GreenLight XPS Laser System Retrospective Chart Review: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for GreenLight XPS Laser System Retrospective Chart Review (NCT02139969), a registered phase not stated study. The primary outcome is International Prostate Symptom Score (IPSS).

2. Clinical Question

3. Trial Design

NCT02139969 is a completed retrospective chart review sponsored by Boston Scientific Corporation. The registry gives a start date of 2014-05 and a primary completion date of 2014-11, with enrollment listed as 956. The study’s stated purpose was to gather information about safety, efficacy, and quality of life among subjects who had undergone the GreenLight XPS procedure.

The listed intervention is the GreenLight XPS Laser System, with the arm description specifying use of the MoXy fiber for BPH treatment in men. A separate comparator arm is not listed. The registry states that this was not a randomized comparison and that allocation was not stated; the listed arms therefore should not be treated as a like-for-like control comparison.

The primary outcome is an IPSS symptom threshold at six months after the procedure. The listed secondary outcomes include procedure characteristics and immediate outcomes, changes in quality of life and objective urologic measures, treatment-related emergency visits and hospital admissions, surgical retreatment, and urinary incontinence. The registry lists 16 outcome measures but no analyses. It does not report the numbers assessed for each outcome, detailed eligibility criteria, or a statistical analysis plan.

The study description says the intention was to collect and analyze data through five years after the procedure, but that the data collected was minimal. The available record therefore describes a broader intended follow-up than the limited results recorded. It does not establish that all participants were followed for the same duration or that every listed outcome was measured for every participant.

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

Analysis population for the primary outcome, as defined in the registry: This study was retrospective chart review of available data collected in the medical records. The intention was to collect and analyze data through five years post-procedure; however, the data collected was minimal. Results posted here are reflective of the results that have been published (through 6-months).

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 International Prostate Symptom Score (IPSS), measured over 6 months post-procedure.

The primary endpoint is the number of participants meeting a symptom threshold, expressed in the study description as the proportion with mild or no BPH symptoms at six months after the procedure. The threshold is an IPSS of eight or less. The IPSS is a symptom score with a stated range of 0-35; scores of 9-21 are described as moderate, and scores greater than 21 as severe.

A threshold-based endpoint gives a clinically interpretable summary: it classifies participants according to whether their recorded symptom score falls on one side or the other of a specified cutoff. It does not, by itself, show how far scores changed from before treatment, nor does it describe the distribution of scores among participants who do or do not meet the threshold. Those questions would require suitable baseline and follow-up measurements, which are not reported as primary endpoint results in the registry record.

The six-month time point defines when the endpoint is intended to be assessed. For a retrospective chart review, interpretation also depends on whether scores were recorded at that time and how many records were usable. The record does not report the primary endpoint count, denominator, or estimate of the proportion. Consequently, it does not quantify the frequency of mild or no symptoms at the stated follow-up.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is a binary classification: each participant with a recorded six-month IPSS can be classified as meeting or not meeting the threshold of eight or less. The corresponding summary is a count and a proportion. General statistical interpretation of such an endpoint depends on both the number meeting the criterion and the number whose scores were available. Neither count is reported for the primary outcome in the registry record.

What does a binary endpoint tell the reader?

A binary endpoint compresses a potentially broader range of measurements into two categories. This can make the result easier to interpret against a prespecified threshold, but it discards detail. Two participants with different IPSS values could be placed in the same category, while participants with scores close to opposite sides of the cutoff could be assigned different categories. The registry describes the threshold and score ranges, but does not report the observed score distribution or the primary endpoint count.

A proportion is meaningful only with a clear denominator. In this retrospective study, the enrollment figure is not necessarily the number with a usable IPSS at the six-month assessment. Missing records, absent follow-up scores, or assessments outside the intended time point could affect who contributes to the endpoint. The number assessed and the handling of unavailable scores are not reported in the registry record. It is therefore not possible to determine whether the endpoint estimate, if calculated elsewhere, would represent all enrolled participants or a subset with recorded follow-up.

How should uncertainty be assessed?

In general, a confidence interval gives a range of values compatible with the observed data under the statistical method used. It conveys sampling uncertainty around an estimate; it does not correct for systematic differences between participants with and without available records, nor does it address bias from study selection or measurement. No primary endpoint estimate or confidence interval is reported in the registry record, so the precision of the symptom result cannot be evaluated.

The record describes a retrospective chart review, not a randomized trial. Randomization can, in general, help make groups comparable on average, while a chart review relies on existing records and does not itself create randomized treatment groups. Here, no comparator group is listed, and allocation is not stated. The data therefore do not provide a randomized treatment contrast. An observed outcome in the intervention group would be descriptive and would not, on its own, establish what would have happened to the same participants under another treatment or without the procedure.

What do the listed analysis details establish?

The registry lists 16 outcome measures and zero analyses. Outcome measures identify what the study intended to assess; they do not show that every measure was available or analyzed. The record does not report model specifications, adjustment variables, hypothesis tests, confidence intervals, or a statistical analysis plan. Those details are not reported in the registry record and should not be inferred from the endpoint descriptions.

General methods for count or proportion outcomes may use a binomial model when event probabilities are adequately represented by that model. Over-dispersion matters when observed variability is greater than the model expects; if ignored, uncertainty can be understated. The record does not report a model for the primary endpoint or information that would allow over-dispersion to be assessed. This is a general statistical consideration, not a claim about the analysis used in this study.

How do planning illustrations differ from observed power?

General sample-size calculations estimate how many participants may be needed to detect a specified effect under stated assumptions. The planning illustrations associated with these results use a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the target effect is a stated fraction of the observed effect. The time-to-event approach is described as using the total number of events, while other calculations are expressed as participants per arm.

These assumptions are planning illustrations, not the design of this chart review. The registry lists one intervention and no randomized comparator, whereas the illustrations assume two equally allocated arms. Such calculations are not observed power and do not establish that this study was designed or conducted with those assumptions. A planning calculation cannot supply the missing primary endpoint count or compensate for unreported follow-up data. In general, power calculations depend on the chosen effect, outcome variability, allocation, and analysis method; these assumptions are distinct from the information needed to interpret an observed result.

Finally, safety counts and symptom outcomes answer different questions. The adverse-event figures are counts of participants recorded in safety categories, while the primary endpoint is a symptom classification at a specified follow-up. Neither type of result can stand in for the other. Without the primary endpoint numerator, denominator, and uncertainty estimate, the registry record does not permit a quantitative assessment of the main symptom outcome.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 16 outcome measures, spanning procedure characteristics, immediate outcomes, quality of life, objective urologic measures, and several safety and retreatment outcomes. It records zero analyses. The registry record does not report whether the outcomes were tested as a family, whether any were designated for confirmatory inference beyond the stated primary endpoint, or whether adjustments for multiple testing were planned or used. Those details are not reported in the registry record.

Multiplicity is a general concern when many outcomes or comparisons are assessed. The more statistical questions considered, the greater the chance that at least one result may appear notable by chance if each is interpreted separately. Methods for addressing this can include prespecifying a primary question or adjusting inference across a defined family of tests. The record identifies a primary endpoint but does not provide an analysis plan or report tests, so no multiplicity procedure can be attributed to this study.

Missing data are especially relevant to a retrospective chart review because measurements depend on what was recorded in medical records. The study description says the intention was to collect and analyze data through five years after the procedure, but that the data collected was minimal. The number of participants with six-month IPSS scores, the amount of missingness for other outcomes, and the reasons for unavailable records are not reported in the registry record.

The analysis populations are also not described. The record does not state whether the primary analysis included all enrolled participants, only participants with a recorded follow-up score, or another defined subset. It does not report imputation or other methods for handling missing measurements. Without these details, readers cannot assess how selection of available records may affect the results. No claim about the completeness of follow-up or the treatment of missing data is justified by the registry entry.

11. 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: bladder neck obstruction (0.4%), hematuria - gross (0.2%), irritative voiding symptoms (0.2%), urinary retention (0.2%), intraoperative bleeding (0.1%).

The registry lists 13 participants with serious adverse events and 182 participants with other adverse events. It gives 956 as the number at risk for each category. These are counts recorded for the GreenLight XPS Laser System group. They are not estimates from a comparison with a control group, and the counts alone do not establish whether an event was caused by the procedure.

The serious-event terms listed include Bladder Neck Obstruction at 0.4%, Hematuria - Gross at 0.2%, Irritative Voiding Symptoms at 0.2%, Urinary Retention at 0.2%, Intraoperative Bleeding at 0.1%, and Clot Retention at 0.1%. These percentages are reported as listed; the registry entry does not provide further detail about their calculation or the number of participants contributing to each term. A term-level percentage should not be interpreted as a treatment comparison.

The deaths field is not populated in the listed safety data, so deaths are not reported in the registry record. The record also does not provide enough detail to assess timing, duration, severity beyond the serious-event classification, or how events were attributed. These counts describe what the registry records and should not be read as a complete comparative safety assessment.

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

The record establishes that NCT02139969 was a completed retrospective chart review of the GreenLight XPS Laser System for BPH, with enrollment listed as 956. It specifies a primary symptom question based on the IPSS at six months and identifies several secondary areas of interest. It also gives safety counts for participants with serious and other adverse events. These registry entries describe the study’s scope and the information entered in the registry.

The record does not report the numerical result for the primary endpoint. It therefore does not show how many participants had an IPSS of eight or less, what proportion met that threshold, or how precise such an estimate would be. The total enrollment cannot be substituted for the unknown number with an evaluable six-month score. Nor can outcome titles be treated as evidence that results were available for each listed measure.

The study has no listed comparator and is not described as randomized. In general, a single-group observation cannot separate a procedure’s effects from other influences on outcomes. The registry entry also does not describe adjustment for other factors or the statistical analysis plan. Thus, the record does not support a causal comparison or a conclusion about what would have occurred under an alternative intervention.

The safety counts are descriptive and relate to the listed intervention group. They do not establish comparative risk, and the registry record does not report deaths in the listed safety data. The terms and percentages can be read as recorded safety information, but they do not provide a complete account of event timing, attribution, or follow-up.

In short, the registry record documents the study design, its symptom endpoint definition, its intended scope, and limited safety counts. It does not provide the primary endpoint result or sufficient detail about missing data and analysis populations to evaluate the symptom outcome quantitatively. The absence of those details is not evidence for a particular clinical outcome; it limits what can be concluded from this record.

13. Why This Trial Matters Statistically

This study is statistically notable because its primary question is clearly framed as a threshold-based symptom outcome, while the registry record does not include the result needed to answer that question quantitatively. The distinction between an endpoint definition and an endpoint result is central: knowing what was intended to be measured does not reveal how many participants met the criterion or how uncertain that estimate is.

The retrospective chart-review design also makes the availability of measurements an important part of interpretation. The study description notes that the intention was to gather information through five years after the procedure, but that the data collected was minimal. Without numbers describing available follow-up, readers cannot establish how the observed records relate to the enrolled group or how missing measurements may have shaped reported outcomes.

Another important statistical feature is the lack of a randomized comparison. The record lists the GreenLight XPS intervention but no control intervention. Consequently, it offers no like-for-like comparison for estimating a difference between treatment groups. This illustrates why descriptive outcome counts and comparative treatment effects are distinct kinds of evidence.

The record also lists multiple outcome domains, including symptoms, quality of life, objective urologic measures, and adverse events, while recording zero analyses. This makes clear that a list of intended outcomes is not equivalent to a report of analyzed findings. For readers, the key statistical task is to distinguish what the record defines, what it quantifies, and what it leaves unreported. In this case, the study’s endpoint and some safety counts are documented, but the main symptom result and its precision are not.

14. Limitations

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

Several limitations specific to this study affect interpretation. First, the retrospective chart-review design relies on existing medical records. The registry does not report how records were selected, how complete they were, or how measurements were handled when absent. This matters for the primary endpoint because the result depends on recorded IPSS scores at six months.

Second, the study description states that data collection was minimal, despite an intention to collect and analyze information through five years after the procedure. The record does not report how many participants contributed data at each follow-up time or whether follow-up was consistent across outcomes. The primary endpoint denominator and missing-data methods are not reported in the registry record.

Third, no comparator is listed, and the study is not a randomized comparison. The record therefore cannot support a controlled estimate of differences between interventions. Allocation is not stated, and the registry does not provide enough information to determine how participants represented in the available records may differ from those without records.

Fourth, the primary endpoint result itself is absent. No count or proportion for participants with an IPSS of eight or less at six months is reported, and no uncertainty estimate is given. Although the registry lists 16 outcome measures, it records zero analyses. It does not describe the statistical plan, analysis populations, multiplicity handling, or methods for missing observations.

Finally, the safety information is limited to recorded counts and listed serious-event terms. The deaths field is not populated, and the record does not provide detail about event timing or attribution. These limitations constrain interpretation of both the symptom outcome and safety information; they do not establish a particular direction or size of any clinical effect.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: GreenLight XPS Laser System Retrospective Chart Review — NCT02139969.
• Registry record last updated 2020-11-09; status last verified 2018-01.
• Results first posted 2020-11-09.
• 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.

18. Record Summary

NCT02139969 is a completed, sponsored retrospective chart review of the GreenLight XPS Laser System for BPH. The registry lists enrollment of 956, with a start date of 2014-05 and primary completion date of 2014-11. The intervention description specifies use of the GreenLight XPS System and MoXy fiber in men treated for BPH.

The primary endpoint is the proportion with an IPSS of eight or less at six months. The registry lists 16 outcome measures and zero analyses, but does not report a numerical primary endpoint result, its denominator, or its precision. The study description notes that data collection was minimal despite an intention to collect information through five years.

The safety record lists 13 participants with serious adverse events and 182 with other adverse events, with 956 at risk in each category. A separate comparator is not listed, and the record does not report deaths in the listed safety data. The available registry information supports description of the design and recorded counts, but not a quantitative conclusion about the primary symptom outcome or a controlled treatment comparison.