A Two-Arm Study to Evaluate the Pharmacokinetics, Efficacy, and Safety of Subcutaneous Administration of the Fixed-Dose Combination of Pertuzumab and Trastuzumab in Combination With Chemotherapy in Chinese Participants With HER2-Positive Early Breast Cancer: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Two-Arm Study to Evaluate the Pharmacokinetics, Efficacy, and Safety of Subcutaneous Administration of the Fixed-Dose Combination of Pertuzumab and Trastuzumab in Combination With Chemotherapy in Chinese Participants With HER2-Positive Early Breast Cancer (NCT04024462), a randomized phase 3 study. The primary outcome is Serum Trough Concentration (Ctrough) of Pertuzumab During Cycle 7 (Pre-Dose Cycle 8).

2. Clinical Question

The comparison is about pharmacokinetic exposure at a specified pre-dose timepoint, not a direct test of whether either treatment improves clinical outcomes. The registry also lists efficacy and safety outcomes. Total pathological complete response is among the secondary outcomes, as are event-free and survival measures and adverse events.

The central statistical issue is whether the concentration data support the prespecified non-inferiority question. The posted result is a geometric mean ratio with a 90% confidence interval. The registry record does not report the non-inferiority margin or the detailed decision rule, so the ratio and its interval can be described, but the formal basis for declaring non-inferiority cannot be checked from the record alone.

3. Trial Design

NCT04024462 is a completed, randomized, multicenter, open-label, parallel, two-arm phase III study. The registry lists an enrollment of 200. The study started on 2020-02-05, and primary completion is dated 2021-12-13. Hoffmann-La Roche is the listed sponsor.

The comparison is between pertuzumab IV plus trastuzumab IV with chemotherapy and pertuzumab and trastuzumab FDC SC with chemotherapy. Both arm descriptions specify 8 cycles of neoadjuvant chemotherapy: 4 cycles of doxorubicin plus cyclophosphamide followed by docetaxel for 4 cycles. Pertuzumab and trastuzumab are described as being given for 4 cycles concurrently with the taxane component. The registry describes the chemotherapy schedule as Q3W.

The study is open-label, so masking is listed as none. Random allocation and parallel arms provide the basis for a between-group comparison, but the registry record does not report the allocation ratio, randomization method, or concealment procedures. It also does not report further details about site numbers or site-level conduct.

The primary endpoint is pharmacokinetic rather than a clinical event outcome. Its analysis population is defined by adherence to prespecified pharmacokinetic assessment criteria, and the posted group sizes for that endpoint are 89.0 in each arm. The secondary pathological complete response results use group sizes of 101.0 and 99.0. Those different analysis populations and denominators matter: they reflect endpoint-specific records and should not be treated as interchangeable.

The study’s brief summary states that it evaluates pharmacokinetics, efficacy, and safety for the subcutaneous fixed-dose combination compared with intravenous pertuzumab and trastuzumab. The registry lists surgery and postoperative radiotherapy among the interventions, but additional details of their use are not reported in the registry record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Before assignment: Participants with human epidermal growth factor receptor 2 (HER2)-positive early breast cancer, who were candidates for preoperative neoadjuvant treatment in the clinical practice, were enrolled in the study.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Pertuzumab Per Protocol PK Population: includes only participants who adhered to the pre-specified criteria for the schedule of pharmacokinetic assessments.

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Serum Trough Concentration (Ctrough) of Pertuzumab During Cycle 7 (Pre-Dose Cycle 8), measured over Pre-dose at Cycle 8 (one cycle is 21 days).

The primary endpoint is serum trough concentration (Ctrough) of pertuzumab during Cycle 7, measured before the Cycle 8 dose. The registry specifies the timeframe as pre-dose at Cycle 8 and notes that one cycle is 21 days. A trough concentration is a drug concentration measured near the end of a dosing interval, before the next dose. As a general pharmacokinetic concept, it describes the amount of drug remaining in circulation at that point in the schedule.

The endpoint is reported as a geometric mean in micrograms per millilitre, with geometric coefficient of variation as its measure of dispersion. The result is intended to compare pertuzumab exposure after the subcutaneous fixed-dose combination with exposure after intravenous pertuzumab and trastuzumab. This is useful because the study’s primary question concerns pharmacokinetics, rather than whether participants experience a clinical event.

The registry describes the measurement as following 3 cycles of pertuzumab IV and trastuzumab IV or the subcutaneous fixed-dose combination. It restricts the Per Protocol PK population to participants who adhered to the prespecified pharmacokinetic assessment schedule. Missing pre-dose samples and several protocol deviations are listed as reasons for exclusion. Consequently, the primary result describes this defined analysis population, not necessarily every enrolled participant.

The choice of a trough measurement does not by itself establish a clinically meaningful threshold. The registry record does not report such a threshold, nor does it report the non-inferiority margin. The concentration and its ratio therefore need to be read as pharmacokinetic evidence with uncertainty, not as a standalone measure of clinical benefit.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The endpoint and comparison require several statistical ideas to be kept distinct: the way concentrations are summarized, the ratio used for the primary comparison, the uncertainty interval, and the binary outcome analysis. The general explanations below describe these concepts; they do not add unreported details about the trial’s analysis plan.

Why use a geometric mean?

A geometric mean is a way of summarizing positive measurements on a multiplicative scale. It is often useful for pharmacokinetic concentrations, which can vary proportionally rather than by a constant additive amount. The reported group summaries are 69.9 and 74.6 micrograms per millilitre. The geometric coefficient of variation describes relative spread around a geometric mean; the reported values are 30.8 and 30.5. It is a dispersion summary, not a confidence interval for the group mean and not a measure of the difference between groups.

In general, a coefficient of variation expresses variability relative to the measurement scale. A geometric coefficient of variation is suited to a log-scale summary. It helps convey how dispersed the individual concentrations are, but it does not show which participants had higher or lower concentrations, and it does not replace the uncertainty interval for the between-group ratio.

How should the ratio and interval be read?

The reported geometric mean ratio is 1.07. A ratio of 1 represents equal geometric means on the ratio scale. Values above or below 1 indicate a relative difference in one direction or the other, but the ratio should be interpreted together with its confidence interval. The 90% interval, 0.99 to 1.15, expresses the uncertainty around the estimated ratio under the analysis used. As a general concept, a confidence interval is a range of estimates compatible with the data and method; it is not a guarantee that the true value lies in that particular interval.

The registry identifies the comparison as non-inferiority. For a formal non-inferiority analysis, a margin defines how much difference can be accepted for the stated question. The interval is then assessed against that margin under a specified decision rule. Because the margin and detailed method are not reported in the registry record, a reader cannot use the posted interval alone to reconstruct that formal decision.

What does the tpCR calculation add?

Total pathological complete response is recorded as a percentage of participants, with group counts and confidence intervals. A risk difference compares the proportions by subtracting one group’s proportion from the other; the recalculated estimate is -0.009, with a confidence interval from -0.146 to 0.129. The recalculated unadjusted p-value is 0.9. These are simple unadjusted calculations from posted summary statistics, not a substitute for the sponsor’s reported analysis or for any prespecified adjusted model. The sponsor reports a difference in tpCR rate of -0.88, with a 95% confidence interval from -15.21 to 13.45. The results are expressed on different numerical scales, so the estimates should not be compared without regard to their units.

A p-value is a measure of how incompatible the observed data are with a specified null hypothesis under the assumptions of the test. It is not the probability that the null hypothesis is true, and it does not measure the size or clinical importance of a difference. The recalculated p-value is unadjusted: it does not account for examining other endpoints or comparisons.

Why do populations and missingness matter?

The primary pharmacokinetic result uses the Per Protocol PK population. Exclusions include a missing pre-dose Cycle 8 sample; a sample collected at least 2 days away from the planned date on Day 21; a dose amount deviating by >20% within 3 cycles from Cycle 5; a dose delay of more than 7 days; use of a Cycle 7 subcutaneous injection site other than the thigh; switched Cycle 8 IV pre-dose and post-dose samples; and an assay error affecting the measurement. Such criteria can make the analyzed population differ from the randomized population. The registry record does not report how excluded or otherwise missing values were handled beyond these stated exclusions.

The tpCR analysis has its own group sizes and confidence intervals. This difference in analysis populations is one reason not to assume that the primary and secondary results summarize exactly the same participants. General statistical practice distinguishes analysis populations because eligibility and endpoint availability can differ; the registry record does not report further details of the tpCR analysis population or missing-outcome handling.

What do planning calculations mean?

Sample-size calculations based on the observed effect are planning illustrations, not observed power. The stated planning assumptions are a two-sided significance level of 0.05, equal allocation, and a normal approximation; the target effect is a stated fraction of the observed effect. Such calculations explore what a future study might require under those assumptions. They do not show the probability that this completed study detected an effect, and they do not establish that the original study was designed using those assumptions. The trial’s own sample-size justification is not reported in the registry record.

Finally, multiplicity is the issue of interpreting results across several endpoints or comparisons. Testing multiple outcomes can increase the chance of observing an apparently notable result by chance. The registry record does not report a multiplicity adjustment or a hierarchy for secondary testing. The secondary estimates should therefore be read as descriptive unless the sponsor’s full analysis plan establishes a different interpretation.

10. Analyses Reported by the Sponsor

The sponsor’s reported primary analysis is a geometric mean ratio of 1.07, with a 90% confidence interval from 0.99 to 1.15, and is labeled as a non-inferiority analysis. No p-value is reported for this primary comparison. The registry record does not include the non-inferiority margin or enough methodological detail to verify the formal conclusion independently.

For tpCR, the sponsor reports a difference in rate of -0.88, with a 95% confidence interval from -15.21 to 13.45. A simple unadjusted recalculation from the posted group summaries gives a risk difference of -0.009, with a confidence interval from -0.146 to 0.129 and an unadjusted p-value of 0.9. The recalculation is expressed on a proportional scale, whereas the sponsor’s result is stated as a difference in rate. The figures should be interpreted with attention to this scale distinction.

The recalculated tpCR result is not a replacement for the sponsor’s analysis. It is a check based on posted summary data and does not reproduce unreported model choices or adjustments. The registry record indicates no discrepancy between the posted result and the recalculation. Where a sponsor’s analysis and a simple recalculation differ, the sponsor’s own analysis takes precedence; that caveat does not change the fact that the recalculation is unadjusted and limited to the available summaries.

11. Multiplicity, Missing Data and Analysis Populations

The primary pharmacokinetic analysis is defined for a Per Protocol PK population. The registry describes eligibility for this population as adherence to prespecified pharmacokinetic assessment criteria and lists reasons for exclusion: a missing pre-dose Cycle 8 sample; collection at least 2 days away from the planned Day 21 date; a dose amount deviation of >20% within 3 cycles from Cycle 5; a dose delay of more than 7 days; a Cycle 7 subcutaneous injection site other than the thigh; switched Cycle 8 IV pre-dose and post-dose samples; or an assay error affecting the Ctrough measurement. The posted primary group sizes are 89.0 in each arm.

These exclusions make the primary estimate conditional on adherence and measurement availability. A per-protocol analysis may answer a focused pharmacokinetic question, but it can differ from an analysis of all randomized participants. The registry record does not report a corresponding intention-to-treat pharmacokinetic result, a detailed missing-data method, or a sensitivity analysis addressing the exclusions. It is also not reported whether participants excluded from the PK population differed systematically from those retained.

The tpCR outcome has separate group sizes of 101.0 and 99.0. The record does not explain in detail how missing pathological assessments were handled, whether all randomized participants were included in that analysis, or how the analysis population was defined. The populations and denominators should therefore be interpreted outcome by outcome rather than assumed to be identical.

Multiplicity matters because the registry lists several secondary outcomes, including response, time-to-event outcomes, survival, and adverse events. The record does not report a formal adjustment for multiple testing, a prespecified hierarchy among endpoints, or whether any interim analyses were planned. Those features are not safe to infer from the endpoint list or from the posted estimates. The sample-size justification and detailed statistical analysis plan are also not reported in the registry record. Without that information, secondary p-values or intervals, where available, should not be treated as though they necessarily control a study-wide error rate.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: alanine aminotransferase increased (4.0%), febrile neutropenia (3.0%), aspartate aminotransferase increased (3.0%), neutrophil count decreased (3.0%), white blood cell count decreased (3.0%).

The registry reports serious adverse events affecting 19 of 100 participants in the intravenous group and 18 of 100 in the subcutaneous fixed-dose combination group. Other adverse events affected 96 of 100 and 98 of 100, respectively. The record also reports 0 deaths in the intravenous group and 1 in the subcutaneous group. These are descriptive counts for the listed groups, not a randomized comparison adjusted for follow-up or other factors.

The most frequently listed serious terms include alanine aminotransferase increased at 4.0%, febrile neutropenia at 3.0%, aspartate aminotransferase increased at 3.0%, neutrophil count decreased at 3.0%, white blood cell count decreased at 3.0%, and postoperative wound infection at 2.0%. The registry identifies adverse-event severity according to NCI CTCAE v4 for the relevant outcome. A serious adverse event is not interchangeable with an event of a particular severity grade.

Counts alone do not establish whether an event was caused by a study treatment, and the record does not provide detail on event timing, duration, exposure-adjusted rates, or comparative statistical testing. The figures describe the adverse events recorded in the registry and should be interpreted within those limits.

13. What the Result Does, and Does Not, Mean

The primary result is evidence about pertuzumab concentration before the Cycle 8 dose in the specified Per Protocol PK population. The reported geometric mean ratio of 1.07 and its 90% confidence interval from 0.99 to 1.15 describe the estimated comparison and its uncertainty. They do not, by themselves, establish a clinical benefit or determine whether the concentrations are clinically adequate.

The registry labels the primary comparison non-inferiority, but the non-inferiority margin and detailed decision rule are not reported in the registry record. Without them, the formal non-inferiority conclusion cannot be verified from the posted estimate alone. The result should not be recast as proof that the regimens are identical: a ratio estimate and confidence interval allow uncertainty rather than exact sameness.

The secondary tpCR estimate is a clinical response measure, distinct from the pharmacokinetic endpoint. Its confidence intervals span differences in either direction and are broad. The simple recalculation is unadjusted and does not replace the sponsor’s analysis. Other listed secondary outcomes have no numerical results reported in the registry record, so their direction or magnitude cannot be described from this information.

Safety counts show that adverse events were recorded in both groups, including serious events, and the registry lists one death in the subcutaneous group and none in the intravenous group. Those counts do not establish causation or comparative safety, and they do not account for unreported details such as exposure time or event timing.

Overall, the posted record supports a bounded description of the measured pharmacokinetic and selected secondary data. It does not justify a broad claim about efficacy, equivalence, non-inferiority under an unknown margin, or comparative safety beyond the stated results. Interpretation should retain the distinction between the endpoint-specific populations, the reported estimates, and information that is not reported in the registry record.

14. Why This Trial Matters Statistically

This study raises a useful statistical distinction between pharmacokinetic comparability and clinical outcome comparison. The primary endpoint is a drug concentration measured at a specific point in the dosing schedule, while the listed secondary outcomes include pathological response, time-to-event outcomes, survival, and adverse events. Each requires its own estimand, analysis population, and interpretation.

The ratio scale is appropriate to the primary question as reported: it expresses the relation between geometric mean concentrations rather than an additive difference. Its confidence interval communicates uncertainty, while the non-inferiority label signals that the intended interpretation depends on a margin. Because that margin and the detailed decision rule are absent from the registry record, the numerical estimate is informative but not enough to reproduce the formal conclusion.

The case also illustrates why analysis populations matter. The primary result uses a per-protocol pharmacokinetic population defined by scheduled sample collection and treatment-adherence criteria. The tpCR result has different group sizes. These populations cannot be assumed to represent the same set of participants or answer the same question.

Finally, secondary findings need context when several outcomes are listed. Without reported multiplicity procedures or a testing hierarchy, isolated secondary results should not be treated as confirmatory evidence. The registry’s missing statistical-plan details limit how far readers can go beyond describing estimates and their precision. This is a reminder that statistical interpretation depends not only on the observed values, but also on the endpoint definition, population, uncertainty, and prespecified decision framework.

15. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The registry record leaves several trial-specific details unavailable. Although the primary analysis is labeled non-inferiority, the margin, detailed model, and decision rule are not reported. The primary result can therefore be described, but its formal non-inferiority interpretation cannot be independently reconstructed from the registry record.

The primary analysis is restricted to the Per Protocol PK population. The exclusions include missing or mistimed samples, dose deviations or delays, a specified injection-site deviation, switched samples, and assay error. The record does not report a corresponding all-randomized pharmacokinetic analysis, the number excluded for each reason, or sensitivity analyses to assess the impact of exclusions. This limits assessment of how selection into the PK population may affect the estimate.

For tpCR, the posted groups have different analysis sizes from the primary PK groups, but the record does not give detailed missing-outcome handling or define the full analysis population. The sponsor’s reported tpCR difference and the simple recalculation are expressed on different numerical scales; the recalculation is unadjusted and cannot reproduce unreported analysis choices.

The registry lists additional survival and safety outcomes, but numerical results for the remaining secondary outcomes are not reported in the registry record. Multiplicity procedures, endpoint hierarchy, interim analysis plans, and the trial’s sample-size justification are also not reported. The open-label design is stated, but the record does not describe additional safeguards for outcome assessment. These limitations do not negate the posted estimates; they define how narrowly they should be interpreted.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: A Two-Arm Study to Evaluate the Pharmacokinetics, Efficacy, and Safety of Subcutaneous Administration of the Fixed-Dose Combination of Pertuzumab and Trastuzumab in Combination With Chemotherapy in Chinese Participants With HER2-Positive Early Breast Cancer — NCT04024462.
• Registry record last updated 2026-02-20; status last verified 2026-02.
• Results first posted 2023-02-16.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

NCT04024462 is a completed phase III, randomized, multicenter, open-label, parallel study sponsored by Hoffmann-La Roche. It compares subcutaneous pertuzumab and trastuzumab fixed-dose combination plus chemotherapy with intravenous pertuzumab and trastuzumab plus chemotherapy in Chinese participants with HER2-positive early breast cancer. The registry lists enrollment of 200, a start date of 2020-02-05, and primary completion on 2021-12-13.

The primary endpoint is pertuzumab trough concentration before Cycle 8 in the Per Protocol PK population. The reported geometric mean ratio is 1.07, with a 90% confidence interval from 0.99 to 1.15. The registry labels the comparison non-inferiority, but does not report the margin or detailed decision rule. The tpCR outcome is also reported, along with adverse-event counts. Numerical results for the remaining listed secondary outcomes are not reported in the registry record.