Feasibility Study for GORE® TAG® Thoracic Branch Endoprosthesis to Treat Proximal Descending Thoracic Aortic Aneurysms: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Feasibility Study for GORE® TAG® Thoracic Branch Endoprosthesis to Treat Proximal Descending Thoracic Aortic Aneurysms (NCT02021812), a na na study. The primary outcome is Number of Participants With Successful Study Device Access.

2. Clinical Question

3. Trial Design

This was a completed, single-group feasibility study of the GORE TAG Thoracic Branch Endoprosthesis for proximal descending thoracic aortic aneurysms. The registry lists the study phase as NA, allocation as NA, masking as none, and the model as single group. It records enrollment of 31 participants. The intervention arm is named Branched TAG Device and is described as treatment with the GORE TAG Thoracic Branch Endoprosthesis.

The record gives a study start of 2014-01 and primary completion of 2016-08, and lists the overall status as completed. Those dates describe the registry timeline; they do not establish the follow-up duration for each participant. The primary endpoint timeframe is during the treatment procedure on day 0. Secondary outcomes listed are the number of participants with 1 month side branch primary patency assessed by an independent core lab and the number without 1 month device-related endoleaks assessed by an independent core lab.

Because this is a single-group study with no like-for-like control arm, its design is suited to describing feasibility and observed outcomes in the treated group, not to estimating a comparative treatment effect. The registry record does not report a protocol-based sample-size justification, detailed eligibility criteria, or a statistical analysis plan. It also does not list outcome analyses. These omissions limit what can be concluded about how participants were selected, how outcomes were analyzed, and whether the reported enrollment was chosen to answer a particular statistical question.

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:

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 Number of Participants With Successful Study Device Access, measured over During treatment procedure (day 0).

The primary endpoint is the number of participants with successful study-device access during the treatment procedure, on day 0. The registry describes the relevant access as reaching the aneurysm and target landing-zone location through conventional vascular access and endovascular techniques. The endpoint is expressed as a count of participants, rather than as a continuous measurement or a time-to-event outcome.

As a feasibility measure, successful access concerns whether the device can be delivered to the intended anatomical location during the procedure. In general, a binary feasibility endpoint can provide a direct description of whether a prespecified procedural step was achieved. Its interpretation depends on a clear operational definition of success and on consistent assessment across participants. The registry description gives the broad access objective, but detailed success criteria, adjudication procedures, and analysis-population rules are not reported in the registry record.

The registry names the endpoint but does not report the count of participants who achieved successful access. It also does not report an estimate of the corresponding proportion or a confidence interval. Consequently, the listed endpoint definition alone cannot establish the observed feasibility result or its statistical precision.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is a participant count: the number meeting the registry’s definition of successful study-device access during the treatment procedure. This is a binary outcome at the participant level, because each participant either meets the success definition or does not. A count can be informative for describing a feasibility endpoint, but interpretation also depends on the denominator, the completeness of outcome assessment, and the criteria used to classify success. The registry record does not report the primary count, the analysis denominator, or further operational criteria beyond obtaining access to the aneurysm and target landing zone.

What would an estimate describe?

In general, a binary outcome can be summarized as a count and as a proportion within a clearly defined analysis population. The count describes how many participants had the outcome; the proportion relates that count to the number assessed. These summaries are descriptive, and their meaning depends on who was included and whether outcome status was known for all included participants. No primary endpoint count, proportion, or analysis population is reported in the registry record, so none can be interpreted for this study.

A confidence interval is a general statistical tool for expressing uncertainty around an estimate. For a binary outcome, it can communicate the range of values reasonably compatible with the observed data under the chosen method and assumptions. Its width is influenced by the amount of information in the data and by the method used. The registry does not report a confidence interval for successful access, and no interval can be inferred from the outcome title or enrollment alone.

What does the single-group design permit?

In general, a single-group study can describe outcomes among participants receiving an intervention. Without a control group, it cannot make a direct randomized comparison with an alternative. A within-group observation is not equivalent to an estimate of a comparative effect, because the study lacks a concurrent group that would help separate the intervention from other influences. Here the registry lists a single-group model and allocation as NA. It does not list a comparator arm or a randomized allocation procedure.

The study is described as a feasibility study, and its stated purpose is to assess use of the device for aneurysms involving the proximal descending thoracic aorta. The endpoint of access is procedural and assessed on day 0. It should not be conflated with the listed secondary outcomes, which concern 1 month side branch primary patency and device-related endoleaks. Those are distinct outcomes with their own timeframes and assessment descriptions. Their observed results are not reported in the registry record.

What analysis details are missing?

The registry lists no outcome analyses. A statistical analysis plan, including the chosen summary measures, treatment of missing endpoint data, and any planned subgroup or sensitivity analyses, is not reported in the registry record. The primary outcome description also does not specify whether success required every procedural component to be completed, how technical failures would be classified, or who made the determination. Without those details, readers cannot assess the reproducibility of the outcome definition or the relationship between the endpoint and the full procedural experience.

In general, prespecified analysis rules are important because they clarify how data will be turned into results and reduce ambiguity about choices made after observing outcomes. A sample-size justification can also explain what degree of precision or detection capability the investigators intended. Neither a protocol-based sample-size justification nor the study’s statistical plan is reported in the registry record. The enrollment of 31 is a registry fact, but it does not, on its own, reveal the reasoning behind the planned sample size or the precision of an endpoint estimate.

How should the safety counts be treated?

The record reports participants at risk and participants affected for serious and other adverse events, as well as a death count. These are descriptive safety data. In general, event counts and affected-participant counts are not necessarily interchangeable: one participant may experience more than one event, and a count of participants affected does not show the total number of occurrences. The posted safety summary does not give enough event-level detail to determine overlap, timing, duration, or attribution. Thus, the counts can be reported as recorded, but they do not establish that the device caused an event or quantify a comparison with another treatment.

The record names several serious adverse-event terms and gives percentages for them. It does not state in the available safety summary what denominator those term percentages use or whether a participant could contribute to more than one term. Those details should not be inferred. No comparative model, adjustment method, or inferential safety analysis is reported. These limitations distinguish descriptive reporting from a formal statistical comparison and constrain the conclusions that can be drawn from the safety figures.

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("Branched TAG® Device")
n      <- c(31)
events <- c(31)
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  Branched TAG® Device  31  31  100.0  88.8  100.0  89.0  100.0  89.1  99.9

11. Multiplicity, Missing Data and Analysis Populations

The registry lists five outcome measures, including the primary successful-access endpoint and secondary outcomes concerning 1 month side branch primary patency and the absence of 1 month device-related endoleaks. It lists no analyses. No multiplicity strategy is reported in the registry record, so it is not possible to tell whether multiple outcomes were intended to be tested, prioritized through a hierarchy, or adjusted for in any formal inference. The listed outcomes alone do not establish that statistical tests were performed.

Missing-data handling is also not reported in the registry record. The primary endpoint description does not state whether every enrolled participant was assessed, how an unobserved access outcome would be treated, or whether any participants were excluded from an analysis. The registry gives an enrollment of 31, but does not provide an endpoint-specific denominator or account of missing outcome values. In general, missing outcomes can affect both the denominator and the interpretation of a proportion, particularly if the reasons for missingness are related to outcome status.

The registry does not describe analysis populations, such as whether the primary result would include all enrolled participants or only those with an attempted procedure and an assessed outcome. It also does not report sensitivity analyses addressing missing outcomes. These details are needed to understand which participants contribute to an estimate and how robust a result might be to incomplete observation.

For the safety figures, the record gives participant counts at risk and affected, but does not provide a narrative of missing safety follow-up or event ascertainment. The scope and completeness of safety observation are therefore not clear from the registry record. No assumptions about complete follow-up, overlapping events, or handling of missing safety information should be made.

12. Safety Results

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

Deaths

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: aspiration pneumonia (9.7%), pulmonary embolism (9.7%), anemia (6.5%), congestive heart failure (6.5%), unknown cause of death (6.5%).

The registry reports 20 of 31 participants at risk as affected by serious adverse events, and 30 of 31 at risk as affected by other adverse events. It also reports 8 deaths. These are descriptive figures for the Branched TAG Device group. The record does not give a comparative safety group, so these counts cannot be interpreted as a comparative risk estimate.

The listed serious adverse-event terms include aspiration pneumonia at 9.7%, pulmonary embolism at 9.7%, anemia at 6.5%, congestive heart failure at 6.5%, unknown cause of death at 6.5%, and Clostridium difficile infection at 6.5%. The registry summary does not specify the denominator used for these term percentages or whether participants could appear under multiple terms. The percentages should therefore be read as listed, without converting them into participant counts or assuming that the terms are mutually exclusive.

In general, adverse-event counts describe events recorded during study observation; they do not, by themselves, establish causation. The registry information does not provide event timing, individual-level overlap, or an attribution analysis sufficient to determine whether an event was caused by the device. The death count likewise should not be treated as a device-related death count, because that attribution is not reported in the registry record.

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

The record establishes that a completed feasibility study evaluated the GORE TAG Thoracic Branch Endoprosthesis for proximal descending thoracic aortic aneurysms. It identifies successful device access during the treatment procedure as the primary endpoint and records an enrollment of 31. It also names secondary outcomes related to 1 month side branch primary patency and device-related endoleaks. These details define the study’s focus, but the primary and secondary outcome results are not reported in the registry record.

Accordingly, the record does not establish how many participants achieved successful access, how often the secondary outcomes occurred, or how precisely any such estimate was measured. No confidence intervals or outcome analyses are listed. The endpoint title is not itself a result, and the enrollment count cannot substitute for the missing outcome count. The information is insufficient to characterize the observed feasibility outcome.

The design also sets limits on interpretation. This is a single-group study with no like-for-like control comparison. The posted information therefore cannot estimate a comparative treatment effect or distinguish outcomes associated with the device from other influences. The safety counts provide descriptive information about participants affected, but they do not show that the device caused those events. Event timing, individual overlap, and relevant attribution information are not reported.

In general, a feasibility study can inform whether a procedural approach was attempted and what outcomes were recorded in a particular study group. The strength of that description depends on complete outcome reporting, clear definitions, and an understandable analysis population. Here, the registry supplies the broad access definition and study design but not the primary result or detailed analysis methods. The appropriate reading is therefore limited: the record documents the question and design and includes some safety counts, while leaving the main feasibility finding and its uncertainty unreported.

14. Why This Trial Matters Statistically

This study illustrates why a registry endpoint definition and an endpoint result answer different questions. The primary endpoint states what investigators intended to count: participants with successful study-device access during the procedure on day 0. But without the observed count and a defined analysis denominator, readers cannot assess how often that procedural milestone was achieved. A well-described question is not a substitute for the result needed to answer it.

The single-group design is another important statistical feature. It can support a description of experience in the treated group, but it does not supply a randomized contrast with another approach. That distinction matters when interpreting both procedural outcomes and adverse events. Descriptive counts may be informative, yet they cannot isolate comparative effects or establish causation on their own.

The record also demonstrates the value of reporting uncertainty and analysis details alongside counts. In general, confidence intervals help readers judge precision, while explicit analysis-population and missing-data rules explain which observations inform an estimate. Neither the primary result nor its uncertainty is reported in the registry record, and detailed analysis rules are not reported. The enrollment of 31 alone does not resolve those gaps.

Finally, safety summaries need careful denominators and attribution. Participant counts, event terms, percentages, and deaths each convey different information. Without details about overlap, timing, and attribution, readers should avoid treating descriptive safety counts as evidence of a causal relationship. These statistical distinctions are central to interpreting feasibility research responsibly, especially when the posted record does not contain the main outcome findings.

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 most consequential limitation of the registry record is that it names the primary outcome but does not report its result. The number of participants with successful device access, the endpoint-specific denominator, and an uncertainty estimate are not reported in the registry record. This prevents direct statistical interpretation of the main feasibility question.

The primary endpoint description is broad: it refers to access to the aneurysm and target landing-zone location using conventional vascular access and endovascular techniques. More detailed criteria for classifying success, handling technical failures, and assessing the outcome are not reported. The registry also does not identify the analysis population or describe missing-outcome handling.

The single-group design does not offer a like-for-like control comparison. The record therefore cannot support a randomized comparative estimate. Although secondary endpoints are named, their results are not reported in the registry record. The registry lists no analyses and does not report a statistical analysis plan, multiplicity approach, or protocol-based sample-size justification.

Safety interpretation is constrained by limited detail. The record gives counts of participants at risk and affected, a death count, and selected serious adverse-event terms with percentages. It does not report term-specific denominators, event overlap, timing, or attribution in the available summary. These omissions prevent a fuller assessment of how the safety figures were assembled and whether events were considered related to the device.

The registry lists enrollment of 31, but does not show whether all enrolled participants contributed to each outcome or whether follow-up was complete. The status is completed, yet that status does not supply missing endpoint results or analysis details. The record is therefore useful for identifying the study design and intended measures, but limited for evaluating the magnitude, precision, and interpretation of observed outcomes.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Feasibility Study for GORE® TAG® Thoracic Branch Endoprosthesis to Treat Proximal Descending Thoracic Aortic Aneurysms — NCT02021812.
• Registry record last updated 2022-09-09; status last verified 2022-08.
• Results first posted 2017-08-02.
• 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

The registry record describes a completed, single-group feasibility study of the GORE TAG Thoracic Branch Endoprosthesis in proximal descending thoracic aortic aneurysms. Enrollment is recorded as 31. Allocation is NA, masking is none, and phase is NA. The listed primary endpoint is the number of participants with successful study-device access during the treatment procedure on day 0.

The registry names secondary outcomes concerning 1 month side branch primary patency and the absence of 1 month device-related endoleaks. It also reports serious and other adverse-event counts and a death count for the Branched TAG Device group. The primary and secondary outcome results, endpoint-specific analysis populations, and statistical analyses are not reported in the registry record. The design has no control group, limiting comparative interpretation of both feasibility and safety observations.