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 Quality of Life Study Using Gabapentin Versus Venlafaxine in Treating Hot Flashes in Patients With Prostate Cancer (NCT01533753), a randomized phase 2 study. The primary outcome is Changes in Quality of Life.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01533753 |
| Phase | Phase 2 |
| Condition | Prostate Cancer |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 5 |
| Arms in the primary outcome | n/a |
| Lead sponsor | University of Wisconsin, Madison |
| Results posted | Yes |
2. Clinical Question
Population
Men with prostate cancer treated for hot flashes related to androgen deprivation therapy were the intended population. The registry record reports enrollment of 5 and states that zero participants were analyzed for the primary outcome because the study was terminated early. It does not report participant characteristics or how many people received each treatment.
Intervention
The intervention was gabapentin. The registry describes an oral starting dose of 300mg at bedtime, with titration encouraged according to effect and tolerability under the treating physician. The maximum dose allowed was 300mg three times a day.
Comparator
The comparator was venlafaxine, administered orally at a starting dose of 37.5mg daily. Titration was allowed according to effect and tolerability under the treating physician, up to a maximum dose of 75mg per day. The trial was randomized and open-label.
Primary question
The intended comparison was the absolute change in the Functional Assessment of Cancer Therapy-Prostate (FACT-P) total score between the treatment groups, observed over a 6 month treatment period. The registry record reports no analyzed participants for this outcome, so it does not answer whether the groups differed in quality-of-life change.
In general, a clinical question is most useful when it makes clear who is being studied, which treatments are compared, and what outcome and follow-up period matter. Those elements identify the aim of this trial, but they do not establish that the planned comparison was completed. The record does not report an outcome estimate for FACT-P, or an analysis showing how change differed between the groups.
3. Trial Design
The registry describes a randomized, open-label, parallel-group phase 2 study sponsored by the University of Wisconsin, Madison. Its stated purpose was to assess change in quality of life over a 6 month period in men with prostate cancer treated for hot flashes related to androgen deprivation therapy. Participants were assigned to gabapentin or venlafaxine. Masking was listed as none, so the design was open-label rather than blinded.
The record lists the study start as 2012-02 and primary completion as 2014-01, with a status of terminated. Enrollment is listed as 5. The primary outcome description states that zero participants were analyzed due to early termination. The reason for termination, the timing of the decision, and the number assigned to each treatment are not reported in the registry record.
The gabapentin arm began at 300mg at bedtime, with titration encouraged to desired effect and tolerability per treating physician; the maximum allowed was 300mg three times a day. The venlafaxine arm began at 37.5mg daily, with titration allowed to desired effect and tolerability per treating physician; the maximum allowed was 75mg per day. For both arms, one cycle was defined as 28 +/- 7 days. The registry does not report the actual doses taken, treatment duration for individual participants, or adherence.
Secondary aims were to compare toxicity rates, assess changes in hot flash scores, and assess changes in quality of life using the Hot Flash Related Daily Interference Scale (HFRDIS). The record lists 4 outcome measures, but does not provide analyzed results for these aims.
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 | Arm A: Gabapentin | Arm B: Venlafaxine |
|---|---|---|
| STARTED | 2 | 3 |
| COMPLETED | 2 | 3 |
| NOT COMPLETED | 0 | 0 |
Analysis population for the primary outcome, as defined in the registry: Zero participants analyzed due to early termination of 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.
| Characteristic | Unit | Arm A: Gabapentin | Arm B: Venlafaxine | Total |
|---|---|---|---|---|
| Participants analysed | 2 | 3 | 5 | |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 0 | 1 | 1 |
| Age, Categorical: >=65 years | Participants | 2 | 2 | 4 |
| Sex: Female, Male: Female | Participants | 0 | 0 | 0 |
| Sex: Female, Male: Male | Participants | 2 | 3 | 5 |
| Race/Ethnicity, Customized: White | participants | 1 | 3 | 4 |
| Race/Ethnicity, Customized: African American | participants | 1 | 0 | 1 |
| Region of Enrollment: United States | participants | 2 | 3 | 5 |
6. Primary Endpoint
The registry lists the primary outcome as Changes in Quality of Life, measured over observed over a 6 month treatment period.
| Element | Registry entry |
|---|---|
| Result type | N/A |
| Measure of spread | not applicable |
| Unit | not stated |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint was the absolute change in the Functional Assessment of Cancer Therapy-Prostate (FACT-P) total score, compared between gabapentin and venlafaxine. The intended population was men with prostate cancer treated for hot flashes related to androgen deprivation therapy, and the stated observation period was 6 month.
FACT-P is a quality-of-life measure used in the context of prostate cancer. In general, a total score can summarize responses across areas relevant to a person’s reported well-being and functioning. Measuring change focuses the comparison on how scores differ between an assessment at the start of treatment and a later assessment. The registry record does not specify the assessment schedule, scoring details, or how the absolute change was to be summarized.
A quality-of-life endpoint is relevant to the trial’s stated aim because it concerns participants’ reported experience during treatment, rather than only a clinical or laboratory measure. In general, the meaning of a change depends on its size, precision, and context, including the instrument’s interpretation. The record contains no FACT-P results, no group-level change estimates, and no measure of uncertainty. It therefore does not show the direction or magnitude of any treatment-group difference.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The central statistical fact is that the primary outcome lists zero participants analyzed due to early termination. Although the registry lists enrollment of 5, it does not report a primary-outcome estimate based on those participants. Enrollment alone cannot establish how many people contributed data, how they were assigned, or what their quality-of-life scores were. The record therefore provides no estimate of the difference in FACT-P change between gabapentin and venlafaxine.
No confidence interval, p-value, standard error, or group-level summary for the primary outcome is reported in the registry record. In general, an estimate describes the observed contrast, while a confidence interval expresses the uncertainty around that estimate under the analysis assumptions. Without an outcome estimate, there is no interval to interpret and no basis for judging the precision of a treatment-group contrast. The absence of a reported comparison is not evidence that the groups had the same outcome.
The record also lists adverse-event counts. For Arm A: Gabapentin, 0 serious adverse events were reported among 2 participants at risk, and 2 participants were affected by other adverse events. For Arm B: Venlafaxine, 0 serious adverse events were reported among 3 participants at risk, and 2 participants were affected by other adverse events. These counts describe the posted safety record; they do not supply the missing quality-of-life comparison. Death counts are not reported in the registry record.
Interpretation is further limited because the registry does not provide participant characteristics, baseline scores, outcome data by assessment time, or details of the analysis population. It does not report how missing measurements were handled or whether the planned analysis was modified after termination. The reason for termination is also not reported in the registry record. These omissions make it impossible to assess whether the participants with safety information represent those originally intended for the efficacy analysis.
The record includes sample-size planning assumptions: a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation, with the effect to detect expressed as a stated fraction of the observed effect. However, no numerical observed-effect estimate or resulting sample-size values are reported in the registry record. Since zero participants were analyzed for the primary outcome, the record does not establish an observed primary-outcome effect to use as an empirical basis for planning. Any planning illustration should be treated as hypothetical, not as observed power or evidence of a treatment difference.
Overall, the registry documents a planned randomized comparison and limited safety counts, but it does not report an analyzed primary endpoint. No conclusion about comparative quality-of-life change can be drawn from these results. That is a limitation of the available statistical evidence, not a finding that either treatment had a particular effect.
9. Statistical Methods Explained
The design was randomized, parallel-group, and open-label. Random allocation is intended, in general, to reduce systematic differences between treatment groups at assignment. It does not guarantee that groups will be balanced on every characteristic, particularly when enrollment is limited. Open-label means masking was not used; the registry lists masking as none. In general, lack of masking can influence experiences, reporting, treatment behavior, and outcome assessment, especially when outcomes include participants’ reports of quality of life. The record does not describe safeguards for those possibilities.
What would a treatment contrast represent?
The primary question concerned the difference between groups in absolute change in FACT-P total score over a 6 month treatment period. In general, an analysis would first summarize change for participants in each group and then compare those summaries using a prespecified statistical approach. The exact approach, including the model, assumptions, and handling of repeated measurements, is not reported in the registry record. There are no reported group summaries from which to describe the contrast.
Change scores depend on both the starting measurement and later measurements. In general, baseline values can help describe the groups and may be used in an adjusted analysis, but the choice between analyzing change and adjusting for baseline must be specified and justified. Baseline FACT-P values and the planned adjustment strategy are not reported in the registry record. The assessment schedule within the stated 6 month period is also not reported, so the structure of any repeated measurements cannot be evaluated.
How should uncertainty be understood?
In general, a confidence interval gives a range of values compatible with the data and the assumptions of an analysis. Its width reflects precision: wider intervals indicate greater uncertainty about the estimated contrast. A p-value is a measure calculated under a specified statistical model and null hypothesis; it is not a measure of the probability that a treatment is effective. Neither confidence intervals nor p-values for the primary comparison are reported in the registry record. With zero participants analyzed for that outcome, no primary comparison can be interpreted from the posted results.
The registry does not report the statistical test, model, variance estimator, or a prespecified analysis plan. It therefore cannot establish whether the investigators intended an unadjusted comparison, a model adjusted for baseline factors, or an analysis using all recorded visits. These are general analysis options, not descriptions of what the trial actually used. A statistical method cannot be inferred from the endpoint description alone.
What do the planning assumptions mean?
The registry describes a planning approach using a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. It says that the effect to detect is a stated fraction of the observed effect. In general, sample-size planning estimates how much information a future study might need to detect a chosen effect under stated assumptions. Such calculations are not observed results, do not demonstrate that a study had adequate power, and do not show that a treatment effect occurred.
The registry does not report numerical sample-size estimates or a numerical observed effect for this primary outcome. It also states that zero participants were analyzed because of early termination. Thus, there is no reported analyzed primary result that can serve as an empirical estimate for those planning assumptions. The record’s statement about using an observed effect should not be read as evidence that a valid primary-outcome effect was estimated in this trial. The planning values, where displayed, are illustrations rather than trial findings.
In general, an assumption-based planning calculation is sensitive to the effect size selected, the variability of the outcome, allocation, and the analysis method. If the true effect differs from the assumed effect, the calculation may not describe the information needed for a future study. The record does not report the outcome variability, the numerical fraction used, or numerical planning outputs. No new planning value can be derived from the information reported.
The registry’s general sample-size convention says time-to-event calculations give the total number of events, while other calculations give participants per arm. That convention explains how such planning outputs are expressed; it does not add an outcome analysis to this trial. No time-to-event primary endpoint is listed for the stated quality-of-life question.
There is no reported interim analysis plan, stopping boundary, or statistical stopping rule. The study status is terminated, but the record does not state why, when, or according to what decision process it stopped. In general, stopping a trial early can affect how much information is collected and can complicate interpretation. Without the relevant details, the termination status should not be attributed to efficacy, safety, recruitment, or any other specific cause.
Finally, the trial’s safety counts are descriptive. In general, counts of participants affected by adverse events are not a substitute for a comparative analysis that accounts for exposure time, event type, and severity. The registry provides counts for serious and other adverse events but does not report event descriptions in the posted categories, exposure duration, or a statistical comparison. Those counts should be read as limited registry reporting rather than as a complete model of safety risk.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 4 outcome measures and identifies a primary quality-of-life endpoint alongside secondary aims concerning toxicity rates, hot flash scores, and HFRDIS. When a study considers multiple outcomes, time points, or comparisons, the chance of obtaining an apparently notable result by chance can be affected by how many analyses are made. In general, a multiplicity strategy may define which outcomes are primary, adjust statistical thresholds, or prioritize interpretation. A multiplicity plan is not reported in the registry record.
The primary outcome description refers to change over a 6 month treatment period. The record also indicates that the primary outcome had several categories or time points and was not reduced to one comparison. The specific categories, assessment times, and analysis strategy are not reported in the registry record. No results are reported for the listed secondary outcomes, and there is no documented hierarchy or adjustment across those outcomes.
Zero participants were analyzed for the primary outcome due to early termination. The registry does not report how many participants had any follow-up measurements, whether outcome measurements were missing, why data might be missing, or how missing values were handled. In general, missing-data methods rely on assumptions about why measurements are absent; different assumptions can lead to different estimates. Those assumptions cannot be assessed without reporting on missingness and the analysis procedure.
The analysis population is also not described beyond the statement that zero participants were analyzed for the primary endpoint. The registry does not report whether analyses were planned by randomized assignment, treatment received, or another population definition. Interim analyses and the statistical stopping plan are not reported in the registry record. These omissions leave the intended inferential framework unclear, quite apart from the absence of an analyzed primary outcome.
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 |
|---|---|---|---|
| Arm A: Gabapentin | 0 | 2 | 0.0% |
| Arm B: Venlafaxine | 0 | 3 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Arm A: Gabapentin | 2 of 2 |
| Arm B: Venlafaxine | 2 of 3 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Arm A: Gabapentin | Arm B: Venlafaxine |
|---|---|---|---|
| Pain | General disorders | 1 of 2 | 1 of 3 |
| Systolic Ejection Murmur | Cardiac disorders | 1 of 2 | 0 of 3 |
| Balance problem | Nervous system disorders | 1 of 2 | 0 of 3 |
| Vivid Dreams | Nervous system disorders | 0 of 2 | 1 of 3 |
| Insomnia | Psychiatric disorders | 0 of 2 | 1 of 3 |
| vertigo | Ear and labyrinth disorders | 1 of 2 | 0 of 3 |
| Urinary Tract Infection | Infections and infestations | 1 of 2 | 0 of 3 |
| Urinary Frequency | Renal and urinary disorders | 1 of 2 | 0 of 3 |
| Sore Throat | Respiratory, thoracic and mediastinal disorders | 1 of 2 | 0 of 3 |
| Nausea | Gastrointestinal disorders | 0 of 2 | 1 of 3 |
The registry reports 0 serious adverse events among 2 participants at risk in Arm A: Gabapentin. It reports 2 participants affected by other adverse events in that arm. For Arm B: Venlafaxine, it reports 0 serious adverse events among 3 participants at risk and 2 participants affected by other adverse events. The registry lists no serious-event terms. Death counts are not reported in the registry record.
These are counts, not estimates of comparative risk. In general, a count of participants affected does not describe event duration, severity beyond the serious-versus-other classification, number of events per person, timing, or treatment exposure. The record does not provide those details or a statistical comparison between groups. It also does not explain how the participants at risk relate to the enrollment figure or to the primary-outcome analysis population.
A reported count of zero serious events means none were recorded in the listed group data; it does not establish that serious events could not occur or that risks are equivalent. The small posted at-risk groups and the lack of exposure and event detail limit what can be inferred. These safety counts should not be treated as a complete account of all possible harms or as evidence about comparative safety beyond what the registry reports.
12. What the Result Does, and Does Not, Mean
The registry record establishes that investigators planned a randomized, open-label comparison of gabapentin and venlafaxine, with change in FACT-P total score as the primary quality-of-life outcome. It also records that the study was terminated and that zero participants were analyzed for this primary outcome. The posted results therefore do not estimate how quality of life changed in either group or whether the groups differed.
This absence of an estimate is not the same as finding no difference. In general, evidence of a small difference requires an estimate precise enough to distinguish a small effect from a meaningful one; no such estimate or uncertainty interval is reported. Nor can the record establish that one treatment performed better. It leaves the primary comparative question unanswered.
The registry does report limited adverse-event counts: 0 serious events among 2 participants at risk in the gabapentin arm and 0 among 3 at risk in the venlafaxine arm, with 2 affected by other adverse events in each arm. Those data describe the posted counts, but they do not establish equivalent safety or provide a full comparison. Death counts are not reported in the registry record.
Enrollment is listed as 5, but enrollment does not show that every enrolled participant contributed usable outcome data. The primary outcome explicitly reports zero analyzed. The record does not give treatment assignment counts, participant characteristics, follow-up completion, or the reason for termination. It is therefore not possible to determine from the registry how much of the intended study process was completed.
The appropriate interpretation is narrow: the registry documents the study’s question, design, treatment descriptions, termination status, primary outcome non-analysis, and limited adverse-event counts. It does not provide evidence to conclude that either treatment improves or fails to improve quality of life, or that one is safer than the other. The result is an unanswerable comparative efficacy question in the posted record, not a finding that the treatments are equivalent or ineffective.
13. Why This Trial Matters Statistically
This trial illustrates why registration details and analyzed results have to be read separately. A registry can describe a clearly framed question, planned treatments, outcomes, and study design without reporting an interpretable estimate of the intended treatment contrast. Here, the primary endpoint is stated, but the registry says zero participants were analyzed for it because of early termination. That distinction prevents the study’s aim from being mistaken for a result.
It also illustrates why enrollment is not a substitute for analysis information. The record lists enrollment of 5, while the primary outcome reports zero analyzed. Those statements refer to different aspects of trial conduct: enrollment indicates a registry count, whereas analysis requires outcome data and a defined analysis population. The record does not explain the relationship between the enrolled participants and the at-risk groups in the safety report.
Planning calculations are another reason for careful interpretation. General sample-size assumptions can help illustrate how a future comparison might be designed, but they are not evidence that a treatment effect was observed, nor are they observed power. Since no numerical primary effect or planning outputs are reported, the planning description cannot replace the missing outcome analysis.
Finally, the posted safety counts show how descriptive adverse-event information can remain available even when the primary efficacy outcome is not analyzed. Such counts are useful as the registry entries but have limited comparative meaning without event detail, exposure information, and uncertainty estimates. The trial is therefore statistically important as an example of the boundary between a documented research question and evidence capable of answering it.
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 most important trial-specific limitation is early termination with zero participants analyzed for the primary outcome. The registry lists enrollment of 5, but does not explain why the trial terminated, when the termination decision occurred, or how much planned follow-up was completed. Without that context, the reason for the missing primary comparison cannot be evaluated.
There are no reported FACT-P baseline values, follow-up values, change summaries, or between-group estimates. The registry does not specify the precise assessment schedule, the analysis model, the handling of repeated observations, or the analysis population. It also does not report participant characteristics, allocation counts, adherence, actual doses, or treatment exposure. These gaps prevent assessment of group comparability, outcome completeness, and the meaning of any potential change.
The record lists secondary outcomes but does not provide analyzed results for toxicity rates, hot flash scores, or HFRDIS. It does not describe multiplicity control, missing-data methods, interim analyses, or a stopping plan. The listed safety data include small at-risk groups and limited event categories; event terms and death counts are not reported in the registry record. Consequently, the available safety information cannot support a detailed comparison of event patterns or exposure-adjusted risk.
These limitations concern what can be learned from the registry record. They do not establish why the study ended or what participants experienced beyond the reported counts. The reason for termination and additional trial conduct details are not reported in the registry record.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Quality of Life Study Using Gabapentin Versus Venlafaxine in Treating Hot Flashes in Patients With Prostate Cancer — NCT01533753.
- Registry record last updated 2019-11-21; status last verified 2014-09.
- Results first posted 2014-09-15.
- 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
The registry describes a randomized, open-label, parallel-group phase 2 study comparing gabapentin with venlafaxine for hot flashes related to androgen deprivation therapy in men with prostate cancer. The stated primary outcome was absolute change in FACT-P total score over a 6 month treatment period. The study is listed as terminated, with enrollment of 5; the primary outcome description reports zero participants analyzed due to early termination.
Limited safety counts are reported for both arms, but the registry provides no analyzed quality-of-life comparison, confidence interval, or p-value. The reason for termination, analysis plan, missing-data approach, and death counts are not reported in the registry record. The posted information documents the planned question and some safety reporting but does not establish a comparative treatment effect.