Creatinine Clearance Chemotherapy Calculator
Calculate creatinine clearance using Cockcroft-Gault formula and carboplatin dosing using Calvert formula with AUC-based targeting
Common targets: 4-5 (conservative), 5 (combination), 6 (untreated), 7 (aggressive)
Carboplatin AUC Targets by Indication
| AUC Target | Cancer Type | Treatment Setting |
|---|---|---|
| AUC 4-5 | Various | Heavily pretreated, elderly, poor performance status |
| AUC 5 | Ovarian cancer | Previously treated, combination with paclitaxel |
| AUC 6 | Ovarian cancer | Previously untreated, initial therapy |
| AUC 6 | Lung cancer (NSCLC) | Combination with other agents |
| AUC 7 | Lung cancer (SCLC) | Aggressive regimens, good performance status |
| AUC 7-8 | Head and neck cancer | High-dose regimens with stem cell rescue |
Note: Always consult current protocol guidelines. AUC targets may vary by institution and specific regimen.
Renal Impairment Dose Adjustments
| CrCl (mL/min) | Renal Function | Dose Adjustment | Monitoring |
|---|---|---|---|
| ≥60 | Normal to mild | No adjustment needed | Standard monitoring |
| 45-59 | Mild impairment | Monitor closely, consider 20-25% reduction | Check CrCl before each cycle |
| 30-44 | Moderate impairment | Reduce dose by 25-50% | Frequent CrCl and CBC monitoring |
| 15-29 | Severe impairment | Reduce dose by 50-75%, use with caution | Very frequent monitoring, consider alternatives |
| <15 | Kidney failure | Avoid or use only with extreme caution | Consider alternative agents |
Formulas Used
Cockcroft-Gault Formula
Standard formula for estimating creatinine clearance. Multiply by 0.85 for females to account for lower muscle mass.
Calvert Formula (Carboplatin)
Pharmacokinetically-derived formula for carboplatin dosing. The constant 25 represents non-renal clearance.
Important Considerations
- Some protocols cap CrCl at 125 mL/min to prevent overdosing in patients with high clearance
- For obese patients (BMI >30), some use ideal body weight instead of actual weight
- GFR measured by other methods (e.g., EDTA clearance, MDRD, CKD-EPI) should NOT be used for Calvert formula
- Maximum single dose typically 800-1000 mg to reduce toxicity risk
Frequently Asked Questions
Why use Cockcroft-Gault instead of other GFR equations?
The Calvert formula was developed and validated using Cockcroft-Gault estimated CrCl, not other GFR equations. Using MDRD or CKD-EPI can lead to incorrect dosing. Always use Cockcroft-Gault for carboplatin dosing calculations.
Should I cap creatinine clearance at 125 mL/min?
Many institutions cap CrCl at 125 mL/min when using the Calvert formula to avoid overdosing young, healthy patients with high clearance. This practice prevents excessive doses that could increase toxicity without improving efficacy. Consult your protocol guidelines.
How do I dose carboplatin in obese patients?
There is debate about using actual vs. ideal body weight in obese patients. Some protocols recommend using ideal body weight for BMI >30, while others use actual weight. The safest approach is to follow your specific protocol guidelines and consider capping the total dose at 800-1000 mg.
What AUC target should I use?
AUC targets depend on cancer type, treatment setting, and combination therapy. Common targets are AUC 5-6 for ovarian cancer and AUC 6-7 for lung cancer. Always verify with current protocol guidelines, as targets may vary by regimen and patient factors.
When should I recalculate creatinine clearance?
Recalculate CrCl before each chemotherapy cycle, especially if the patient experienced toxicity, has changing renal function, or significant weight changes. Even small changes in creatinine can significantly impact carboplatin dosing.
What if calculated dose exceeds 1000 mg?
Most protocols specify a maximum single dose of 800-1000 mg to reduce the risk of severe myelosuppression. If your calculation exceeds this, cap the dose at the institutional maximum and document the decision. Some protocols may allow higher doses with careful monitoring.
How do I adjust for subsequent cycles after toxicity?
If the patient experiences grade 3-4 thrombocytopenia or neutropenia, consider reducing the target AUC by 1 unit (e.g., from AUC 6 to AUC 5) for subsequent cycles. For grade 2 toxicity, close monitoring without dose reduction may be appropriate. Always follow protocol-specific guidelines.
Can I use this calculator for other platinum agents?
No. This calculator is specifically for carboplatin using the Calvert formula. Cisplatin and oxaliplatin use BSA-based dosing (mg/m²), not AUC-based dosing. Use the appropriate calculator for each agent.
Related Calculators
BSA Chemotherapy Calculator
Calculate body surface area for chemotherapy dosing
Renal Dose Adjustment Calculator
Calculate medication dose adjustments for renal impairment
Febrile Neutropenia Risk Calculator
MASCC Risk Index for chemotherapy patients
Cancer Staging TNM Reference
TNM staging system reference guide
BUN/Creatinine Ratio Calculator
Assess renal function and hydration status
Weight-Based Dose Calculator
Calculate mg/kg dosing for medications
Understanding Carboplatin Dosing with AUC
Carboplatin is a platinum-based chemotherapy agent widely used in the treatment of ovarian, lung, head and neck, and other solid tumors. Unlike most chemotherapy agents that are dosed based on body surface area (BSA), carboplatin is typically dosed using the Calvert formula, which targets a specific area under the curve (AUC) of drug exposure based on renal function.
The Calvert Formula: A Pharmacokinetic Approach
The Calvert formula represents a significant advancement in chemotherapy dosing. Developed in the 1980s, it uses individual patient characteristics to predict drug clearance and calculate the dose needed to achieve a target AUC. The formula is: Dose (mg) = Target AUC × (GFR + 25), where GFR is estimated using the Cockcroft-Gault formula for creatinine clearance.
Why Cockcroft-Gault is Essential
It is critical to use the Cockcroft-Gault formula specifically for carboplatin dosing calculations. The Calvert formula was developed and validated using Cockcroft-Gault estimated creatinine clearance, not modern GFR equations like MDRD or CKD-EPI. While these newer equations may be more accurate for assessing kidney disease, they will yield incorrect carboplatin doses if substituted into the Calvert formula. This is not interchangeable - always use Cockcroft-Gault for carboplatin.
Selecting the Appropriate AUC Target
The target AUC must be selected based on cancer type, treatment intent, combination therapy, and patient factors. For ovarian cancer, AUC 5-6 is standard depending on whether the patient is previously treated or untreated. Lung cancer regimens often use AUC 6-7. Lower targets (AUC 4-5) may be appropriate for elderly patients, those with poor performance status, or heavily pretreated individuals. Higher targets (AUC 7-8) are sometimes used in aggressive regimens or with stem cell support.
Dose Capping Considerations
Many institutions cap creatinine clearance at 125 mL/min when using the Calvert formula to prevent excessive dosing in young, healthy patients with high renal clearance. Additionally, maximum single doses of 800-1000 mg are commonly employed to reduce the risk of severe myelosuppression. These safety measures help balance efficacy with tolerability.
Special Populations: Obesity and Renal Impairment
Dosing carboplatin in obese patients presents challenges. Some protocols recommend using ideal body weight rather than actual weight for patients with BMI greater than 30, while others use actual weight with dose caps. There is no universal consensus, so following protocol-specific guidelines is essential. For patients with renal impairment, the Calvert formula automatically adjusts the dose based on creatinine clearance, but additional reductions may be necessary for severe impairment (CrCl less than 30 mL/min).
Monitoring and Dose Adjustments
Carboplatin's primary toxicities are myelosuppression (particularly thrombocytopenia and neutropenia) and nephrotoxicity. Creatinine clearance should be recalculated before each cycle, as even small changes in renal function can significantly impact dosing. If grade 3-4 hematologic toxicity occurs, reducing the target AUC by 1 unit for subsequent cycles is often appropriate. Complete blood counts should be monitored regularly, with nadir typically occurring 14-21 days after administration.
Clinical Best Practices
Always verify that you are using the Cockcroft-Gault formula for creatinine clearance, not other GFR equations. Double-check all calculations and have another qualified healthcare provider verify the dose before administration. Document the creatinine clearance, target AUC, and final dose in the patient record. Consider dose capping at 125 mL/min CrCl and maximum single dose limits. Monitor renal function and blood counts closely throughout treatment and adjust doses based on tolerance and response.