A comparison of measured and estimated glomerular filtration rate for carboplatin dose calculation in stage I testicular seminoma

Dose calculation of adjuvant carboplatin chemotherapy for stage I testicular seminoma, based on area under the concentration curve (AUC), incorporates the glomerular filtration rate (GFR). This retrospective study compares ‘gold standard’ 51Cr-ethylenediamine tetraacetic acid (51Cr-EDTA) GFR measurements with renal function estimations derived from the Cockcroft–Gault, Jelliffe and Wright formulae. Inclusion criteria: stage I testicular seminoma treated with a single dose of carboplatin AUC7 at one centre in South Wales, UK, between 2005 and 2011, with contemporaneous 51Cr-EDTA GFR measurement and serum creatinine. Renal function estimates obtained using Cockcroft–Gault, Jelliffe and Wright formulae were analysed for bias (mean percentage error, MPE) and precision (mean absolute percentage error, MAPE) compared to the gold standard. Sixty-eight patients were identified, median age 40 (range 17–66), median creatinine 82 (range 55–120). For the Cockcroft–Gault, Jelliffe and Wright formulae, respectively, MPE was +12.4, −32.3 and +8.8; MAPE was 16.0, 32.7 and 12.9; and substitution of the calculated GFR result for 51Cr-EDTA measurement would have resulted in a >10 % discrepancy in carboplatin dose in 41.1, 97.1 and 42.6 % of patients (predominantly overdoses for the Cockcroft–Gault and Wright formulae, underdoses for the Jelliffe formula). Of the formulae analysed, none accurately correlated with 51Cr-EDTA GFR measurements.