Background: Lung cancer is the leading cause of cancer-related mortality. Carboplatin is a commonly used cytotoxic chemotherapy agent. Dosing of carboplatin is related to renal function, which if overestimated may lead to supratherapeutic dosing and toxicity. Conversely, underestimation of renal function may lead to underdosing and therapeutic failure. Although the ‘Modification of Diet in Renal Disease’ (MDRD) and the ‘Chronic Kidney Disease Epidemiology Collaboration’ (CKD-EPI) equations reportedly have higher accuracy in estimating glomerular filtration rate (eGFR), the Cockcroft–Gault (CG) formula is commonly used for carboplatin dosing internationally, including Australia. We aimed to compare these three formulae to identify the patient profiles that are associated with significant carboplatin dose variation.

Methods: We retrospectively analysed the carboplatin regimen of 43 patients with lung cancer (small cell and non-small cell) treated at the Sunshine Coast University Hospital. Hypothetical carboplatin doses were calculated using eGFR generated by MDRD and CKD-EPI equations. These two hypothetical doses were compared to actual CG-based doses given. The age, weight, and serum creatinine values measured at the commencement of chemotherapy were used.

Results: MDRD and CKD-EPI equations resulted in comparable carboplatin doses while CG doses diverged from both for the majority of patients. Forty percent of the patients received less than MDRD- and CKD-EPI-estimated carboplatin doses, with 16% receiving at least 20% lower dose (theoretical undertreatment). Conversely, 44% of the patients received higher than MDRD- and CKD-EPI-estimated carboplatin doses, with 14% receiving at least 20% higher doses (theoretical overtreatment).

Conclusion: We have found that there are significant differences in potential carboplatin dosing depending on the equation used. Thus, a harmonised method for eGFR calculation that identifies and adjusts for the carboplatin dose variations is still needed in order to provide the maximum therapeutic benefit whilst minimising toxicity.