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 GTx-758 on Serum Prostate-specific Antigen (PSA) in Men With Castrate Resistant Prostate Cancer (NCT01420861), a na phase 2 study. The primary outcome is Decline in Serum PSA.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01420861 |
| Phase | Phase 2 |
| Condition | Prostate Cancer |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | Double |
| Enrollment | 18 |
| Arms in the primary outcome | n/a |
| Lead sponsor | GTx |
| Results posted | Yes |
2. Clinical Question
Population
Men with castration-resistant prostate cancer who were maintained on androgen deprivation therapy. The registry identifies the primary-outcome population as treated patients. It records 18 participants enrolled, but does not report the number included in an analysis of the PSA outcome.
Intervention
The intervention was GTx-758. The arm is named 1000 mg GTx-758 BID, while its description says subjects would receive daily doses of 1000 mg GTx-758. Because those descriptions do not fully align, the dosing schedule cannot be resolved from the registry record alone.
Comparator
No comparator arm is described. The study model is single group and allocation is listed as NA. It therefore does not provide a like-for-like comparison between GTx-758 and a control group. Changes in PSA, if reported, would need to be interpreted within that single-group design.
Primary question
The registered primary outcome asks whether treated patients had a decline in serum PSA over 30 days. PSA response and PSA progression are mentioned in the study purpose, but the registry lists one outcome measure, titled Decline in Serum PSA. The record does not report an outcome result or an analysis estimate, so it does not establish how many participants had a decline or how precisely that outcome was measured.
3. Trial Design
This was a Phase 2, single-group study of GTx-758 in men with castration-resistant prostate cancer who remained on androgen deprivation therapy. The registry records enrollment of 18 and identifies GTx as the sponsor. The study started in 2011-09, had a primary completion date of 2012-12, and is listed as terminated. The reason for termination is not reported in the registry record.
The arm is titled 1000 mg GTx-758 BID. Its description says subjects would receive daily doses of 1000 mg GTx-758. BID ordinarily denotes twice daily, so the arm title and description leave the dosing schedule unclear; the registry record does not reconcile them. The official title calls the study open label, whereas the structured masking field says double. These descriptions are inconsistent, and the registry record does not explain how masking was implemented.
Allocation is listed as NA, and the model is single group. There is no control arm to support a randomized treatment comparison. The study's stated purpose concerns serum PSA response and progression, while the registered primary outcome is decline in serum PSA among treated patients over 30 days. The record lists one outcome measure and no analyses. It does not report a protocol, eligibility details beyond the stated population, the reason for termination, or the statistical analysis plan. The design information therefore supports a description of the study structure, but not a reconstruction of how the investigators planned or conducted all analyses.
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
| Stage | 1000 mg GTx-758 BID |
|---|---|
| STARTED | 18 |
| Randomized | 11 |
| Treated | 9 |
| COMPLETED | 0 |
| NOT COMPLETED | 18 |
Reasons for not completing this period:
| Reason | 1000 mg GTx-758 BID |
|---|---|
| Adverse Event | 2 |
| Study terminated by Sponsor | 7 |
| Screen failure | 7 |
| Randomized not Treated | 2 |
Analysis population for the primary outcome, as defined in the registry: Treated Patients
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 | 1000 mg GTx-758 BID |
|---|---|---|
| Participants analysed | 9 | |
| Age, Continuous | years | 73.3 (SD 10.6) |
| Sex/Gender, Customized: Male | Participants | 9 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 1 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 8 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 0 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 |
| Race (NIH/OMB): Asian | Participants | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 |
| Race (NIH/OMB): Black or African American | Participants | 1 |
| Race (NIH/OMB): White | Participants | 8 |
| Race (NIH/OMB): More than one race | Participants | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 |
6. Primary Endpoint
The registry lists the primary outcome as Decline in Serum PSA, measured over 30 days.
| Element | Registry entry |
|---|---|
| Result type | Count Of Participants |
| Measure of spread | not applicable |
| Unit | Participants |
| Endpoint classification | Binary Endpoint |
The primary outcome is titled Decline in Serum PSA. It is recorded as a count of participants, with the unit Participants, and the population is treated patients. The timeframe is 30 days. This makes the intended outcome a binary event for each participant: whether a decline was recorded or not. The registry record does not define the threshold or rules used to classify a decline, and it does not state whether the measure was based on a particular percentage change, absolute change, or other criterion.
In general, a PSA response measure can translate a laboratory measurement into a clinically interpretable event category. A count of participants with the event can be easier to describe than a series of individual laboratory values. However, converting a continuous measurement into a binary outcome discards information about the size and timing of individual changes. A definition of the decline and a clear analysis population are needed to interpret such a count.
The study purpose also mentions PSA progression, but the registry lists Decline in Serum PSA as its one outcome measure. No result for that outcome is reported in the registry record. Thus the endpoint label and intended time window are available, but the event definition, observed count, and uncertainty around that count are not.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry describes a single-group Phase 2 study with 18 participants enrolled and a primary outcome of decline in serum PSA over 30 days among treated patients. It does not report the outcome result or an analysis for that outcome. Consequently, there is no posted estimate of the number of participants with a decline, no uncertainty interval, and no statistical test to interpret. The record also does not report a result for PSA progression, despite mentioning progression in the study purpose.
This absence matters: an endpoint description is not an endpoint result. A reader cannot determine from the registry record how often a decline occurred, how large any PSA changes were, or how consistent the changes were among participants. The record also does not state the rule used to define decline. Without that rule and the analysis population, even a reported event count would need careful qualification.
The single-group design further limits what any within-study outcome could establish. In general, observations in one group can describe what happened during follow-up, but without a concurrent control they do not isolate the effect of the intervention from other explanations. This is a design limitation, not a judgment about the direction or size of an unreported outcome. There is no randomized comparison in this record, and the registry explicitly cautions that the arms are not a like-for-like control comparison.
The sample-size material is described as a planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. Those assumptions describe an illustrative planning calculation, not the design of this single-group study or an analysis of observed power. The registry record does not report the study's own sample-size justification or provide the effect estimate needed to assess those illustrations. No inference about statistical power or efficacy can be drawn from the enrollment count alone.
There are also inconsistencies in how the intervention and masking are described. The arm title says 1000 mg GTx-758 BID, while the arm description says daily doses of 1000 mg. The official title calls the study open label, while the masking field says double. The registry record does not resolve either discrepancy. These issues do not supply missing outcome evidence, but they limit the precision with which the intervention and study conduct can be characterized.
9. Statistical Methods Explained
What kind of outcome is registered?
The primary outcome is a participant count for Decline in Serum PSA, with treated patients as the population and 30 days as the timeframe. In general, a binary outcome classifies each participant according to whether an event occurred. A count of events needs a clear denominator: readers need to know which participants were eligible for the analysis, how many had outcome data, and how missing observations were handled. Those details are not reported in the registry record for this endpoint.
A binary outcome can provide a concise summary, but it does not describe the amount of change in PSA or the pattern of measurements over time. A prespecified event definition is important because different thresholds or assessment rules can classify the same underlying measurements differently. The registry record does not report the decline threshold, measurement schedule, or classification rules. It lists the outcome name and timeframe, but not an operational definition.
What would an estimate and confidence interval tell a reader?
In general, an estimate summarizes the observed data, while a confidence interval conveys the statistical uncertainty associated with that estimate under the analysis assumptions. A wide interval indicates less precision; a narrow interval indicates more precision. Neither an estimate nor an interval can be recovered from an outcome title alone. The registry record lists no analysis results for the primary outcome, and it does not provide a confidence interval or other uncertainty measure.
In a single-group study, an event proportion could describe the observed group, provided the numerator, denominator, and missing-data handling were stated. It would not by itself estimate a treatment contrast against a concurrent control. That distinction is general: describing outcomes in a treated group and attributing a difference to treatment are different statistical tasks. This record has no randomized comparator, so a comparative treatment effect is not available from its design.
What can the planning assumptions establish?
The sample-size assumptions describe a planning illustration based on an observed effect: a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The illustrations are planning quantities, not observed power. They do not show what the single-group study actually found, and they are not evidence that the study was designed using those assumptions. The registry record does not report the study's own sample-size justification.
In general, a planning calculation depends on a target effect, variability or event-rate assumptions, an analysis method, and design choices. Equal allocation between two arms is not the design recorded for this study, which is single group. The assumptions therefore should not be mistaken for a description of the trial's allocation or an analysis conducted on its participants. No additional planning inputs or numerical planning results are reported in the registry record.
Why do analysis methods matter?
Statistical methods should match the outcome and design. For a binary endpoint, analyses may estimate an event proportion or compare event proportions across groups when a suitable comparison is present. For repeated laboratory measurements, methods could instead describe change over time, but the registry record does not state that such an analysis was performed. No specific statistical model, adjustment method, hypothesis test, or handling of repeated measurements is reported.
Over-dispersion is a general concern when count data vary more than a chosen model assumes; ignoring it can make uncertainty estimates too optimistic. It is not possible to assess over-dispersion for this endpoint from the registry record because no outcome counts or analysis are posted, and the endpoint is described as a count of participants rather than a rate model. This general concept should not be taken as evidence that over-dispersion occurred or that a particular model was used.
The record lists no analyses. It therefore does not provide a test statistic, p-value, effect estimate, confidence interval, or adjusted analysis for the primary endpoint. The absence of those results is distinct from a finding of no effect: no result is reported, so the direction, magnitude, and precision of the endpoint remain unknown in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists one outcome measure, Decline in Serum PSA, but the study purpose also mentions PSA response and PSA progression. It does not explain how these concepts relate to the registered measure or whether additional outcomes were specified elsewhere. The registry record lists no analyses, and it does not report a multiplicity plan, such as which outcomes were primary or how statistical testing across outcomes would be handled. It is therefore not possible to assess whether any reported statistical tests were adjusted for multiple comparisons; no such tests are posted.
Missing-data methods are also not reported in the registry record. The primary outcome population is described as treated patients, but the record does not state how many treated patients had an evaluable PSA assessment, whether all enrolled participants received treatment, or how unavailable measurements were treated. A count of participants with an event is most interpretable when the analysis denominator and completeness of follow-up are clear. Those details are absent for this endpoint.
The registry does not report an intention-to-treat population, a per-protocol population, or other analysis-population definitions. It does not describe exclusions, imputation, sensitivity analyses, or methods for handling participants who discontinued or lacked an assessment. These omissions do not establish that such procedures were or were not used; they mean the registry record does not document them. With no endpoint results or analysis details, neither missing-data impact nor multiplicity can be evaluated.
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 |
|---|---|---|---|
| 1000 mg GTx-758 BID | 1 | 9 | 11.1% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| 1000 mg GTx-758 BID | 0 of 9 |
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 |
|---|---|
| 1000 mg GTx-758 BID | 7 of 9 |
Most frequent serious adverse event terms
| Event term | Organ system | 1000 mg GTx-758 BID |
|---|---|---|
| Stroke | Nervous system disorders | 1 of 9 |
Most frequent non-serious adverse event terms
| Event term | Organ system | 1000 mg GTx-758 BID |
|---|---|---|
| Diarrhoea | Gastrointestinal disorders | 2 of 9 |
| Gastroesophageal Reflux Disease | Gastrointestinal disorders | 2 of 9 |
| Vomiting | Gastrointestinal disorders | 2 of 9 |
| Chills | General disorders | 2 of 9 |
Serious events with the highest arm-level rate: stroke (11.1%).
The adverse-event record lists one serious adverse event among 9 participants at risk in the 1000 mg GTx-758 BID group. It lists other adverse events affecting 7 among 9 at risk, and deaths are recorded as 0. The registry also lists Stroke at 11.1% among the top serious terms. The record does not state the denominator or calculation details for that percentage, so it should be read as a listed registry figure rather than independently reconstructed.
These figures are descriptive. They do not provide a comparison with an untreated or control group, and the single-group design does not support a like-for-like safety contrast. The serious-event and other-event entries are separate categories; the registry record does not explain their overlap or how events were attributed, coded, or followed over time. The participant counts at risk should not be assumed to represent every enrolled participant or the primary-outcome analysis population.
In general, a small safety record can describe events recorded during a study but cannot by itself establish comparative risk. The registry does not report additional detail about event timing, severity beyond the serious classification, relationship to treatment, or the reason for termination. No conclusions about the cause of the reported events can be drawn from these entries alone.
12. What the Result Does, and Does Not, Mean
The registry record establishes the study's stated question and design: a Phase 2, single-group study of GTx-758 in men with castration-resistant prostate cancer maintained on androgen deprivation therapy, with decline in serum PSA registered as the primary outcome over 30 days. It records 18 enrolled participants and lists the study as terminated. These registry entries describe the study; they do not supply the missing primary-outcome result.
The record does not report how many treated patients experienced a PSA decline, the definition used for decline, or an estimate of uncertainty. It also does not report a PSA-progression result. Therefore, the posted record cannot establish the frequency or size of PSA changes, the precision of any outcome estimate, or whether outcomes differed from what would have occurred without GTx-758.
Even if a within-group result were available, a single-group study without a control arm could describe observed outcomes but could not provide a randomized comparison. In general, observed changes may reflect more than the intervention alone. This is why a control group and a clearly defined analysis can be important for causal interpretation. The record does not include a control group, and its own notes caution that the arms are not a like-for-like comparison.
The safety entries show recorded adverse-event counts for the listed arm, including one serious event among 9 at risk, 7 participants with other adverse events among 9 at risk, and 0 deaths. They are not a comparative safety estimate. The listed Stroke figure of 11.1% also lacks a stated denominator in the record. These details should be read as descriptive registry entries, not as a complete account of safety or evidence of causation.
Overall, the registry documents a study question, an endpoint label, and limited design and safety information, but does not post the outcome analyses needed to quantify the primary result. The absence of a posted result should not be interpreted as a positive or negative finding.
13. Why This Trial Matters Statistically
This study is statistically notable because its registry record illustrates the difference between a registered outcome and a reported result. A primary endpoint can be clearly named and assigned a timeframe, yet without an event definition, analysis population, observed count, and uncertainty estimate, readers cannot quantify the finding. Here, Decline in Serum PSA is listed for treated patients over 30 days, but no analysis results are reported.
The single-group structure is also important for interpretation. In general, a within-group description answers what was recorded in that group; it does not supply the counterfactual comparison needed to isolate a treatment effect. The registry lists allocation as NA and cautions that the arms are not a like-for-like control comparison. This makes it especially important not to present an unreported or hypothetical contrast as evidence from this study.
Record consistency affects reproducibility too. The arm label uses 1000 mg GTx-758 BID, but the arm description refers to daily doses of 1000 mg. The official title describes an open-label study, while the masking field states double. Without clarification, readers cannot confidently reconstruct the regimen or masking from the registry alone.
Finally, the study's sample-size material is explicitly framed as a planning illustration based on an observed effect, with assumptions for a hypothetical two-arm calculation. Such planning figures are not observed power and do not substitute for a reported analysis. The record does not give its own sample-size justification, primary-outcome result, or missing-data methods. These gaps limit what can be learned statistically, regardless of the study's enrollment or termination status.
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.
Several trial-specific limitations constrain interpretation. First, the registry records a single-group model and no randomized comparator. Any outcome description from this design would not, by itself, separate changes associated with the intervention from other explanations. The registry also explicitly warns that the arms are not a like-for-like control comparison.
Second, the primary endpoint is incompletely specified. The record names decline in serum PSA, identifies treated patients, and gives a 30-day timeframe, but does not define the decline threshold or report the outcome count. It also does not report the denominator used in the primary analysis, completeness of PSA assessments, or handling of missing measurements. The study purpose mentions progression, but no progression result is registered among the listed outcome information.
Third, there are unresolved record inconsistencies. The arm is titled 1000 mg GTx-758 BID, while its description says daily doses of 1000 mg. The official title calls the study open label, while the masking field says double. The record does not clarify the regimen or masking, so those aspects should not be reconstructed by assumption.
Finally, the study is listed as terminated, but the reason is not reported in the registry record. The record contains no primary-outcome analysis, no statistical plan, no missing-data approach, and no study-specific sample-size justification. These limitations describe what is absent from the registry record; they do not establish why the information is absent or what the unreported results would have shown.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: GTx-758 on Serum Prostate-specific Antigen (PSA) in Men With Castrate Resistant Prostate Cancer — NCT01420861.
- Registry record last updated 2023-10-06; status last verified 2023-09.
- Results first posted 2023-10-06.
- 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
NCT01420861 is a Phase 2, single-group study sponsored by GTx, investigating GTx-758 in men with castration-resistant prostate cancer maintained on androgen deprivation therapy. The registry records 18 participants enrolled, a start of 2011-09, primary completion in 2012-12, and terminated status. The reason for termination is not reported in the registry record.
The primary outcome is Decline in Serum PSA among treated patients over 30 days. No analysis results are listed. The record describes the arm as 1000 mg GTx-758 BID but says daily doses of 1000 mg in the arm description; masking information also conflicts between the official title and structured field. Safety entries list one serious adverse event among 9 at risk, other adverse events affecting 7 among 9 at risk, and 0 deaths. The record does not provide a comparative control group or enough analysis detail to estimate the primary outcome or its precision.