This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Eribulin Mesylate in Treating Patients With Previously Treated Metastatic Breast Cancer (NCT01908101), a na phase 2 study. The primary outcome is PFS.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01908101 |
| Phase | Phase 2 |
| Condition | Recurrent Breast Carcinoma, Stage IV Breast Cancer |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 86 |
| Arms in the primary outcome | n/a |
| Lead sponsor | University of Washington |
| Results posted | Yes |
2. Clinical Question
Population
Patients with metastatic breast cancer whose disease had progressed following at least one prior chemotherapy regimen in the metastatic setting. The registry record also identifies recurrent breast carcinoma and stage IV breast cancer as conditions.
Intervention
Eribulin mesylate, administered intravenously over 2-5 minutes on days 1, 8, and 15. Courses were scheduled to repeat every 4 weeks while there was no disease progression or unacceptable toxicity. Laboratory biomarker analysis was also listed as an intervention.
Comparator
There was no concurrent comparator arm. The registry record describes a single-group study with allocation listed as NA and masking listed as none. Consequently, the study does not directly compare eribulin with another treatment or with a control group.
Primary question
The primary endpoint was median progression-free survival (PFS), measured from study enrollment until disease progression or death, assessed up to 1 year. The registry record does not report the numerical median or its confidence interval.
The clinical question is therefore descriptive: what PFS was observed among patients with previously treated metastatic breast cancer receiving the study regimen? It is not a randomized comparative question. Without a concurrent control group, the registry record cannot estimate a treatment contrast against another therapy within this trial.
The eligibility description focuses on metastatic disease that had progressed after prior chemotherapy in the metastatic setting. The number of prior metastatic treatment regimens was also relevant to the planned endpoint description: Kaplan-Meier curves were to describe PFS overall and stratified by that number. The registry record does not report the resulting subgroup estimates or the distribution of participants across those strata.
The study enrolled 86 participants. That enrollment figure gives context for the scale of the study, but it does not by itself establish how many participants contributed to the endpoint analysis. The analysis population and endpoint-specific participant counts are not reported in the registry record.
3. Trial Design
This was a phase II trial sponsored by the University of Washington. The registry record describes the design as single-group, with allocation listed as NA and masking as none. The study status is completed. Its recorded start date was 2014-01-08, and its primary completion date was 2019-05-04. Enrollment was 86.
Participants received eribulin mesylate intravenously over 2-5 minutes on days 1, 8, and 15. Courses were scheduled every 4 weeks, continuing in the absence of disease progression or unacceptable toxicity. Laboratory biomarker analysis was also listed, but its procedures and role in the endpoint analysis are not reported in the registry record.
A single-group design describes outcomes among participants who received the study regimen. It does not create a randomized, like-for-like control comparison. Differences between this group and patients treated elsewhere or in another study could reflect differences in patient characteristics, care, follow-up, or other factors. This design feature limits causal interpretation of any observed outcome.
The primary outcome was PFS, with a timeframe from enrollment until the earliest date of disease progression or death, assessed up to 1 year. The planned description specified Kaplan-Meier curves, overall and stratified by number of prior metastatic treatment regimens, and a 95% confidence interval for median PFS using the Brookmeyer and Crowley method.
The registry record lists one outcome measure and one analysis. It does not report the numerical PFS estimate, its confidence interval, subgroup estimates, or the number of participants included in the endpoint analysis. Details such as the full protocol, sample-size justification, and prespecified analysis populations 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: 86 patients signed the study informed consent, but only 68 patients started the Eribulin treatment. Out of those 68 patients only 59 of them were evaluable.
Overall Study
| Stage | Treatment (Eribulin Mesylate) |
|---|---|
| STARTED | 68 |
| COMPLETED | 59 |
| NOT COMPLETED | 9 |
Reasons for not completing this period:
| Reason | Treatment (Eribulin Mesylate) |
|---|---|
| Physician Decision | 1 |
| Withdrawal by Subject | 1 |
| Incorrect Diagnosis | 2 |
| Incorrect Starting Dose | 1 |
| Did not complete the first cycle | 4 |
Analysis population for the primary outcome, as defined in the registry: Patients with metastatic breast cancer (MBC) whose disease has progressed following at least one prior regimen of chemotherapy in the setting of metastatic breast cancer
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.
| Characteristic | Unit | Treatment (Eribulin Mesylate) |
|---|---|---|
| Participants analysed | 59 | |
| Age, Categorical: <=18 years | Participants | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 45 |
| Age, Categorical: >=65 years | Participants | 14 |
| Age, Continuous | years | 52 (18 to 86) |
| Sex: Female, Male: Female | Participants | 59 |
| Sex: Female, Male: Male | Participants | 0 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 6 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 52 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 1 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 2 |
| Race (NIH/OMB): Asian | Participants | 4 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 |
| Race (NIH/OMB): Black or African American | Participants | 4 |
| Race (NIH/OMB): White | Participants | 49 |
| Race (NIH/OMB): More than one race | Participants | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 |
| Region of Enrollment: United States | Participants | 59 |
6. Primary Endpoint
The registry lists the primary outcome as PFS, measured over From study enrollment until the earliest date of disease progression or death, assessed up to 1 year.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | 95% Confidence Interval |
| Unit | months |
| Endpoint classification | Time-to-Event Analysis |
Progression-free survival measures the time from study enrollment until disease progression or death, whichever occurs first. The registry record specifies that the endpoint was assessed up to 1 year. Its reported summary measure was the median: the time by which half of the analyzed participants would be expected to have experienced the defined event, based on the survival analysis.
PFS is used in clinical trials because it combines two clinically important events into a time-to-event outcome and accounts for the timing of events, rather than only counting how many participants experienced an event by a single date. In general, time-to-event methods can also accommodate participants whose event has not been observed by the end of their available follow-up, provided that the analysis handles censoring appropriately. The registry record does not describe how censoring or incomplete follow-up was handled in the posted analysis.
The planned approach was to use Kaplan-Meier survival curves to describe PFS overall and by number of prior metastatic treatment regimens. The confidence interval for the median was to be calculated using the Brookmeyer and Crowley method. A confidence interval expresses statistical uncertainty around an estimate; it does not guarantee that the true value falls within its limits.
The numerical median PFS and its 95% confidence interval are not reported in the registry record. Thus, the endpoint definition and planned statistical approach can be described, but the magnitude and precision of the observed PFS cannot be assessed from the record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies PFS as the primary endpoint and describes how it was intended to be analyzed. It does not give the numerical median PFS or its 95% confidence interval. As a result, the posted information does not establish the observed duration of PFS or how precisely that duration was estimated. A numerical interpretation of the primary outcome is not possible from the record.
The trial’s single-group structure is central to interpretation. Outcomes among participants receiving eribulin can be described, but the design does not provide a concurrent group receiving a different treatment or control condition. Therefore, even if an outcome estimate were available, it would not by itself show what would have happened to comparable participants under another treatment. The record does not support a randomized treatment-effect comparison.
The protocol description says PFS was to be summarized overall and stratified by number of prior metastatic treatment regimens. No numerical estimates for these strata, nor information about the number of participants within them, are reported in the registry record. It is therefore not possible to assess whether PFS differed across prior-treatment groups or how uncertain any subgroup estimates might be.
The registry record lists enrollment of 86 participants. Enrollment is not necessarily the same as the number included in an endpoint analysis. The analysis population, the number of progression events, the number of deaths contributing to PFS, and the amount of follow-up are not reported in the registry record. Without these details and the estimate itself, the precision and completeness of the endpoint evidence cannot be evaluated.
The record also does not report a hazard ratio or a numerical comparison with another group. A hazard ratio would describe a relative event rate over follow-up under specified assumptions; it is not the same quantity as median PFS. No such value should be inferred from the endpoint description alone.
Accordingly, the sound statistical reading is limited: this was a phase II, single-group study with PFS designated as its primary endpoint, but the registry record does not report the primary numerical result. The design and endpoint definition clarify what the study sought to describe, while the missing estimate prevents conclusions about the observed PFS magnitude or its precision.
9. Statistical Methods Explained
What does a single-group design allow?
This trial is described as a single-group study, with allocation listed as NA and masking listed as none. In general, a single-group study can describe outcomes among participants receiving the study regimen. It does not provide an internal concurrent control group against which to estimate a treatment contrast. Differences from results in other groups or studies would not necessarily reflect treatment, because the groups may differ in eligibility, prior care, follow-up, or other characteristics.
The design therefore matters even before considering any numerical result. A PFS estimate from participants in this study would characterize their observed experience under the study conditions. It would not, on its own, estimate how much PFS changed because of eribulin compared with an alternative. The registry record does not report a comparative effect estimate.
How is a time-to-event endpoint summarized?
Progression-free survival is defined as time from study enrollment to the earliest date of disease progression or death. For each participant, the endpoint concerns the time until the first of those events. The registry record states that assessment was planned up to 1 year. The primary summary measure was the median PFS.
In general, the median of a time-to-event distribution is the time at which the estimated probability of remaining free of the defined event reaches one half. It summarizes the middle of the distribution, not every participant’s experience. A median does not describe the full shape of the survival curve, and different curves can have the same median while differing at other follow-up times.
Kaplan-Meier methods estimate the probability of remaining event-free over time while accounting for participants whose event time is not observed during their available follow-up. Those participants are generally censored at the last time they are known to be event-free. This general explanation does not establish how censoring was implemented in this study; the detailed censoring procedures are not reported in the registry record.
What does the confidence interval contribute?
The planned 95% confidence interval for median PFS was to be calculated using the Brookmeyer and Crowley method. In general, a confidence interval communicates uncertainty in an estimated quantity. A wider interval indicates less precision than a narrower interval, all else equal. It is not a range guaranteed to contain the true value, nor does it show the distribution of individual participant outcomes.
The actual median and confidence limits are not reported in the registry record. Consequently, there is no numerical estimate or interval to interpret. The planned method can be identified, but its result cannot be evaluated for precision from the available record.
Why might stratification be used?
The registry description states that Kaplan-Meier curves were to be presented overall and stratified by number of prior metastatic treatment regimens. Stratification can describe whether outcome patterns vary across groups defined by a characteristic of participants. It can also help readers see whether an overall summary masks different patterns in subgroups.
Stratified descriptions do not automatically establish that a subgroup characteristic modifies a treatment effect. In a single-group study, subgroup estimates remain descriptions of outcomes within the treated group. The record does not report subgroup results, subgroup sizes, or a formal test comparing strata.
What can be said about planning calculations?
General sample-size calculations are planning illustrations: they describe the amount of information that might be needed under specified assumptions. They are not observed power, and they do not substitute for the trial’s actual outcome estimates. The registry record does not report a sample-size justification for the study’s original design.
The planning description specifies a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect expressed as a stated fraction of the observed effect. For time-to-event outcomes, it specifies a Schoenfeld event-count approach and describes the resulting quantity as total events. These assumptions do not change the fact that the trial itself is single-group; the registry record does not describe a two-arm randomized comparison in this study.
The planning description is not evidence that the trial achieved a particular power or that its endpoint result was statistically significant. No numerical result, hazard ratio, or event count for the primary endpoint is reported in the registry record. Accordingly, no conclusion about statistical significance or achieved precision follows from the planning assumptions.
10. Multiplicity, Missing Data and Analysis Populations
The registry record identifies PFS as the primary outcome and lists one outcome measure and one analysis. It describes planned overall and stratified Kaplan-Meier summaries. It does not report whether there were additional prespecified analyses beyond those descriptions, how any multiple testing was handled, or whether an adjustment for multiplicity was planned. These details are not reported in the registry record.
Multiplicity is a general concern when many outcomes, time points, subgroups, or statistical tests are examined. As the number of analyses increases, the chance of at least one apparently unusual finding can increase. This does not mean that multiplicity necessarily affected this study; the record does not provide enough information to assess the analysis scope or any adjustment strategy.
The record does not report missing-data procedures, loss to follow-up, censoring rules, or the completeness of disease assessments. For a time-to-event endpoint, follow-up ending before progression or death can lead to censoring. In general, interpretation of a Kaplan-Meier estimate depends on appropriate handling of censoring and the assumptions underlying it. The record does not provide enough detail to evaluate those assumptions for this analysis.
The registry record lists enrollment of 86 participants but does not report the number included in the PFS analysis or the analysis population definition. It also does not state how participants who did not receive treatment, had incomplete assessments, or lacked follow-up were handled. No conclusion about intention-to-treat, per-protocol, or another analysis population can be drawn.
These omissions limit assessment of the endpoint’s completeness, reproducibility, and robustness. They do not establish that the analyses were inadequate; rather, the relevant procedures and numerical details are not reported in the registry record.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Treatment (Eribulin Mesylate) | 2 | 59 | 3.4% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Treatment (Eribulin Mesylate) | 44 of 59 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Treatment (Eribulin Mesylate) | 23 of 59 |
Most frequent serious adverse event terms
| Event term | Organ system | Treatment (Eribulin Mesylate) |
|---|---|---|
| Sepsis | Blood and lymphatic system disorders | 1 of 59 |
| myocardial infarction | Cardiac disorders | 1 of 59 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Treatment (Eribulin Mesylate) |
|---|---|---|
| Neutropenia | Nervous system disorders | 13 of 59 |
| White blood cell decreased | Blood and lymphatic system disorders | 4 of 59 |
| Fatigue | General disorders | 3 of 59 |
| Lymphocyte count decreased | Blood and lymphatic system disorders | 3 of 59 |
| Peripheral neuropathy | Nervous system disorders | 3 of 59 |
Serious events with the highest arm-level rate: sepsis (1.7%), myocardial infarction (1.7%).
The registry record lists 59 participants at risk for serious adverse events and 2 affected by serious adverse events. For other adverse events, it lists 59 participants at risk and 23 affected. It also lists 44 deaths. These counts describe the posted safety figures; the record does not clarify the relationship among the categories or provide enough detail to determine whether participants could appear in more than one category.
The listed serious adverse event terms are sepsis and myocardial infarction, each reported as 1.7%. These percentages are presented as registry figures. The record does not provide further detail about event timing, severity grading, duration, recurrence, or whether the events were judged related to treatment.
Counts of participants affected are not the same as counts of individual events: one participant can experience more than one event, and an event category may include different clinical occurrences. The registry record does not specify the counting conventions or definitions behind the listed safety totals. The 44 deaths should not be interpreted as deaths caused by treatment; the record does not report that attribution. These figures alone also do not establish a comparative safety difference because there is no concurrent control group.
12. What the Result Does, and Does Not, Mean
The study record describes a phase II investigation of eribulin mesylate in previously treated metastatic breast cancer. It identifies a single-group design and names median PFS as the primary endpoint. The regimen involved intravenous eribulin on days 1, 8, and 15, with courses repeating every 4 weeks in the absence of progression or unacceptable toxicity. These registry entries describe the study question and conduct, not a conclusion about treatment effect.
The registry record does not report the numerical median PFS or its 95% confidence interval. Therefore, it is not possible to state the observed PFS duration or how precisely it was estimated. No hazard ratio or comparative PFS result is reported in the registry record. The endpoint’s planned statistical method cannot replace the missing numerical result.
Even if the PFS estimate were available, a single-group study would provide an outcome description rather than a randomized comparison. It could not, by itself, establish what would have occurred in a comparable group receiving another treatment. The record also does not report subgroup estimates by number of prior metastatic treatment regimens, although such stratification was described in the planned analysis.
The safety figures list 2 participants with serious adverse events among 59 at risk, 23 with other adverse events among 59 at risk, and 44 deaths. Those figures do not establish that treatment caused the events or deaths. Event attribution, definitions, follow-up context, and comparative safety data are not reported in the registry record.
The defensible conclusion is therefore about the design and available reporting: the study was completed and enrolled 86 participants, but the primary numerical outcome and several details needed to assess it are not reported in the registry record. The absence of those details should not be converted into a positive or negative finding about the regimen.
13. Why This Trial Matters Statistically
This trial illustrates why design and reporting need to be read together. A phase II label and a stated primary endpoint identify the study’s purpose, but they do not supply the result. Here, the registry record defines PFS, specifies a planned Kaplan-Meier description, and names a method for the confidence interval around median PFS. It does not report the numerical estimate or interval. Readers can understand what was intended to be measured without being able to assess the observed magnitude or precision.
The single-group design is another important statistical feature. It supports describing outcomes in the enrolled group, but it cannot provide a randomized within-trial contrast with another treatment. This distinction prevents an outcome description from being misread as evidence of comparative benefit or harm. The same caution applies to the safety counts: without a concurrent comparator, they describe recorded events in the study group rather than a comparative safety effect.
The planned stratification by number of prior metastatic treatment regimens also highlights the value of reporting subgroup estimates and their uncertainty. The registry record gives the intended descriptive approach but not the subgroup results or sizes. Without those details, readers cannot judge how the overall outcome relates to prior-treatment history.
Finally, enrollment, endpoint analysis population, and safety denominators are distinct quantities. The record lists enrollment of 86 and safety risk sets of 59, but does not explain the relationship between these figures or report the PFS analysis population. Making those distinctions explicit is essential to transparent interpretation of clinical trial evidence.
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 principal limitation for statistical interpretation is that the registry record does not report the numerical PFS result or its 95% confidence interval. The endpoint can be described, but its magnitude and precision cannot be assessed. No numerical hazard ratio or comparison with a control group is reported.
The single-group design does not include a concurrent comparator. As a result, the trial cannot estimate a randomized contrast between eribulin and another treatment. This is a design limitation for causal and comparative interpretation, independent of the endpoint method.
The registry record lists enrollment of 86 participants, but does not report the number contributing to the PFS analysis, the endpoint event count, follow-up completeness, or censoring details. It also does not report the subgroup sizes or numerical estimates for the planned stratification by number of prior metastatic treatment regimens. These omissions restrict evaluation of the analysis population, precision, and subgroup interpretation.
Details of missing-data handling, multiplicity, and any additional analysis procedures are not reported in the registry record. The record also does not provide a sample-size justification for the study’s original design. These unreported details should not be assumed to indicate a particular analysis choice or flaw.
For safety, the record gives participant counts and two serious adverse event terms, but does not report attribution, event-level detail, or the relationship among the safety categories and deaths. The safety figures therefore cannot establish causation or comparative risk. These limitations concern the information available in the registry record and do not determine what may have been documented elsewhere.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Eribulin Mesylate in Treating Patients With Previously Treated Metastatic Breast Cancer — NCT01908101.
- Registry record last updated 2020-07-23; status last verified 2020-05.
- Results first posted 2020-07-23.
- 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.
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18. Record Summary
This completed phase II study, sponsored by the University of Washington, enrolled 86 participants with previously treated metastatic breast cancer. It used a single-group design, with allocation listed as NA and masking as none. Eribulin mesylate was administered intravenously on days 1, 8, and 15, with courses scheduled every 4 weeks in the absence of disease progression or unacceptable toxicity.
The primary endpoint was median PFS from enrollment to disease progression or death, assessed up to 1 year. The planned method used Kaplan-Meier curves and a Brookmeyer and Crowley confidence interval for the median. The numerical PFS result and confidence interval are not reported in the registry record.
The safety record lists 59 participants at risk for serious adverse events, 2 affected; 59 at risk for other adverse events, 23 affected; and 44 deaths. Sepsis and myocardial infarction are listed as serious adverse event terms, each at 1.7%. The record does not establish treatment attribution.