Carboplatin is cleared largely by the kidneys, so exposure (and toxicity) tracks with renal function. That’s why most centers don’t use BSA for carboplatin: instead, they use AUC-targeted dosing with the Calvert formula, which ties dose directly to GFR. This approach improves consistency of exposure and helps reduce hematologic toxicity (notably thrombocytopenia).

https://info.pharkeep.com/auc-calculator.html

Why not dose by BSA?

Carboplatin is eliminated largely by the kidneys; hematologic toxicity (especially thrombocytopenia) tracks with clearance. BSA-based dosing cannot account for wide differences in renal function. AUC-based dosing aligns the dose with the pharmacokinetics that matter most for this drug.

The Calvert Formula

Dose (mg) = AUC target × ( GFR + 25 )
  • AUC target (mg·min/mL): protocol-dependent, commonly 4–6 (e.g., AUC 5–6 with paclitaxel).
  • GFR (mL/min): measured (preferred when available) or estimated.
  • 25 (mL/min): approximate non-renal clearance term from the original PK studies.
Remember: The Calvert result is a mg dose, not mg/m².

Estimating Renal Function (when measured GFR isn’t available)

Creatinine clearance is commonly estimated using the Cockcroft–Gault (CG) equation. Many institutions apply additional guardrails to avoid overestimation/overdosing in specific scenarios (e.g., sarcopenia, very fit patients).

CrCl (mL/min) = ((140 − age) × weight) / (72 × SCr) × (0.85 if female)

Weight selection (common practice)

  • Use Actual Body Weight (ABW) if BMI < 30.
  • Use Adjusted Body Weight (AdjBW) if BMI ≥ 30:
    AdjBW = IBW + 0.4 × (ABW − IBW)
  • Ideal Body Weight (IBW):
    Male: 50 + 2.3 × (inches over 60)
    Female: 45.5 + 2.3 × (inches over 60)

Institutional policies vary. Many use an SCr floor (e.g., 0.7 mg/dL in frail/elderly) and a GFR cap (e.g., 125 mL/min) when calculating the Calvert dose.

Dosing Pathway

Why “+25” in the Calvert Equation?

Typical AUC Targets (examples)

  • Carboplatin + paclitaxel (ovarian): AUC 5–6
  • Carboplatin + etoposide: AUC 5
  • Weekly low-dose radiosensitization: AUC 2

Always confirm with your local protocol or order set.

Practical tips & pitfalls

  • Prefer measured GFR (e.g., iothalamate) when available or when estimates are unreliable.
  • Consider an SCr floor (e.g., 0.7 mg/dL) in frail/sarcopenic patients to avoid overestimating CrCl.
  • Consider a GFR cap (e.g., 125 mL/min) for dosing to avoid overdosing very fit patients.
  • Use AdjBW in obesity (BMI ≥ 30) for CG; verify your institution’s policy.
  • Calvert’s performance is limited when GFR/CrCl is very low (≈<15–20 mL/min); consult specialists.

Worked example

62-year-old female, 160 cm, 80 kg, SCr 0.9 mg/dL, target AUC 5.

  1. IBW = 45.5 + 2.3 × (63 in − 60) = 52.4 kg
  2. AdjBW = 52.4 + 0.4 × (80 − 52.4) = 63.4 kg
  3. CrCl (CG) = ((140 − 62) × 63.4) / (72 × 0.9) × 0.85 ≈ 66.3 mL/min
  4. Dose = 5 × (66.3 + 25) ≈ 458 mg → 460 mg

When Is Carboplatin AUC Dosing Used?

Cancer Type Typical AUC
Ovarian cancer (first-line with paclitaxel) AUC 5–6
AUC-adjusted regimens like CARBO/ETOPOSIDE AUC 5
Weekly low-dose radiosensitization AUC 2
Germ cell tumors (salvage) AUC 6–7
Good renal function but toxicity concern AUC 4–5

References & Further Reading

  1. Calvert AH, et al. Carboplatin dosage: prospective evaluation of a simple formula based on renal function. 1989. (Original Calvert equation; prospective validation.)
  2. FDA Paraplatin® (carboplatin) Labeling. (Includes the Calvert formula in the official dosing section; dose in mg rather than mg/m².)
  3. NCCN Chemotherapy Order Templates – Appendix B: Carboplatin Dosing. (NCCN-aligned templates reflecting common practices such as SCr floors and GFR caps; access may require login.)
  4. Janowitz T, et al. New Model for Estimating GFR in Oncology. JCO 2017. (ASCO journal article underscoring the centrality of GFR estimation for carboplatin dosing.)
  5. Schwenk MH. Carboplatin Dosing on the Basis of Renal Function. Kidney360 2024. (Clear explanation of the “GFR + 25” clearance relationship.)
  6. Praiss AM, et al. Carboplatin Dosing in the Treatment of Ovarian Cancer. Cancers 2023. (Discusses practice of capping at 125 mL/min and related outcomes considerations.)
  7. MemorialCare institutional calculator (2022 update). (Summarizes NCCN-recommended safeguards: GFR cap 125, SCr floor 0.7, AdjBW in obesity.)
  8. NCI/label-based summaries of the Calvert method and common AUC targets.