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 Embozene Microspheres for Uterine Fibroid Embolization (UFE) (NCT01675011), a randomized na study. The primary outcome is Primary Endpoint.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01675011 |
| Phase | NA |
| Condition | Uterine Fibroids |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Double |
| Enrollment | 4 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Boston Scientific Corporation |
| Results posted | Yes |
2. Clinical Question
Population
Women aged 30–50 years with symptoms from uterine fibroids were the intended study population. The registry summary describes a planned study of 225 subjects, while the recorded enrollment was 4.
Intervention
Uterine fibroid embolization using Embozene Microspheres. The registry describes injecting embolizing particles into the uterine artery as part of the procedure.
Comparator
Uterine fibroid embolization using Embosphere. The registry describes the procedure in the same terms for this group.
Primary question
At 12 months after the procedure, what proportion of subjects met the registry’s definition of menstrual blood loss success: a 50% reduction or less than 80 ml of menstrual blood loss per cycle, measured by the Alkaline Hematin method?
The study was designed as a randomized, prospective, multicenter comparison. Its clinical question concerns the relative effectiveness of two embolic devices when used in uterine fibroid embolization, with menstrual blood loss serving as the primary effectiveness measure. The endpoint focuses on a prespecified threshold for change in menstrual blood loss rather than a comparison of average blood loss.
In practice, the registry does not report an answer to that comparative question. It states that the study was terminated because enrollment was inadequate and that no patients completed the 12-month visit. Consequently, the primary endpoint cannot be compared between the randomized groups from the posted results. The record also does not report a primary-effect estimate or an analysis of the intended comparison.
3. Trial Design
The registry identifies this as a randomized, prospective, multicenter study with a parallel-group model and double masking. Participants were assigned to uterine fibroid embolization with either Embozene Microspheres or Embosphere. The treatment descriptions specify the same general procedure in each group, with the embolizing particles differing by device. The record does not specify which people were masked or how masking was maintained.
The brief summary describes a planned study of 225 women aged 30–50 years who had symptoms from uterine fibroids. It also describes follow-up for thirty-six months after embolization. The recorded enrollment, however, is 4. Enrollment is therefore substantially limited in the record relative to the planned number in the summary, but the number enrolled by treatment group is not reported as an efficacy analysis population.
The record gives a study start of 2012-08 and a primary completion date of 2013-12. The study status is terminated, with inadequate enrollment identified as the reason. Although the summary describes follow-up over thirty-six months, the primary endpoint was assessed at 12 months after the procedure. The record specifically states that no patients completed that 12-month visit.
The record lists one outcome measure and no analyses. It does not provide an allocation sequence method, details of concealment, a statistical analysis plan, or a sample-size justification for the trial. The planning assumptions associated with the sample-size illustration are not a substitute for such a justification, and the available record does not report calculated sample-size results for this comparison.
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: 11 patients screened and 4 randomized.
Overall Study
| Stage | Embozene® Microspheres | Embosphere® |
|---|---|---|
| STARTED | 3 | 1 |
| COMPLETED | 0 | 0 |
| NOT COMPLETED | 3 | 1 |
Reasons for not completing this period:
| Reason | Embozene® Microspheres | Embosphere® |
|---|---|---|
| Trial terminated by Sponsor | 3 | 1 |
Analysis population for the primary outcome, as defined in the registry: The study was terminated due to inadequate enrollment; no patients completed the 12 month visit.
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 | Embozene® Microspheres | Embosphere® | Total |
|---|---|---|---|---|
| Participants analysed | 3 | 1 | 4 | |
| Age, Continuous | years | 45 (40 to 49) | 45 (45 to 45) | 45 (40 to 49) |
| Sex: Female, Male: Female | Participants | 3 | 1 | 4 |
| Sex: Female, Male: Male | Participants | 0 | 0 | 0 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 0 | 0 | 0 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 3 | 1 | 4 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Asian | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Black or African American | Participants | 2 | 1 | 3 |
| Race (NIH/OMB): White | Participants | 1 | 0 | 1 |
| Race (NIH/OMB): More than one race | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 |
| Region of Enrollment: United States | participants | 3 | 1 | 4 |
6. Primary Endpoint
The registry lists the primary outcome as Primary Endpoint, measured over 12 Months post study procedure.
| Element | Registry entry |
|---|---|
| Result type | N/A |
| Measure of spread | not applicable |
| Unit | not stated |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is the proportion of subjects who meet the registry’s definition of success at 12 months after the study procedure. Success is defined as either a 50% reduction in menstrual blood loss or menstrual blood loss of less than 80 ml per cycle. Menstrual blood loss is evaluated using the Alkaline Hematin method.
This is a binary endpoint: each assessed subject would be classified as meeting or not meeting the stated success definition. The group-level proportion would then describe how many assessed subjects in each treatment group met the threshold. A proportion can be useful when a clinical question is framed around reaching a defined level of improvement, rather than around the average amount of change across all participants.
The definition uses two routes to success: a specified reduction from baseline, or an amount of menstrual blood loss below a stated threshold. These routes need to be applied as written when classifying outcomes. The record does not provide endpoint values, baseline measurements, or a count of successes in either group. It states that no patients completed the 12-month visit, so the intended endpoint comparison is not available in the posted results.
The endpoint’s timing matters because it is tied to the 12-month visit. Follow-up described in the study summary extends longer, but later follow-up cannot replace the unobserved primary endpoint in the registry record without an analysis plan and data that are not reported.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The central statistical fact is that the trial did not produce a reported 12-month primary endpoint comparison. The registry says the study was terminated because enrollment was inadequate and that no patients completed the 12-month visit. It lists one outcome measure and zero analyses. There is therefore no reported proportion meeting the endpoint in either group, no estimate of the difference between groups, and no confidence interval or significance test for the primary effectiveness question.
The recorded enrollment is 4, while the brief summary describes a planned study of 225 subjects. These figures refer to different aspects of the record: the summary describes the intended study size, and the enrollment field gives the recorded enrollment. They should not be treated as an efficacy sample and a completed analysis population. The record does not report how the four enrolled participants were distributed across the groups for the primary endpoint, nor does it provide their 12-month outcome data.
Randomization is intended to support a fair comparison by reducing systematic differences between groups at assignment. It does not, by itself, create interpretable evidence when the relevant endpoint is unavailable. With no completed primary visits reported, the randomized comparison cannot yield an observed treatment-effect estimate from this record. Nor can the absence of a reported comparison be read as evidence that the devices had equal effects or different effects.
The safety entries are limited counts among the participants listed as at risk. For Embozene Microspheres, the registry reports 3 at risk, 0 affected by serious adverse events, and 0 affected by other adverse events. For Embosphere, it reports 1 at risk, 0 affected by serious adverse events, and 1 affected by other adverse event. These counts are descriptive and do not provide a precise comparative safety estimate. Death counts are not reported in the registry record.
The study’s termination and lack of primary endpoint completion constrain what can be learned from its posted results. The record documents a planned randomized comparison and a specific primary endpoint, but it does not report a result for that endpoint. Any conclusion about comparative effectiveness or a precise estimate of risk would go beyond the information recorded.
9. Statistical Methods Explained
The registry describes a randomized, double-masked, parallel-group trial. In a randomized trial, assignment is intended to make treatment groups comparable on average with respect to measured and unmeasured characteristics. This design feature supports causal comparison when outcomes are collected and analyzed as planned. It does not guarantee comparable groups in a very small enrolled sample, and it cannot compensate for an endpoint that was not observed or reported.
How the primary endpoint would be analyzed
The endpoint is defined as success or no success at 12 months. For each group, a basic analysis would estimate the proportion meeting the success definition among participants with evaluable endpoint data. A comparison could then express how much the proportions differ, with uncertainty described using an interval estimate. The registry record reports none of these endpoint counts or estimates. Because no patients completed the 12-month visit, the primary comparison is unavailable in the posted results.
A confidence interval is a statistical range intended to express uncertainty around an estimate under the assumptions of the analysis. It can show whether the data are compatible with a range of possible effects, rather than giving only a single point estimate. An interval would not resolve problems caused by absent endpoint data, and no interval for the primary comparison is reported in this record. A p-value, which assesses how compatible data are with a specified null model, is also not reported for the endpoint.
What randomization and masking contribute
Random assignment helps guard against deliberate or predictable allocation of participants to a particular device. Masking can reduce the influence of expectations on care, assessments, or reporting, depending on who is masked. The registry identifies the study as double-masked but does not state which parties were masked or describe the procedures used. These design labels therefore describe the recorded design, but the record does not supply enough detail to assess implementation.
The parallel-group model means the two device groups were intended to be compared as separate groups. The intervention descriptions indicate that both groups received uterine fibroid embolization, with Embozene Microspheres or Embosphere used for the procedure. The registry does not report an adjusted analysis or specify which covariates, if any, would be included in an analysis.
Enrollment and planning assumptions
The brief summary describes 225 planned subjects, whereas recorded enrollment is 4. The record identifies inadequate enrollment as the reason for termination. A sample-size justification for the original trial, including the target effect and the assumptions used to select the planned enrollment, is not reported in the registry record.
The sample-size illustration assumptions describe a general planning approach: a two-sided significance level of 0.05, equal allocation between groups, and a normal approximation. They also describe planning for a stated fraction of an observed effect. These assumptions do not constitute evidence that the trial enrolled enough participants, and no calculated planning results for this comparison are reported in the record. A planning illustration is not observed power, and it cannot substitute for an endpoint estimate.
For a binary endpoint, the amount of uncertainty depends in part on the number of participants with outcome data and on how common success is. When outcome data are absent, an estimate cannot be recovered simply from the original allocation design or planned enrollment. The record does not state whether any endpoint observations were obtained before termination, and it does not report a method for handling missing outcomes.
Scope of the available analysis
The registry lists one outcome measure and no analyses. It does not report an intention-to-treat population, a per-protocol population, or another analysis population for effectiveness. These terms refer generally to different choices about which randomized participants are included in an analysis; the particular choices for this trial are not reported in the registry record.
Multiplicity concerns arise when several outcomes, time points, or treatment comparisons are tested, because repeated testing can increase the chance of a false-positive finding. The registry record does not report a multiplicity strategy. Although the summary describes follow-up through thirty-six months, the stated primary endpoint is at 12 months; other outcome definitions and analysis plans are not reported in the registry record. No claim about adjustment or testing across outcomes can therefore be made.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists one outcome measure, but no analyses. It identifies a 12-month primary endpoint and describes follow-up for thirty-six months in the study summary. It does not report a statistical plan explaining how the primary endpoint would be analyzed alongside any secondary outcomes, follow-up time points, or other comparisons. A strategy for controlling multiplicity is not reported in the registry record.
Multiplicity matters when several statistical questions are evaluated. Testing many outcomes or time points can make a nominally unusual result more likely to occur by chance somewhere among the tests. Prespecified priorities and an appropriate testing strategy can help readers understand how such results should be interpreted. The available record does not state whether such a strategy was planned or used.
Missing data are central to this study’s primary outcome because the record says no patients completed the 12-month visit. It does not report whether any partial endpoint information was available, why individual participants lacked follow-up, or how missing outcomes would be handled analytically. Methods such as imputation or sensitivity analyses are not described in the registry record, so their use should not be assumed.
The record also does not define the population used for an effectiveness analysis. It does not report whether analyses were intended to include all randomized participants, only those who received a procedure, or another group. Without reported outcome data, analysis populations, and missing-data methods, the primary endpoint cannot be reconstructed or interpreted as a completed randomized comparison.
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 |
|---|---|---|---|
| Embozene® Microspheres | 0 | 3 | 0.0% |
| Embosphere® | 0 | 1 | 0.0% |
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 |
|---|---|
| Embozene® Microspheres | 0 of 3 |
| Embosphere® | 1 of 1 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Embozene® Microspheres | Embosphere® |
|---|---|---|---|
| Constipation | Gastrointestinal disorders | 0 of 3 | 1 of 1 |
The registry reports safety counts by group. In the Embozene Microspheres group, 3 participants were listed as at risk; 0 were affected by serious adverse events and 0 by other adverse events. In the Embosphere group, 1 participant was listed as at risk; 0 were affected by serious adverse events and 1 by other adverse event. The registry record does not report death counts.
These are small descriptive counts, not a precise comparison of safety between devices. The record does not provide enough information to determine event timing, duration, severity beyond the serious-versus-other classification, or any relationship to the study procedure or device. A count of zero affected participants in the listed group does not establish that an event could not occur; it describes only what is recorded for the participants at risk.
The categories should also remain distinct: the single other adverse event reported for Embosphere is not listed as a serious adverse event. The figures do not support calculation of a reliable comparative risk estimate, and no such estimate is reported in the registry record.
12. What the Result Does, and Does Not, Mean
The record establishes that a randomized, prospective, multicenter comparison of Embozene Microspheres and Embosphere was planned for uterine fibroid embolization. It specifies a primary effectiveness endpoint based on menstrual blood loss at 12 months and records the trial as double-masked and parallel-group. It also documents termination due to inadequate enrollment.
The record does not establish the comparative effectiveness of the two devices. No patients completed the 12-month visit, and no analyses are listed. Without endpoint observations, the proportion meeting the success definition in either group and the difference between groups are not available. The record therefore cannot tell whether one group had a higher success proportion, whether their results were similar, or how uncertain a comparison would have been.
Likewise, the safety counts should not be read as a definitive comparison. They are limited to the participants listed as at risk, and the record does not provide a detailed safety analysis or death counts. These entries describe reported adverse-event categories and counts, not a complete estimate of comparative safety.
The planned enrollment of 225 in the study summary and recorded enrollment of 4 help explain the limited scope of the posted evidence, but neither figure supplies missing endpoint results. A planned study size is not an observed analysis sample, and a small recorded enrollment does not indicate what the results would have been had recruitment continued.
Accordingly, the registry record is informative about the intended question, design, termination, and limited safety entries. It does not answer the primary clinical comparison or support a precise estimate of treatment effect. Any stronger statement about benefit, lack of benefit, equivalence, or comparative risk would exceed what the posted results report.
13. Why This Trial Matters Statistically
This trial illustrates an important distinction between a registered research question and an answered research question. A clear endpoint and a randomized design can define how a comparison was intended to work, but they do not generate an effect estimate when the endpoint is not observed. Here, the registry specifies a 12-month menstrual blood loss endpoint, yet reports that no patients completed that visit.
The enrollment information also highlights why planned and recorded sample sizes must be kept separate. The summary describes 225 intended subjects, while the enrollment field records 4. The termination reason is inadequate enrollment. These registry entries help readers understand why the record contains no primary analysis, but they do not permit calculation of the result that a larger study might have produced.
Statistically, the absence of an estimate is not the same as an estimate of no effect. Without success counts, a group comparison, or uncertainty intervals, the record cannot distinguish a meaningful difference from similar outcomes. A randomized label does not remove this limitation; randomization is a design property, while an interpretable comparison also depends on outcome data and a reported analysis.
The record is also a reminder that safety counts need context. The reported adverse-event figures are descriptive and based on small numbers at risk. They cannot establish a precise relative safety profile, particularly when other details and death counts are not reported in the registry record.
For statistical readers, the key contribution is transparent documentation of what was planned and what was not completed. The study’s design and endpoint are recorded, while its primary comparative result is not. Keeping that distinction explicit prevents an incomplete trial record from being mistaken for evidence of equivalence or effectiveness.
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 is that the trial was terminated because enrollment was inadequate and no patients completed the 12-month primary endpoint visit. The registry lists no analyses, so the intended effectiveness comparison is unavailable. Recorded enrollment is 4, whereas the brief summary describes a planned study of 225 subjects.
The registry record does not report enrollment by treatment group for an effectiveness analysis, endpoint observations, baseline menstrual blood loss, or the number of participants who received each procedure. It also does not describe the analysis populations or explain how missing outcomes would be handled. These omissions prevent assessment of the primary endpoint beyond its stated definition.
Further design details are not reported, including the method for generating and concealing randomization, which parties were masked, and how masking was implemented. A statistical analysis plan, sample-size justification, and multiplicity strategy are also not reported in the registry record. The brief summary describes follow-up through thirty-six months, but other outcome definitions and analyses are not listed.
Safety information is limited to the adverse-event counts and at-risk counts recorded for the two groups. Event details and death counts are not reported in the registry record. Given the limited enrollment and absence of a reported analysis, the safety entries should be treated as descriptive rather than as a precise comparison.
These limitations constrain conclusions about both effectiveness and safety. They arise from the information recorded and the lack of completed primary endpoint follow-up; they do not establish what the results would have been under a larger or completed trial.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Embozene Microspheres for Uterine Fibroid Embolization (UFE) — NCT01675011.
- Registry record last updated 2016-03-11; status last verified 2016-02.
- Results first posted 2015-02-12.
- 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
NCT01675011 is a randomized, double-masked, parallel-group study comparing Embozene Microspheres with Embosphere for uterine fibroid embolization. The registry describes a planned multicenter study of 225 women aged 30–50 years with symptoms from uterine fibroids and records enrollment of 4. The study is listed as terminated due to inadequate enrollment.
The primary endpoint was the proportion meeting the specified menstrual blood loss success definition at 12 months, assessed by the Alkaline Hematin method. The record states that no patients completed the 12-month visit and lists no analyses. It reports limited adverse-event counts by group, with death counts not reported in the registry record.