Dopamine Receptor Agonist Therapy for Pain Relief in Women Suffering From Endometriosis: A Pilot Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Dopamine Receptor Agonist Therapy for Pain Relief in Women Suffering From Endometriosis: A Pilot Study (NCT02542410), a randomized phase 2 study. The primary outcome is Change in Score in Worst Pain Over the Last Month.

2. Clinical Question

3. Trial Design

This was a completed phase 2, randomized, quadruple-masked, parallel-group pilot study sponsored by Boston Children's Hospital. The registry record gives enrollment as 10. The study start is recorded as 2016-05, and primary completion as 2018-09. Randomization means allocation was intended to be determined by chance, while a parallel design means participants were assigned to an arm rather than crossing between treatments. The registry record does not describe the randomization sequence or the procedures used to conceal allocation.

The two recorded arms were cabergoline and norethindrone acetate. The experimental arm received cabergoline 0.5 mg PO twice weekly for 6 months. The control arm received norethindrone acetate 5 mg PO daily for 6 months. These are the treatment schedules recorded in the registry. The record does not report whether participants could switch treatments, how adherence was assessed, or whether use of other therapies was permitted.

Quadruple masking indicates that the registry classifies the study as masked at four levels, but it does not identify those levels or explain how masking was maintained. The exact protocol and operational details are not reported in the registry record. In general, masking is intended to reduce the influence of treatment knowledge on participants’ reports, clinical care, and outcome assessment. Whether that protection was achieved cannot be determined from the available record.

The pilot designation is consistent with the stated aim of estimating efficacy and safety, but the registry record does not report a sample-size justification or a protocol for progression to a larger study. It also does not report interim analyses or a prespecified statistical analysis plan. The status is completed, but completion alone does not establish that all planned outcomes or analyses were posted.

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.

Overall Study

5. Baseline Characteristics

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

6. Primary Endpoint

The registry lists the primary outcome as Change in Score in Worst Pain Over the Last Month, measured over Baseline, 6 months.

The primary endpoint was change in score for worst pain over the last month. Pain was assessed using a visual analog scale with a minimum of 0 and a maximum of 10; higher scores represent worse pain. The recorded change is the value at 6 months minus the value at baseline. Therefore, a negative change denotes a lower score at 6 months than at baseline, while a positive change denotes a higher score. This describes the direction of the endpoint, not the cause of a change.

The registry identifies the summary measure as a median and the measure of dispersion as a standard deviation. It reports a median change of -0.5 with a standard deviation of 1.5 among 4 participants in the norethindrone acetate arm, and -5.0 with a standard deviation of 2.5 among 5 participants in the cabergoline arm. The registry record does not explain the calculation of the standard deviations or report confidence intervals for these summaries.

In general, measuring pain at baseline and follow-up allows change to be described relative to each participant’s starting score. A patient-reported scale can capture a subjective experience that may not be represented by a clinical observation alone. Its interpretation still depends on how the question was administered and how complete the follow-up measurements were; those details are not reported in the registry record. A secondary outcome, changes in pain interference scores, is listed, but its results are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies the study as randomized, quadruple-masked, and parallel. These are design descriptions, not a complete statistical analysis plan. Randomization assigns participants to groups by chance and, in general, is used to limit systematic differences in treatment assignment. Masking is intended to reduce the influence of knowledge about assignment on behavior, care, and outcome assessment. A parallel design compares groups followed under their assigned regimens. The registry record does not describe the procedures used to implement these features.

How to read the change score

The primary outcome is a change score calculated as the 6-month value minus the baseline value. Because the scale runs from 0 to 10 and higher values indicate worse pain, a negative change represents a lower follow-up score than baseline. This arithmetic direction is part of the endpoint definition; it does not identify the reason for the change. In general, a change score summarizes within-participant movement over time, but an arm-level change does not alone estimate the causal effect of treatment compared with a control group.

The registry reports a median for the primary outcome and a standard deviation as its dispersion. In general, the median is the middle of an ordered set of observations and is less affected by extreme values than the mean. A standard deviation ordinarily describes how observations vary around a mean. The record does not explain why this dispersion measure accompanies a median, how it was calculated, or whether there were additional distributional summaries. The posted summaries should be reproduced as recorded rather than treated as if they were a different statistic.

What a treatment comparison would require

In general, a comparative analysis estimates the difference between outcomes under the assigned arms and describes uncertainty in that estimate. A confidence interval is a range of values generated by a statistical procedure that conveys uncertainty under the method’s assumptions. A p-value is a measure calculated under a specified statistical model and null hypothesis; it is not the probability that a treatment is effective. The registry record does not report a confidence interval, p-value, or formal two-arm estimate for the primary endpoint. No such quantities can be inferred just from the arm summaries.

The record lists no analyses and indicates that values were missing or not estimable for a two-arm comparison for the other endpoint. It does not provide a detailed analysis method, adjustment variables, or an approach to repeated measurements. General methods such as regression or rank-based testing might be considered in other studies, but there is no basis to claim that any such method was used in this trial. The analysis plan is not reported in the registry record.

Why uncertainty matters

In general, outcome values vary among participants, and a small set of observations can give an imprecise picture of the population pattern. Measures of spread describe variation in the observed data, whereas confidence intervals for a treatment contrast describe uncertainty about the estimated comparison. These concepts are related but are not interchangeable. The posted standard deviations do not supply the missing confidence interval or comparative estimate.

Over-dispersion is a general concern when outcome variation is greater than assumed by a statistical model. If a model underestimates variation, its uncertainty estimates can be too narrow. This trial record does not report a model or an assessment of dispersion, so there is no basis to say that over-dispersion was assessed or affected the analysis. More generally, outcome distributions can be asymmetric or contain extreme values, which can influence how well a chosen summary or model represents the data. The record does not provide the participant-level data needed to assess those features.

Planning calculations are not observed power

In general, sample-size planning uses assumptions about a target effect, variability, significance level, and allocation to estimate the enrollment needed for a design goal. Such a planning calculation is not a description of what the completed trial demonstrated. The registry’s planning assumptions describe an illustration based on a fraction of the observed effect, a two-sided significance level of 0.05, equal allocation, and a normal approximation. No resulting participant counts or effect fractions are reported in the registry record. These planning assumptions do not establish the study’s original design rationale, and sample-size illustrations are not observed power.

The registry record does not report a sample-size justification, interim analyses, a prespecified testing procedure, or a detailed statistical analysis plan. These absences limit the ability to assess whether the posted summaries match the intended analysis. In general, a statistical result is most interpretable when its endpoint definition, analysis population, missing-data method, and comparison model are specified in advance. Those details cannot be reconstructed from the posted arm summaries.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists changes in pain interference scores as a secondary outcome and records two outcome measures. Results for the secondary outcome are not reported in the registry record. The record does not describe a multiplicity strategy, such as a hierarchy of outcomes or an adjustment to account for testing more than one outcome. In general, when multiple outcomes or analyses are examined, the chance of at least one apparently notable result can increase. Without a stated plan, the implications of multiple testing cannot be assessed.

The primary outcome has posted summaries for 4 participants in the norethindrone acetate arm and 5 participants in the cabergoline arm. Enrollment was 10. The registry record does not explain the difference between enrollment and the number of participants represented in the primary outcome summaries. It does not say whether participants withdrew, lacked a measurement, or were excluded for another reason. The reason for any missing endpoint data is not reported in the registry record.

There is no reported method for handling missing data, no description of an analysis population, and no account of whether participants were analyzed according to their randomized assignment. In general, missing-data methods rely on assumptions about why measurements are absent. Different assumptions can lead to different estimates, so the method and its rationale matter. No missing-data assumption can be attributed to this trial from the registry record.

The registry does not report whether the primary outcome analysis was intention-to-treat, per-protocol, or based on another population. It also does not report a participant flow account or reasons for exclusions from the endpoint summaries. These omissions prevent a full assessment of how the reported summaries relate to all randomized participants.

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 non-serious adverse event terms

The registry reports serious adverse events for 4 participants at risk in the control group and 5 at risk in the experimental group. No serious adverse events were recorded in either group, and deaths were recorded as 0 in both groups. These are the posted counts; they do not show that the risk of a serious event is absent.

The registry also records other adverse events for 4 participants at risk in the control group and 5 at risk in the experimental group. Other adverse events were recorded for 4 participants in the control group and 5 in the experimental group. The record does not describe the specific events, their severity, timing, duration, or relationship to treatment. Serious adverse events and other adverse events are separate categories in the registry, so the counts should not be combined or treated as descriptions of the same events.

In general, adverse-event counts describe what was recorded among participants under observation. A zero count in a small group does not establish that an event cannot occur, and counts alone do not provide a precise comparison of safety between treatments. The registry record does not report a statistical safety comparison, exposure-adjusted event rates, or detailed adverse-event narratives. These figures are descriptive and do not support a broader conclusion about comparative safety.

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

The registry record documents a randomized, masked pilot study of cabergoline and norethindrone acetate in young women with endometriosis-associated pain. For the primary endpoint, it posts an arm-specific median change in worst pain score from baseline to 6 months, together with a standard deviation and participant count. The recorded median changes are -0.5 for norethindrone acetate and -5.0 for cabergoline. Because lower scores indicate less severe pain on the scale, both reported changes are in the direction of lower scores relative to baseline.

Those summaries do not establish a comparative treatment effect. The registry does not report a formal two-arm estimate, confidence interval, or p-value for the primary outcome. The observed pattern cannot be separated from chance variation or interpreted with quantified precision using the posted results alone. No adjusted result is reported, and the record does not explain the difference between enrollment and the participant counts for the outcome.

The study’s pilot scale is important for interpretation. In general, pilot studies can provide preliminary information about feasibility, measurement, and outcome variability, but estimates from a small study can be unstable. The registry does not report a sample-size justification or a protocol specifying how the results would inform a subsequent study. It is not possible to assess precision beyond the posted descriptive statistics.

The registry lists a secondary pain-interference outcome but does not report its results. It also reports no serious adverse events in either arm and records other adverse events for all participants represented in the adverse-event counts. Event details are absent, and the small counts cannot establish the absence of safety risks or a reliable difference between arms.

Accordingly, the results are best read as descriptive observations from a completed pilot trial, not as a definitive evaluation of comparative efficacy or safety. They do not establish that either regimen does or does not work. The registry record leaves important questions about missing data, analysis populations, and statistical methods unanswered.

13. Why This Trial Matters Statistically

This trial illustrates why a randomized design and a posted numerical result are not, by themselves, enough to interpret a treatment comparison. Randomization is intended to support a fair contrast, but the registry record must also report how outcomes were analyzed and how uncertainty was quantified. Here, the primary endpoint summaries are available by arm, while a formal comparative estimate and its uncertainty are not reported.

The trial also highlights the distinction between a descriptive change and a treatment effect. A change score describes movement from baseline within an arm. To attribute a difference in changes to treatment, an analysis must compare the arms and account for uncertainty under a defined method. The registry does not report that comparison. This distinction is especially important in a pilot with small outcome counts, where observed summaries may be sensitive to individual participants.

Another statistical issue is transparency around the endpoint and its spread. The outcome is identified as a median with a standard deviation, but the registry does not explain how the dispersion was calculated. This does not invalidate the posted numbers, but it limits the precision with which readers can understand the distributional summaries. The absence of participant-level data and detailed analysis methods further restricts independent evaluation.

Finally, the record makes the difference between planning and inference relevant. A planning illustration based on an observed effect is not evidence of adequate power and is not a substitute for the trial’s original sample-size rationale. That rationale is not reported in the registry record. For clinical researchers, the case underscores the value of reporting prespecified analyses, confidence intervals, missing-data handling, participant flow, and clearly defined analysis populations alongside arm-level results.

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 primary limitations specific to interpretation of this trial are the small enrollment and the smaller arm-level counts reported for the primary endpoint. The registry records enrollment of 10, but the primary outcome summaries include 4 participants in the norethindrone acetate arm and 5 in the cabergoline arm. The registry record does not explain the difference or provide reasons for missing outcome values. This prevents an assessment of whether the endpoint summaries represent all randomized participants.

The registry does not report a formal comparison of the primary outcome, confidence intervals, p-values, or an adjusted estimate. It does not describe the statistical analysis plan, the analysis population, or the handling of missing data. The stated median summary is accompanied by standard deviations, but how those dispersion values were calculated is not explained. These gaps limit interpretation of both the result and its precision.

The secondary outcome, changes in pain interference scores, is listed without posted results. The registry does not report a multiplicity strategy or interim analyses. It also does not provide detailed participant characteristics, eligibility criteria, adherence information, or use of additional treatments. These omissions make it difficult to characterize the study population and understand factors that may have influenced the recorded outcomes.

For safety, the record gives counts but not event descriptions, severity details, timing, or assessments of treatment relatedness. Zero serious adverse events in the recorded groups is a descriptive observation, not evidence that serious events cannot occur. The small pilot and limited safety detail restrict conclusions about comparative safety.

Finally, although the record identifies the trial as randomized and quadruple-masked, it does not explain how allocation or masking was implemented. The registry does not report the sample-size justification or enough protocol detail to determine whether the posted outcomes and analyses correspond to a prespecified plan.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Dopamine Receptor Agonist Therapy for Pain Relief in Women Suffering From Endometriosis: A Pilot Study — NCT02542410.
• Registry record last updated 2020-02-05; status last verified 2020-01.
• Results first posted 2020-02-05.
• 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

NCT02542410 is a completed randomized, quadruple-masked, parallel phase 2 pilot study sponsored by Boston Children's Hospital. Enrollment was 10. The study compared cabergoline 0.5 mg PO twice weekly for 6 months with norethindrone acetate 5 mg PO daily for 6 months in young women with endometriosis-associated pain.

The primary outcome was change in worst pain score over the last month from baseline to 6 months on a 0-to-10 visual analog scale, with higher scores indicating worse pain. The registry posts a median change of -0.5 with a standard deviation of 1.5 for 4 participants in the norethindrone acetate arm, and -5.0 with a standard deviation of 2.5 for 5 participants in the cabergoline arm. A secondary pain-interference outcome is listed, but its results are not reported in the registry record.

The record reports no serious adverse events or deaths in either group and records other adverse events for 4 control participants and 5 experimental participants. It does not report a formal primary-outcome comparison, confidence intervals, p-values, missing-data methods, or analysis populations.