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 Pembrolizumab and Enobosarm in Treating Patients With Androgen Receptor Positive Metastatic Triple Negative Breast Cancer (NCT02971761), a na phase 2 study. The primary outcome is Response Rate (Complete Response or Partial Response).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02971761 |
| Phase | Phase 2 |
| Condition | Androgen Receptor Positive, Estrogen Receptor Negative, HER2/Neu Negative |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 18 |
| Arms in the primary outcome | n/a |
| Lead sponsor | City of Hope Medical Center |
| Results posted | Yes |
2. Clinical Question
Population
The trial enrolled patients with androgen receptor positive metastatic triple-negative breast cancer. The registry also lists estrogen receptor negative, HER2/Neu negative, and progesterone receptor negative disease, as well as stage IV breast cancer. The total enrollment was 18. These features define a specific clinical population; the record does not establish that the enrolled participants represent all people with triple-negative breast cancer or all people with metastatic disease.
Intervention
The intervention was the combination of pembrolizumab and enobosarm, also identified in the official title as the selective androgen receptor modulator GTX-024. Pembrolizumab was given intravenously on day 1, and enobosarm was taken orally once daily on days 1–21. Courses repeated every 21 days, for up to 35 cycles, unless disease progression or unacceptable toxicity occurred. Laboratory biomarker analysis is also listed as an intervention.
Comparator
No comparator arm is recorded. The study is described as a single-group trial, with allocation listed as NA and masking listed as none. The registry’s brief summary raises pembrolizumab alone as a possible point of comparison in its rationale, but the recorded design does not include a pembrolizumab-alone group. Consequently, the trial does not provide a direct randomized comparison between the combination and pembrolizumab alone.
Primary question
The primary endpoint is the number of participants with a complete or partial response, assessed using Response Evaluation Criteria in Solid Tumors version 1.1. The stated timeframe is up to 36 months. This endpoint describes tumor response under the study’s assessment criteria. The response count and an analysis of that endpoint are not reported in the registry record, so the registry information does not establish the observed response result or its precision.
3. Trial Design
This is a phase II, completed, single-group study sponsored by City of Hope Medical Center. The registry records enrollment of 18 participants. It lists allocation as NA, no masking, and a single-group model. There is therefore no concurrent control group in the recorded design. The trial evaluates the combination of pembrolizumab and enobosarm in patients with androgen receptor positive metastatic triple-negative breast cancer.
Participants received pembrolizumab intravenously over 30 minutes on day 1 and enobosarm by mouth once daily on days 1–21. Courses repeated every 21 days for up to 35 cycles in the absence of disease progression or unacceptable toxicity. This describes the regimen recorded in the registry; details about adherence, dose modifications, treatment discontinuation, or actual exposure are not reported in the registry record.
The primary outcome is response rate, defined by complete response or partial response using Response Evaluation Criteria in Solid Tumors version 1.1, with a timeframe of up to 36 months. Secondary outcomes include progression-free survival, clinical benefit rate, and overall survival; progression-free survival is listed twice. The registry records five outcome measures but no analyses. It does not report the primary response result or the methods used to analyze secondary outcomes.
The trial status is completed. Its single-group design can describe outcomes observed among participants receiving the combination, but it cannot isolate the effect of the combination from other explanations using a randomized control comparison. The registry does not report a sample-size justification or a detailed 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: Study was conducted from June 1, 2017 to October 28, 2019.
Overall Study
| Stage | Treatment (Pembrolizumab, Enobosarm) |
|---|---|
| STARTED | 18 |
| COMPLETED | 16 |
| NOT COMPLETED | 2 |
Reasons for not completing this period:
| Reason | Treatment (Pembrolizumab, Enobosarm) |
|---|---|
| GTx-024 drug supply was withdrawn | 2 |
5. Baseline Characteristics
The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.
| Characteristic | Unit | Treatment (Pembrolizumab, Enobosarm) |
|---|---|---|
| Participants analysed | 16 | |
| Age, Continuous | years | 64 (36 to 81) |
| Sex: Female, Male: Female | Participants | 16 |
| Sex: Female, Male: Male | Participants | 0 |
| Race/Ethnicity, Customized: non-Hispanic White | Participants | 8 |
| Race/Ethnicity, Customized: Hispanic | Participants | 5 |
| Race/Ethnicity, Customized: Asian | Participants | 2 |
| Race/Ethnicity, Customized: African American | Participants | 1 |
| Region of Enrollment: United States | participants | 16 |
| Number of previous lines of therapy: Received 0-1 previous lines of therapy | Participants | 9 |
| Number of previous lines of therapy: Received >=2 previous lines of therapy | Participants | 7 |
| Performance Status (ECOG): ECOG stage 0 | Participants | 7 |
| Performance Status (ECOG): ECOG stage 1 | Participants | 9 |
| Nottingham Histological grade: Grade 1 | Participants | 2 |
| Nottingham Histological grade: Grade 2 | Participants | 5 |
| Nottingham Histological grade: Grade 3 | Participants | 9 |
| Initial tumor stage: Stage I | Participants | 6 |
| Initial tumor stage: Stage II | Participants | 8 |
| Initial tumor stage: Stage III | Participants | 2 |
| Prior surgery: Lumpectomy | Participants | 7 |
| Prior surgery: Mastectomy | Participants | 9 |
| Prior radiation: Yes, received prior radiation | Participants | 15 |
| Prior radiation: No | Participants | 1 |
6. Primary Endpoint
The registry lists the primary outcome as Response Rate (Complete Response or Partial Response), measured over Up to 36 months.
| Element | Registry entry |
|---|---|
| Result type | Count Of Participants |
| Measure of spread | not applicable |
| Unit | Participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint counts participants who achieve either a complete response or a partial response, according to Response Evaluation Criteria in Solid Tumors version 1.1. A complete response and a partial response are distinct categories of tumor response under that assessment framework; the registry groups them for the primary response endpoint. The recorded timeframe is up to 36 months.
As a binary outcome, each participant is classified according to whether the endpoint event occurred. A response count can describe how many enrolled participants met the response criteria during the specified follow-up. When paired with an appropriate denominator and analysis, it can also support an estimate of the proportion meeting those criteria. The registry record does not report the response count or an estimated response proportion, so neither can be characterized from the available result fields.
Response is used in oncology trials because it captures a defined change in disease status under prespecified assessment criteria. It is not the same as progression-free survival or overall survival: those outcomes concern time-related events, whereas the primary endpoint is a response classification. The registry does not report details of scan timing, confirmation requirements, or handling of unevaluable participants beyond the stated endpoint description.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The central interpretive limitation is that the primary response result is not reported in the registry record. The endpoint definition and timeframe are available, but the number of participants with complete or partial response, the denominator used in the endpoint analysis, and an estimate of uncertainty are not. As a result, the registry information does not establish the observed response frequency or how precisely it was estimated.
The design is single-group and unmasked. Participants received pembrolizumab with enobosarm, and no concurrent comparator is recorded. Any outcome observed in this group would describe experience under the regimen and trial conditions. Without a comparator, the registry record cannot show how those outcomes compare with pembrolizumab alone or another treatment, and it cannot separate the contribution of each drug from the contribution of the combination. The brief summary’s comparison with pembrolizumab alone is part of the study rationale, not a recorded treatment arm.
Enrollment was 18. A study of this size can yield imprecise estimates, particularly for outcomes that occur in only some participants. Precision depends on the actual outcome count and analysis; because the response result is absent, the degree of uncertainty for the primary endpoint cannot be assessed from this record. No confidence interval for the response endpoint is reported in the registry record.
The safety record lists 4 participants affected by serious adverse events among 18 at risk, and 18 affected by other adverse events among 18 at risk. It also records 8 deaths. These are descriptive counts in a single treatment group. The registry information does not establish whether any individual event or death was caused by treatment, nor does it provide a comparative estimate of risk. The serious event terms listed include heart failure, hyponatremia, flank pain, adult respiratory distress syndrome, and dyspnea, each with a reported value of 5.6%.
Secondary outcomes include progression-free survival, clinical benefit rate, and overall survival, but their analysis results are not reported in the registry record. The record also does not provide the timing or completeness of follow-up, the handling of missing outcome assessments, or the analysis population. Interpretation should therefore remain limited to the recorded design, endpoint definitions, and descriptive safety counts, rather than claims about comparative effects.
9. Statistical Methods Explained
What does the response count represent?
The primary outcome is a binary participant-level endpoint: a participant either meets the complete-or-partial-response definition or does not. The endpoint uses Response Evaluation Criteria in Solid Tumors version 1.1 and has a timeframe of up to 36 months. A count is a direct description of the number classified as having the event. An estimated response proportion would relate that count to a defined analysis denominator. Neither the response count nor its denominator is reported in the registry record.
For a binary outcome, a confidence interval describes uncertainty around an estimated proportion under the statistical method used. It is not a range of individual participant outcomes, and it does not account automatically for every source of bias. The registry record does not provide a confidence interval or state which method, if any, was used for the primary endpoint analysis. General statistical interpretation therefore cannot substitute for an unreported result.
Why does the single-group design matter?
A single-group study observes outcomes in participants who receive the study regimen, without a concurrent control arm. It can describe the experience of that group, but it does not directly estimate a treatment contrast against another arm. Differences between outcomes in this trial and outcomes reported elsewhere would not constitute a randomized comparison; populations, follow-up, assessment, and other conditions could differ. In this trial, the registry lists allocation as NA and the model as single group. Its summary mentions pembrolizumab alone as a rationale for considering the combination, but no pembrolizumab-alone arm is recorded.
The study is unmasked. In general, lack of masking can matter when decisions about assessment, follow-up, or event classification could be influenced by knowledge of treatment. The registry record does not describe additional safeguards or outcome adjudication procedures, so their use is not reported in the registry record.
What can a planning illustration tell readers?
Planning sample-size illustrations are not results from participants and are not observed power. The stated assumptions for the planning illustration are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect expressed as a fraction of the observed effect. These assumptions describe the illustration, not the actual design of this single-group trial. In particular, equal allocation between two arms does not describe the recorded enrollment structure.
An illustration based on an observed effect is conditional on that effect and the assumptions used. The observed primary response effect is not reported in the registry record, so its magnitude cannot be evaluated from the registry information. Planning estimates should be read as hypothetical design calculations, not as evidence that the trial had a particular probability of detecting an effect, and not as evidence that an effect was present.
Why do analysis choices matter?
For a binary endpoint, the analysis needs to define which participants are included in the denominator and how missing or unevaluable assessments are treated. Different choices can change the estimated response proportion. A prespecified analysis plan would ordinarily explain the analysis population, response assessment rules, and uncertainty estimation. Those details are not reported in the registry record. The record lists no analyses, so no sponsor-reported inferential result is available for the primary outcome.
Over-dispersion is a general concern when observed variability exceeds what a simple statistical model expects. It is relevant when the chosen model assumes a particular level of variability, but the registry does not report a model for the response endpoint or information that would establish over-dispersion. This concept should not be taken as a finding about this trial.
For time-to-event outcomes such as progression-free survival and overall survival, analysis typically depends on event timing and censoring, where follow-up may end before an event is observed. The registry lists these outcomes but does not report event counts, follow-up distributions, censoring rules, or analyses. Any interpretation of their estimates or precision is therefore unavailable from the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists several secondary outcomes, including progression-free survival, clinical benefit rate, and overall survival; progression-free survival appears twice. When a study examines multiple outcomes or multiple comparisons, the chance of at least one apparently notable result can increase. Statistical plans may address this issue by defining a primary outcome, specifying a testing order, or adjusting inference. The registry record does not report a multiplicity strategy or a detailed statistical analysis plan.
The primary endpoint is identified as response rate, which distinguishes it from the secondary outcomes. However, no primary endpoint analysis is recorded, and no secondary outcome analyses are listed. It is therefore not possible to determine whether formal hypothesis tests were conducted, how any testing was organized, or whether conclusions were adjusted for multiple outcomes. The absence of reported analyses is not evidence that a particular method was or was not used outside the registry record.
Missing data handling is also not reported in the registry record. The endpoint description does not specify how participants without an evaluable response assessment were classified, whether follow-up assessments were incomplete, or how missing measurements were treated. For a participant-count endpoint, these choices matter because the analysis denominator and outcome classification affect interpretation.
The analysis populations are not described. The registry does not identify whether the primary endpoint was analyzed among all enrolled participants, those who started treatment, or another defined group. Interim analyses and sample-size justification are not reported in the registry record. Without these details, readers cannot reconstruct the planned inferential framework or determine whether the posted information represents all analyses intended by the trial plan.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Treatment (Pembrolizumab, Enobosarm) | 4 | 18 | 22.2% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Treatment (Pembrolizumab, Enobosarm) | 8 of 18 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Treatment (Pembrolizumab, Enobosarm) | 18 of 18 |
Most frequent serious adverse event terms
| Event term | Organ system | Treatment (Pembrolizumab, Enobosarm) |
|---|---|---|
| 10019279-Heart failure | Cardiac disorders | 1 of 18 |
| 10021038-Hyponatremia | Metabolism and nutrition disorders | 1 of 18 |
| 10016750-Flank pain | Musculoskeletal and connective tissue disorders | 1 of 18 |
| 10001409-Adult respiratory distress syndrome | Respiratory, thoracic and mediastinal disorders | 1 of 18 |
| 10013963-Dyspnea | Respiratory, thoracic and mediastinal disorders | 1 of 18 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Treatment (Pembrolizumab, Enobosarm) |
|---|---|---|
| 10016256-Fatigue | General disorders | 13 of 18 |
| 10020772-Hypertension | Vascular disorders | 12 of 18 |
| 10019211-Headache | Nervous system disorders | 9 of 18 |
| 10012727-Diarrhea | Gastrointestinal disorders | 8 of 18 |
| 10013963-Dyspnea | Respiratory, thoracic and mediastinal disorders | 7 of 18 |
| 10028813-Nausea | Gastrointestinal disorders | 6 of 18 |
| 10047700-Vomiting | Gastrointestinal disorders | 6 of 18 |
| 10003988-Back pain | Musculoskeletal and connective tissue disorders | 6 of 18 |
| progressive disease | Neoplasms benign, malignant and unspecified (incl cysts and polyps) | 6 of 18 |
| 10002272-Anemia | Blood and lymphatic system disorders | 5 of 18 |
Serious events with the highest arm-level rate: 10019279-heart failure (5.6%), 10021038-hyponatremia (5.6%), 10016750-flank pain (5.6%), 10001409-adult respiratory distress syndrome (5.6%), 10013963-dyspnea (5.6%).
The registry records 4 participants affected by serious adverse events among 18 at risk in the treatment group. It also records 18 participants affected by other adverse events among 18 at risk, and 8 deaths. These figures are counts, not comparative risk estimates. No control group is recorded, so the counts do not provide a comparison with an untreated group or another regimen.
The listed serious adverse event terms are heart failure, hyponatremia, flank pain, adult respiratory distress syndrome, and dyspnea. Each term is accompanied by a reported value of 5.6%. These entries describe events recorded in the registry; they do not by themselves establish that the events were caused by either study drug. The record does not provide event timing, duration, severity grading beyond the serious-event classification, or participant-level overlap among event terms.
Deaths are recorded as a count of 8. The registry information does not state that these deaths were treatment-related, and the count should not be interpreted as a causal attribution. More detailed context about causes, timing, and follow-up is not reported in the registry record. Safety interpretation is consequently descriptive and limited to the recorded counts and terms.
12. What the Result Does, and Does Not, Mean
The registry describes a completed phase II study of pembrolizumab and enobosarm in an enrolled group of 18 patients with androgen receptor positive metastatic triple-negative breast cancer. It specifies a single-group, unmasked design and defines response as complete or partial response under Response Evaluation Criteria in Solid Tumors version 1.1, with assessment up to 36 months. It also records adverse-event counts and several secondary outcomes.
The registry record does not report the primary response count, a response estimate, or an uncertainty interval. It therefore does not support a conclusion about the observed response frequency or its precision. The outcome definition is not itself an outcome result. The secondary outcome names likewise do not establish what was observed for progression-free survival, clinical benefit rate, or overall survival.
The study has no recorded comparator arm. Its data cannot directly determine how the combination compares with pembrolizumab alone, despite that comparison appearing in the study rationale. Without randomization to a concurrent comparison group, outcomes in the treatment group cannot establish the effect attributable specifically to the combination.
The serious adverse event and other adverse event counts describe what the registry records in the treated group. They do not prove that the regimen caused those events, and they do not quantify a comparative safety difference. The count of deaths also requires context that is not reported in the registry record.
In general, a clinical trial result is interpreted through its endpoint definition, study design, analysis population, missing-data handling, and uncertainty. Several of those elements are not reported. The appropriate reading is therefore limited: the record establishes how the study was designed and what safety counts were posted, while the central efficacy result and much of the inferential detail remain unavailable.
13. Why This Trial Matters Statistically
This trial is statistically informative as an example of the distinction between a study question and a design capable of answering a comparative question. The rationale mentions whether the combination might outperform pembrolizumab alone, but the recorded study has one treatment group and no comparator. A single-group study can characterize outcomes in its participants; it cannot provide the same direct comparative evidence as a randomized trial with a control arm.
The endpoint is clearly named as a participant count for complete or partial response, with an assessment framework and timeframe. Yet the response result is not reported in the registry record. This illustrates why endpoint definitions and outcome estimates must be considered separately: a well-defined measure does not convey the magnitude or precision of an observed result.
The enrollment of 18 also makes transparent reporting of counts, denominators, and uncertainty especially important. A count without a clearly stated analysis denominator or confidence interval leaves readers unable to judge precision. The registry does not report those primary response details, nor does it describe the analysis population or handling of missing assessments.
The safety entries illustrate another statistical distinction: observed event counts are descriptive, whereas causal attribution and comparative risk require additional design and analysis information. With no comparator recorded, the posted counts cannot distinguish treatment effects from other causes of events. Overall, the record underscores how design, complete outcome reporting, and explicit analysis methods jointly shape what can be concluded from a clinical trial.
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 interpretation is the absence of a reported primary response result. The registry provides the endpoint definition and timeframe but not the number of participants with complete or partial response, the analysis denominator, or an uncertainty estimate. The response outcome therefore cannot be quantified from the registry record.
The single-group design and lack of masking limit comparative interpretation. No control arm is recorded, and the registry does not provide a direct comparison with pembrolizumab alone. The design cannot establish the comparative effect of the combination from outcomes in the treatment group alone.
Enrollment was 18, and the record does not report a sample-size justification. It also does not provide a detailed analysis plan, analysis population, missing-data approach, or multiplicity strategy. Interim analyses are not reported in the registry record. These gaps prevent reconstruction of the intended inferential approach and make it difficult to assess how outcomes would have been analyzed under incomplete follow-up or unevaluable response assessments.
The registry lists 8 deaths and adverse-event counts, but does not provide the context needed to determine timing, cause, or treatment attribution. It also does not report detailed follow-up or participant-level overlap among event categories. The secondary outcomes are listed without analysis results. These limitations are specific to the information recorded for this trial and constrain conclusions about both efficacy and safety.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Pembrolizumab and Enobosarm in Treating Patients With Androgen Receptor Positive Metastatic Triple Negative Breast Cancer — NCT02971761.
- Registry record last updated 2024-02-20; status last verified 2024-02.
- Results first posted 2022-06-10.
- Data retrieved from ClinicalTrials.gov on 2026-11-09.
- Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.
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18. Record Summary
This completed phase II trial, sponsored by City of Hope Medical Center, enrolled 18 patients with androgen receptor positive metastatic triple-negative breast cancer. It used a single-group, unmasked design of pembrolizumab plus enobosarm. Pembrolizumab was administered intravenously on day 1 and enobosarm orally on days 1–21, with courses repeating every 21 days for up to 35 cycles.
The primary endpoint was the count of participants with complete or partial response under Response Evaluation Criteria in Solid Tumors version 1.1, assessed up to 36 months. The primary response result and analysis are not reported in the registry record. The record lists serious adverse events affecting 4 participants, other adverse events affecting 18 participants, and 8 deaths; it does not establish treatment causality. No comparator arm or detailed analysis plan is recorded.