Creatinine tests missed kidney disease in nearly half of 1,200 cancer patients
In a study of 1,200 people with solid tumours in São Paulo, measured kidney function identified chronic kidney disease in 18.9%, compared with 10.2% using creatinine-based estimates. MDMagazine reports that adding cystatin C raised the estimate to 15.7%, but still left a gap; the researchers warn that inaccurate readings near treatment thresholds may affect chemotherapy eligibility and dosing.
Bottom line — Measured GFR is the more direct check when kidney function determines a chemotherapy decision.
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MDMagazine reports that among patients whose measured GFR was 45–59 mL/min/1.73 m², 72.1% had a creatinine-based estimate above 60.
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For patients with measured GFR below 45 mL/min/1.73 m², 52.5% had a creatinine-based estimate above 45, MDMagazine reports.
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Verônica Torres Costa e Silva of the University of São Paulo said these errors may mean some patients receive higher doses than their kidney function supports.
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The study measured GFR using clearance of chromium-51-labelled EDTA before treatment began.
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A 2025 review in Kidney360 says KDIGO recommends combining creatinine and cystatin C when creatinine estimates are less reliable and treatment decisions depend on GFR.
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The Kidney360 review notes that cystatin C can also be affected by factors including inflammation, high adiposity, thyroid function and glucocorticoids.