Calvert Carboplatin Dose Calculator
Calvert Carboplatin Dose Calculator
Dose (mg) = target AUC × (GFR + 25). The 25 is a non-renal clearance term in mL/min, so the kidney function fed in must be absolute and not indexed to 1.73 m² — and whether to cap it at 125 mL/min is a live disagreement this page prints both sides of.
Carboplatin dose by the Calvert formula
AUC and kidney function to mgTarget AUC 5; laboratory eGFR 110 mL/min/1.73 m2; body surface area 2.05 m2; cap applied
The formula, and the two things that go wrong with it
De-indexing, where the GFR is a laboratory eGFR: absolute (mL/min) = indexed (mL/min/1.73 m²) × BSA (m²) ÷ 1.73
Capped maximum, per the FDA recommendation: target AUC × (125 + 25) — so 600 mg at AUC 4, 750 mg at AUC 5, 900 mg at AUC 6
- the 25
- non-renal clearance, in mL/min. An absolute rate, which forces the GFR term to be absolute too: an indexed eGFR is a rate per 1.73 m² of notional body, and adding that to an absolute rate is a unit error returning a plausible number
- the GFR Calvert used
- a GFR measured by chromium-51 EDTA clearance: “In these studies, GFR was measured by 51Cr-EDTA clearance.” A 2006 analysis of 178 patients concluded that for targeted exposure “the original Calvert formula, measuring GFR using the 51Cr-EDTA clearance, remains the method of choice”
- which estimate, if not measured
- ADDIKD, which eviQ implements, prefers a measured GFR and names a BSA-adjusted eGFR as the alternative. A 2010 survey of 515 US practitioners found 94.1% using an estimated creatinine clearance, 89.3% of them Cockcroft-Gault. Not interchangeable
- the assay standardisation the capping advice assumes
- isotope-dilution mass spectrometry. Cancer Care Ontario: “the IDMS method generally produces lower serum creatinine levels in patients with normal renal function”, “which could result in an overestimation of the calculated creatinine clearance”, so a Calvert dose built on it “could be higher”. That is the hinge for the cap
Worked example
Target AUC 5; laboratory eGFR 110 mL/min/1.73 m2; body surface area 2.05 m2; cap applied
De-index first: 110 × 2.05 ÷ 1.73 = 130.3 mL/min absolute. The reported eGFR understated the clearance by 20 mL/min, because this patient is larger than the 1.73 m² reference
Capped at 125: 5 × (125 + 25) = 750 mg, exactly the maximum Cancer Care Ontario prints for a target AUC of 5
Uncapped: 5 × (130.3 + 25) = 777 mg. The cap withholds 27 mg, and whether it should is the disagreement below
Now the error this page exists to prevent: feed the reported 110 straight in and 5 × (110 + 25) = 675 mg, 102 mg below the correct uncapped dose — a 13% under-dose looking like an answer
The direction depends on the patient: at 1.40 m² an eGFR of 85 de-indexes to 68.8 mL/min, and 469 mg against the indexed figure's 550 mg is an 81 mg over-dose. At 1.73 m² exactly the error vanishes, which is why it survives
Does the kidney function value get capped? Four published positions
| Source | Position | What it says |
|---|---|---|
| US FDA, disseminated 2010 | Cap at 125 mL/min | Reproduced in the Cancer Care Ontario monograph as “To avoid toxicity, FDA recommends capping the carboplatin dose for a desired AUC”, with the maximum dose stated as target AUC × (125 + 25). The generic carboplatin label itself does not carry the cap. |
| US National Cancer Institute, 2010 | Cap at 125 mL/min | Quoted by Morrow et al. as “the GFR value within the Calvert formula should not exceed 125 mL/min”. A journal report of the recommendation records it as limiting the GFR “regardless of the SCr value”. |
| ADDIKD / eviQ (Cancer Institute NSW) | Do not cap | “Kidney function should not be capped at 125 mL/min for use in the Calvert formula.” ADDIKD prefers a directly measured GFR and, failing that, a BSA-adjusted eGFR in mL/min. |
| Practice, as surveyed | Split almost evenly | In a 2010 HOPA survey of 515 practitioners, 47.6% applied a cap. The mean cap applied was 133 ± 15 mL/min, with a range of 100 to 166 mL/min. There was no single number in use. |
The indexing error at one eGFR of 85 mL/min/1.73 m2, target AUC 5
| Body surface area (m2) | Absolute GFR (mL/min) | Dose on the absolute figure (mg) | Dose on the indexed figure (mg) | Error (mg) |
|---|---|---|---|---|
| 1.40 | 68.8 | 469 | 550 | +81 over-dose |
| 1.60 | 78.6 | 518 | 550 | +32 over-dose |
| 1.73 | 85.0 | 550 | 550 | 0 — the reference body |
| 2.10 | 103.2 | 641 | 550 | 91 under-dose |
| 2.45 | 120.4 | 727 | 550 | 177 under-dose |
Two inputs, two ways to get them wrong
Carboplatin is dosed to an exposure rather than to a size. Its clearance is almost entirely renal and almost linearly related to glomerular filtration, so the area under the concentration-time curve can be predicted from kidney function alone: dose in milligrams equals the target AUC multiplied by the GFR plus 25. It is one of the few cytotoxics whose dose is not computed from body surface area at all, and the label says so — the dose is in mg, not mg/m².
The first way to get it wrong is the units of the GFR. The 25 is a non-renal clearance term in mL/min, an absolute rate for an actual kidney in an actual body. A laboratory eGFR is not that: it is reported per 1.73 m² so kidney function can be compared across people of different sizes, which is exactly the normalisation a dose must undo. Putting the reported figure straight in under-doses a large patient and over-doses a small one, by up to a third of the correct dose at the extremes of adult size, and the error is silent because the number it returns is plausible.
The second is which estimate to put in at all. Calvert and colleagues built the formula against a GFR measured by chromium-51 EDTA clearance in eighteen patients, with values up to about 133 mL/min. Almost nobody measures GFR that way for a dose: a 2010 survey of 515 practitioners found 94.1% substituting an estimated creatinine clearance, usually Cockcroft-Gault. That is a different quantity, and when US laboratories moved to IDMS-traceable creatinine the problem sharpened — standardised assays return lower creatinine at normal values, so every estimate built on them runs higher and an uncapped dose runs higher with it. Hence the capping disagreement, which is unresolved. In 2010 the FDA and the National Cancer Institute recommended limiting the GFR to 125 mL/min, fixing the maximum dose at 150 times the target AUC; national formularies reproduce it and the generic label does not carry it. ADDIKD, which eviQ implements, states the opposite, and a retrospective analysis argued that capping a patient whose true GFR is genuinely above 125 “will likely lead to a lower AUC rather than the intended AUC target”. Surveyed practice splits almost evenly, and among those who cap the cap ran from 100 to 166 mL/min. A figure from a cohort is not this patient’s outcome and a response category is not a diagnosis: a stratum in which 42 per cent were alive at fifteen years tells you about that stratum, not which 42 per cent. This page computes a published quantity and states the criteria behind it. It renders no dose, no prescription and no treatment decision — that is the treating team’s.
Frequently asked questions
What is the Calvert formula?
Dose in mg equals the target AUC in mg/mL per min multiplied by the GFR in mL/min plus 25, where the 25 represents non-renal clearance. The dose comes out in milligrams and not mg/m², which is unusual for a cytotoxic and is stated on the label.
Can I use my laboratory’s eGFR in the Calvert formula?
Not as reported. A laboratory eGFR is indexed to 1.73 m² and the formula needs an absolute rate in mL/min, because the 25 it is added to is one. Multiply by the patient’s body surface area and divide by 1.73 first: at 2.45 m² that correction is worth 177 mg at a target AUC of 5.
Should the GFR be capped at 125 mL/min?
Published guidance disagrees. The FDA and the NCI recommended capping it in 2010 and national formularies reproduce that, giving maxima of 600 mg at AUC 4, 750 at AUC 5 and 900 at AUC 6. ADDIKD states that kidney function should not be capped. A 2010 survey found 47.6% capping, with caps from 100 to 166 mL/min.
Why does IDMS creatinine standardisation matter here?
Standardised assays return lower creatinine than older methods at the normal end of the range, so every creatinine-based GFR estimate built on them runs higher and an uncapped Calvert dose with it. That is the reasoning behind the capping advice, and why it is tied to assay standardisation rather than to carboplatin.
Related calculators
References
- Carboplatin injection, USP: full prescribing information. DailyMed, SPL 5484d2f0-0cc2-4bba-8f26-c7f6539a9606.
- Cancer Care Ontario. Drug Formulary monograph: CARBOplatin, Section E, dose calculation. Toronto: Ontario Health.
- Oncology Nursing Society. Oncology Drug Reference Sheet: Carboplatin. ONS Voice, October 2025.
- eviQ, Cancer Institute NSW. Carboplatin dose calculator, and the ADDIKD carboplatin dosing recommendations as reproduced in eviQ treatment protocols.
- Morrow A, Garland C, Yang F, De Luna M, Herrington JD. Analysis of carboplatin dosing in patients with a glomerular filtration rate greater than 125 mL/min: to cap or not to cap? J Oncol Pharm Pract. 2019;25(5):1130–7.
- Hematology/Oncology Pharmacy Association. How to assess renal function for dosing carboplatin: results of a HOPA member survey. HOPA News. 2010;7(4).
Not medical advice. For healthcare professionals and education. Reference intervals vary by laboratory and assay — always use your own laboratory's. Never base a dose or a treatment decision on this page alone. Full disclaimer at calcengines.com/disclaimer/