Applicability of the Japanese equation for estimating glomerular filtration rate in patients with advanced-stage thoracic cancer.

Background: The 24-h creatinine clearance (24-h Ccr) and the Cockcroft-Gault equation (CG) are commonly used as markers of renal function in clinical practice. However, the utility of the Japanese equation for estimating glomerular filtration rate (eGFR) in cancer patients has not yet been evaluated. The aim of this cross-sectional study was to investigate the extent and correlating factors for differences between eGFR and both 24-h Ccr and CG in advanced-stage thoracic cancer patients.
Methods: eGFR, 24-h Ccr, and CG were calculated in 90 patients with thoracic malignancies. We evaluated how these three parameters are affected by clinical factors, including age, body surface area, serum creatinine concentration, and body mass index.
Results: eGFR and CG were significantly correlated with 24-h Ccr (r=0.64, p<0.001 and; r=0.67, p<0.001, respectively). However, the median value derived from eGFR was higher than the median 24-h Ccr and the CG value (74.0, 65.2, and 63.9mL/min, respectively). Age had a significant positive correlation with the differences between eGFR and both 24-h Ccr and CG value (r=0.30, p=0.005 and; r=0.47, p<0.001, respectively). The differences between eGFR and the other two parameters were significantly higher in older patients (age≥70 years) than in younger patients (age<70 years) (p=0.023, p<0.001, respectively).
Conclusions: eGFR is likely to overestimate the renal function of elderly cancer patients. A modified equation for evaluating the renal function of Japanese older patients might be needed.
(Copyright © 2016 The Japanese Respiratory Society. Published by Elsevier B.V. All rights reserved.)