Journal of Clinical Oncology September 23, 2026

Reply to: “Creatinine Assay Methods and Carboplatin Dosing Transparency in the neoCARHP Trial”

Hong-Fei Gao et al.

Bottom Line

The neoCARHP trial investigators clarify their creatinine assay and carboplatin dosing methodology, affirming that the higher rate of hematologic toxicity in the carboplatin arm was due to expected myelotoxicity rather than systematic overdosing.

Key Findings

1. Serum creatinine was measured uniformly at all 15 participating centers using IDMS-traceable enzymatic assays (compliant with China standard WS/T 413-2013); Jaffe-based assays were not used.

2. Carboplatin was administered at a target AUC of 6 every 3 weeks, calculated via the Calvert formula with creatinine clearance estimated by the Cockcroft-Gault equation.

3. Calculated creatinine clearance was strictly capped at 125 mL/min, corresponding to a maximum carboplatin dose of 900 mg per cycle, preventing massive accidental overdoses.

4. Protocol-specified dose reductions were required in 25.3% (97 of 384) of patients in the carboplatin (TCbHP) group, predominantly due to hematologic toxicity.

5. Grade 3 or higher adverse events occurred in 34.6% of patients receiving TCbHP compared to 20.7% of those receiving the carboplatin-sparing THP regimen, a difference driven by expected carboplatin-induced myelosuppression.

Study Design

Design

Correspondence / Trial Reply

Open-Label

Sample

766

Patients

Duration

N/A

Median

Setting

15 centers, China

Population Women ≥18 years old with previously untreated, stage II-III, HER2-positive invasive breast cancer (neoCARHP trial cohort)

Intervention Neoadjuvant taxane, carboplatin, trastuzumab, and pertuzumab (TCbHP)

Comparator Neoadjuvant taxane, trastuzumab, and pertuzumab (THP) without carboplatin

Outcome Clarification of carboplatin dosing and toxicity (original trial primary outcome: pathologic complete response)

Study Limitations

• As a correspondence reply, this publication provides methodological clarifications rather than new primary efficacy or survival data.

• The authors acknowledge that estimating renal function using the older Cockcroft-Gault equation (rather than modern alternatives like CKD-EPI or direct GFR measurement) remains inherently imprecise, though it reflects standard practice in many oncology trials.

Clinical Significance

This correspondence validates the safety protocols of the neoCARHP trial, confirming that appropriate safeguards against systematic carboplatin overdosing were in place. It reassures clinicians that the higher toxicity observed in the TCbHP arm reflects the true biological burden of carboplatin, thereby supporting the trial's overarching conclusion that carboplatin can potentially be omitted in selected patients with early-stage HER2-positive breast cancer to safely reduce treatment morbidity.

Historical Context

The phase 3 neoCARHP trial, published earlier in 2026, was a landmark non-inferiority study showing that omitting carboplatin from the standard neoadjuvant TCbHP regimen for stage II-III HER2-positive breast cancer reduced toxicity without compromising pathologic complete response (pCR) rates. Critics subsequently raised valid concerns that discrepancies between older creatinine measurement methods (for which historical GFR equations were designed) and modern IDMS-standardized assays can lead to overestimation of renal function and subsequent carboplatin overdosing. This reply explicitly addresses those concerns by detailing the modern uniform assays and dosing caps employed.

Guided Discussion

High-yield insights from every perspective

Med Student

Medical Student

Why is carboplatin dosed based on renal function using the Calvert formula rather than body surface area, and what is its primary dose-limiting toxicity?

Key Response

Carboplatin is cleared almost entirely by glomerular filtration. The Calvert formula targets a specific Area Under the Curve (AUC) to optimize efficacy while mitigating its primary dose-limiting toxicity, which is myelosuppression, specifically thrombocytopenia.

Resident

How does the modern use of IDMS-traceable creatinine assays affect carboplatin dosing when using the classic Cockcroft-Gault equation, and how should clinicians mitigate this risk?

Key Response

IDMS-traceable assays typically yield lower serum creatinine values than older methods. When plugged into the Cockcroft-Gault equation, this artificially inflates the estimated GFR, potentially leading to carboplatin overdosing and severe myelosuppression. Clinicians must cap the GFR, typically at 125 mL/min, to prevent this.

Fellow

In evaluating the neoCARHP trial investigators' claim that their toxicity was expected rather than an artifact of systematic overdosing, what pharmacokinetic and clinical parameters would you analyze to differentiate expected synergistic myelotoxicity from a dosing calculation error?

Key Response

A fellow should evaluate the depth, nadir timing, and recovery duration of cytopenias. Overdosing due to inflated GFR estimates presents with disproportionately prolonged and profound cytopenias compared to historical controls for a given AUC. Differentiating this requires auditing the specific body weight used, GFR capping rules, and evaluating the overlapping marrow-suppressive effects of concurrent agents in the regimen.

Attending

Given the ongoing controversies regarding creatinine assays and carboplatin dosing highlighted in the neoCARHP correspondence, what standardized institutional protocols should be implemented to ensure safe carboplatin administration across diverse patient populations?

Key Response

Attendings should standardize the GFR estimation method across their practice, mandating a strict GFR cap (e.g., 125 mL/min), specifying the use of adjusted or ideal body weight in obese patients, and identifying clinical scenarios (e.g., extremes of muscle mass) where measured 24-hour urine creatinine or exogenous filtration markers should override standard formulas.

Scholarly Review

Critical appraisal through the lens of expert reviewers and guideline development

PhD

When designing a multi-center oncology trial that utilizes narrow therapeutic index drugs dependent on renal clearance, what methodological controls should be embedded in the protocol to prevent inter-laboratory creatinine assay variance from confounding safety and efficacy endpoints?

Key Response

Trial protocols must proactively standardize assay methodology by either mandating a central laboratory for all dosing-related chemistry panels or requiring local labs to mathematically harmonize their creatinine values to a single traceable standard. Additionally, the protocol must explicitly define the exact pharmacokinetic equations and caps to eliminate investigator-level dosing heterogeneity.

Journal Editor

As a peer reviewer evaluating a manuscript like the neoCARHP trial, what specific elements of chemotherapy dosing methodology must be strictly reported to prevent post-publication disputes regarding treatment-emergent toxicity?

Key Response

Editors must require authors to explicitly detail the exact formula used for GFR estimation, the creatinine assay standard, the weight metric utilized, and any maximum GFR or dose caps applied. Omission of these variables compromises the reproducibility of the study and obscures the true etiology of reported toxicities.

Guideline Committee

How does the debate surrounding IDMS-traceable assays and carboplatin toxicity inform current ASCO and NCI guidelines on the Calvert formula, and what evidence is required to transition from the Cockcroft-Gault equation to modern formulas like CKD-EPI?

Key Response

Current NCI guidance recommends using the Cockcroft-Gault equation with a GFR cap of 125 mL/min to prevent overdosing in the era of IDMS-traceable assays. Transitioning guidelines to recommend CKD-EPI requires robust pharmacokinetic cross-validation studies demonstrating that CKD-EPI-based AUC targeting achieves therapeutic equivalence and non-inferior toxicity profiles compared to historical Calvert formula outcomes.

Clinical Landscape

Noteworthy Related Trials

1989

Calvert Study

n = 59 · JCO

Tested

Carboplatin dosed via Calvert formula (Target AUC)

Population

Patients with solid tumors

Comparator

Empirical body surface area dosing models

Endpoint

Carboplatin clearance and AUC predictability

Key result: Established the Calvert formula as a highly accurate method for carboplatin dosing based on glomerular filtration rate (GFR).

2014

CALGB 40603

n = 443 · JCO

Tested

Carboplatin added to standard neoadjuvant chemotherapy

Population

Patients with operable stage II-III triple-negative breast cancer

Comparator

Standard neoadjuvant chemotherapy

Endpoint

Pathological complete response (pCR)

Key result: The addition of carboplatin significantly improved pCR rates but substantially increased grade 3 and 4 hematologic toxicities.

2018

BrighTNess Trial

n = 634 · Lancet Oncol

Tested

Addition of carboplatin to neoadjuvant chemotherapy

Population

Patients with stage II-III triple-negative breast cancer

Comparator

Standard neoadjuvant chemotherapy alone

Endpoint

Pathological complete response (pCR)

Key result: Adding carboplatin significantly increased the pCR rate compared to standard chemotherapy alone in early-stage triple-negative breast cancer.

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