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 Use of Silodosin to Treat Moderate to Severe Abacterial Chronic Prostatitis/Chronic Pelvic Pain Syndrome. (NCT00740779), a randomized phase 2 study. The primary outcome is National Institutes of Health-Chronic Prostatitis Symptom Index (NIH-CPSI) Total Score..
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00740779 |
| Phase | Phase 2 |
| Condition | Abacterial Chronic Prostatitis/Chronic Pelvic Pain Syndrome |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Double |
| Enrollment | 153 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Watson Pharmaceuticals |
| Results posted | Yes |
2. Clinical Question
Population
Participants with moderate to severe abacterial chronic prostatitis/chronic pelvic pain syndrome. The record describes the population as subjects with this condition and reports total enrollment of 153. Further eligibility details are not reported in the registry record.
Intervention
Silodosin taken once daily at either 4 mg or 8 mg. The arm descriptions specify daily dosing, and the trial objective was to compare each dose with placebo over a 12 week treatment period.
Comparator
Placebo, described as one placebo capsule daily. The registry identifies a parallel-group, randomized, double-blind, placebo-controlled design. Details of how randomization was implemented are not reported in the registry record.
Primary question
How did NIH-CPSI total score change from baseline to Week 12 in the silodosin groups compared with placebo? The registry names this change as the primary outcome, but it does not provide a single treatment comparison or its estimate, confidence interval, or significance test.
The clinical question concerns symptoms rather than a laboratory measurement. The NIH-CPSI total score combines pain, urinary symptoms, and quality-of-life impact. Its stated range is 0 to 43, with 0 representing best symptoms and 43 representing worse symptoms. A lower score therefore corresponds to fewer reported symptoms on this scale, but the registry record does not report the group-level changes needed to describe how the study arms compared.
The trial also had a secondary objective concerning safety. Registry entries list serious and other adverse events by treatment group. Those safety counts are descriptive information and do not establish a comparative safety effect on their own. Further details about how safety outcomes were defined, collected, or analyzed are not reported in the registry record.
3. Trial Design
This was a Phase 2, randomized, double-blind, parallel-group trial with placebo control. The official title describes it as a multi-center investigation. It enrolled 153 participants and is recorded as completed. The registry lists Watson Pharmaceuticals as the sponsor. The recorded start was 2008-09, and primary completion was 2009-10.
The intervention groups were silodosin 4 mg daily and silodosin 8 mg daily; the comparator group received one placebo capsule daily. The stated primary objective was to compare both silodosin doses with placebo for efficacy in moderate to severe abacterial chronic prostatitis/chronic pelvic pain syndrome during a 12 week treatment period. The stated secondary objective was to compare safety across those groups.
Randomization is intended, in general, to make treatment groups comparable on average with respect to measured and unmeasured baseline characteristics. Double masking is intended to limit the influence of treatment knowledge on participant reports, care, and outcome assessment. These are general design purposes; details of the randomization sequence, allocation concealment, and masking procedures are not reported in the registry record.
The registry lists one outcome measure and zero analyses. The primary outcome is NIH-CPSI total-score change from baseline at Week 12, but the registry does not reduce it to a single treatment comparison. It notes that the primary outcome has several categories or time points. Consequently, the available record does not identify which specific comparison or time point should be treated as the definitive efficacy estimate.
Arm-specific numbers randomized, treated, and included in the primary analysis, as well as reasons for withdrawal, are not reported in the registry record. Safety denominators are reported separately for the listed adverse-event categories, but they should not be taken as a substitute for a full participant-flow account.
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 | Silodosin 4 mg | Silodosin 8 mg | Placebo |
|---|---|---|---|
| STARTED | 52 | 45 | 54 |
| COMPLETED | 43 | 31 | 41 |
| NOT COMPLETED | 9 | 14 | 13 |
Reasons for not completing this period:
| Reason | Silodosin 4 mg | Silodosin 8 mg | Placebo |
|---|---|---|---|
| Adverse Event | 4 | 6 | 3 |
| Protocol Violation | 1 | 1 | 1 |
| Lack of Efficacy | 0 | 0 | 2 |
| Withdrawal by Subject | 2 | 4 | 2 |
| Lost to Follow-up | 2 | 3 | 5 |
Analysis population for the primary outcome, as defined in the registry: The number of participants for analysis is determined by Last Observation Carried Forward (LOCF).
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 | Silodosin 4 mg | Silodosin 8 mg | Placebo | Total |
|---|---|---|---|---|---|
| Participants analysed | 52 | 45 | 54 | 151 | |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 44 | 41 | 51 | 136 |
| Age, Categorical: >=65 years | Participants | 8 | 4 | 3 | 15 |
| Age Continuous | years | 49.2 (SD 13.34) | 46.7 (SD 15.57) | 49.0 (SD 11.62) | 48.4 (SD 13.43) |
| Sex: Female, Male: Female | Participants | 0 | 0 | 0 | 0 |
| Sex: Female, Male: Male | Participants | 52 | 45 | 54 | 151 |
| Region of Enrollment: United States | participants | 52 | 45 | 54 | 151 |
6. Primary Endpoint
The registry lists the primary outcome as National Institutes of Health-Chronic Prostatitis Symptom Index (NIH-CPSI) Total Score., measured over 12 weeks.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | Units on a 0 to 43 scale |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is change from baseline in the National Institutes of Health-Chronic Prostatitis Symptom Index (NIH-CPSI) total score at Week 12. It is a continuous measure, reported in units on a 0 to 43 scale. The scale includes pain, urinary symptoms, and quality-of-life impact; its direction is explicit: 0 indicates best symptoms and 43 indicates worse symptoms.
In general, a symptom index is useful because it turns a set of patient-reported experiences into a common measure that can be compared over time and between treatment groups. Change from baseline focuses on whether scores moved during follow-up rather than relying only on the final score. For interpretation, the direction and size of a group’s change matter, as does the between-group contrast. A within-group change alone cannot establish that the intervention caused a difference, because change can also reflect time, expectations, or other influences.
The registry identifies the endpoint and says that the analysis population is determined by Last Observation Carried Forward (LOCF). It does not report the baseline or Week 12 group means, mean changes, standard deviations, treatment contrasts, confidence intervals, or test results. It therefore does not allow the size or precision of the primary treatment comparison to be described. A clinically meaningful threshold for NIH-CPSI change is also not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record establishes the study question and names an appropriate symptom outcome for it: NIH-CPSI total-score change from baseline at Week 12. It does not provide a single efficacy comparison for the silodosin doses versus placebo. No group mean changes, treatment-effect estimates, confidence intervals, or hypothesis-test results are reported among the listed analysis information. The primary outcome is explicitly not reduced to one comparison because it has several categories or time points.
Accordingly, the available entries do not establish the direction, magnitude, or precision of a difference between either silodosin group and placebo. The absence of a reported estimate is not evidence that the groups were identical, and it is not evidence that either dose had a favorable or unfavorable effect. It means that the comparative efficacy question cannot be answered from the primary outcome information in this registry record.
In general, an estimated treatment contrast is more informative than separate within-group changes. A confidence interval would show the range of effects compatible with the data under the analysis assumptions. A narrow interval can indicate more precise estimation than a wide interval, but interpretation also depends on the outcome’s scale and on what size of difference matters. Since the registry record does not report such an estimate or interval, neither the size nor the uncertainty of an efficacy effect can be assessed.
The safety entries report serious adverse events affecting 2 of 52 participants in the 4 mg group, 0 of 45 in the 8 mg group, and 0 of 54 in the placebo group. Other adverse events affected 22 of 52, 25 of 45, and 12 of 54 participants, respectively. These are counts within the recorded groups, not adjusted comparisons. The record does not supply a statistical analysis of these outcomes or enough detail to determine whether the groups differed beyond what might arise from random variation.
General statistical interpretation also distinguishes event counts from evidence about causation. An event occurring in a trial participant does not by itself show that treatment caused it. Comparing event frequencies requires attention to event definitions, follow-up, exposure, and uncertainty. The registry lists urosepsis and syncope among the top serious adverse-event terms, each at 1.9%, but does not state in that listing which treatment group each term belongs to. Death counts are not reported in the registry record.
The design features—randomization, double masking, parallel groups, and placebo control—are relevant strengths in principle for a comparative trial. They do not replace outcome estimates or analysis details. With no reported primary comparison, the firm conclusion is limited to what was measured, how the trial was organized, and which safety counts the record lists. The data do not support a conclusion about whether silodosin improved symptoms or differed from placebo in safety.
9. Statistical Methods Explained
What does a continuous endpoint represent?
The NIH-CPSI total score is a continuous outcome: participants can have scores at different points on a numerical scale, and analysis can summarize both the central tendency and variability of those scores. The registry identifies the parameter as a mean and the dispersion as a standard deviation. In general, a mean describes the average score or average change, while a standard deviation describes how spread out individual observations are around that average. A mean does not imply that every participant experienced a similar change.
For a change-from-baseline outcome, the analysis compares later scores with each participant’s starting score. The treatment question is usually framed as a contrast between average changes in different randomized groups. That contrast is distinct from asking whether one group’s average changed from baseline. The registry record does not report group-level means, standard deviations, or a single contrast, so no numerical efficacy comparison can be interpreted.
What would a confidence interval add?
General explanation: a confidence interval expresses uncertainty around an estimated effect under the assumptions of the analysis. It helps readers assess both the range of effects compatible with the data and the precision of the estimate. It does not give the probability that a particular fixed effect is true. A confidence interval for a treatment contrast would be useful alongside the estimate, because statistical significance alone does not describe the possible size of an effect. No such interval is reported in the registry record.
Likewise, a p-value is not a measure of effect size or clinical importance. It describes how unusual data at least as incompatible with a specified null model would be, assuming that model and the analysis conditions. A p-value cannot replace an effect estimate and its uncertainty. The registry lists zero analyses, and no p-value for the primary comparison is reported.
How should the analysis population be understood?
The record says that the number of participants for the primary outcome analysis is determined by Last Observation Carried Forward (LOCF). In general, LOCF fills a missing later measurement with a participant’s last observed measurement. This produces an analysis dataset with carried-forward values, but it relies on an assumption about what an unobserved outcome would have been. That assumption may be implausible when symptoms change over time or when missingness is related to a participant’s condition or treatment experience.
LOCF does not, by itself, show how many participants had missing Week 12 values, why values were missing, or whether missingness differed among groups. Those details, the number analyzed in each arm, and any sensitivity analyses are not reported in the registry record. General practice is to examine the extent and pattern of missing data and to assess whether conclusions depend on the assumptions used to handle them. The registry entries do not describe such assessments.
What can be said about multiplicity?
Multiplicity arises when multiple hypotheses, outcomes, doses, domains, or time points are examined. If many comparisons are interpreted without accounting for their number or prespecifying a primary contrast, the chance of at least one apparently unusual result can increase. This is a general concern, not a claim about what happened in this trial. The record states that the primary outcome has several categories or time points and was not reduced to one comparison. It does not report a multiplicity strategy, hierarchy of comparisons, or any adjustment to significance levels.
The study objective names comparisons of both silodosin doses with placebo. The registry does not state how those comparisons were prioritized, whether domain scores were confirmatory or descriptive, or how repeated time points were handled. Without a prespecified analysis description and reported results, it is not possible to determine how multiplicity was addressed.
What do the planning assumptions mean?
The registry’s sample-size assumptions describe planning illustrations based on the observed effect, not the trial’s own design justification. They specify a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation; the effect to detect is described as a stated fraction of the observed effect. These are assumptions for an illustrative calculation, not evidence of the trial’s planned sample size or actual statistical power. No numerical planning results or effect fraction are reported in the record.
In general, planning calculations ask how many participants would be needed to detect an assumed effect under specified statistical conditions. Such calculations depend on assumptions about the effect, variability, significance level, allocation, and analysis. They do not show that a completed trial had a particular probability of finding an effect after its results are known. The planning illustrations should therefore not be read as observed power or as a justification documented by the trial sponsor.
For event outcomes, general methods also differ from those for continuous outcomes. The registry’s stated distinction is that time-to-event planning tables use the total number of events, whereas other planning tables give participants per arm. No time-to-event primary outcome is listed for this trial. The primary outcome is a continuous mean, and the registry record does not provide the effect estimate needed to assess an efficacy comparison.
Finally, a statistical analysis plan would clarify the estimator, covariates, handling of missing measurements, treatment of multiple comparisons, and analysis populations. Those details are not reported in the registry record. General methodological concepts can explain what such choices mean, but they cannot fill in unreported decisions or results for this study.
10. Multiplicity, Missing Data and Analysis Populations
The primary outcome is NIH-CPSI total-score change at Week 12, but the record says the outcome has several categories or time points and is not reduced to one comparison. The registry does not identify a single primary treatment contrast for interpretation. It also does not report whether comparisons between each silodosin dose and placebo were ordered, whether other score domains or times were treated as secondary, or how multiplicity was handled. These items are not reported in the registry record.
Multiplicity matters in general because testing several hypotheses can increase the chance of a nominally unusual result occurring by chance. Prespecifying a primary comparison or applying an adjustment can help control that concern. Without the planned analysis and reported tests, readers cannot determine whether the efficacy findings were protected against multiplicity—or whether any findings were statistically significant at all.
For missing data, the registry states that the number of participants in the primary analysis is determined using LOCF. General explanation: LOCF carries a participant’s last observed value forward to replace a missing later score. This is one method of handling missing observations, but it rests on assumptions about the unobserved outcome. The record does not report how many values were missing, reasons for missingness, participant flow by arm, or sensitivity analyses using alternative assumptions.
Further analysis-population definitions are not reported in the registry record. It is not stated whether the primary analysis included all randomized participants, only those who began treatment, or another defined group. The recorded enrollment of 153 does not establish how many participants contributed to each primary outcome analysis. These omissions limit assessment of both the analysis population and the robustness of any possible result.
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 |
|---|---|---|---|
| Silodosin 4 mg | 2 | 52 | 3.8% |
| Silodosin 8 mg | 0 | 45 | 0.0% |
| Placebo | 0 | 54 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 3% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Silodosin 4 mg | 22 of 52 |
| Silodosin 8 mg | 25 of 45 |
| Placebo | 12 of 54 |
Most frequent serious adverse event terms
| Event term | Organ system | Silodosin 4 mg | Silodosin 8 mg | Placebo |
|---|---|---|---|---|
| Urosepsis | Infections and infestations | 1 of 52 | 0 of 45 | 0 of 54 |
| Syncope | Nervous system disorders | 1 of 52 | 0 of 45 | 0 of 54 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Silodosin 4 mg | Silodosin 8 mg | Placebo |
|---|---|---|---|---|
| Retrograde Ejaculation | Reproductive system and breast disorders | 14 of 52 | 18 of 45 | 1 of 54 |
| Dizziness | Nervous system disorders | 1 of 52 | 5 of 45 | 4 of 54 |
| Headache | Nervous system disorders | 1 of 52 | 2 of 45 | 2 of 54 |
| Nasal Congestion | Respiratory, thoracic and mediastinal disorders | 2 of 52 | 3 of 45 | 0 of 54 |
| Sinusitis | Infections and infestations | 3 of 52 | 2 of 45 | 0 of 54 |
| Libido Decreased | Reproductive system and breast disorders | 1 of 52 | 2 of 45 | 1 of 54 |
| Nasopharyngitis | Infections and infestations | 1 of 52 | 1 of 45 | 2 of 54 |
| Back Pain | Musculoskeletal and connective tissue disorders | 1 of 52 | 0 of 45 | 2 of 54 |
| Nausea | Gastrointestinal disorders | 0 of 52 | 0 of 45 | 3 of 54 |
| Neurogenic Bladder | Renal and urinary disorders | 2 of 52 | 0 of 45 | 1 of 54 |
Serious events with the highest arm-level rate: urosepsis (1.9%), syncope (1.9%).
The registry reports serious adverse events by group. In the silodosin 4 mg group, serious events affected 2 of 52 participants; in the silodosin 8 mg group, they affected 0 of 45; and in the placebo group, they affected 0 of 54. The listed top serious adverse-event terms are urosepsis at 1.9% and syncope at 1.9%. The record does not identify the treatment group for each term in that listing. Death counts are not reported in the registry record.
Other adverse events affected 22 of 52 participants in the 4 mg group, 25 of 45 in the 8 mg group, and 12 of 54 in the placebo group. These figures describe participants affected as recorded; they do not indicate event severity, duration, or whether a participant experienced more than one event. The record does not report those details or a formal statistical comparison of adverse-event rates.
General interpretation: a zero count means no affected participants were recorded in that group for that category, not that the underlying risk is certainly zero. Small counts are imprecise, and event comparisons should account for uncertainty, follow-up, and how events were defined and collected. The registry numbers alone cannot establish that an event was caused by a treatment or that one group was safer than another.
12. What the Result Does, and Does Not, Mean
The record documents a randomized, double-blind, placebo-controlled investigation of silodosin 4 mg and 8 mg for moderate to severe abacterial chronic prostatitis/chronic pelvic pain syndrome. It specifies a 12 week treatment period and identifies NIH-CPSI total-score change at Week 12 as the primary outcome. These details clarify the question the trial was designed to address.
However, the registry record does not report a single primary outcome comparison, group changes, an estimated treatment difference, confidence interval, or test result. It therefore does not establish whether symptoms changed differently in either silodosin group than in the placebo group, nor does it describe the precision of a possible difference. The record’s lack of a comparative result should not be interpreted as evidence of no effect or as evidence of an effect.
The reported adverse-event counts provide a descriptive account of serious and other adverse events among participants in each group. They do not, without definitions, exposure details, statistical comparisons, and uncertainty estimates, establish that treatment caused or prevented any event. The serious-event term listing does not assign its terms to particular groups, and death counts are not reported in the registry record.
General statistical interpretation distinguishes what a trial measured from what its reported analyses establish. A well-defined endpoint and randomized design can support a valid comparison when the outcome data, analysis, and uncertainty are reported. Here, the registry identifies the intended endpoint and broad design but does not provide the necessary primary efficacy result. Further details about missing data, analysis populations, multiplicity, and the statistical plan are also not reported in the registry record.
The trial record can therefore be used to describe its design, endpoint, and listed safety counts, but not to reach a conclusion about the comparative efficacy of the two silodosin doses or their comparative safety. This distinction is important: incomplete reporting in a registry is not itself a result about the treatments.
13. Why This Trial Matters Statistically
This trial illustrates why a clearly named outcome is only one part of a statistical account. The NIH-CPSI total score supplies a defined symptom measure, including its scale direction and the time at which change was intended to be assessed. Those details let readers understand what an efficacy analysis would concern. But a study question cannot be answered from the endpoint definition alone; the treatment contrast and its uncertainty are also needed.
The registry identifies a randomized, double-blind, parallel-group, placebo-controlled Phase 2 design. In general, these features are intended to support a fair comparative assessment and reduce some sources of bias. Their value in interpreting results depends on transparent reporting of who was analyzed, how outcomes were handled, and what estimates were obtained. The registry does not report a single primary comparison or the analysis details needed to evaluate those matters.
The record also makes a useful distinction between the intended trial design and illustrative sample-size calculations based on an observed effect. Planning calculations are conditional on assumptions and cannot substitute for the trial’s own design rationale or observed results. The stated assumptions alone do not reveal a calculated sample size, effect estimate, or observed power.
Safety counts show why descriptive event reporting must be separated from comparative inference. Counts can flag what was recorded, but interpretation requires context about definitions, follow-up, uncertainty, and attribution. Here, serious and other adverse-event counts are listed, while a statistical comparison and several relevant details are not reported.
More broadly, this record demonstrates the importance of complete outcome reporting. An endpoint, design, and enrollment figure describe the study’s framework, but readers need analyzable results and their precision to judge the evidence. When those are absent, a careful interpretation states the limits rather than filling them with assumptions.
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 limitation for interpretation is that the registry record does not provide a single primary treatment comparison. It identifies NIH-CPSI change at Week 12 but notes that the primary outcome has several categories or time points and was not reduced to one comparison. Group-level results, effect estimates, confidence intervals, and test results are not reported. The efficacy question therefore remains unanswered by the available record.
The record lists LOCF as the method used to determine the primary analysis population, but it does not report the number of missing outcomes, reasons for missingness, or sensitivity analyses. It also does not define the analysis population beyond that statement. Readers cannot assess whether the missing-data assumptions were appropriate or whether results might depend on them.
Multiplicity procedures and a detailed statistical analysis plan are not reported in the registry record. The record does not specify how the two dose comparisons, the endpoint’s categories, or its time points were prioritized or adjusted. This prevents assessment of whether a particular comparison was prespecified and how multiple testing was addressed.
Safety information is limited to affected-participant counts and a listing of top serious-event terms. Event definitions, timing, duration, exposure, severity details beyond the serious/other categories, and formal comparisons are not reported. The term listing does not identify the corresponding treatment groups. Death counts are not reported in the registry record.
Further limitations include absent arm-specific participant flow and baseline outcome summaries. The enrollment total and safety denominators do not show how many participants contributed to the primary analysis or why participants may have stopped follow-up. These omissions limit assessment of the completeness and comparability of the outcome data.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Use of Silodosin to Treat Moderate to Severe Abacterial Chronic Prostatitis/Chronic Pelvic Pain Syndrome. — NCT00740779.
- Registry record last updated 2012-02-24; status last verified 2012-01.
- Results first posted 2012-02-24.
- Data retrieved from ClinicalTrials.gov on 2026-11-09.
- Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.
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18. Record Summary
The registry describes a completed, randomized, double-blind, parallel-group Phase 2 trial of silodosin for moderate to severe abacterial chronic prostatitis/chronic pelvic pain syndrome. It lists enrollment of 153, Watson Pharmaceuticals as sponsor, a recorded start of 2008-09, and primary completion in 2009-10. The study compared daily silodosin 4 mg and 8 mg with placebo over a 12 week treatment period.
The primary outcome was change from baseline in NIH-CPSI total score at Week 12, on a 0 to 43 scale where 0 is best and 43 indicates worse symptoms. The record specifies LOCF for determining the primary analysis population but does not report a single efficacy comparison or its estimate and uncertainty. Safety entries provide serious and other adverse-event counts by group; deaths are not reported in the registry record.