Common Kidney Function Tests May Miss CKD in Cancer Patients

In oncology, kidney function assessment often relies on estimated glomerular filtration rate rather than direct measurement, potentially leaving CKD unrecognized. This can create diagnostic uncertainty in patients receiving anticancer therapy. New findings highlight this limitation, showing that commonly used kidney function tests may miss CKD in adults with solid tumors.

University of São Paulo Medical School (FMUSP) researchers evaluated kidney function assessment in 1,200 adults with solid tumors. They compared measured glomerular filtration rate, which directly assesses kidney filtration using a specialized clearance marker, with estimated glomerular filtration rate values derived from the blood markers creatinine, cystatin C, or both.

CKD prevalence was 18.9% based on measured glomerular filtration rate, compared with 10.2% using creatinine-based estimates and 15.7% using estimates combining creatinine and cystatin C. This discrepancy was particularly evident among patients with measured filtration rates of 45–59 mL/min/1.73 m²: 72.1% had creatinine-based estimates above 60, potentially masking their reduced kidney function.

The discrepancy extended to patients with more advanced CKD. Among those with measured glomerular filtration rates below 45 mL/min/1.73 m², 52.5% had creatinine-based estimates above 45. Adding cystatin C to creatinine reduced the discrepancy between measured and estimated filtration rates, although concordance remained poor.

Presented at ASN Kidney Week 2026, held October 22–25, the findings highlight differences at thresholds relevant to drug eligibility and dose adjustment. Drug clearance often decreases as kidney function declines, making these assessments important for treatment decisions. Cisplatin dosing recommendations, for example, use glomerular filtration rate thresholds to guide dose reduction or determine treatment eligibility.

“The results suggest that errors in GFR estimation may contribute to excessive toxicity in patients with cancer receiving anticancer therapy,” said Veronica Torres Costa e Silva, M.D., Ph.D., corresponding author at the University of São Paulo Medical School.

Related Links
University of São Paulo Medical School
American Society of Nephrology