A Long-Term Study Examining the Treatment of Benign Prostatic Hyperplasia With Photoselective Vaporization: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Long-Term Study Examining the Treatment of Benign Prostatic Hyperplasia With Photoselective Vaporization (NCT00465101), a na phase 4 study. The primary outcome is Percentage of Participants With Treatment Success.

2. Clinical Question

This question is about the proportion of treated participants crossing a prespecified symptom-score threshold, not about a between-group difference. Without a comparator, the endpoint can describe the observed outcome among participants meeting the stated population criteria, but it cannot by itself distinguish the treatment experience from changes that might occur over time or from other influences. The record lists additional outcomes concerning complications, uroflow, post-void residual urine volume, quality of life, hematuria, treatment success, return to physical activity, and retrograde ejaculation. Their presence does not substitute for a reported primary-outcome estimate. The endpoint's actual numerator, denominator, and uncertainty are not reported in the registry record.

3. Trial Design

This is a prospective clinical study listed as phase 4, with a single-group model and no masking. Allocation is recorded as NA. The registry identifies GreenLight HPS as the intervention and benign prostatic hyperplasia as the condition. It lists an enrollment of 150 and a status of completed. The start is recorded as 2007-05 and primary completion as 2012-08.

The study's stated aim was to gain clinical experience with the GreenLight HPS System, which is described as designed to vaporize and coagulate tissue in the treatment of benign prostatic hyperplasia to reduce lower urinary tract symptoms. The official title describes a prospective clinical study for GreenLight HPS in obstructive benign prostatic hyperplasia. There is no separate control arm described. Because the design is single group, the record does not support a randomized comparison between GreenLight HPS and another treatment or a control condition.

The primary endpoint is the percentage of participants with treatment success at 6 months. The endpoint population is defined as participants who received the study treatment and for whom the outcome measure is available. The success criterion is based on change in I-PSS from baseline to 6 months, with a reduction of at least 50% of baseline I-PSS meeting the definition.

The registry lists 15 outcome measures and identifies several secondary outcomes, including treatment-related complications, clinically significant improvement in uroflow and post-void residual urine volume, quality of life from I-PSS through 5 years, gross hematuria, return to pre-treatment physical activity excluding sexual activity, and retrograde ejaculation. It does not report the protocol details, recruitment flow, analysis population counts, or a statistical analysis plan. Although the study is marked completed, completion status alone does not establish that every listed outcome has a posted analysis.

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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Participants who received the study treatment and for whom the outcome measure is available.

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.

6. Primary Endpoint

The registry lists the primary outcome as Percentage of Participants With Treatment Success, measured over 6 months.

The primary endpoint is the percentage of participants meeting the study's definition of treatment success at 6 months. For each participant, the definition compares baseline I-PSS with I-PSS at 6 months: the reduction from baseline must be at least 50% of baseline I-PSS. The endpoint is therefore binary at the participant level—each eligible participant either meets the threshold or does not—and is then expressed as a percentage of participants.

A threshold-based endpoint can make a continuous symptom score easier to interpret in terms of how many participants crossed a specified level of change. It also has limitations: participants just on opposite sides of the cutoff are classified differently even if their score changes are very similar, while differences in the size of improvement among participants who cross the threshold are not represented by the percentage alone. These are general features of dichotomizing a continuous measure, not additional findings from this study.

The registry defines the primary population as participants who received the study treatment and for whom the outcome measure is available. The number meeting the success criterion, the analyzed denominator, the resulting percentage, and an uncertainty estimate are not reported in the registry record. The endpoint definition is reported, but a definition is not itself an outcome result. The listed 6-month timeframe applies to this primary measure; it should not be confused with the separate quality-of-life outcome described as extending from baseline through 5 years.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a prospective, single-group study, with no masking and allocation recorded as NA. These features determine what kinds of statistical conclusions the design can support. A single-group study can describe outcomes among the participants who received the intervention, but it does not provide a concurrent comparator for estimating a between-group treatment contrast. The registry record does not report further details of the statistical analysis plan, including any adjustment strategy or prespecified handling of incomplete observations.

What does the primary percentage represent?

The primary outcome is a binary participant-level classification summarized as a percentage. A participant is classified as a success if the reduction from baseline I-PSS to I-PSS at 6 months is at least 50% of baseline I-PSS. The endpoint description therefore specifies both the comparison time and the threshold. A percentage would require a numerator—the number meeting the criterion—and a denominator—the number of eligible participants with an available endpoint. Neither count nor the resulting estimate is reported in the registry record.

For a binary percentage, statistical uncertainty generally depends on the number of observations and on how the observed outcomes are distributed. A confidence interval is a way to express uncertainty around an estimate under specified statistical assumptions; it is not a guarantee about an individual participant's outcome. The registry record does not give a confidence interval for the primary endpoint, or report an analysis from which its precision can be assessed.

What does the cutoff leave out?

Turning a score change into a success-or-not classification is called dichotomization. As a general statistical matter, it can simplify communication by reporting how many participants crossed a clinically specified threshold. However, the classification does not preserve the full range of score changes. It does not distinguish a participant who barely meets the threshold from one with a much larger reduction, and it classifies participants on either side of the boundary differently even when their score changes are close. The record reports the threshold but not the underlying score distributions or a continuous analysis of change.

Why does the design matter?

In a comparative trial, the treatment contrast can be estimated by comparing outcomes between groups, subject to the design and analysis assumptions. Here, the registry lists a single group and no comparator. A descriptive percentage, if reported, would characterize the outcome among eligible treated participants. Without a comparison group, it cannot separate the treatment experience from other possible explanations for change, such as the passage of time, concurrent care, measurement variation, or participant selection. These are general interpretive considerations, not findings reported for this study.

The registry lists enrollment of 150. That is an enrollment figure, not a confirmed primary-analysis denominator. The endpoint population is limited to participants who received the treatment and had an available outcome measure. The number meeting that definition is not reported in the registry record, nor does the record explain how participants without an available outcome were handled.

What can be inferred from the listed planning assumptions?

The record describes planning illustrations based on the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is described as a stated fraction of the observed effect. Those assumptions describe hypothetical planning calculations, not the study's actual single-group design. The study itself is not described as having equal allocation between two arms. The registry record does not report the study's own sample-size justification, and the planning assumptions should not be read as evidence that the trial was designed or conducted with a particular power.

Sample-size illustrations based on an observed effect are planning tools: they show what sample size would be required under the assumptions used for that illustration. They are not observed power and do not repair the absence of a comparator or an unreported endpoint estimate. The particular illustration values and effect fractions are not reported in the registry record. No sample-size result should therefore be treated as a finding about the trial's observed outcomes.

What does the safety summary measure?

The safety fields distinguish serious adverse events from other adverse events and give participants at risk and affected for the GreenLight HPS Laser System group. Such counts describe reported safety experience in that group; they do not provide a controlled comparison of risks. The listed serious-event terms are accompanied by percentages, but the registry record does not provide enough information in these fields to establish causal attribution or to compare those events with another treatment group. Statistical interpretation should keep descriptive safety counts separate from the unreported primary efficacy analysis.

More broadly, a registry outcome definition, a completed study status, and a posted analysis are distinct pieces of information. The record gives the primary endpoint definition and several outcome names, but the number of analyses is listed as 0. Results for the primary endpoint and the listed secondary outcomes are not reported in the registry record. The design and definitions can be described, but they do not support reconstructing unposted estimates or uncertainty measures.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("GreenLight HPS Laser System")
n      <- c(119)
events <- c(101)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  GreenLight HPS Laser System  119  101  84.9  77.2  90.8  77.4  90.2  77.3  90.2

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 15 outcome measures, including a primary treatment-success measure and secondary outcomes spanning complications, uroflow, post-void residual urine volume, quality of life, gross hematuria, treatment success, return to physical activity, and retrograde ejaculation. Considering multiple outcomes can raise a general multiplicity issue: when many statistical tests are conducted, the chance of at least one apparently notable result can increase unless the analysis plan addresses that issue. The registry record does not report a multiplicity adjustment, a testing hierarchy, or other prespecified strategy for interpreting multiple outcomes.

The number of analyses is listed as 0. No primary-outcome estimate, secondary-outcome analysis, or statistical test result is reported in the registry record. It is therefore not possible to determine which analyses were conducted, whether all planned outcomes were analyzed, or whether multiplicity procedures were used. The presence of multiple outcome definitions alone does not show that all were tested or that any result was statistically significant.

The primary outcome population includes participants who received the study treatment and had the outcome measure available. The registry does not report how many participants met that definition, how many lacked a 6-month measure, or how missing measurements were handled. It also does not report whether the analysis followed an intention-to-treat approach or another analysis-population rule. The enrollment figure of 150 should not be assumed to equal the primary analysis denominator.

Missing outcomes can affect interpretation because the analyzed participants may differ from those without recorded results. As a general matter, complete-case estimates can be biased when availability of the outcome is related to the outcome itself or to participant characteristics. The record does not provide information to assess whether missingness occurred or what assumptions would be appropriate. These limitations prevent evaluation of attrition, analysis-population selection, and the robustness of any primary-outcome estimate.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: other (3.7%), pain / discomfort - other (2.9%), other: prostate cancer (2.2%), perforation - prostate (1.5%), other: death (1.5%).

For the GreenLight HPS Laser System group, the registry lists 136 participants at risk for serious adverse events and 35 affected. For other adverse events, it lists 136 at risk and 97 affected. These are descriptive counts in the registry's safety fields. They do not show a comparison with a control group, because the study is listed as single group with no separate comparator.

The listed serious-event terms and percentages are Other at 3.7%, Pain / Discomfort - Other at 2.9%, Other: Prostate Cancer at 2.2%, Perforation - Prostate at 1.5%, Other: Death at 1.5%, and Other: Atrial Arrhythmia at 1.5%. These labels and percentages should be read as the registry's reported categories, not as evidence that the device caused each event. The registry does not report a death count in the death field; the serious-event term Other: Death at 1.5% is a separate listed item.

The record does not give detailed definitions, timing, exposure adjustment, or a causal assessment for these safety summaries. The counts do not establish the comparative risk of an event, and they should not be interpreted as a treatment-effect estimate. The serious and other adverse-event fields also should not be added together: the record does not establish that the categories are mutually exclusive or report unique participants across both categories.

13. What the Result Does, and Does Not, Mean

The registry record documents a completed, prospective, phase 4, single-group study of GreenLight HPS for benign prostatic hyperplasia. It defines the primary outcome as treatment success at 6 months, using a threshold of at least 50% reduction from baseline I-PSS. It also records safety counts and names several secondary outcomes. These details describe the study's intended question and some reported safety information, but they are not a reported estimate of primary treatment success.

The primary outcome percentage, its numerator and denominator, and its uncertainty are not reported in the registry record. Consequently, the record does not show what proportion of eligible participants met the success definition or how precise such an estimate would be. The enrollment of 150 does not establish the number with an available 6-month outcome. A completed status does not fill that reporting gap.

Even if a single-group percentage were available, it would describe outcomes among the participants included in that analysis rather than a contrast against an untreated or alternative-treatment group. As a general matter, without a comparator, changes cannot be attributed to the intervention simply from observing outcomes after treatment. The record does not provide a randomized comparison from which to estimate a treatment difference.

The endpoint's threshold also does not capture the full distribution of score changes. It identifies whether participants crossed the specified boundary, but not how much participants improved or how score changes varied. The registry lists quality of life through 5 years as a secondary outcome, as well as other clinical and safety outcomes, but analyses for those measures are not reported in the registry record.

The safety fields report adverse-event counts and several serious-event categories, but do not establish comparative risk or causation. Taken together, the record supports a description of the design, endpoint definition, listed outcomes, and recorded adverse-event summaries. It does not support a conclusion about the primary endpoint's observed frequency, a comparative treatment effect, or the precision of an efficacy estimate.

14. Why This Trial Matters Statistically

This study is statistically informative as an example of the difference between a clearly described endpoint and a reported endpoint result. The registry specifies a binary treatment-success definition, its 6-month timeframe, and the population in which it is intended to be assessed. Those details allow readers to understand what the planned percentage would mean. Yet the registry record does not report the actual percentage, its denominator, or an uncertainty estimate. A study's endpoint definition alone cannot answer its outcome question.

The single-group design also makes the comparison structure important. A percentage among treated participants can be descriptive, but it is not a randomized treatment contrast. Recognizing that distinction helps prevent an observed change, if reported, from being interpreted as a causal effect without a comparator. The registry identifies allocation as NA, masking as none, and the model as single group, so a like-for-like control comparison is not described.

The study also illustrates why enrollment and analysis population are not interchangeable. Enrollment is listed as 150, while the primary endpoint population requires treatment receipt and an available outcome. The number meeting those criteria is not reported in the registry record. For a percentage endpoint, access to both the success count and the eligible denominator is essential to understand the estimate and its precision.

Finally, multiple outcomes and safety summaries need separate interpretation. The record lists 15 outcome measures, but the number of analyses is 0 and the results for those outcomes are not reported. The adverse-event counts provide descriptive safety information but do not establish comparative risk or causation. Statistically, the record is most useful for clarifying what was to be measured and identifying what is not available for assessing efficacy, uncertainty, missingness, or multiplicity.

15. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The main trial-specific limitation is the absence of a reported primary treatment-success analysis. The registry defines the endpoint and timeframe but does not give the number of participants meeting the criterion, the denominator analyzed, the percentage, or an uncertainty estimate. Without these values, the primary outcome cannot be quantitatively interpreted from the registry record.

The design is single group, with allocation recorded as NA and masking as none. There is no separate comparator group described, so the design does not support a randomized, like-for-like comparison. This constrains interpretation of any outcome change as a treatment effect. The record does not report additional design details that might clarify participant selection or how other influences were considered.

Although enrollment is listed as 150, the primary analysis population is defined by treatment receipt and outcome availability. The number meeting those criteria, loss to follow-up, and handling of unavailable observations are not reported in the registry record. The endpoint's threshold definition also means that a success percentage would omit the magnitude and distribution of score changes.

The registry lists 15 outcome measures and several secondary outcomes, but reports 0 analyses. It does not report a statistical analysis plan, a multiplicity strategy, or results for the listed secondary measures. The safety fields include event counts and categories, but do not provide a comparative group or establish causal attribution. The death count field is not reported in the registry record, although Other: Death appears among the listed serious-event terms.

The record describes planning assumptions for illustrations, but does not report the trial's own sample-size justification. Those illustrations use assumptions different from the actual single-group design and cannot be treated as observed power or as evidence of an outcome. Collectively, these reporting and design constraints limit assessment of efficacy, precision, missing-data effects, and comparative safety.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: A Long-Term Study Examining the Treatment of Benign Prostatic Hyperplasia With Photoselective Vaporization — NCT00465101.
• Registry record last updated 2015-10-28; status last verified 2012-06.
• Results first posted 2015-10-28.
• 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.

19. Record Summary

The registry identifies NCT00465101 as a completed, prospective, phase 4, single-group study of GreenLight HPS for benign prostatic hyperplasia. Enrollment is listed as 150; the start is recorded as 2007-05 and primary completion as 2012-08. The study is described as having no masking, with allocation recorded as NA.

The primary outcome is the percentage of participants with treatment success at 6 months, defined as a reduction from baseline I-PSS of at least 50%. The eligible population is participants who received treatment and had an available outcome. The primary outcome result and analyzed denominator are not reported in the registry record. The registry lists 15 outcome measures and 0 analyses.

Safety fields list 136 at risk and 35 affected for serious adverse events, and 136 at risk and 97 affected for other adverse events in the GreenLight HPS Laser System group. Listed serious-event terms include Other at 3.7% and Pain / Discomfort - Other at 2.9%. The record does not describe a comparator group or report a primary efficacy analysis.