Accuracy of GFR estimation by the Cockroft and Gault, MDRD, and Wright equations in Oncology patients with renal impairment

Estimation of renal function is crucial to guidance of systemic chemotherapy. With stable creatinine levels, the glomerular filtration rate (GFR) is often estimated from a single measurement of serum creatinine. We compared accuracy of the Cockroft and Gault (C&G), modifying diet in renal diseases (MDRD) and Wright estimates in Oncology patients with renal impairment. Analysis was carried out on the basis of monodentate platinum treatment as the nephrotoxic mechanism of these drugs may affect accuracy of these estimates. Sixty-two consecutive patients with stable creatinine levels who had isotopic GFR measurement of ≤ 60 ml min⁻¹ at a regional cancer center were reviewed. Twenty-nine were on monodentate platinum treatment. Isotopic GFR was compared with estimated GFR by the three equations. We defined three categories of estimate based on the fractional difference from isotopic GFR: ‘perfect’ (< 10%), ‘reasonable’ (≥ 10% but < 30%) and ‘poor’ (≥ 30%). There was a trend toward provision of more perfect estimates by the MDRD equation particularly in patients on monodentate platinum treatment. Similar numbers had poor estimates from either of these equations, particularly at extremes of body weight. The MDRD formula may be the most accurate of these equations in Oncology patients with renal impairment, particularly with monodentate platinum treatment.