Standard kidney estimates may undercount CKD in cancer patients
In 1,200 adults with solid tumors, directly measured kidney filtration identified chronic kidney disease more often than standard creatinine-based estimates. Measured GFR indicated CKD in 18.9% of patients, compared with 10.2% by creatinine-based eGFR and 15.7% when cystatin C was added. The researchers warn that such underestimation could lead to excessive anticancer drug doses and more toxicity.
The study enrolled 1,200 adults with solid tumors and compared direct filtration measurement using a specialized clearance marker against estimates from creatinine alone and creatinine plus cystatin C. Direct measurement classified 18.9% as having CKD; creatinine-based estimates classified 10.2%, and combined estimates classified 15.7%.
Discrepancies persisted at clinically relevant thresholds. Of patients whose measured filtration was 45–59 ml/min/1.73 m², 72.1% had creatinine-based estimates above 60; among those below 45, 52.5% had creatinine-based estimates above 45. Adding cystatin C reduced but did not resolve poor agreement. These thresholds guide anticancer drug eligibility and dosing, such as cisplatin reductions.
People with solid tumors and reduced kidney function may be affected if standard estimates lead clinicians to overestimate filtration. This could result in higher anticancer drug doses than appropriate, potentially increasing toxicity and treatment complications. Because dosing and eligibility decisions often rely on these estimates, patients near threshold values—especially those considered for cisplatin—may face avoidable risks. Better recognition of CKD could prompt more cautious prescribing and monitoring, though access to direct measurement and cystatin C testing may vary.