Why is AUC preferred over BSA for carboplatin dosing?

• A. Carboplatin is renally cleared, so expressing exposure as AUC is more reliable
• B. BSA-based dosing is more accurate for most patients
• C. AUC dosing reduces the need for monitoring and adjustments
• D. BSA-based dosing is universally used and AUC adds no benefit

Answer: (A)

Dosing carboplatin by exposure rather than body size is preferred because the drug’s clearance is mainly through the kidneys, so how much drug stays in the body—and therefore its effect and toxicity—depends largely on renal function. Body surface area doesn’t capture differences in kidney function, so two patients with the same size or body surface area can end up with very different drug exposures. Using a target exposure, expressed as the area under the concentration–time curve (AUC), links dose to how well the kidneys clear the drug, producing more predictable systemic exposure across patients.

The practical approach uses the Calvert formula, which calculates dose from the target AUC and the patient’s glomerular filtration rate (GFR): Dose = target AUC × (GFR + 25). The “+25” accounts for non-renal clearance, making the exposure more consistent. This standardization helps balance efficacy and toxicity better than BSA-based dosing.

So, the reason AUC-based dosing is best is that it directly accounts for renal clearance and yields more consistent drug exposure across diverse patients, whereas BSA-based dosing does not reliably reflect how much drug will be in the body. Monitoring and adjustments may still occur for toxicity, but AUC dosing reduces the variability seen with BSA-based dosing.