# Creatinine-based eGFR overestimated kidney function in 1200 patients with solid tumors in Brazilian study - Published: 2026-11-12 18:18 UTC - Section: Life & Health › Medicine - Tags: eGFR overestimation, measured GFR, creatinine eGFR, cystatin C, solid tumors, chemotherapy dosing, cisplatin, carboplatin, Kidney Week 2026 - URL: https://realtech.media/news/rt-2e70d498db102958618b1577_creatinine_based_egfr/ **Measured GFR found stage 3 or higher CKD in 18.9% of patients, while creatinine-based eGFR showed 10.2%. The authors link estimation errors to dosing of platinum drugs.** ![Creatinine-based eGFR overestimated kidney function in 1200 patients with solid tumors in Brazilian study](https://realtech.media/media/2026/11/f8784a71ef8d6bc7.webp) *cancertherapyadvisor.com* Researchers led by Veronica Torres Costa e Silva of Universidade de Sao Paulo Faculdade de Medicina reported at the American Society of Nephrology's Kidney Week 2026 that current eGFR equations overestimate kidney function in patients with solid tumors, according to cancertherapyadvisor.com. The cross-sectional Brazilian study, conducted in 2015-2017, assessed 1200 patients with the 2021 CKD-EPI equations based on serum creatinine (eGFRcr), cystatin C (eGFRcys), or both markers (eGFRcr-cys). Measured GFR (mGFR) was determined on the same day by plasma clearance of 51Cr-EDTA and averaged 78.5 mL/min/1.73 m2. [1] The most common cancer sites were the breast (22.6%), prostate (19.8%) and gastrointestinal tract (13.4%). Metastases were present in 14.8% of patients, and mean age was 58.8 years. [1] ## Measured versus estimated GFR Stage 3 or higher chronic kidney disease (CKD) was found in 18.9% of patients by mGFR, 10.2% by eGFRcr and 15.7% by eGFRcr-cys. Among patients with an mGFR of 45 to 59 mL/min/1.73 m2, 72.1% had an eGFRcr above 60 on their lab reports. Among those with an mGFR below 45 (stage 3b CKD), 52.5% received an eGFRcr report above 45. [1] The combined eGFRcr-cys equation reduced these discrepancies but did not match mGFR. It was more accurate above 90 or below 45 mL/min/1.73 m2 and less accurate for stage 3a CKD (45-59). [1] Torres Costa e Silva said the errors may contribute to excess toxicity in patients receiving anticancer therapy. As an example she cited cisplatin, for which most recommendations call for a 25-50% dose reduction at a GFR of 45-60 and exclude patients below 45. She called for more robust instruments to assess GFR in clinical practice. [1] ## Platinum dosing and outcomes A separate Kidney Week poster included 943 adults who started cisplatin or carboplatin in 2023-2025. It compared dosing by the closest-fit eGFRcr-cys equation with dosing by the Cockcroft-Gault creatinine clearance equation. [1] For each 10% by which eGFRcr-cys was lower, the risk of platinum-associated hospitalization rose by 39% (sHR 1.39; 95% CI 1.24-1.56). Each 10% lower eGFRcr-cys was also associated with higher risks of grade 3 or higher anemia (sHR 1.38), grade 3 or higher thrombocytopenia (sHR 1.57), acute kidney injury (sHR 1.35) and all-cause mortality (HR 1.70). Each 25-mg increase in carboplatin dose above the eGFRcr-cys-predicted dose was associated with a 1.15-fold risk of hospitalization (95% CI 1.04-1.27). [1] Meghan E. Sise of Massachusetts General Hospital and colleagues concluded that there is a continuous, independent association between the eGFR difference and platinum-associated adverse events. [1] ## Sources 1. [cancertherapyadvisor.com](https://www.cancertherapyadvisor.com/news/estimated-kidney-function-aka-egfr-may-be-inaccurate-harmful-in-patients-with-cancer/) 2. [lomazoma.com](https://lomazoma.com/kreatininbasierte-egfr-ueberschaetzt-haeufig-die-nierenfunktion-bei-krebspatienten-news-deutsches-aerzteblatt) --- Source: RealTech, realtech.media — https://realtech.media/news/rt-2e70d498db102958618b1577_creatinine_based_egfr/