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 Erythropoietin to Enhance Recovery of Erectile Function in Men Following Radical Prostatectomy (NCT00737893), a randomized phase 2 study. The primary outcome is Erectile Function as Assessed by the International Index of Erectile Function (IIEF) Questionnaire Erectile Function Domain.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00737893 |
| Phase | Phase 2 |
| Condition | Prostate Cancer, Erectile Dysfunction |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Triple |
| Enrollment | 56 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Johns Hopkins University |
| Results posted | Yes |
2. Clinical Question
Population
Men undergoing bilateral nerve-sparing radical retropubic prostatectomy for clinically localized prostate cancer. The registry lists prostate cancer and erectile dysfunction as conditions. Further eligibility details are not reported in the registry record.
Intervention
Erythropoietin (EPO): 20,000 units on the day before surgery, the day of surgery, and the day after surgery.
Comparator
Placebo doses on the day before surgery, the day of surgery, and the day after surgery.
Primary question
At 6 months after surgery, what erectile-function scores were recorded on the International Index of Erectile Function (IIEF) erectile-function domain in the EPO and placebo groups?
The registry describes the study as testing whether EPO might protect nerves and support recovery of erectile function after surgery. The primary endpoint focuses on the erectile-function domain of the IIEF rather than the questionnaire’s overall score. It is recorded as a median score with an inter-quartile range (IQR), separately for each arm.
The posted median was 14.0 in the EPO group and 19.0 in the placebo group. The registry record does not post a statistical comparison of these groups, such as a test result or confidence interval. The medians therefore answer a descriptive question about the recorded scores, but do not establish whether the groups differed beyond what could plausibly arise from sampling variation.
3. Trial Design
This is a randomized, triple-masked, parallel-group phase 2 trial. The registry records an enrollment of 56 participants. The posted primary-outcome results include 29 participants in the EPO group and 27 in the placebo group. The identities of the people or roles covered by triple masking are not reported in the registry record, so the masking label cannot be made more specific.
The EPO arm received 20,000 units on the day before surgery, the day of surgery, and the day after surgery. The placebo arm received placebo doses on the same three occasions. Both groups were undergoing bilateral nerve-sparing radical retropubic prostatectomy for clinically localized prostate cancer, as described in the study summary. Details about the randomization procedure, such as how the allocation sequence was generated or concealed, are not reported in the registry record.
The registry lists the study as completed. Its recorded start date is 2017-07-01, and its primary completion date is 2019-12-31. Those dates describe the registry record; they do not provide information about the timing of individual participants’ follow-up or any changes made during the study.
The primary outcome is the IIEF erectile-function domain score at 6 months after surgery. The registry describes the score as ranging from 0 to 30, with higher scores representing better erectile function. It also lists 21 secondary outcomes and 22 outcome measures. The protocol’s full schedule of assessments and the prespecified statistical analysis plan are not reported in the registry record.
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 | Erythropoietin (EPO) | Placebo |
|---|---|---|
| STARTED | 29 | 27 |
| COMPLETED | 29 | 27 |
| NOT COMPLETED | 0 | 0 |
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 | Erythropoietin (EPO) | Placebo | Total |
|---|---|---|---|---|
| Participants analysed | 29 | 27 | 56 | |
| Age, Continuous | years | 54 (51 to 60) | 57 (52 to 61) | 55.5 (51.5 to 60) |
| Sex: Female, Male: Female | Participants | 0 | 0 | 0 |
| Sex: Female, Male: Male | Participants | 29 | 27 | 56 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Asian | Participants | 1 | 0 | 1 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Black or African American | Participants | 2 | 5 | 7 |
| Race (NIH/OMB): White | Participants | 26 | 22 | 48 |
| Race (NIH/OMB): More than one race | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 |
| Region of Enrollment: United States | participants | 29 | 27 | 56 |
6. Primary Endpoint
The registry lists the primary outcome as Erectile Function as Assessed by the International Index of Erectile Function (IIEF) Questionnaire Erectile Function Domain, measured over At 6 months post-surgery.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Inter-Quartile Range |
| Unit | score on a scale |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is erectile function at 6 months after surgery, measured with the erectile-function domain of the International Index of Erectile Function (IIEF) questionnaire. The registry describes an overall score range from 0 to 30 and states that higher scores represent better erectile function. The posted results use the median and IQR to describe scores in each treatment group.
This domain is relevant to the stated study question because the trial concerns recovery of erectile function after prostate surgery. In general, a domain score concentrates on the subject area addressed by that part of a questionnaire, while an overall questionnaire score can reflect a broader set of questions. The registry also lists patient scores on the overall IIEF questionnaire among secondary outcomes.
A single assessment at 6 months gives a snapshot at that follow-up point; it does not, by itself, describe the trajectory or timing of recovery. The registry record does not report how scores were handled when a participant did not complete the questionnaire, nor does it describe the scoring rules beyond the stated range and direction. The posted endpoint summary is descriptive and is not accompanied by a reported inferential comparison between groups.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
At 6 months after surgery, the median IIEF erectile-function domain score was 14.0 among the 29 participants in the EPO group and 19.0 among the 27 participants in the placebo group. The IQR was 6.5 to 24.0 for EPO and 8.0 to 23.0 for placebo. Because higher scores represent better erectile function, the posted median is higher in the placebo group. These are descriptive summaries, not estimates accompanied by a reported test of the difference.
The IQR describes the middle half of the observed scores in each group. It gives information about the spread of scores around each median, but it is not a confidence interval and does not quantify uncertainty in the estimated group median. A confidence interval, in general, expresses uncertainty about an estimate under a statistical model. No confidence interval for the primary outcome is reported in the registry record.
The registry record lists no analyses for the posted outcomes. It therefore does not report a p-value, an adjusted comparison, or an analysis accounting for baseline characteristics. The posted results do not establish whether the observed difference between medians is statistically distinguishable from sampling variation. They also do not establish equivalence or absence of a group difference; those conclusions require appropriate analyses and uncertainty estimates.
The randomized design is intended to support a fair comparison by allocating participants to study groups rather than allowing treatment choice to determine group membership. In general, randomization can reduce systematic differences between groups, especially across a sufficiently large set of participants. It does not guarantee that the groups are identical, and the registry record does not include baseline characteristics with which to examine their balance.
The outcome is measured at one stated time point. Consequently, these summaries do not show whether scores changed from before surgery, whether recovery was faster in one group, or whether any pattern persisted beyond 6 months. Baseline scores, repeated-measures results, and an analysis of the course of recovery are not reported in the registry record. The medians and IQRs should be read as the posted group summaries at the specified follow-up, rather than as a complete account of recovery.
There is no sponsor-versus-recalculation discrepancy reported for this endpoint. That does not fill the gap left by the absence of a statistical comparison. The central interpretive limit remains that group-level descriptive results are available, while the registry record does not report the inferential analysis needed to quantify the uncertainty around the between-group contrast.
9. Statistical Methods Explained
The registry identifies a randomized, parallel-group design with triple masking. The posted primary outcome is summarized by the median and IQR, rather than by a mean and standard deviation. No statistical analyses are listed for the outcome results, so the methods used for a formal between-group comparison cannot be identified from the registry record.
What does the median describe?
In general, the median is the central value when observations are ordered. It is less affected by very high or very low observations than the mean, which can be useful when a score distribution is skewed. Here, the posted median for EPO is 14.0, and the posted median for placebo is 19.0. These values describe the central score in each observed group; they do not, alone, provide an estimate of uncertainty or a test of whether the groups differ.
The IQR describes the range covering the middle half of observations. In general, it is a measure of spread that is relatively resistant to extreme scores. The posted IQR is 6.5 to 24.0 for EPO and 8.0 to 23.0 for placebo. The registry does not report a confidence interval for either median or for a comparison between them. An IQR should not be interpreted as a confidence interval: the two quantities answer different statistical questions.
What does randomization contribute?
In general, random allocation aims to make treatment groups comparable at the start of a trial, including with respect to measured and unmeasured characteristics. This supports interpreting later differences as comparisons between assigned groups, subject to the trial’s implementation, follow-up, and analysis. Randomization does not ensure that groups will have the same baseline characteristics in a particular trial. Baseline characteristics and details of sequence generation or allocation concealment are not reported in the registry record.
The parallel-group label means participants were assigned to one of the two groups, rather than each participant receiving both study interventions in sequence. Triple masking indicates that masking was recorded, but the registry does not identify which parties were masked or describe how masking was maintained. Those details should not be inferred from the label alone.
What can be concluded without a reported test?
A statistical test evaluates how compatible observed results are with a specified null hypothesis under stated assumptions. A p-value, in general, is not the probability that the null hypothesis is true, nor does it measure the size or importance of an effect. The registry record reports no p-value or other test result for this primary outcome. It also does not identify a comparison model or report an adjusted estimate.
A confidence interval, in general, gives a range of values compatible with the data and the interval’s assumptions. It communicates the precision of an estimate, not whether a result is clinically important. No confidence interval for the primary outcome comparison is reported in the registry record. Without such an interval or another uncertainty measure for the comparison, the precision of the between-group result cannot be assessed from the posted medians and IQRs alone.
How should planning calculations be understood?
The registry’s sample-size assumptions describe planning illustrations based on the observed effect, not the trial’s own design justification. The stated assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation; the effect to detect is a stated fraction of the observed effect. For time-to-event outcomes, the illustrations concern the total number of events; for other outcomes, they concern participants per arm.
Such illustrations are conditional planning exercises. In general, they show how a hypothetical future study’s size could depend on the effect it aims to detect and on its statistical assumptions. They are not evidence about the probability that this completed trial found a true effect, and they are not observed power. The registry record does not report the trial’s own sample-size justification. No planning counts are stated in the registry record described for this analysis, so no participant or event targets can be interpreted.
Over-dispersion is a general concern when observed variability exceeds what a chosen model assumes; it can make standard errors and resulting uncertainty estimates unreliable if not addressed. The registry record does not report a model for this outcome, an assessment of distributional assumptions, or an approach to over-dispersion. The score summaries alone do not reveal what inferential model, if any, would have been appropriate or used.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 22 outcome measures, including 21 secondary outcomes, and reports no analyses for the posted outcomes. The primary outcome is the IIEF erectile-function domain score at 6 months after surgery. The registry also lists other measures, including the erectile-function domain at other assessments, overall IIEF questionnaire scores, and a health-related quality-of-life score. The timing and complete specifications for all these outcomes are not detailed in the registry entries.
When a study examines multiple outcomes or time points, the chance of obtaining at least one apparently notable result can increase. In general, multiplicity procedures can address that issue, but they may also affect how individual results are interpreted. The registry record does not report whether any adjustment for multiple comparisons was planned or used. No adjustment should be assumed.
Missing-data methods are not reported in the registry record. It does not state how many participants completed the primary questionnaire, whether missing scores occurred, what reasons were recorded, or how missing values were handled. The posted primary-outcome group counts are 29 for EPO and 27 for placebo, but those counts do not, on their own, identify the analysis population or establish whether every randomized participant contributed a score.
The registry record also does not report whether the analysis followed intention-to-treat, per-protocol, or another population definition. Baseline score handling, covariate adjustment, and sensitivity analyses are not reported. These omissions limit assessment of the analysis choices and of how missing observations or departures from assigned treatment may have affected the results.
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 |
|---|---|---|---|
| Erythropoietin (EPO) | 1 | 29 | 3.4% |
| Placebo | 1 | 27 | 3.7% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Erythropoietin (EPO) | 0 of 29 |
| Placebo | 0 of 27 |
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 |
|---|---|
| Erythropoietin (EPO) | 0 of 29 |
| Placebo | 3 of 27 |
Most frequent serious adverse event terms
| Event term | Organ system | Erythropoietin (EPO) | Placebo |
|---|---|---|---|
| Clavien III | Surgical and medical procedures | 1 of 29 | 1 of 27 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Erythropoietin (EPO) | Placebo |
|---|---|---|---|
| Clavien I-II | Surgical and medical procedures | 0 of 29 | 3 of 27 |
Serious events with the highest arm-level rate: clavien iii (3.7%).
The posted safety counts list one participant with a serious adverse event among 29 participants in the EPO group and one among 27 participants in the placebo group. The registry also lists zero participants with other adverse events in the EPO group and three in the placebo group. No deaths are listed in either group. These are counts as recorded; they do not describe the event types or timing in sufficient detail to establish why an event occurred.
The registry lists “Clavien III” at 3.7% among the top serious-event terms. The registry entries do not give a corresponding group assignment or explain the term further. It should therefore be read as a reported serious-event term, not as a basis for attributing an event to one intervention.
In general, adverse-event counts describe events observed and recorded during a specified monitoring period. They do not by themselves establish causation, and small counts provide limited information about the range or frequency of possible harms. The registry record does not report the adverse-event collection period, severity criteria beyond the listed serious-event term, or a statistical comparison of safety outcomes. The counts should be read descriptively, not as proof that either treatment caused or prevented an event.
12. What the Result Does, and Does Not, Mean
The posted primary-outcome result is a descriptive comparison of IIEF erectile-function domain scores at 6 months after surgery. The median was 14.0 in the EPO arm and 19.0 in the placebo arm; higher scores represent better erectile function. The IQRs were 6.5 to 24.0 and 8.0 to 23.0, respectively. The registry record does not report a statistical test or confidence interval for the comparison.
These figures do not establish that EPO improved or worsened erectile function, and they do not establish that the interventions were equivalent. A difference between observed medians can arise from a true group difference, sampling variability, or both. Estimating how precisely the groups differ requires an appropriate comparative analysis and uncertainty estimate, neither of which is reported in the registry record.
The result also does not show how participants’ scores changed from before surgery. A single endpoint at 6 months cannot describe the timing or rate of recovery, and it cannot establish whether a pattern continued at later follow-up. The registry lists other outcomes, but analyses of those outcomes are not reported. The posted primary summary therefore should not be treated as a full account of every measured aspect of erectile function or quality of life.
In general, a randomized trial can provide a structured comparison of assigned interventions, but interpretation depends on the analysis population, follow-up, missing data, and reporting of uncertainty. The registry record does not provide enough detail to evaluate those elements fully. The appropriate statistical reading is limited to the recorded group summaries and the explicit information about study design and outcome measurement.
13. Why This Trial Matters Statistically
This trial addresses a focused statistical question: how erectile-function scores at 6 months after surgery were distributed in two randomized groups. The endpoint is a patient questionnaire score with a stated direction, and the registry reports a median and IQR for each arm. That makes it possible to describe the observed central scores and spread without implying more than the posted results support.
It also illustrates why an outcome summary is not the same as a treatment-effect analysis. Group medians can help readers understand the observed scores, but they do not quantify the uncertainty of the between-group comparison. A test result or confidence interval would help assess how compatible the data are with a range of possible differences. The registry record reports neither for the primary endpoint.
The trial is randomized and masked, but design labels do not substitute for details of implementation or analysis. In general, randomization supports comparability, while masking can reduce some risks of biased care or assessment. The registry’s triple-masking label does not identify who was masked, and it does not report the allocation procedure. Those details matter when evaluating how the design was carried out.
The record also highlights the importance of analysis transparency when multiple outcomes are listed. There are 22 outcome measures, yet no analyses are reported. Without a stated multiplicity approach, missing-data handling, and defined analysis population, readers cannot reconstruct how the endpoint results were tested or how robust a formal conclusion might be. These are statistical reporting limits, not findings about the intervention itself.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The primary outcome is reported at 6 months after surgery, and no inferential comparison is posted. The registry reports medians and IQRs, but no confidence interval, p-value, or adjusted estimate for the group comparison. As a result, the precision of the between-group contrast cannot be assessed from the registry record.
The total enrollment was 56, with primary-outcome group counts of 29 for EPO and 27 for placebo. These numbers describe the trial and posted endpoint groups; they do not establish how many randomized participants were included in a particular analysis or whether scores were missing. The analysis population and missing-data handling are not reported in the registry record.
The registry lists 21 secondary outcomes as well as the primary outcome, but does not report analyses or a multiplicity strategy. The full statistical analysis plan, sample-size justification for the trial, randomization procedure, allocation concealment, and identities of those covered by triple masking are not reported in the registry record. Baseline scores and other group characteristics are also not included in the registry record described for this analysis.
The primary score describes erectile function at one follow-up point. It does not, by itself, establish change from baseline or the course of recovery over time. Additional details about questionnaire completion, adherence, follow-up, and adverse-event monitoring are not reported in the registry record. These limits constrain how completely the results can be evaluated; they do not determine what an unreported analysis would have found.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Erythropoietin to Enhance Recovery of Erectile Function in Men Following Radical Prostatectomy — NCT00737893.
- Registry record last updated 2021-04-08; status last verified 2020-07.
- Results first posted 2020-08-13.
- 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.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
18. Record Summary
NCT00737893 is a completed randomized, triple-masked, parallel-group phase 2 trial of erythropoietin versus placebo in men undergoing bilateral nerve-sparing radical retropubic prostatectomy for clinically localized prostate cancer. The registry records enrollment of 56 participants. EPO was given at 20,000 units on the day before surgery, the day of surgery, and the day after surgery; placebo doses were given on the same days.
The primary outcome was the IIEF erectile-function domain score at 6 months after surgery, with higher scores on the 0 to 30 scale representing better erectile function. The posted median was 14.0 (IQR 6.5 to 24.0) for EPO and 19.0 (IQR 8.0 to 23.0) for placebo. The registry lists 21 secondary outcomes and 22 outcome measures, but reports no analyses. A statistical comparison, confidence interval, missing-data method, and analysis population are not reported in the registry record.