Comparison of carboplatin dosing derived from Cockcroft–Gault creatinine clearance and race-free CKD-EPI estimated glomerular filtration rate

IntroductionRecent guidelines recommend race-free CKD-EPI estimated glomerular filtration rate (eGFR) over the Cockcroft-Gault creatinine clearance (eCrC-CG) for dosing medications. However, many institutions continue using eCrCl-CG due to uncertainty regarding the clinical impact of this transition. This study evaluated differences in carboplatin doses using both equations in a real-world dataset.MethodsThis was a retrospective cohort study that included adult patients with cancer who received carboplatin between January and July 2025. Patients were identified using institutional medical records. For each patient, we determined the actual carboplatin dose prescribed, which used the eCrCl_CG for renal function, and we recalculated the dose using the CKD-EPI eGFR. The Calvert formula was used to determine the carboplatin doses. Only first-cycle patient data were analyzed. The primary outcome was the proportion of patients with clinically significant differences between the two dosing methods, defined as ≥10%. Multivariable logistic regression was used to identify predictors of a clinically significant discrepancy, with results reported as odds ratios.ResultsOver the study period, 366 patients were included. The median age was 58 years (IQR 47-65), 271 (74%) were females, and the most common type of cancer was breast (n = 142, 39%). Estimated renal function was median of 82 mL/min (IQR 68-97) using the eCrCl-CG equation and 98 mL/min (IQR 83-106) with the CKD-EPI eGFR equation. A difference of ≥10% in carboplatin doses was reported in 142 patients (39%), with the CKD-EPI resulting in higher doses in most cases (99%). Factors associated with clinically significant differences between the two formulas were age (OR 1.14, 95% CI 1.10-1.18, p < 0.001), serum creatinine (OR 0.094, 95% CI 0.018-0.453, p = 0.004) and body weight (OR 0.96, 95% CI 0.95-0.98, p < 0.001).ConclusionsCarboplatin dosing varies according to the renal function estimation method. In 4 out of 10 patients, eCrCl-CG resulted in more than 10% lower doses than those calculated using CKD-EPI eGFR. Age, serum creatinine, and weight predict significant dose differences.