Background: Assessment of renal function is important for safe cancer chemotherapy, and eligibility criteria for clinical trials often include creatinine clearance. However, creatinine clearance overestimates glomerular filtration rate, and various new formulae have been proposed to estimate glomerular filtration rate. Because these were developed mostly in patients with chronic kidney disease, we evaluated their validity in cancer patients without kidney disease.
Methods: Glomerular filtration rate was measured by inulin clearance in 45 Japanese cancer patients, and compared with creatinine clearance measured by 24-h urine collection as well as that estimated by the Cockcroft-Gault formula, Japanese estimated glomerular filtration rate developed in chronic kidney disease patients, the Modification of Diet in Renal Disease study equation and the Chronic Kidney Disease Epidemiology Collaboration equation. The Modification of Diet in Renal Disease study and Chronic Kidney Disease Epidemiology Collaboration equations were adjusted for the Japanese population by multiplying by 0.808 and 0.813, respectively.
Results: The mean inulin clearance was 79.2 ± 18.7 ml/min/1.73 m(2). Bias values to estimate glomerular filtration rate for Japanese estimated glomerular filtration rate, the Cockcroft-Gault formula, creatinine clearance measured by 24-h urine collection, the 0.808 × Modification of Diet in Renal Disease study equation and the 0.813 × Chronic Kidney Disease Epidemiology Collaboration equation were 0.94, 9.75, 29.67, 5.26 and -0.92 ml/min/1.73 m(2), respectively. Precision (root-mean square error) was 14.7, 22.4, 39.8, 16.0 and 14.1 ml/min, respectively. Of the scatter plots of inulin clearance versus each estimation formula, the Japanese estimated glomerular filtration rate correlated most accurately with actual measured inulin clearance.
Conclusion: The Japanese estimated glomerular filtration rate and the 0.813 × Chronic Kidney Disease Epidemiology Collaboration equation estimated glomerular filtration rate with lower bias and higher precision than the other formulae. We therefore propose Japanese estimated glomerular filtration rate for the estimation of glomerular filtration rate in Japanese cancer patients.