Carboplatin dosing based on estimated Glomerular Filtration Rate (GFR) using IDMS creatinine: A comparison of estimated GFR based on IDMS creatinine in the Cockroft-Gault (CG) formula (IDMS-GFR), with measured GFR using 51Cr-EDTA (51Cr-GFR).

2576 Background: 51Cr-GFR is considered a gold standard of GFR assessment, but the CG formula is routinely used to estimate GFR for dosing of Carboplatin. Gynaecological cancer trials adopted the convention that Carboplatin be dosed at AUC5 in patients using 51Cr-GFR, and AUC6 in patients using IDMS-GFR. IDMS-GFR is routinely capped at 125ml/min for Carboplatin dosing, as low IDMS levels in patients with normal renal function can generate spuriously high GFR estimates. Methods: We performed a multicenter retrospective study of patients who had a 51Cr-GFR assessment, with a matched serum IDMS creatinine. IDMS-GFR and 51Cr-GFR were compared in each patient. Carboplatin dose based on 51Cr-GFR in the Calvert formula at AUC 5 was used as the reference. Results: 551 patients were available for analysis. Median age 62 (19 – 90), 64% female. Indication for GFR evaluation: malignancy (85%), assessment for live kidney donation (12%), other (3%). Median ratio of IDMS-GFR : 51Cr-GFR 1.04 (0.43 – 3.38); < 0.8 in 72 pa...