Comparison of methods for estimating glomerular filtration rate in head and neck cancer patients treated with cisplatin.

Cisplatin is a chemotherapeutic agent widely used in the treatment of various solid tumors. Cisplatin induces nephrotoxicity and may lead to long-term reduction of kidney function. Consequently, determination of glomerular filtration rate (GFR) is used to monitor potential kidney damage. This study aimed to compare two commonly used algorithms for estimating GFR (eGFR) from plasma creatinine (PCr) with 51Cr-EDTA clearance (CrCl) as a reference method. This was a retrospective single center study of 94 head and neck cancer patients treated with cisplatin. CrCl was performed once before, during, and after treatment, and PCr was measured concurrently. eGFR was assessed from PCr applying the Cockcroft-Gault (CG) and the Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI) equations. Agreement was assessed applying the statistical methods of Bland and Altman. A predefined limit of clinically acceptable variation between CrCl and eGFR of 14% was applied. Comparison of CrCl and eGFRCKD revealed a positive slope of the linear regression line, suggesting proportional bias (p < 0.001). No systematic bias was found for eGFRCG. Pre-treatment, 42 (46%), 53 (56%) and 48 (53%) observations were within the clinically acceptable limit of variation for standardized eGFRCKD, BSA corrected eGFRCKD, and eGFRCG, respectively. The observed body weight changes were significant. In conclusion, estimated GFRCKD cannot sufficiently replace CrCl in the assessment of GFR during treatment with cisplatin due to systematic bias. Consequently, if CrCl is unavailable, then the CG equation is the better choice provided proper attention is paid to the large variation between methods.