RESUMEN
PURPOSE: Determination of renal function is a prerequisite for planning therapy in cancer patients. Limitations of creatinine as marker for the glomerular filtration rate (GFR) led to the proposal of cystatin C as a more accurate biomarker especially in mild renal insufficiency or in patients with low muscle mass. We compared the accuracy of cystatin C- and creatinine-based equations to estimate GFR in head and neck cancer (HNC) patients receiving platinum-based radiochemotherapy. PATIENTS AND METHODS: The study population consisted of 52 HNC patients (GFR range, 37-105 mL/min/1.73 m(2) complemented by 17 patients with known renal insufficiency (GFR range, 10-60 mL/min/1.73 m(2)). Intraclass correlation coefficients were calculated between the reference method (51)Cr-EDTA clearance and estimated GFR by creatinine clearance and equations based on creatinine (Cockroft-Gault, modification of diet in renal disease (MDRD), Wright) or cystatin C (Larsson, Dade-Behring, Hoek). In addition, sensitivity and specificity to discriminate GFR > 60 mL/min/1.73 m(2) were evaluated by receiver operating characteristic curve (ROC). RESULTS: The highest correlation coefficients were found for the cystatin C-based estimates in comparison with creatinine-based estimates or creatinine clearance, even though Bland-Altman plots revealed GFR overestimation for all equations tested. The cystatin C-based Hoek formula exhibited the highest overall precision and accuracy. GFR of < 60 mL/min/1.73 m(2) was assumed as a cut-off for chemotherapy. ROC analyses revealed the highest AUC to predict a GFR > 60 mL/min/1.73 m(2) for the creatinine-based Wright formula, closely followed by the MDRD formula and cystatin C-based equations of Larsson, Dade-Behring, and Hoek. CONCLUSION: Cystatin C-based GFR estimates showed the overall strongest correlation to the reference method. Thus, we recommend cystatin C for GFR estimation in HNC patients as an alternative method to the estimated creatinine clearance in clinical practice.