Intrathecal Trastuzumab for Leptomeningeal Metastases in HER2+ Breast Cancer: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Intrathecal Trastuzumab for Leptomeningeal Metastases in HER2+ Breast Cancer (NCT01325207), a registered phase 1, phase 2 study. The primary outcome is Number of Dose Limiting Toxicities (DLT) of IT Trastuzumab in Sequential Cohorts of Escalating Doses for Patients With Leptomeningeal Metastases in HER2+ Breast Cancer..

2. Clinical Question

The central statistical question is how dose-limiting toxicity was assessed as the dose increased across sequential cohorts. This differs from asking whether trastuzumab is better than an alternative: the registry describes no randomized comparator. The observations can describe what was recorded in the treated cohorts, but they cannot by themselves isolate the effect of treatment from the course of the disease or other influences.

The clinical setting is specified as HER2-positive breast cancer with leptomeningeal metastases. The registry summary describes tumor cells in spinal fluid, and the study administered the drug directly into the spinal fluid. Further details about eligibility, prior treatments, disease severity or other participant characteristics are not reported in the registry record. Those details would help readers assess how closely the enrolled population represents other patients in this clinical setting.

It is also important to keep the dose-escalation question separate from the Phase II question. The listed primary endpoint concerns dose-limiting toxicities during the first 4 weeks. While the study’s description says it would also determine how effective the treatment is, the registry record does not report an efficacy endpoint result. Safety counts and serious adverse event listings do not substitute for an efficacy analysis.

3. Trial Design

The registry classifies the study as Phase I/II and describes it as a sequential dose-escalation trial. It lists an enrollment of 34, a completed status, and no masking. The study start is recorded as 2011-08-01 and primary completion as 2016-06-20. These record details give context for the trial but do not establish how participants were selected or how all analyses were conducted.

The planned dose sequence was 10 mg intrathecally in Cohort 1, 20 mg in Cohort 2, 40 mg in Cohort 3, 60 mg in Cohort 4 and 80 mg in Cohort 5. The listed administration schedule was twice per week. The registry describes standard 3+3 escalation for Cohorts 1 and 2, an accelerated phase for Cohorts 3 and 4, and a return to a standard 3+3 approach for Cohort 5. It separately lists a Phase II cohort at 80 mg intrathecally twice per week.

In the planned accelerated phase, one patient would enter each of Cohorts 3 and 4. If toxicity occurred, the cohort would expand to 6 patients, with the design allowing 1/6 patients to have a dose-limiting toxicity before dose escalation. Cohort 5 was planned to enroll 6 patients regardless of toxicity in its first patient. The description says Cohort 4 would be reopened to enroll a total of 6 patients if 2 or more dose-limiting toxicities were observed in Cohort 5. It also states that the dose declared the maximum tolerated dose should have 6 patients total and that 1/6 dose-limiting toxicities in Cohort 5 would be considered the maximum tolerated dose.

These are protocol descriptions, not evidence that every planned step occurred exactly as described. The registry record does not report a complete account of dose-escalation decisions, deviations from the planned cohort sequence, or a final maximum tolerated dose. Allocation details beyond the sequential cohort design are not reported. Since there was no randomized control comparison described, differences across cohorts should not be interpreted as controlled dose effects.

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.

Completed 4 Weeks/1 Cycle of Treatment

Reasons for not completing this period:

Completed 8 Weeks/2 Cycles of Treatment

Reasons for not completing this period:

Started 9th Week/Cycle 3 of Treatment

Reasons for not completing this period:

Follow-up Every 3 Months Until Death

Reasons for not completing this period:

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.

Only the first 6 of 7 groups are shown.

6. Primary Endpoint

The registry lists the primary outcome as Number of Dose Limiting Toxicities (DLT) of IT Trastuzumab in Sequential Cohorts of Escalating Doses for Patients With Leptomeningeal Metastases in HER2+ Breast Cancer., measured over From treatment initiation through the first 4 weeks of treatment..

The primary endpoint is the number of dose-limiting toxicities of intrathecal trastuzumab in sequential cohorts receiving escalating doses. The stated observation period runs from treatment initiation through the first 4 weeks of treatment. A dose-limiting toxicity is used in dose-escalation studies to identify clinically important toxicity that may constrain further increases in dose. The registry record does not give a more detailed definition of which events qualified as a dose-limiting toxicity, how severity was graded, or how attribution to treatment was determined.

Counts of dose-limiting toxicities are appropriate to the stated escalation question because the design uses toxicity observations to guide whether later cohorts receive higher doses or whether a cohort expands. The count is not itself a measure of comparative efficacy, and it does not describe the full range of possible harms over longer follow-up. Its interpretation depends on the event definition, observation window and number of patients observed at each dose.

The planned cohort rules specify how toxicity could lead to expansion or affect escalation. For example, the description refers to expansion after a toxicity in the accelerated phase and gives a specific rule for Cohort 5. These rules clarify the intended decision process, but the registry record does not report the observed dose-limiting toxicity counts or the final dose decision. Consequently, the primary endpoint’s result cannot be inferred from the serious adverse event listings: those are separately reported safety data, and their relationship to the dose-limiting toxicity definition is not stated.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The following statistical explanations are general; the registry record does not report a complete statistical analysis plan for this study. General statistical concepts can help explain the design, but they should not be mistaken for methods confirmed to have been used in the trial.

What does sequential dose escalation mean?

In a sequential escalation design, cohorts receive doses in an ordered sequence, and observations in one cohort inform decisions about the next cohort. This differs from random allocation among dose groups. The trial description specifies an escalation sequence from 10 mg through 80 mg and gives rules for expansion in certain circumstances. As a result, later dose groups are not simply parallel groups selected at the same time under randomization. Time, cohort composition and decisions made during escalation can all affect which observations are available at each dose.

The record describes standard 3+3 rules for Cohorts 1 and 2, an accelerated phase for Cohorts 3 and 4, and a standard 3+3 approach for Cohort 5. In general, a 3+3 design bases escalation decisions on observed toxicity in small cohorts. Such a design is principally a dose-finding approach, rather than a design intended to estimate a precise treatment effect or compare efficacy against a control. The exact operating characteristics of this trial’s rules are not reported in the registry record.

What does a dose-limiting toxicity count measure?

A count records how many qualifying events were observed within a specified group and observation period. Here, the stated period is from treatment initiation through the first 4 weeks. The count’s meaning depends on the definition of a qualifying event, how events are graded and whether attribution to treatment is required. Those details are not reported in the registry record. Without them, readers cannot determine whether different event types were treated alike or whether the endpoint captured all clinically important toxicity.

General statistical interpretation also distinguishes the count from a rate or risk. A count alone does not account for how many people were observed or how long each person was followed. The design description supplies planned cohort rules, but the primary endpoint result and the corresponding observed denominators are not reported in the registry record. Therefore, a dose-specific risk of dose-limiting toxicity cannot be reconstructed from the endpoint description alone.

Why is a control group important for comparisons?

General causal inference asks how outcomes under one treatment compare with outcomes that would have occurred under an alternative. Random allocation can make groups more comparable on average, which strengthens interpretation of treatment contrasts. The registry describes a sequential dose-escalation study and does not describe a randomized control group. It also notes that the arms are not a like-for-like control comparison. Comparisons among the listed dose cohorts should thus be treated as descriptive, not as randomized estimates of the effect of changing dose.

Sequential cohorts can differ for reasons beyond dose. Their entry occurs at different steps in the escalation process, and decisions about expanding a cohort depend on observed toxicity. The registry record does not report participant characteristics by cohort or adjustments for potential differences. A simple difference in observed outcomes between doses, even if such a comparison were available, would not by itself separate a dose effect from cohort differences or other influences.

What does precision mean?

General statistical explanation: a confidence interval expresses the range of estimates reasonably compatible with the data under a specified statistical model. Wider intervals indicate greater uncertainty, while narrower intervals indicate more precision. The registry record does not report confidence intervals for the primary endpoint or for the listed safety entries. No claim about the precision of the dose-limiting toxicity result can therefore be made from the record.

Small cohort observations are especially limited in how precisely they can characterize uncommon outcomes. A cohort with few observations may provide little information about the range of toxicity that could occur in a broader population. This is a general limitation of sparse data, not a calculation of uncertainty for this trial. The registry’s listed cohort sizes vary, and the record does not supply an uncertainty analysis for those groups.

How should the adverse event percentages be understood?

General statistical explanation: a percentage is interpretable as a frequency only when its denominator and counting method are clear. The record lists serious adverse event terms with percentages, but does not report the denominator or method for those percentages. They should not be read as directly comparable risks across dose cohorts without that information. Likewise, a term appearing in a serious-event listing does not establish a causal link to study treatment.

Over-dispersion is a general issue for count data when variability exceeds what a simple count model expects. It can arise when observations are more heterogeneous than the model assumes. Whether over-dispersion is relevant depends on the data and the analysis; the registry record does not report a count model, a dispersion estimate or a model-based analysis for this endpoint. No conclusion about over-dispersion in this trial is warranted.

What analysis details are missing?

The record does not report whether primary endpoint analyses were descriptive or inferential, whether any model was used, how missing outcome data were handled, or which analysis population was used. It does not report an analysis of efficacy outcomes or any confidence intervals, hypothesis tests or adjusted estimates for the primary endpoint. The registry record also does not report sample-size justification or interim analyses. These omissions prevent a full assessment of the planned and performed statistical methods.

Planning illustrations based on an observed effect are not observed power. In general, such illustrations ask how many participants might be needed under stated assumptions to detect an effect of a chosen size. They do not show the probability that this completed trial detected a true effect, and they do not replace a trial’s own design justification. The record’s planning-assumption description refers to two-sided significance level 0.05, equal allocation, a normal approximation and fractions of an observed effect, but the current trial is sequential and not described as an equal-allocation randomized comparison. Those assumptions do not establish the trial’s original sample-size rationale.

Accordingly, the methods that can be described with confidence are the registry’s stated sequential design, planned cohort sequence and primary observation window. Further statistical details, including the actual endpoint analysis, are not reported in the registry record. General statistical principles help explain what those design features imply, but they cannot supply missing trial-specific results or methods.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 7 outcome measures and 1 analysis, but the details of that analysis are not reported in the registry record. The primary endpoint is the number of dose-limiting toxicities during the first 4 weeks. The record does not explain how the other listed outcomes were ordered, whether any were designated as secondary or exploratory for analysis, or which results were intended to support formal claims.

Multiplicity arises when several outcomes, time points, groups or statistical tests are examined. In general, examining many tests can increase the chance of at least one apparently notable result by chance. Statistical plans may address this with a prespecified hierarchy or adjustment, but such a plan is not reported in the registry record. It is not possible to determine whether multiplicity was considered or how it was handled.

Missing-data methods and analysis populations are also not reported in the registry record. The registry entries do not state how participants with incomplete follow-up, unavailable outcome assessments or early discontinuation were handled. Nor do they define whether the analysis included all enrolled participants, only those who received treatment, or another population. These are important details because the endpoint is defined over a treatment period and the safety entries have cohort-specific denominators.

The record also does not report the extent of missing data, reasons for missingness, sensitivity analyses, or whether outcome assessment was blinded. No assumptions about missing outcomes or analysis membership should therefore be made. The reported cohort entries can be described as registry counts, but they do not establish how the trial handled every participant in its analyses.

11. 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 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: pain in back and extremities (100.0%), enterocolitis infectious (100.0%), muscle weakness (100.0%), worsening neurological symptoms (66.7%), clinical deterioration (33.3%).

The registry presents adverse-event information by cohort, with fields for participants at risk and affected for serious and other events, and a separate deaths field. These entries should be read as recorded safety counts, not as evidence that trastuzumab caused an event. The record does not report event attribution, follow-up duration for these fields, or the definitions used to classify serious and other events.

• Cohort 1, 10 mg intrathecally twice per week: 3 at risk and 1 affected for serious events; 3 at risk and 3 affected for other events; deaths: 3.

• Cohort 2, 20 mg intrathecally twice per week: 3 at risk and 2 affected for serious events; 3 at risk and 3 affected for other events; deaths: 3.

• Cohort 3, 40 mg intrathecally twice per week: 1 at risk and 1 affected for serious events; 1 at risk and 1 affected for other events; deaths: 1.

• Cohort 4, 60 mg intrathecally twice per week: 1 at risk and 1 affected for serious events; 1 at risk and 1 affected for other events; deaths: 1.

• Cohort 5, 80 mg intrathecally twice per week: 7 at risk and 3 affected for serious events; 7 at risk and 7 affected for other events; deaths: 5.

• The Phase II cohort at 80 mg intrathecally twice per week: 19 at risk and 13 affected for serious events; 19 at risk and 19 affected for other events; deaths: 17.

The registry also lists serious-event terms with percentages, but does not report their denominator or the calculation method. Neither those percentages nor the death counts establish causality. The record does not report whether these events met the primary endpoint’s dose-limiting toxicity definition.

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

The trial’s stated purpose was to assess safety during intrathecal dose escalation and then investigate treatment effects in HER2-positive breast cancer with leptomeningeal metastases. The registry provides a planned escalation sequence and selected cohort-level safety entries. These details describe the study question and the recorded safety information, but they are not a substitute for the primary endpoint result.

The primary endpoint result—the number of dose-limiting toxicities through the first 4 weeks—is not reported in the registry record. The record also does not state the final maximum tolerated dose. The available serious adverse event counts do not answer either question because the registry does not specify whether those events met the dose-limiting toxicity definition or how they were attributed. A conclusion about dose-limiting toxicity cannot be drawn from the separate safety fields alone.

The registry description says the trial would determine how effective the treatment is, but an efficacy result is not reported in the record. The adverse event entries cannot show whether disease outcomes improved, and they do not provide a comparison with another treatment or a control group. The absence of a randomized comparator also means the sequential dose cohorts cannot be interpreted as a controlled test of dose-related benefit.

General statistical interpretation distinguishes an observed result from its uncertainty and from a causal claim. A result may be uncertain when few observations are available, and a comparison may be confounded when groups are not randomized. In this record, endpoint estimates and confidence intervals are not reported, so the precision of the main toxicity result cannot be assessed. The listed adverse-event percentages also lack a reported denominator.

Thus the registry supports a description of a completed Phase I/II sequential study, its intended population, intervention, dose-escalation rules and reported adverse-event entries. It does not establish the size or precision of a treatment effect, whether treatment caused the listed events or deaths, or how the treatment compares with an alternative. The interpretation should remain limited to the information actually recorded.

13. Why This Trial Matters Statistically

This trial raises a distinctive statistical problem: the question is not initially a comparison between randomized treatment groups, but how to learn about toxicity while doses increase in sequence. Dose-escalation designs use observations from earlier cohorts to guide later decisions. That makes the decision rules and the definition of dose-limiting toxicity central to interpreting the study.

The registry gives a concrete planned sequence, from 10 mg to 80 mg intrathecally, and describes both standard 3+3 and accelerated steps. It also explains when certain cohorts would expand. Such rules matter because a count of toxicities is meaningful only in relation to the dose, the cohort size, the observation window and the criteria used to classify an event. The record identifies a first-4-weeks window but does not report a full toxicity definition or the observed primary endpoint result.

The design also illustrates the limits of comparing sequential cohorts. Later cohorts are not described as randomized alongside earlier ones, and the registry does not report adjustment for differences between groups. Descriptive cohort differences therefore cannot be treated as an isolated dose effect. This is an important distinction for clinical researchers reading early-phase studies: a dose-finding design has a different purpose from a controlled efficacy trial.

Finally, the registry’s serious-event counts and terms show why definitions, denominators and attribution details matter. The figures can describe what was recorded, but they cannot alone establish treatment causality or answer the primary dose-escalation question. Clear reporting of endpoint definitions, analysis populations, missing data, uncertainty and decision outcomes would be needed for a fuller statistical assessment. The record leaves those elements unreported, so its statistical contribution is best understood as documentation of a planned design and selected safety observations rather than a complete estimate of efficacy or risk.

14. 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. It does not report the observed primary dose-limiting toxicity counts, the criteria used to define a dose-limiting toxicity, or the final maximum tolerated dose. Although the escalation rules are described, the record does not provide a full account of which decisions were made at each step or whether the planned rules were followed without modification.

The study is described as sequential and unmasked, and a randomized control group is not reported. Allocation is not stated. This limits interpretation of differences across dose cohorts, which are not described as like-for-like groups. The registry does not provide cohort-level baseline characteristics or statistical adjustment for potential differences among participants.

For the adverse-event data, the record does not report attribution to treatment, duration of follow-up, event definitions, or the relationship between serious adverse events and dose-limiting toxicities. It also does not report the denominator or calculation method for the listed serious-event percentages. Death counts are recorded, but their timing, circumstances and relationship to treatment are not reported in the registry record.

The registry does not provide an efficacy result despite describing efficacy as a study aim. It also does not report confidence intervals or other measures of uncertainty for the primary endpoint, missing-data methods, analysis populations, sample-size justification, interim analyses or a complete multiplicity plan. These omissions restrict assessment of both the statistical reliability and the clinical interpretation of the study’s results.

Finally, the registry lists planned doses and a Phase II cohort, but does not supply enough information to connect every cohort entry to the full analysis set or to determine how incomplete observations were handled. The listed enrollment figure and the cohort safety entries should therefore be kept distinct rather than combined into reconstructed totals.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Intrathecal Trastuzumab for Leptomeningeal Metastases in HER2+ Breast Cancer — NCT01325207.
• Registry record last updated 2019-09-26; status last verified 2019-09.
• Results first posted 2019-05-28.
• 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.

18. Record Summary

The registry describes NCT01325207 as a completed, unmasked Phase I/II sequential dose-escalation trial sponsored by Northwestern University. It lists an enrollment of 34 and concerns intrathecal trastuzumab for leptomeningeal metastases in HER2-positive breast cancer. The recorded study start is 2011-08-01, and primary completion is 2016-06-20.

The planned dose sequence was 10 mg, 20 mg, 40 mg, 60 mg and 80 mg intrathecally, twice per week, followed by a listed Phase II cohort at 80 mg twice per week. The primary endpoint was the number of dose-limiting toxicities from treatment initiation through the first 4 weeks. Cohort escalation and expansion rules are described, but the primary endpoint result and final maximum tolerated dose are not reported in the registry record.

The record includes cohort-level serious and other adverse-event fields and deaths, but does not report causality, follow-up details or the denominator method for serious-event percentages. An efficacy result, confidence intervals, missing-data methods, analysis populations and a complete statistical analysis plan are not reported. The available information therefore supports a limited description of the design and recorded safety entries, not a comparative or causal estimate.