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Carboplatin dosing (Calvert formula)
1. Select GFR calculation method
Estimated GFR:
Cockroft Gault formula If BMI ≥ 25 we calculate Cockroft Gault using Adjusted Body Weight (see below). Estimated GFR is also capped at a maximum of 125ml/min.
Measured GFR: e.g. Using 99mTc-DTPA or 51Cr-EDTA
GFR:
ml/min


Gender:


Age:
years


Height:
feet inches cm


Weight:
st lbs kg


Creatinine:


GFR (Cockroft Gault)*:
(*If BMI ≥ 25, Adjusted Body Weight is used. GFR capped at 125ml/min)
2. Carboplatin dose using Calvert formula
Target AUC Area under the curve. Reflects target concentration of carboplatin in the blood measured in mg/ml/min. Values between 4 to 7 are commonly used.
mg/ml/min


Carboplatin dose:

Carboplatin dosing (Calvert formula)

Interpretation:

The clearance of carboplatin is closely related to glomerular filtration rate (GFR). Approximately 70% of carboplatin is excreted in the urine unchanged after 24 hours, therefore dosing needs to account for renal function.

The Calvert formula(1) established a dosage formula to achieve a target area under the curve (AUC) plasma concentration of carboplatin based on the patient’s GFR. The Calvert formula is:

Carboplatin dose (mg) = target AUC x (GFR + 25)

AUC (area under the curve) reflects the plasma concentration of carboplatin over time and measured as mg/ml/min. Target AUC will depend on the specific chemotherapy regimen and indication the drug is being used for.

GFR can be estimated using the Cockroft Gault formula or more accurately measured using radiotracer decay (e.g. 51Cr-EDTA or DTPA). Where possible measured GFR should be used but this is not always available.

Cockroft Gault GFR estimation can be inaccurate in patients with obesity, fluid retention or muscle wasting. It can overestimate creatinine clearance in overweight patients(2). In patients with BMI ≥ 25, we use adjusted body weight to calculate Cockroft Gault as it has been shown to more accurately estimate GFR(3,4). We also cap GFR at a maximum of 125ml/min when calculating Cockroft-Gault(4).

Formulae used in GFR estimation:
Ideal body weight (IBW) = 45.5 + (0.91x(height_in_cm – 152)) [female] 50 + (0.91x(height_in_cm – 152)) [male]
Adjusted body weight = IBW + 0.4(weight_in_kg – IBW)
Cockroft Gault (CrCl) = ((140 – age)xweight_in_kgx1.23)/creatinine_in_umol/L [x0.85 if female]

References:
1. Calvert AH, Newell DR, Gumbrell LA, et al. Carboplatin dosage: prospective evaluation of a simple formula based on renal function. J Clin Oncol. 1989;7(11):1748-1756. doi:10.1200/JCO.1989.7.11.1748
2. Jhaveri TA, Gil B, Zou M, Hartwell N, Sands J. Evaluation of carboplatin toxicities and efficacy using different body weight descriptors in the Calvert formula. J Clin Oncol. 2017;35(15_suppl):e14017-e14017. doi:10.1200/JCO.2017.35.15_suppl.e14017
3. Samani A, Bennett R, Eremeishvili K, et al. Glomerular filtration rate estimation for carboplatin dosing in patients with gynaecological cancers. ESMO open. 2022;7(2):100401. doi:10.1016/j.esmoop.2022.100401
4.https://www.nccn.org/docs/default-source/clinical/order-templates/appendix_b.pdf?sfvrsn=6286822e_6