Loading
Carboplatin is not dosed by your size but by how well your kidneys clear it. The team picks a target exposure (the 'AUC', often 5 or 6) and multiplies it by your kidney filtration rate plus 25. Your kidney function is either measured with a special test or estimated from a blood test, and the newest international guidance prefers the measured test when treatment aims to cure.
The Calvert formula (1989) gives the total dose in mg as target AUC x (GFR + 25). It was derived and validated with GFR measured by 51Cr-EDTA clearance, and the US label prints it with that note. The kidney function fed into it is where practice differs.
ADDIKD (2025), the first international consensus on anticancer drug dosing in kidney dysfunction, prefers directly measured GFR, not standardised to body surface area, especially with curative intent, extremes of body size or muscle mass, amputation or paraplegia, or an eGFR above 125 or at or below 45 ml/min/1.73 m2. Where measured GFR is not feasible, it recommends eGFR by CKD-EPI de-indexed to the patient's own BSA (clinical consensus; strong). KDIGO 2024 says non-indexed eGFR may be indicated at extremes of body weight for narrow-therapeutic-range drugs, and its text names carboplatin. Much of the world still uses Cockcroft-Gault creatinine clearance, which overestimates GFR by 10 to 20% and, with modern IDMS-standardised creatinine assays, can overdose: in a UK cohort of 2,471 patients, 25.5% of Cockcroft-Gault doses were more than 20% off against 18.6% for BSA-adjusted CKD-EPI (Janowitz 2017).
ADDIKD advises against lowering the target AUC because of reduced kidney function, and against recalculating each cycle unless kidney function changes by more than 20% or the patient's condition changes. In the UK, adult doses are then banded to national tables (BOPA 2025) and the pharmacist checks the AUC calculation at verification.
Why: Carboplatin leaves the body almost entirely through the kidneys, so the dose that gives a predictable exposure depends on kidney function rather than body size.
“Dose (mg) = target AUC x (GFR + 25) is now the recommended formula.”
Why: Higher AUC gives more blood count toxicity, and combination regimens use their own targets.
“The target AUC of 4 mg/mL•min to 6 mg/mL•min using single agent carboplatin appears to provide the most appropriate dose range in previously treated patients.”
Why: The formula was built on measured GFR; estimates drift furthest from the truth in people with very high or low kidney function or unusual body build.
“ADDIKD proposes that directly measured GFR (not standardised to body surface area [BSA]) as the preferred kidney function value to be used to mirror the original Calvert formula study.”
eClinicalMedicine (Sandhu et al.) 2025 · clinical consensus; strong
Why: BSA-adjusted CKD-EPI is closer to measured GFR than Cockcroft-Gault in people with cancer, so the dose is closer to the intended one.
“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 m 2 , 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.”
eClinicalMedicine (Sandhu et al., ADDIKD Working Group, eviQ / Cancer Institute NSW) 2025 · clinical consensus; strong
Why: A creatinine estimate assumes steady kidney function; after an acute kidney injury the blood level can lag one to three days behind.
“eGFR CKD-EPI requires stable kidney function and should be performed as close as possible to the time of administering the anticancer drug(s) to ensure it is a reflective estimation of the patient’s steady state kidney function.”
eClinicalMedicine (Sandhu et al., ADDIKD Working Group, eviQ / Cancer Institute NSW) 2025 · clinical consensus; strong
Why: Reducing both the GFR and the AUC would cut the dose twice and may cost treatment benefit.
“This includes a recommendation against lowering target AUC in reduced kidney function, as it may compromise clinical benefit.”
Why: Small cycle-to-cycle wobbles in creatinine do not need a new dose; a real change in kidney function does.
“The recalculation of carboplatin doses at each cycle was also deemed unnecessary, except when baseline kidney function (e.g., eGFR) alters by > 20% or when there is a change in the clinical status of the patient.”
Why: An independent check catches arithmetic and unit errors before the drug is made.
“Check drug dose calculations (Flat, BSA, weight, AUC) and units are appropriate.”
Why: A banded dose is already rounded, so comparing against it can hide or exaggerate a real change.
“Warning: it is NOT appropriate to use the previous banded dose to work out a percentage dose change threshold as this risks under or overestimating the actual carboplatin dose when banding.”
How care is usually carried out, read from the guidelines and standards cited. Your own team's protocol and their judgement come first; this page is for understanding it, not for doing it yourself.
Dose = target AUC x (GFR + 25), with GFR measured directly (not BSA-indexed) where available and always for curative treatment, extremes of body size or muscle mass, or an eGFR above 125 or at or below 45 ml/min/1.73 m2 (ADDIKD 2025, clinical consensus, strong). Where measured GFR is not feasible, ADDIKD and KDIGO 2024 favour CKD-EPI eGFR de-indexed to the patient's BSA over Cockcroft-Gault, supported by the 2,471-patient Cambridge cohort (Janowitz 2017) and the UK gynaecological cohorts of Samani 2022. Do not lower the AUC for kidney function; recalculate when kidney function changes by more than 20%. Guidance disagrees on the estimate: the US label and much software still use creatinine clearance, and the Gynecologic Oncology Group recommended Cockcroft-Gault with adjusted body weight above a BMI of 25.
eClinicalMedicine (Sandhu et al., ADDIKD Working Group, eviQ / Cancer Institute NSW) 2025 · eClinicalMedicine (Sandhu et al.) 2025 · KDIGO (Kidney International) 2024 · Journal of Clinical Oncology (Janowitz et al.) 2017 · ESMO Open (Samani et al.) 2022 · Journal of Clinical Oncology (Calvert et al.) 1989
Where it differs: Estimates GFR as creatinine clearance by Cockcroft-Gault, sometimes with ideal or adjusted body weight, and puts that into the formula. The US label's renal dose table for single-agent carboplatin is set in creatinine clearance bands.
Evidence: Cockcroft-Gault was built on 249 hospitalised men with a creatinine assay that predates IDMS standardisation, and overestimates GFR by 10 to 20% (ADDIKD). In 2,471 UK patients it gave a dose more than 20% off in 25.5% against 18.6% for BSA-adjusted CKD-EPI (Janowitz 2017). In two UK centres, unadjusted Cockcroft-Gault and Wright performed worst and adjusted-body-weight Cockcroft-Gault among the best (Samani 2022).
eClinicalMedicine (Sandhu et al., ADDIKD Working Group, eviQ / Cancer Institute NSW) 2025 · Journal of Clinical Oncology (Janowitz et al.) 2017 · ESMO Open (Samani et al.) 2022 · US National Library of Medicine, DailyMed 2026
Where it differs: Uses adjusted rather than actual body weight in Cockcroft-Gault for patients with a BMI of 25 or more, to avoid overestimating clearance in larger people.
Evidence: Recommended by the GOG after the switch to IDMS creatinine assays, as cited by Samani 2022, where CG with adjusted body weight was among the most accurate estimators against nuclear medicine GFR in two UK cohorts. The GOG document itself was not read.
Where it differs: Some UK centres and trials dose at AUC 6 when GFR is estimated and AUC 5 when it is measured, on the reasoning that estimates run low.
Evidence: Samani 2022 found this practice in its survey and that dosing on AUC 6 with an estimate carried a risk of overdosing compared with measured GFR at AUC 5; it advises centres to avoid it.
Where it differs: Estimates GFR with a model developed in people with cancer at Cambridge University Hospitals rather than CKD-EPI.
Evidence: In 2,471 patients it reduced doses more than 20% off to 14.2% (Janowitz 2017), and version 2 was the most accurate estimator in the UK gynaecological cohorts (Samani 2022). Not adopted by ADDIKD or KDIGO.
Journal of Clinical Oncology (Janowitz et al.) 2017 · ESMO Open (Samani et al.) 2022
Carboplatin doses depend on an estimate of kidney function. The 2025 international guideline (ADDIKD) recommends a newer estimate (BSA-adjusted CKD-EPI) over the old Cockcroft-Gault formula when kidney function cannot be measured directly, because it is more accurate. No study has yet shown that switching changes side effects or how well treatment works.
| Recommendation | Grade, as printed | Source |
|---|---|---|
| eGFR by CKD-EPI to assess kidney function, except where measured GFR is clinically necessary “We recommend the use of estimated glomerular filtration rate calculated via the Chronic Kidney Disease—Epidemiology Collaboration (eGFR CKD-EPI ) equation to guide the assessment of kidney function, except where directly measured glomerular filtration rate (GFR) is clinically necessary.” | Evidence quality/certainty: clinical consensus; strength of recommendation: strong | eClinicalMedicine (Sandhu et al., ADDIKD Working Group, eviQ / Cancer Institute NSW) 2025 |
| eGFR CKD-EPI to guide dosing of kidney-dependent anticancer drugs, with measured GFR preferred for carboplatin, cisplatin and others in specific situations “We recommend eGFR CKD-EPI to guide the dosing of anticancer drugs whose dose is dependent on kidney function, except in specific clinical situations or for a select group of anticancer drugs where eGFR CKD-EPI may be unsuitable.” | Evidence quality/certainty: clinical consensus; strength of recommendation: strong | eClinicalMedicine (Sandhu et al., ADDIKD Working Group, eviQ / Cancer Institute NSW) 2025 |
| Non-BSA-indexed eGFR at extremes of body weight, for narrow-therapeutic-range drugs “In people with extremes of body weight, eGFR nonindexed for body surface area (BSA) may be indicated, especially for medications with a narrow therapeutic range or requiring a minimum concentration to be effective.” | Practice Point 4.2.4 | KDIGO (Kidney International) 2024 |
Shares Carboplatin dosing by kidney function: the Calvert formula and how kidney function is measured, Anticancer treatment prescribing and pharmacy verification before each cycle.
Shares Anticancer treatment prescribing and pharmacy verification before each cycle, Pharmacokinetics (PK), half-life and exposure.
Shares Carboplatin dosage: prospective evaluation of a simple formula based on renal function, Carboplatin dosing by kidney function: the Calvert formula and how kidney function is measured, Carboplatin.
Shares Anticancer treatment prescribing and pharmacy verification before each cycle.
Shares Carboplatin dosing by kidney function: the Calvert formula and how kidney function is measured, Anticancer treatment prescribing and pharmacy verification before each cycle, Pharmacokinetics (PK), half-life and exposure.
Shares Anticancer treatment prescribing and pharmacy verification before each cycle, Carboplatin.