Investigation of Mifepristone (RU486) on Stress Sensitivity and Relapse Prevention in Cocaine Dependent Patients: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Investigation of Mifepristone (RU486) on Stress Sensitivity and Relapse Prevention in Cocaine Dependent Patients (NCT01134198), a randomized phase 2, phase 3 study. The primary outcome is Number of Participants With Relapse by Days 10 and 28.

2. Clinical Question

The trial asked whether mifepristone, a glucocorticoid antagonist, could affect stress sensitivity and relapse risk among treatment-seeking people with cocaine dependence. Its stated research focus included blocking central and peripheral glucocorticoid receptors. The primary outcome was narrower and more concrete: participants with documented cocaine use, counted at days 10 and 28.

The registry's primary outcome description treats documented use as relapse. The assessment was conducted during 8 weeks of trial, with the outcome reported for days 10 and 28. These are distinct assessment times, so a comparison at one time does not automatically answer the question at the other. The record does not report numerical relapse counts or a statistical comparison between the treatment groups. Consequently, the research question can be described, but the posted record does not establish how the groups differed on the primary outcome.

3. Trial Design

The registry classifies this as a randomized, triple-masked, parallel-group trial. Participants were assigned to mifepristone or placebo. The intervention descriptions identify mifepristone as a drug and specify Mifepristone 600mg; the comparator is listed as placebo. The record does not explain the randomization procedure, the masking roles, or how treatment assignment was concealed.

Enrollment is listed as 58. This is the total enrollment reported in the registry, not an indication of how many participants were assigned to each group or included in the primary outcome analysis. Group-specific primary outcome denominators are not reported. The outcome population is described as participants entering phase 2 of the trial, but the record does not provide a participant flow or explain how enrollment related to entry into that phase.

The trial is listed as phase 2 and phase 3. Its status is completed. The recorded start is 2010-05, and primary completion is listed as 2016-09. The sponsor is New York State Psychiatric Institute. These registry entries describe the trial's recorded design and timeline; they do not supply information about adherence, treatment duration, or the reasons participants may have left the trial.

The stated objective was to evaluate the impact of blocking glucocorticoid receptors on stress sensitivity and relapse risk. The primary outcome record concerns documented cocaine use, assessed through self-report and urine toxicology. No separate primary measure of stress sensitivity is described in the posted outcome information. The registry does not report the planned allocation ratio, a sample-size justification, or details of the statistical analysis plan.

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: 58 participants signed consent and were enrolled into the trial. Only 32 entered the randomized phase of the study with only 29 being assigned to one of the treatment arms.

Phase 1

Phase 2

Analysis population for the primary outcome, as defined in the registry: participants entering phase 2 of trial

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.

Population: demographics for 29 participants who were randomized and started Phase 1

6. Primary Endpoint

The registry lists the primary outcome as Number of Participants With Relapse by Days 10 and 28, measured over assessed during 8 weeks of trial, but reported for days 10 and 28 of trial.

The primary outcome is titled Number of Participants With Relapse by Days 10 and 28. It counts participants with documented cocaine use, rather than measuring the amount or frequency of use. Documentation was based on self-reported use and urine toxicology; a participant with documented use was considered to have relapsed. The recorded population is participants entering phase 2.

The outcome was assessed during 8 weeks of trial but reported at days 10 and 28. These time points can describe relapse status at different stages of follow-up. Interpreting either requires knowing the number assessed at that time, the number meeting the relapse definition, and how missing assessments were handled. Those outcome counts and handling details are not reported in the registry record.

A binary event count is useful because it gives a clinically interpretable summary of how many participants met a prespecified event definition. However, a count alone does not show how uncertain a group comparison is, and counts at separate time points should not be treated as interchangeable. The posted record identifies the measure but does not report the group-specific results or an inferential comparison. It therefore supports describing what was intended to be measured, but not drawing a conclusion about the relative relapse outcomes.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry gives design labels and an outcome definition, but does not report the statistical analysis used for relapse. The points below explain the general statistical concepts relevant to interpreting this kind of endpoint; they do not describe an analysis plan that is absent from the registry record.

What does a binary outcome count?

A binary outcome classifies each participant according to whether an event occurred under a defined rule. Here, the event is documented cocaine use, which the registry says was treated as relapse. A count of participants with the event is meaningful alongside the number of participants assessed. The count alone cannot tell whether event occurrence was common or uncommon in that group, because the denominator is also needed. For this trial, the primary outcome denominators and event counts are not reported.

Self-report and urine toxicology are two sources used to document cocaine use, according to the outcome description. The record does not specify how disagreements between those sources were resolved, what testing schedule was used, or how an unavailable test or self-report was classified. Such operational details can affect which observations meet an event definition. They are not reported in the registry record.

How should time-specific outcomes be understood?

Relapse status at days 10 and 28 represents outcomes at separate points in follow-up. A participant's status can be assessed at one time without the record establishing the status at another. A time-specific count is not automatically a time-to-event analysis: the registry describes counts at the stated days and does not report an event-time analysis. A time-to-event method would use information about when events occurred and how long participants were observed, but whether that approach was used is not reported.

When a study assesses an outcome at multiple times, the analysis needs to define which comparison is primary and how the results are to be interpreted together. If several comparisons are treated as confirmatory, the chance of a false-positive finding can increase unless the analysis accounts for multiple testing. This is a general statistical concern, not a statement about what happened in this trial. The registry does not report a multiplicity strategy or identify a single primary comparison among the reported days.

What does a group comparison require?

A comparison of event counts usually considers the event frequency in each randomized group, with the number assessed in each group defining the denominator. An effect estimate can express the contrast between groups, and an uncertainty interval can show the range of values reasonably compatible with the data under the model. A confidence interval is a general statistical tool for communicating uncertainty around an estimate; it does not guarantee that the true effect lies within a particular interval. No effect estimate or confidence interval for relapse is reported in the registry record.

A p-value, when reported, describes how incompatible the observed data are with a specified null model under the assumptions of the analysis. It is not the probability that the null hypothesis is true, and it does not measure clinical importance. A p-value cannot replace the effect estimate or its uncertainty. The registry does not report a p-value or identify a statistical model for the primary endpoint.

Why do analysis populations matter?

The registry names participants entering phase 2 as the primary outcome population. It does not specify whether participants were analyzed according to randomized assignment, whether any eligibility or treatment exposure conditions applied, or how departures from the intended treatment were treated analytically. These distinctions can affect interpretation. The participant flow and analysis population details are not reported in the registry record.

Missing outcome data also matter. If participants without assessments differ in their relapse risk from those with observed results, analyses limited to observed outcomes may not represent the full population. Statistical methods can make different assumptions about missing outcomes, but those assumptions should be described and examined. The registry does not report the amount of missing primary outcome data or its handling.

The record includes a planning-illustration description based on an observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. It does not include the resulting planning values in the registry record for interpretation. Such sample-size illustrations are not observed trial results or observed power, and they cannot fill the gap left by unreported primary outcome counts. The trial's own sample-size justification is not reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The primary outcome is reported at days 10 and 28. Assessing an outcome at multiple times raises a question about which time-specific comparison is intended to carry the primary inferential claim and whether any adjustment or other strategy was planned. The registry does not report a multiplicity approach or explain how results across the assessment times were to be interpreted together. Because the primary outcome counts and analyses are not listed, the record also does not show whether any planned comparisons were actually performed.

Missing-data information is similarly limited. The registry does not report the number of participants with an available relapse assessment at either time, the number missing, reasons for missingness, or how missing observations were treated. It does not state whether participants with no documented use but no usable assessment were treated as having no event, excluded, or handled through another method. No such assumption should be inferred from the endpoint definition alone.

The described outcome population is participants entering phase 2, but the registry does not report the number entering that phase or how that population relates to the randomized enrollment. It also does not identify a primary analysis population rule, such as whether analysis followed randomized assignment. The analysis populations and the handling of departures from assigned treatment are not reported in the registry record.

These omissions limit interpretation independently of whether results might exist elsewhere. Without a defined comparison, complete denominators, and an account of missing observations, a reader cannot assess how robust an apparent result would be to analysis choices. The registry record does not report an interim-analysis plan or the statistical plan for multiplicity and missing data.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

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 lists serious adverse events separately from other adverse events. In the mifepristone group, 0 serious adverse events are recorded among 16 participants at risk; in the placebo group, 0 are recorded among 13 participants at risk. For other adverse events, the record lists 13 among 16 at risk in the mifepristone group and 5 among 13 at risk in the placebo group.

These figures are counts with group-specific denominators. They describe what the registry records, rather than establishing whether a treatment caused an event. The record does not list the specific terms for the other adverse events in this entry, so their nature and severity cannot be characterized from these figures alone. A zero recorded serious-event count does not establish that an event was impossible or that no unrecorded event occurred.

The deaths field has no reported count. It should not be read as a stated zero. The registry record also does not provide a statistical comparison of adverse-event groups, a description of how events were collected, or an assessment of whether events were considered treatment-related. These safety counts should therefore be read as descriptive registry entries, not as a complete comparative safety analysis.

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

The registry record establishes that a randomized, triple-masked trial compared mifepristone with placebo and defined relapse as documented cocaine use. It identifies self-report and urine toxicology as the basis for documenting use, names participants entering phase 2 as the outcome population, and specifies assessment at days 10 and 28 during 8 weeks of trial. These details explain what the primary outcome was intended to capture.

However, the record does not report the relapse counts, the denominators assessed at either time, or a statistical comparison. As a result, it does not show whether the groups had similar or different relapse outcomes. It does not establish the size or direction of any treatment-group difference, nor the precision of an estimate. The registry's completed status does not provide those missing outcome data.

The record also cannot answer whether the groups differed in stress sensitivity: the available primary outcome description is about documented cocaine use, and no stress-sensitivity results are reported in the posted information. It does not establish how missing assessments were handled, whether the outcome analyses followed randomized assignment, or whether results from the assessment times were adjusted for multiplicity.

The adverse-event counts offer limited descriptive information: no serious adverse events are listed in either group, while other adverse events are recorded in both groups. Those entries do not establish causality or provide a complete account of event types, and the deaths field does not report a count. Without the primary relapse results and analysis details, the registry supports a description of the trial question and recorded safety counts, not a conclusion about treatment benefit, lack of benefit, or comparative safety.

13. Why This Trial Matters Statistically

This trial is statistically notable because the registry connects a biological research question—blocking central and peripheral glucocorticoid receptors—with an observable behavioral outcome: documented cocaine use. The endpoint description makes the event definition explicit and identifies self-report and urine toxicology as its evidence sources. Clear event definitions are essential for interpreting a binary outcome count.

The record also illustrates why a trial design and its results are different kinds of information. Randomization, masking, parallel groups, and enrollment describe how the study was organized. They do not reveal the observed relapse pattern. Without group-specific event counts and denominators, the primary treatment comparison cannot be reconstructed or judged for precision.

Multiple assessment times bring an additional interpretive issue. Results at days 10 and 28 could convey different aspects of follow-up, and an analysis needs to clarify how those results relate to the primary question. The registry does not report that analytic choice or a strategy for multiplicity. This makes it impossible to assess how an inferential claim would have been defined.

The record is also a reminder that safety counts require context. Serious and other adverse events are listed with denominators, but event descriptions, collection details, and comparative analyses are not reported. The available counts are informative as registry entries while remaining insufficient to characterize causation or the broader safety profile.

For clinical researchers and biostatisticians, the central lesson is that a named endpoint and a completed trial do not by themselves support statistical conclusions. Interpretable results require outcome counts, denominators, a defined analysis population, and uncertainty estimates or other analysis details. Those elements are not reported for the primary relapse outcome in this registry record.

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 main limitation for interpreting this specific trial record is the absence of numerical primary outcome results. Although relapse is defined and assessment times are identified, the record does not report event counts or denominators for either group. Without these, neither a descriptive comparison nor an estimate of its uncertainty is possible.

The endpoint is listed at days 10 and 28, but the record does not identify which time point was the principal inferential target or how findings at the different times were to be integrated. It also does not report the statistical method, multiplicity handling, confidence intervals, p-values, or analysis estimates. These omissions prevent assessment of the planned and performed inferential approach.

The registry names participants entering phase 2 as the outcome population, but does not report how many entered, how that group relates to total enrollment, or how many contributed data at each assessment. Participant flow, analysis population definitions, adherence, treatment exposure, and missing-outcome handling are not reported. The record also does not explain how self-report and urine toxicology were combined if their findings differed.

Safety information is limited to serious-event and other-event counts with at-risk denominators. Specific other-event terms, event collection details, treatment attribution, and a comparative safety analysis are not reported. The deaths field does not contain a reported count. Finally, the registry does not report the trial's own sample-size justification or statistical plan. These limitations concern what can be concluded from the registry record and do not establish that additional information was not collected.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Investigation of Mifepristone (RU486) on Stress Sensitivity and Relapse Prevention in Cocaine Dependent Patients — NCT01134198.
• Registry record last updated 2018-12-20; status last verified 2018-11.
• Results first posted 2018-08-24.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

18. Record Summary

The registry lists NCT01134198 as a completed randomized, triple-masked, parallel trial in cocaine dependence, with phase 2 and phase 3 designations and enrollment of 58. The intervention was Mifepristone 600mg, compared with placebo. The recorded start is 2010-05, primary completion is 2016-09, and the sponsor is New York State Psychiatric Institute.

The primary outcome was the number of participants with relapse, defined as documented cocaine use based on self-reported use and urine toxicology. The outcome was assessed during 8 weeks of trial and reported for days 10 and 28 among participants entering phase 2. Primary outcome counts and analyses are not reported in the registry record.

Safety entries list no serious adverse events among 16 at risk in the mifepristone group or 13 at risk in the placebo group. Other adverse events are listed for 13 of 16 and 5 of 13, respectively. A deaths count is not reported.