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 Pilot Study of MRI-Guided High Intensity Focused Ultrasound Ablation of Uterine Fibroids (NCT00837161), a na phase 1, phase 2 study. The primary outcome is Treatment-related Adverse Events (AE) Per Subject Resulting From HIFU Treatment of the Uterine Fibroids.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00837161 |
| Phase | Phase 1, Phase 2 |
| Condition | Uterine Fibroids, Uterine Leiomyomata |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 11 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Philips Healthcare |
| Results posted | Yes |
2. Clinical Question
Population
Women with symptomatic uterine fibroids were the intended population. The registry describes fibroids as uterine leiomyomas and states that the study participants underwent MRI-guided treatment followed by hysterectomy. The safety population is reported as all 11 participants evaluated for adverse events after HIFU treatment. The registry does not give further eligibility details or demographic characteristics, so the scope of the findings across different patient groups cannot be assessed from this record.
Intervention
The intervention was the Philips MR guided HIFU system. High-intensity focused ultrasound uses ultrasound energy to heat and thermally destroy targeted tissue. The registry describes MRI as a way to observe the ultrasound path and monitor temperature increases in fibroid tissue during treatment. The study aimed to assess the safety and treatment capabilities of this system for fibroid ablation.
Comparator
There was no separate comparator group. The registry lists a single-group model, allocation as NA, and no masking. Participants received HIFU treatment; the record does not describe a randomized or concurrent control arm. Hysterectomy after treatment was part of the study approach, but it is not a treatment comparator.
Primary question
The primary question concerned the mean number of treatment-related adverse events per treated participant, assessed through follow-up ending at hysterectomy or, at latest, day 30 after treatment. Investigators judged whether events were related to treatment on a case-by-case basis. The registry also lists a secondary outcome about whether the HIFU treatment location matched findings at hysterectomy. The record does not report a numerical result for the primary endpoint, so the primary question cannot be answered from the posted results.
3. Trial Design
The registry describes a completed pilot study of the Philips MR guided HIFU system for uterine fibroids. It lists the study as phase 1 and phase 2, with a single-group model, allocation recorded as NA, and no masking. The intervention is a device, and the described arm consists of patients receiving HIFU treatment. Because there is no separate control arm, this design does not estimate a treatment contrast against usual care, another procedure, or no treatment.
The study's stated purpose was to assess the safety and treatment capabilities of MRI-guided HIFU for fibroid ablation. The brief summary describes women with symptomatic fibroids undergoing HIFU and then hysterectomy. It says the hysterectomy would allow assessment of whether targeted tissue could be treated without harming surrounding normal tissue. The registry lists a secondary outcome concerning correspondence between the HIFU treatment location and the location identified at hysterectomy. This design therefore included a post-treatment opportunity to examine tissue findings, but the record does not report the result of that outcome.
The enrollment field lists 11 participants. The brief summary also describes the planned pilot as a study of 10 women, while the primary endpoint population states that all 11 participants were evaluated for adverse events. These descriptions are not identical; the registry record does not explain the difference. The status is completed. The listed start is 2009-01 and primary completion is 2010-02.
The registry lists secondary outcomes covering treatment-location agreement at hysterectomy, time to return to normal activities, pain on a numerical rating scale, and discomfort. It lists five outcome measures overall, but gives no analysis records. A single-group pilot can characterize observations among treated participants, but without a comparator it cannot establish how those observations differ from outcomes under another treatment or no treatment.
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: Patients were screened prior to treatment and the primary exclusion criteria was either uterine size per gestational age or fibroid size.
Overall Study
| Stage | HIFU Treated |
|---|---|
| STARTED | 11 |
| COMPLETED | 9 |
| NOT COMPLETED | 2 |
Reasons for not completing this period:
| Reason | HIFU Treated |
|---|---|
| refused hysterectomy | 2 |
Analysis population for the primary outcome, as defined in the registry: Safety was assessed per protocol; all 11 participants were evaluated for adverse events after HIFU treatment.
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 | HIFU Treated |
|---|---|---|
| Participants analysed | 11 | |
| Age, Categorical: <=18 years | Participants | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 11 |
| Age, Categorical: >=65 years | Participants | 0 |
| Age Continuous | years | 46.7 (SD 5.7) |
| Sex: Female, Male: Female | Participants | 11 |
| Sex: Female, Male: Male | Participants | 0 |
| Region of Enrollment: United States | participants | 11 |
6. Primary Endpoint
The registry lists the primary outcome as Treatment-related Adverse Events (AE) Per Subject Resulting From HIFU Treatment of the Uterine Fibroids, measured over end of follow-up (date of hysterectomy, at latest day 30 after treatment).
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Full Range |
| Unit | treatment-related AE/patient |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is the mean number of treatment-related adverse events per treated participant. The registry defines it as the number of treatment-related adverse events reported during the study divided by the total number of treated subjects. Relatedness was judged case-by-case by the investigator. Follow-up was defined as ending on the date of hysterectomy or, at latest, day 30 after treatment.
This endpoint is used to describe the burden of events judged related to the procedure in the observed safety population. Expressing events as a mean per participant can account for the fact that participants may experience different numbers of events, rather than reporting only whether any event occurred. It is a summary measure, however, and does not by itself describe event severity, timing, duration, or the number of participants experiencing at least one event. Those details require separate reporting.
The registry record does not report the observed mean, its range, or an uncertainty interval for this primary endpoint. Although the adverse-event record separately reports serious and other adverse-event counts, those figures do not substitute for the stated primary measure of treatment-related events per participant. The posted results therefore do not provide enough information to quantify the primary endpoint as defined.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record describes a single-group pilot and reports adverse-event counts for the HIFU Treatment group. It lists 11 participants at risk for serious adverse events and zero affected by serious adverse events. It also lists 11 at risk and six affected under other adverse events. The record does not give serious adverse-event terms, and its list of top serious terms is empty. The other-adverse-event count should be read as the registry's category-level count; the record does not identify the event types or give a narrative account that would clarify their nature.
These counts are descriptive. Without a comparator group, they cannot show whether the observed event pattern is higher or lower than it would have been under another intervention or without HIFU. The zero serious adverse-event count means that no serious event was recorded in this group during the reported observation window; it does not establish that serious events cannot occur. A small pilot's observations can be compatible with a wide range of underlying event rates, and the registry record does not supply an uncertainty interval for these counts.
The primary endpoint is the mean number of treatment-related adverse events per subject, but that numerical result is not reported. The adverse-event section distinguishes serious from other events, while the primary endpoint concerns treatment-related events judged by the investigator. These classifications are not interchangeable. In particular, the record does not state how many of the six other adverse events were judged treatment-related, nor how many events each participant experienced. The primary endpoint therefore cannot be reconstructed from the adverse-event counts.
There is also a difference between the brief summary's description of a pilot involving 10 women and the enrollment and safety-population entries of 11. The record does not explain this discrepancy. It is appropriate to report each registry entry as written rather than select one as the definitive count for every purpose.
In statistical terms, the posted counts provide a limited description of recorded safety events during a defined follow-up period. They do not provide a controlled estimate of treatment effect, a complete account of event severity or type, or a result for the prespecified primary measure. The registry lists secondary outcomes, including location correspondence at hysterectomy, pain, discomfort, and return to normal activities, but does not report their numerical findings. Accordingly, the available record supports only a narrow descriptive reading of adverse events and does not support broader conclusions about comparative safety or treatment capability.
9. Statistical Methods Explained
What does the primary endpoint summarize?
The primary endpoint is a mean count: the number of treatment-related adverse events divided by the number of treated subjects. A mean count compresses participant-level experience into a single summary. It can reflect multiple events in the same participant, so it is not equivalent to the proportion of participants who experienced any event. The registry record does not report the mean result, the event count used to calculate it, or the participant-level distribution. Consequently, the definition is available, but the result cannot be independently checked or interpreted quantitatively.
Event relatedness was judged case-by-case by the investigator. This makes the attribution a clinical judgment recorded within the study, rather than a classification that can be independently derived from the aggregate counts. The record does not give adjudication procedures, event descriptions, or the criteria used to make those judgments. Readers should therefore understand the endpoint as the registry-defined investigator-attributed count, not as an objective count of all events caused by treatment.
Why distinguish counts from rates and averages?
A count reports how many events were recorded in the group. A mean per participant scales the event count by the number of participants, but can hide variation: participants may have no event, a single event, or several events. A proportion with at least one event answers a different question, because it counts affected participants rather than all events. These summaries are not interchangeable. The registry's adverse-event entries report affected counts for serious and other events, while the primary endpoint is defined as a mean number of treatment-related events per subject. The record does not provide enough detail to translate between them.
Follow-up duration also matters when interpreting event summaries. The primary endpoint timeframe ends at hysterectomy or, at latest, day 30 after treatment. A participant observed for a shorter period may have less opportunity for events to be recorded than a participant followed longer. The registry does not report individual follow-up durations or time-based event rates. The endpoint should therefore be read within its stated observation window and not as a measure of longer-term safety.
What does a confidence interval add?
In general, a confidence interval expresses the statistical uncertainty around an estimated quantity under a specified analysis. It helps readers distinguish a precise estimate from one that is compatible with a broad range of values. For event counts or proportions, intervals are especially useful when the observed group is small, because a seemingly simple count may still leave substantial uncertainty about the underlying frequency. No confidence interval for the primary endpoint or adverse-event counts is reported in the registry record. No interval should be inferred from the event counts alone in this explanation.
For a mean count, an interval calculation would depend on the participant-level data or on assumptions about the distribution of events. Event counts may be unevenly distributed, with some participants contributing multiple events. If variability exceeds what a simple count model assumes, over-dispersion is present. In general, accounting for over-dispersion can avoid overstating precision. The registry does not report a model for the primary endpoint, participant-level event counts, or an assessment of over-dispersion, so it is not possible to determine which approach, if any, was used.
What can a single-group design estimate?
A single-group design can describe what was observed among those receiving the intervention. It cannot directly estimate a comparative effect because it has no concurrent control group. Outcomes can reflect the intervention, the participants' underlying condition, the procedure surrounding treatment, measurement practices, or other influences. Without a comparison, those influences cannot be separated statistically by contrasting groups. The record lists allocation as NA and the model as single group; it does not report a randomized comparison.
The hysterectomy after treatment is part of the study approach, not a randomized control condition. It offers a potential means to examine the treated tissue and the location of treatment, consistent with the listed secondary outcome. But a tissue assessment after treatment does not, by itself, create a comparison that estimates what would have happened without HIFU. The registry record does not provide the result of the location outcome or the methods used to assess agreement.
What does the registry say about analysis methods?
The record lists five outcome measures and zero analysis records. It does not report statistical tests, a model for the primary endpoint, covariate adjustment, a confidence-interval method, or a statistical analysis plan. It also does not report a sample-size justification or interim analyses. These items should be treated as unreported in the registry record, not assumed absent from all study documents. The available record alone cannot establish what methods may have been described elsewhere.
Because no randomized or controlled contrast is reported, a treatment comparison is not available to analyze. No recalculated treatment effect is presented in the registry data, and there is no basis for deriving one. The figures should be read as descriptive entries, not as evidence of a hypothesis test or an estimate adjusted for confounding.
How should sample-size planning be understood?
Planning illustrations based on an observed effect are not results from this pilot and are not observed power. A planning calculation asks how many participants might be needed under stated assumptions to detect an effect of a specified size. Such a calculation is conditional on the assumed significance level, allocation, approximation, and effect size. It does not establish the probability that the study's observed result is true, nor does it repair the absence of a comparator or missing endpoint results. The registry record does not report the trial's own sample-size justification. Any planning illustration should therefore be kept separate from the observed safety counts and from the study's stated primary endpoint.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists five outcome measures, including the primary adverse-event measure and secondary measures concerning treatment location at hysterectomy, return to normal activities, pain, and discomfort. It lists zero analysis records. The record does not state whether the study used a prespecified hierarchy of outcomes, adjusted for multiple comparisons, or treated secondary analyses as exploratory. These multiplicity procedures are not reported in the registry record.
Multiplicity matters when several outcomes or statistical tests are considered. In general, conducting multiple tests can increase the chance of at least one apparently notable finding even when there is no underlying effect. A prespecified testing strategy can clarify which result is primary and how other results should be interpreted. Here, numerical results for the listed secondary outcomes are not reported, and the primary endpoint result is also absent. There are therefore no posted outcome estimates or tests from which to assess how multiplicity was handled.
The record states that all 11 participants were evaluated for adverse events after HIFU treatment. It does not provide a missing-data summary for the primary measure or secondary outcomes, explain whether all participants contributed to each outcome, or describe how missing observations were handled. It also does not report an analysis population for outcomes other than the safety population description. The enrollment field lists 11, while the brief summary describes a pilot involving 10 women; the registry does not reconcile these entries. These gaps limit assessment of completeness and analysis-population consistency.
The registry record does not report an analysis plan or explain whether any outcome data were excluded. It is therefore not possible to infer that missing data were absent, that all analyses followed an intention-to-treat principle, or that a particular population definition was used. Such details remain unreported 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 |
|---|---|---|---|
| HIFU Treatment | 0 | 11 | 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 |
|---|---|
| HIFU Treatment | 6 of 11 |
Most frequent non-serious adverse event terms
| Event term | Organ system | HIFU Treatment |
|---|---|---|
| Pain at Rib Cage or Chest Level | Musculoskeletal and connective tissue disorders | 2 of 11 |
| Neck Pain | Musculoskeletal and connective tissue disorders | 1 of 11 |
| Right leg pain | Musculoskeletal and connective tissue disorders | 1 of 11 |
| Lower back pain | Musculoskeletal and connective tissue disorders | 1 of 11 |
| Rectal Bleeding | Gastrointestinal disorders | 1 of 11 |
| Fatigue | Reproductive system and breast disorders | 1 of 11 |
| Diarrhea | Gastrointestinal disorders | 1 of 11 |
| Shin discomfort | Musculoskeletal and connective tissue disorders | 1 of 11 |
| pain right buttock | Musculoskeletal and connective tissue disorders | 1 of 11 |
| Pruritis | General disorders | 1 of 11 |
The serious adverse-event entry reports 11 participants at risk and zero affected. The separate other-adverse-event entry reports 11 at risk and six affected. The registry's top serious terms list is empty. These figures describe recorded entries during the study; they do not establish that the risk of a serious event is zero or that events would not occur in a larger or differently observed group.
The primary endpoint is not the same as these category counts. It concerns treatment-related adverse events per treated subject, with relatedness judged by the investigator. The registry does not state how many other adverse events were considered treatment-related, or how many events occurred in each participant. It also does not provide event descriptions for the six affected under other adverse events. The counts should not be interpreted as an event rate, an incidence percentage, or a treatment-attributable count beyond the categories as recorded.
The observation period for the primary endpoint ran through hysterectomy or, at latest, day 30 after treatment. The record does not provide longer-term safety findings. The small, single-group pilot offers a descriptive snapshot rather than a controlled safety comparison. A zero count in this record is an observation within that study and follow-up definition, not proof of absence of risk.
12. What the Result Does, and Does Not, Mean
The posted results describe a completed, single-group pilot of MRI-guided HIFU for uterine fibroids. The adverse-event record shows zero participants affected by serious adverse events among 11 at risk and six affected under other adverse events among 11 at risk. These entries provide a limited descriptive account of the safety data recorded for the treated group.
The record does not report the primary endpoint result, which was defined as the mean number of treatment-related adverse events per participant. Nor does it report the numerical results for the listed secondary outcomes. As a result, the available entries do not show how many treatment-related events occurred per participant, whether treatment locations corresponded with hysterectomy findings, or what participants reported about pain, discomfort, and return to normal activities.
The study had no separate control group. It therefore cannot establish whether the observed adverse-event pattern or any other outcome is different from what would have occurred under another treatment or without HIFU. The record also does not report statistical analyses, uncertainty intervals, or details of missing outcome data. The absence of a reported serious adverse event in this group should not be interpreted as proof that serious events are impossible.
The registry's description of the intended pilot size differs from its enrollment and safety-population entries: the brief summary refers to 10 women, while the enrollment field and safety population state 11. The record does not explain the difference. This should be retained as a reporting ambiguity rather than resolved by assumption.
Overall, the registry supports a narrow description of recorded adverse-event categories in this pilot. It does not provide the primary endpoint estimate or enough comparative and outcome information to establish efficacy, comparative safety, or the broader treatment capabilities of the device. The study's stated purpose and design should be distinguished from results that are actually reported.
13. Why This Trial Matters Statistically
This trial is statistically informative as an example of the limits and uses of a single-group pilot. A pilot can document whether a procedure was carried out in a defined study setting and can describe recorded events. The registry identifies a safety population, a follow-up window, and a primary endpoint based on treatment-related event counts per participant. Those definitions are important for interpreting what the study intended to measure.
At the same time, the design determines which questions can be answered. With a single group and no randomized comparator, observed outcomes cannot be attributed uniquely to the intervention or contrasted with an alternative. This is especially important for safety: a count of events in treated participants is not itself a comparative estimate of excess or reduced risk. The record's event entries are descriptive, and the missing primary endpoint result makes even the intended event summary unavailable.
The study's post-treatment hysterectomy approach also illustrates the distinction between a measurement opportunity and a control group. The registry lists treatment-location correspondence as a secondary outcome, which is relevant to the stated interest in targeting tissue. However, the record does not report that outcome's findings. The design description cannot substitute for the observed result.
Finally, the different participant counts in the brief summary and enrollment/safety entries, the absence of numerical outcome analyses, and the lack of reported missing-data and multiplicity procedures all affect interpretability. These are not reasons to infer a result in either direction. They indicate where registry reporting leaves uncertainty about the study's analyses and findings. For statisticians and clinical researchers, the key lesson is to keep design intent, observed counts, endpoint definitions, and unreported results distinct.
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 important limitations for interpreting this pilot. It describes a single-group study without a comparator, so there is no direct basis for estimating a contrast against another treatment or a no-treatment condition. The record lists allocation as NA and masking as none. It does not report methods for addressing influences that may affect outcomes apart from the intervention.
The primary endpoint is defined but its numerical result is not reported. The adverse-event entries provide serious and other category counts, but not event types, participant-level counts, severity details for the other category, or the number of events judged treatment-related. Thus the listed safety data cannot be used to reconstruct the primary measure. The registry also does not provide uncertainty intervals or a statistical model for the event data.
The follow-up timeframe ends at hysterectomy or, at latest, day 30 after treatment. No longer-term safety results are reported. The listed secondary outcomes include treatment-location agreement, return to normal activities, pain, and discomfort, but numerical findings for them are not present in the record. The methods for assessing these outcomes are also not reported.
The enrollment field lists 11 participants, and the safety population states that all 11 were evaluated for adverse events, while the brief summary describes a pilot of 10 women. The record does not explain this difference. It also does not report missing-data handling, the analysis population for each outcome, multiplicity procedures, or a statistical analysis plan. These reporting gaps prevent a full evaluation of how outcomes were analyzed and how precise the estimates would be, even apart from the limits inherent in a single-group pilot.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Pilot Study of MRI-Guided High Intensity Focused Ultrasound Ablation of Uterine Fibroids — NCT00837161.
- Registry record last updated 2012-12-04; status last verified 2012-11.
- Results first posted 2011-11-28.
- 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.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
18. Record Summary
The record describes a completed phase 1 and phase 2, single-group pilot of the Philips MR guided HIFU system for uterine fibroids. Allocation is listed as NA and masking as none. The enrollment field lists 11; the safety population entry states that all 11 participants were evaluated for adverse events. The brief summary separately describes a pilot involving 10 women, a difference the record does not explain.
The primary endpoint is the mean number of treatment-related adverse events per participant through hysterectomy or, at latest, day 30 after treatment. Its numerical result is not reported. The adverse-event entries list zero serious adverse events among 11 at risk and six affected under other adverse events among 11 at risk. Five outcome measures are listed, with zero analysis records. Numerical results for the listed secondary outcomes and details of missing-data handling and statistical methods are not reported in the registry record.