paulo, Brazil, recruited between April 2015 and September 2017. Serum creatinine and cystatin C were measured before treatment initiation using certified reference materials, on the same day as mGFR by plasma clearance of chromium 51-labeled EDTA.1