PROTECT Continued Access Post Marketing Surveillance Trial: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for PROTECT Continued Access Post Marketing Surveillance Trial (NCT00846846), a na phase 4 study. The primary outcome is To Evaluate Overall Stent Thrombosis Rate of the Endeavor® Zotarolimus Eluting Coronary Stent System in a Patient Population Requiring Stent Implantation.

2. Clinical Question

3. Trial Design

PROTECT Continued Access Post Marketing Surveillance Trial (NCT00846846) is listed as a Phase 4, single-group study with no masking. Allocation is recorded as NA. The intervention is the Endeavor® Zotarolimus Eluting Coronary Stent System, and the registry lists an enrollment of 1018.

The continued-access study was added to the PROTECT Trial to expand safety information for patients treated with the Endeavor system or a next-generation model. The record gives a start date of 2009-01, a primary completion date of 2013-03, and a status of completed. It identifies coronary artery disease as a condition of interest.

The primary outcome is a 3-year rate of ARC-defined definite or probable stent thrombosis. Although the trial title includes “Versus,” this continued-access record does not describe a second study arm or a randomized allocation. A comparative treatment effect should therefore not be inferred from its single-group design.

The primary endpoint description refers to 1018 ITT patients and says 947 were included in the endpoint analysis. Inclusion required at least 1050 days of follow-up or stent thrombosis before 1080 days. The record does not explain the status or endpoint contribution of the ITT patients not included in that analysis. Details such as the recruitment process, device implantation procedures, and follow-up schedule beyond the endpoint qualification are not reported in the registry record.

Two secondary outcome measures are listed: composites of cardiac death and large non-fatal myocardial infarctions. Their results and analysis details are not reported in the registry record. The record lists no analyses, so it does not establish how the primary or secondary outcomes were statistically evaluated.

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.

Before assignment: Subjects were excluded from participation if they did not meet inclusion/exclusion criteria.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Of the one thousand and eighteen (1018) ITT patients, a total of nine hundred and forty seven (947) patients were included in the primary endpoint analysis. These patients had at least 1050 days of follow-up or had experienced stent thrombosis prior to 1080 days.

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 To Evaluate Overall Stent Thrombosis Rate of the Endeavor® Zotarolimus Eluting Coronary Stent System in a Patient Population Requiring Stent Implantation, measured over 3 years.

The primary endpoint is the rate, at 3 years, of stent thrombosis classified as definite or probable under ARC definitions. It is expressed as a percentage of participants. Stent thrombosis is a device-related clinical event, so measuring its occurrence can contribute to safety surveillance for a coronary stent system. The registry’s stated endpoint is specific to definite or probable events; it should not be read as covering every possible device complication or every cardiovascular outcome.

The endpoint description identifies the analysis population as 947 of the 1018 ITT patients. It includes patients with at least 1050 days of follow-up and those who experienced stent thrombosis before 1080 days. That qualification indicates that the reported endpoint was intended to reflect follow-up around the 3-year time point, while also including an event that occurred before that point. The registry does not report further rules for event adjudication, censoring, or handling participants whose follow-up did not meet the stated criterion.

The endpoint’s dispersion is specified as a 95% confidence interval, but the event count, percentage, and interval limits are not reported in the registry record. Without those values, the observed rate and its precision cannot be assessed from this record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the endpoint percentage represent?

For a binary endpoint, the basic quantity is the proportion of participants who experience the defined event during the period of interest. A percentage is that proportion expressed on a percentage scale. In this study, the specified event is ARC-defined definite or probable stent thrombosis at 3 years. The registry gives the endpoint type and identifies a 95% confidence interval as its measure of dispersion, but it does not report the event count or percentage. No endpoint estimate can therefore be interpreted from the registry record.

A confidence interval describes uncertainty around an estimate under the statistical method used. It is not a guarantee that the true rate lies within the interval, and it does not measure the range of outcomes for individual participants. A narrower interval generally indicates greater precision, while a wider interval indicates more uncertainty. Here, the interval limits are not reported in the registry record, so its width and the precision of the endpoint estimate cannot be assessed.

Why does the analysis population matter?

The endpoint description calls the overall group ITT and states that 947 patients were included in the primary endpoint analysis. It specifies eligibility for that analysis in terms of follow-up of at least 1050 days or stent thrombosis before 1080 days. These details matter because an endpoint rate is interpreted relative to the participants included in its analysis and the rules determining inclusion. The record does not report further details about follow-up completeness, censoring, or the endpoint status of the ITT patients outside the stated analysis population.

In general, exclusion from an endpoint analysis can affect interpretation if inclusion is related to outcome risk or follow-up. That possibility is a methodological consideration, not evidence that bias occurred in this study. The registry does not report reasons for the difference in analysis populations or enough information to assess its consequences.

What can a single-group design estimate?

A single-group study can describe the outcomes observed among participants who received the intervention. It does not, without a suitable comparison group and appropriate design, directly estimate what would have happened to those participants under a different treatment. The continued-access record is listed as single group, with allocation NA and masking none. It does not describe a randomized comparator. Thus the design information in this record does not support a randomized between-group treatment-effect interpretation.

Even when an event rate is available, comparisons with rates from other studies require care. Differences in participant characteristics, endpoint definitions, follow-up, and event ascertainment can make simple comparisons misleading. These are general considerations; the registry record does not provide a comparative analysis for this continued-access study.

What does the safety counting show?

The safety fields distinguish participants at risk from participants affected. The Endeavor group lists 1018 at risk for serious adverse events and 415 affected; for other adverse events it lists 1018 at risk and 134 affected. The record also lists serious adverse-event terms with percentages, including Unevaluable Event at 14.8%, Chest Pain at 6.8%, and Angina Pectoris at 4.8%.

These entries are descriptive. The record does not specify whether participants could appear under more than one term, whether the percentages use all participants at risk as their denominator, or how events were attributed or timed. The term “Unevaluable Event” is itself a listed category and should not be interpreted as a specific clinical diagnosis. These figures should not be treated as a comparison of risks against another device.

What is the role of planning illustrations?

General sample-size planning asks how much information a future study might need to detect a specified effect under chosen statistical assumptions. The stated planning approach uses a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and effects defined as fractions of the observed effect. For time-to-event outcomes, the stated convention is to report total events; for other outcomes, it is participants per arm.

Such calculations are planning illustrations, not observed trial outcomes and not observed power. They do not establish that this continued-access study was designed using those assumptions. The trial’s own sample-size justification and statistical plan are not reported in the registry record. Because this record has a single-group design, a hypothetical two-arm planning calculation should not be mistaken for a comparison performed within this study.

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("Endeavor® Zotarolimus Eluting Coronary Stent Syste")
n      <- c(947)
events <- c(11)
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  Endeavor® Zotarolimus Eluting Coronary Stent Syste  947  11  1.2  0.6  2.1  0.6  2.1  0.7  2.1

11. Multiplicity, Missing Data and Analysis Populations

The registry lists two secondary outcome measures: composites of cardiac death and large non-fatal myocardial infarctions. It also identifies one primary endpoint, the 3-year rate of ARC-defined definite or probable stent thrombosis. The actual results for these endpoints are not reported in the registry record.

When a study evaluates multiple outcomes or performs multiple statistical tests, the chance of at least one apparently notable result can increase. Statistical methods may address that issue by defining a hierarchy of outcomes or adjusting inference across tests. These are general concepts. The registry record does not report a multiplicity strategy, a testing hierarchy, or details of any adjustment.

The record lists no analyses. It therefore does not describe the statistical model, confidence-interval method, handling of censoring, or analysis of secondary outcomes. It also does not report interim analyses or a prespecified statistical analysis plan. Those details should not be inferred from the endpoint descriptions.

The primary endpoint population is described as 947 of the 1018 ITT patients, with the stated follow-up or early-event criterion. The registry does not explain the endpoint status or reasons for non-inclusion for the remaining ITT patients. It does not report how missing follow-up was handled, whether any imputation was used, or whether sensitivity analyses were conducted. These omissions limit assessment of how missing outcome information might affect the endpoint estimate.

Because the endpoint event count and interval are also absent, it is not possible to evaluate the primary result’s precision or its relationship to any secondary findings. The listed outcome definitions alone do not establish which analyses were completed or how their results should be interpreted.

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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: unevaluable event (14.8%), chest pain (6.8%), angina pectoris (4.8%), acute myocardial infarction (2.9%), coronary artery dissection (2.8%).

The safety record lists 1018 participants at risk for serious adverse events and 415 affected. For other adverse events, it lists 1018 at risk and 134 affected. These are descriptive counts for the Endeavor group; the record does not provide a comparator group in this continued-access study.

The listed serious adverse-event terms include Unevaluable Event at 14.8%, Chest Pain at 6.8%, Angina Pectoris at 4.8%, Acute Myocardial Infarction at 2.9%, Coronary Artery Dissection at 2.8%, and Angina Unstable at 2.6%. The percentages are reported as terms in the registry, but their denominator and counting rules are not reported in the registry record. It is also not stated whether participants could contribute to more than one term.

These figures should not be read as event rates over a defined follow-up period, nor do they establish that an event was caused by the stent. The registry does not specify the timing, duration, severity grading, or attribution process for these entries. They describe recorded safety categories, not a controlled estimate of excess risk or a comparison between devices.

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

The record establishes that this was a completed, Phase 4, single-group continued-access study of the Endeavor® Zotarolimus Eluting Coronary Stent System. Its stated purpose was to expand safety information. The primary question concerned ARC-defined definite or probable stent thrombosis at 3 years, and the primary endpoint description specifies an analysis population and follow-up criteria.

However, the registry record does not report the primary endpoint event count, percentage, or 95% confidence interval. It therefore does not show the observed stent-thrombosis rate or the precision of that rate. The listed secondary composites also have no reported results in this record. These absences mean that the endpoint results cannot be evaluated from the registry information.

The safety fields provide counts of participants affected by serious and other adverse events, along with percentages for selected serious adverse-event terms. They do not establish that the device caused those events. The record does not provide the event attribution, timing, overlap, or denominator details needed for a more specific interpretation.

The single-group design is also important. It can describe outcomes recorded among participants in the study, but it does not provide a randomized comparison with another stent or treatment. The title’s reference to “Versus” does not change the design recorded for this continued-access study. A treatment difference or causal effect cannot be inferred from the single group alone.

In short, the registry describes the study’s purpose, intervention, design, endpoint definition, and selected safety counts. It does not report enough outcome information to determine the primary endpoint rate, judge its statistical precision, or compare the device with an alternative. Those limitations concern what can be concluded from this registry record; they are not evidence that an unreported outcome was favorable or unfavorable.

14. Why This Trial Matters Statistically

This study illustrates a common distinction in clinical research: a registry can describe an endpoint and the intended analysis population without reporting the numerical result needed to interpret that endpoint. Knowing that stent thrombosis was assessed at 3 years does not reveal how often it occurred. A rate and its uncertainty are needed to judge the observed frequency and precision.

It also shows why analysis populations matter. The registry identifies 1018 ITT patients and 947 in the primary endpoint analysis, with a stated follow-up or early-event criterion. Readers need to know how such populations are defined and how participants outside an endpoint analysis are handled, because those choices shape the population to which an estimate applies.

The study’s single-group design is another important statistical feature. Safety surveillance can describe events among people receiving a device, but without a suitable comparator it cannot isolate the effect of the device from other explanations. A title that sounds comparative should not substitute for checking the recorded allocation and model.

Finally, the listed safety counts and serious adverse-event terms are descriptive information, not a complete comparative safety analysis. Their interpretation depends on definitions, denominators, timing, event overlap, and attribution. These details are not reported in the registry record. The case therefore reinforces the importance of separating study purpose and endpoint definitions from observed results and from causal conclusions.

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 limitation for interpreting this specific record is that it does not report the primary endpoint result. The event count, percentage, and 95% confidence interval for 3-year ARC-defined definite or probable stent thrombosis are not reported in the registry record. The two listed secondary outcome measures also have no reported results.

The record describes a single-group design, with allocation NA and no masking. It does not provide a randomized control group for a like-for-like comparison. Accordingly, even a reported event rate would be descriptive of this study group rather than a direct randomized estimate of a difference between treatments.

The endpoint analysis population is stated as 947 of the 1018 ITT patients. The eligibility criterion is described, but the record does not explain the endpoint status or reasons for non-inclusion of other ITT patients. Details about missing follow-up, censoring, event adjudication, and sensitivity analyses are not reported in the registry record.

Safety information is also limited by absent context. The record does not state the denominator for the listed serious adverse-event term percentages, whether categories overlap, when events occurred, or how attribution was determined. It does not report a statistical analysis plan, sample-size justification, or multiplicity strategy. These gaps prevent a fuller assessment of outcome ascertainment, analysis choices, and the robustness of any result.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: PROTECT Continued Access Post Marketing Surveillance Trial — NCT00846846.
• Registry record last updated 2015-05-04; status last verified 2015-04.
• Results first posted 2014-07-02.
• 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

NCT00846846, PROTECT Continued Access Post Marketing Surveillance Trial, is listed as a completed Phase 4, single-group study of the Endeavor® Zotarolimus Eluting Coronary Stent System. The registry gives an enrollment of 1018, a start date of 2009-01, and a primary completion date of 2013-03. Allocation is recorded as NA and masking as none.

The primary endpoint was the 3-year rate of ARC-defined definite or probable stent thrombosis. The endpoint description identifies 947 of the 1018 ITT patients for analysis under stated follow-up or early-event criteria. The endpoint count, percentage, and 95% confidence interval are not reported in the registry record. Two secondary composite outcomes are listed without results. The record also lists serious and other adverse-event counts and selected serious-event terms, but does not report key details needed for comparative interpretation.