The dosing reference

How it works

The Calvert formula sets the total carboplatin dose (mg) = target AUC × (GFR + 25), where GFR is in mL/min. Because the dose scales directly with GFR, an accurate renal-function estimate is the single most important safety step: a falsely high GFR overdoses, a falsely low one underdoses. When creatinine is measured with modern IDMS-standardized assays — or in patients with low muscle mass — estimated GFR can be spuriously high. Capping the GFR estimate at 125 mL/min is the guard some experts and guidelines (FDA, ASCO, GOG) recommend against overdose — a dosing convention, not a physiologic ceiling, and one that trades an overdose risk for delivering less than the intended AUC when the high GFR is real.

The creatinine clearance here uses Cockcroft-Gault: CrCl = [(140 − age) × weight(kg) × (0.85 if female)] / (72 × serum creatinine in mg/dL). Prefer a measured or isotopic GFR when one is available (enter it in the override field).

Note what the equation is standing in for. Calvert derived and validated the formula against a measured GFR, not against any creatinine-based estimate; Cockcroft-Gault is the substitute used when no measured GFR exists, and it is what most protocols and product labels still specify — which is why it is what this calculator computes. The direction of consensus has moved, though: the 2025 ADDIKD international guideline recommends assessing kidney function for anticancer dosing by GFR — measured, or CKD-EPI eGFR — rather than by Cockcroft-Gault creatinine clearance, and reports that its carboplatin recommendation differs from existing guidance. The two methods do not agree, so the equation a protocol names is part of the dose.

The calculator offers both. ADDIKD's preference order is measured GFR → BSA-adjusted CKD-EPI eGFR → creatinine clearance, and its Part 1 recommendation is quoted whole: BSA-adjusted eGFR_CKD-EPI is “a suitable alternative to directly measured GFR for use in the Calvert formula when dosing carboplatin, especially where eGFR_CKD-EPI 45–125 mL/min/1.73 m², treatment intent is non-curative and the patient is neither an amputee, paraplegic or has conditions of skeletal muscle and is without extremes of body size or muscle mass.” Everything after the eGFR range is a condition, not a flourish: curative-intent treatment, and extremes of body size or muscle mass, are situations in which ADDIKD asks for a directly measured GFR instead.

Be precise about what carboplatin is an exception to. ADDIKD recommends CKD-EPI eGFR to guide anticancer dosing generally — that part is not carboplatin-specific at all. What it does not routinely advise is the BSA adjustment: using an eGFR de-normalised to the individual's own body surface area in place of the standardised, indexed one, except for carboplatin. The reason for that default explains the exception: a drug already dosed by a weight descriptor (mg/m², mg/kg) would count body size twice. Carboplatin is dosed to an AUC rather than by body size, so that objection does not apply to it. Part 2 records KDIGO, Advanced Pharmacy Australia and the American Society of Onco-Nephrology as supporting BSA-adjusted eGFR for carboplatin over creatinine clearance.

For scale, Part 1's own worked example — a 65-year-old man, 67 kg, 170 cm, creatinine 97 µmol/L, AUC 5 — gives 443 mg by Cockcroft-Gault and 485 mg by BSA-adjusted eGFR, a 9% difference whose clinical consequence the guideline describes as unknown. This calculator reproduces both numbers exactly.

An eGFR is reported indexed to 1.73 m² while the Calvert formula takes an absolute clearance, so the calculator de-normalises it by the patient's own body surface area (Mosteller, which is the formula ADDIKD's worked example uses) and shows that arithmetic rather than hiding it. Skipping the conversion misdoses in proportion to how far the patient's BSA sits from 1.73 m².

The 125 cap then applies to that absolute result, exactly as it does on the Cockcroft-Gault path — so the dose ceiling is the same whichever method you pick: AUC × 150, i.e. 750 mg at AUC 5. They are different rules that happen to share a number: the cap is the FDA/ASCO/GOG overdose guard on the clearance entering Calvert; ADDIKD recommends no cap at all, and its 45–125 figure is a statement that an estimate becomes less reliable outside that range — which is why this calculator flags it and changes nothing.

Reference: Calvert AH et al. Carboplatin dosage: prospective evaluation of a simple formula based on renal function. J Clin Oncol 1989;7(11):1748–56 — PMID 2681557. See also the carboplatin profile and the eGFR dosing assistant.