Belgian Trial Investigating the LifeStream Stent in Complex TASC C and D Iliac Lesions: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Belgian Trial Investigating the LifeStream Stent in Complex TASC C and D Iliac Lesions (NCT03349996), a na na study. The primary outcome is Primary Patency Rate Before Completion of the 12-month Follow-up Period..

2. Clinical Question

The trial concerns treatment of iliac lesions described as stenotic or occlusive and classified as TASC C or D. Its primary efficacy endpoint is primary patency at 12 months. The registry defines patency by the absence of a hemodynamically significant stenosis on duplex ultrasound, together with freedom from target lesion revascularization before the end of the 12-month follow-up window. The stated ultrasound criterion refers to stenosis >50% and a systolic velocity ratio greater than 2.5.

The posted primary result states that three patients experienced loss of primary patency before completion of the 12-month follow-up period. The record does not report the total number assessed for that endpoint, a patency proportion, or an uncertainty interval. The safety question listed in the trial summary is freedom from periprocedural serious adverse events; the adverse-event summary lists event counts and terms, but does not present a numerical result for that stated safety endpoint.

3. Trial Design

BELSTREAM is listed as a completed, single-group, non-randomized study of the LifeStream Peripheral Stent Graft System. The registry record lists an enrollment of 70 and identifies peripheral arterial disease as the condition. The study is described as physician-initiated and concerns treatment of complex TASC C and D lesions in native iliac arteries. No separate control arm is listed.

The intervention was the LifeStream Peripheral Stent Graft System. The brief summary states that pre-dilatation and post-dilatation could be performed at the physician’s discretion. Consequently, the registry description does not specify a uniform use of those procedures for all participants. The listed follow-up schedule includes visits at 1, 6, 12, 24, 36, 48 and 60 months after the procedure.

The primary efficacy endpoint is primary patency before completion of the 12-month follow-up period. The primary safety endpoint is described as freedom from periprocedural serious adverse events. Secondary outcomes include primary patency at other follow-up times, stent graft occlusion, ankle-brachial index, amputation, technical success and clinical success. The registry lists 8 outcome measures.

The study start is recorded as 2017-10-31 and primary completion as 2020-10-21; the current status is completed. The registry record does not report the statistical analysis plan, the sample-size justification, or whether interim analyses were conducted. There is no randomized comparison, so the design can describe outcomes observed in the treated group but cannot by itself estimate a comparative treatment effect against an untreated or alternative-treatment group.

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: Three patients experienced loss of primary patency before completion of the 12-month follow-up 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 Primary Patency Rate Before Completion of the 12-month Follow-up Period., measured over Before the end of the 12 month follow-up window.

The primary endpoint is primary patency before completion of the 12-month follow-up period. The registry defines a patent target lesion as having no hemodynamically significant stenosis on duplex ultrasound and having freedom from target lesion revascularization (TLR) during the specified period. The ultrasound criterion is described as stenosis >50% and a systolic velocity ratio greater than 2.5. The endpoint therefore combines an imaging assessment with whether a repeat procedure to revascularize the target lesion occurred.

General: Patency endpoints are used to describe whether a treated vessel or lesion remains open according to a prespecified clinical or imaging definition. Combining an imaging criterion with freedom from TLR can capture both a measured narrowing and a subsequent intervention. The definition matters because a different stenosis threshold, imaging method, or handling of revascularization could change which observations count as loss of patency.

The posted result says that three patients experienced loss of primary patency before completion of the 12-month follow-up period. It does not state the number with evaluable follow-up, the number meeting the patency definition, or a patency estimate with an uncertainty interval. The record also does not explain how missing or technically uninterpretable duplex assessments were handled. Those details are needed to assess the precision and completeness of the endpoint result.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical interpretation begins with the distinction between a count and an estimated rate. The primary result is reported as three patients experiencing loss of primary patency before completion of the 12-month follow-up period. A count gives the number of observed events, but a rate or proportion also requires a clearly stated denominator. The registry record does not report the number of patients included in the primary endpoint analysis or the number with complete follow-up. No percentage should be inferred from the event count without that information.

What does a confidence interval add?

General: A confidence interval communicates the uncertainty around an estimated quantity, such as a patency proportion. It reflects the fact that an estimate from a study group may vary across comparable samples. A narrow interval indicates greater precision under the assumptions of the analysis; a wide interval indicates less precision. An interval does not remove potential bias from missing observations, outcome measurement, patient selection, or the absence of a comparison group. The registry record does not report a confidence interval for the primary endpoint.

For a binary endpoint, the underlying information is often whether each participant met the endpoint definition or did not. The endpoint is not simply a test result: the definition includes duplex ultrasound findings and freedom from TLR before the end of the follow-up window. A complete analysis would need a rule for classifying observations when an ultrasound result is unavailable or when follow-up ends before the window closes. Such a rule is not reported in the registry record. Without the rule and the endpoint denominator, the event count cannot be translated reliably into an estimated proportion.

Why does the single-group design matter?

General: A single-group study can describe outcomes under the care received by its participants. A treatment contrast, by comparison, asks how outcomes differ between treatment strategies. Random allocation can help make groups comparable with respect to measured and unmeasured characteristics, on average, but BELSTREAM is listed as non-randomized and single-group. Its results therefore do not provide a randomized estimate of a difference between treatments. They also cannot distinguish treatment-related outcomes from changes that might have occurred because of participant characteristics, clinical decisions, or other factors.

The absence of masking is also recorded. Masking can sometimes reduce the influence of knowledge about treatment assignment on outcome assessment or participant and clinician behavior. The registry record lists masking as none, but does not describe procedures intended to reduce potential assessment bias. The primary endpoint includes an ultrasound assessment and TLR, so consistent assessment and endpoint classification are relevant. The record does not state how those processes were standardized or reviewed.

How should the follow-up schedule be read?

The listed visits occur at 1, 6, 12, 24, 36, 48 and 60 months after the procedure. These are intended assessment times, not evidence that every participant completed every visit. The registry record does not report visit completion, loss to follow-up, censoring, or missing endpoint data. Longer-term outcomes can be particularly sensitive to incomplete follow-up: participants no longer observed may differ from those who remain under observation. General: Time-to-event methods can account for different observation durations when their assumptions and event times are reported, but the registry entries do not identify such an analysis for BELSTREAM.

The registry lists the primary endpoint as a number of participants, and the posted result gives an event count. The registry entries do not provide a model-based estimate, an adjusted analysis, a p-value, or a confidence interval. No statistical test should be inferred from the presence of a reported count. Likewise, no adjustment for participant or lesion characteristics should be assumed. The statistical analysis plan is not reported in the registry record.

What do the planning assumptions mean?

General: A sample-size illustration describes how many participants might be required under a set of assumptions about an effect, significance level, allocation, and statistical method. It is a planning calculation, not a measure of the probability that a completed study detected an effect. The stated planning assumptions refer to two-sided significance level 0.05, equal allocation between two arms, a normal approximation, and an effect expressed as a fraction of the observed effect. Time-to-event illustrations are described as giving total events, while other illustrations give participants per arm. These conventions do not change BELSTREAM’s recorded single-group design and should not be read as the actual trial allocation or as observed power.

The registry record does not report that these planning assumptions were used to design BELSTREAM, nor does it report the trial’s sample-size justification. A planning illustration based on an observed effect is dependent on that effect estimate and on the assumptions stated for the illustration. It does not establish that the effect is precise, reproducible, or clinically meaningful. No planning values beyond the stated assumptions are available in the record details, and no new sample-size calculation can be derived from the primary event count alone.

General: Over-dispersion is extra variability beyond what a statistical model assumes. It can make standard errors too small if ignored, leading to intervals that are too narrow and tests that appear more decisive than warranted. This concept is relevant when outcomes are clustered or vary more than a model allows, but the registry record does not describe a model or report an over-dispersion assessment for this trial. It would be inappropriate to claim that over-dispersion was present or corrected for.

In summary, the clearest statistical reading is limited to the reported primary event count and the descriptive adverse-event summary. A fuller assessment would require the endpoint denominator, completeness of follow-up, handling of missing observations, analysis details, and uncertainty estimates. Those items are not reported in the registry record.

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("LifeStream Peripheral Stent Graft System")
n      <- c(70)
events <- c(3)
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  LifeStream Peripheral Stent Graft System  70  3  4.3  0.9  12.0  1.5  11.9  1.6  11.9

11. Multiplicity, Missing Data and Analysis Populations

The trial summary lists a primary efficacy endpoint and a primary safety endpoint, along with secondary outcomes assessed at several follow-up times. Multiple outcomes and repeated assessments create a multiplicity question: when many hypotheses or time points are examined, the chance of at least one apparently unusual result can increase if each is tested without adjustment. General: A prespecified hierarchy or multiplicity adjustment can help control how results are interpreted across several comparisons. The registry record does not report a statistical analysis plan or a multiplicity strategy, and the registry entries include no analysis results for these outcomes.

The primary efficacy endpoint is primary patency before completion of the 12-month follow-up period. Secondary outcomes include primary patency at 1, 6, 24, 36, 48 and 60 months, stent graft occlusion, ankle-brachial index, amputation, technical success and clinical success. The registry record does not provide details on which outcomes were formally tested, whether any were exploratory, or how repeated assessments were handled statistically. The number of outcome measures listed does not establish that every outcome was analyzed in the same way.

Missing data are also consequential for longitudinal outcomes. The registry describes planned follow-up at 1, 6, 12, 24, 36, 48 and 60 months, but does not report attendance, withdrawals, loss to follow-up, or missing measurements. It does not explain whether participants without an observed endpoint were excluded, treated as having an event, or handled through another method. The analysis population is not reported in the registry record. No intention-to-treat or per-protocol population can be assumed from the available information.

These omissions limit assessment of both bias and precision. Without an analysis population and missing-data rules, it is unclear how the primary count relates to the enrolled group. Without a multiplicity plan, interpretation of any results across multiple endpoints and visits would require caution. The primary efficacy count remains descriptive; it does not resolve these unreported analysis details.

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 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: perforation of right iliac artery (18.6%), fatal metastatic cancer (4.3%), heart failure (2.9%), right hip fracture (2.9%), copd exacerbation (2.9%).

The adverse-event summary lists the LifeStream Peripheral Stent Graft System group with 70 at risk for serious adverse events and 38 affected. For other adverse events, it lists 70 at risk and 28 affected. The summary also lists 12 deaths. These are separate reported entries; the record does not describe overlap among categories, explain the relationship between deaths and other event entries, or state the analysis population underlying each count.

The listed serious adverse event terms and percentages include Perforation of right iliac artery, 18.6%; Fatal metastatic cancer, 4.3%; heart failure, 2.9%; Right hip fracture, 2.9%; COPD exacerbation, 2.9%; and Severe anemia causing dyspnea and malaise, 1.4%. The registry record does not specify the denominator behind these term percentages in the registry record. They should therefore be read as reported descriptive percentages, not recalculated into counts.

The primary safety endpoint is described as freedom from periprocedural serious adverse events. The adverse-event summary does not report a corresponding numerical result for that specific endpoint or clarify which listed events were periprocedural. Event occurrence alone does not establish that the device or procedure caused an event. The registry record does not provide an attribution analysis or a comparative safety estimate.

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

The primary efficacy finding is that three patients experienced loss of primary patency before completion of the 12-month follow-up period. This is a clinically defined outcome that combines duplex ultrasound criteria with freedom from target lesion revascularization. It is a useful description of what was recorded, but the count alone does not show the proportion of participants who maintained patency. The primary endpoint denominator and uncertainty interval are not reported in the registry record.

The result also does not establish how outcomes would compare under another device or treatment strategy. BELSTREAM is a single-group study with no randomized comparator. A descriptive result in the treated group is not an estimate of the difference between treatment options, and it does not remove the possibility that patient characteristics, lesion severity, follow-up completeness, or clinical decisions influenced the observed outcomes.

The record lists adverse-event counts and serious event terms, but those entries should not be taken as proof that the intervention caused an event. The summary does not clarify how the adverse-event entries overlap, how they align with the stated periprocedural safety endpoint, or what attribution process was used. The listed deaths cannot be assigned a cause or treatment relationship from the count alone.

The study planned follow-up through 60 months, but the primary efficacy endpoint concerns the 12-month period. The registry entries available do not report numerical findings for later patency, occlusion, ankle-brachial index, amputation, technical success, or clinical success. Nor do they report missing follow-up, analysis populations, confidence intervals, or a statistical analysis plan. Those gaps prevent a complete assessment of durability, precision, and possible bias.

General: A study result is most informative when its endpoint definition, denominator, uncertainty, and analysis population are clear. A count can accurately convey the events reported while still leaving the rate and its precision uncertain. The BELSTREAM primary result should therefore be read as a descriptive registry finding, not as a comparative estimate or a definitive statement about performance beyond the information recorded.

14. Why This Trial Matters Statistically

This trial is statistically notable because its primary outcome is a binary clinical status assessed during follow-up, while the registry reports the primary result as an event count. Counts are easy to understand, but without a denominator and uncertainty estimate they do not show how precisely the underlying patency experience has been estimated. Transparent reporting of the analysis population and endpoint ascertainment would help readers assess the result’s reliability.

The study also illustrates the distinction between describing outcomes and estimating comparative effects. A completed single-group study can document outcomes after treatment, but cannot provide the same treatment contrast as a randomized comparison. This distinction is especially important when the reported outcome could be affected by participant characteristics, lesion complexity, clinician decisions, and completeness of follow-up. The registry identifies a complex lesion population and physician discretion for pre-dilatation and post-dilatation, but does not report how these factors were handled analytically.

Repeated follow-up and multiple secondary outcomes pose further statistical challenges. Patency is considered at the primary 12-month point and at other listed times, alongside outcomes such as occlusion and ankle-brachial index. Clear prespecification, handling of missing observations, and a plan for interpreting multiple endpoints are important to avoid overstating isolated findings. Those methods are not reported in the registry record.

Finally, safety counts require careful distinction between event description and causal attribution. The registry lists affected counts, deaths, and serious event terms, but does not provide enough detail to map them to the defined periprocedural safety endpoint or establish causation. Taken together, these features make BELSTREAM a useful example of why endpoint definitions, denominators, uncertainty, comparison design, and complete analysis reporting all matter when interpreting clinical trial results.

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 central limitation for interpreting the primary result is that the registry reports three patients with loss of primary patency but does not report the endpoint denominator, the number assessed, or an uncertainty interval. The enrolled group is listed as 70, but that does not establish how many contributed evaluable data to the primary endpoint. The record also does not specify how missing or incomplete duplex ultrasound results were classified.

The single-group, non-randomized design means there is no concurrent control for estimating a comparative effect. Masking is listed as none. The record does not describe independent endpoint review or procedures to reduce bias in imaging interpretation or TLR classification. Pre-dilatation and post-dilatation were left to physician discretion, so treatment details could vary; the record does not report how that variation was summarized or analyzed.

Follow-up was planned at multiple visits through 60 months, but completion and attrition are not reported in the registry record. This leaves uncertainty about the completeness of longer-term outcome ascertainment. The registry also lists secondary outcomes without numerical results here, and does not report a statistical analysis plan, analysis populations, multiplicity approach, or missing-data method.

For safety, the listed counts and percentages are not linked in the record to a clear denominator for each term, and the relationship between the adverse-event summary and the stated periprocedural safety endpoint is not explained. The event list does not establish causation. These limitations constrain conclusions about precision, longer-term outcomes, and comparative safety or efficacy.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Belgian Trial Investigating the LifeStream Stent in Complex TASC C and D Iliac Lesions — NCT03349996.
• Registry record last updated 2026-03-05; status last verified 2026-01.
• Results first posted 2026-02-09.
• 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.

19. Record Summary

The registry record describes BELSTREAM, a completed, physician-initiated, single-group study of the LifeStream Peripheral Stent Graft System for complex TASC C and D iliac lesions in people with peripheral arterial disease. Enrollment is listed as 70. The primary efficacy endpoint is primary patency before completion of the 12-month follow-up period, defined using duplex ultrasound findings and freedom from target lesion revascularization. The posted primary result states that three patients experienced loss of primary patency.

The registry lists freedom from periprocedural serious adverse events as the primary safety endpoint and includes secondary outcomes covering patency, occlusion, ankle-brachial index, amputation, technical success, and clinical success. The adverse-event summary lists 38 affected for serious adverse events, 28 affected for other adverse events, and 12 deaths. The registry record does not report a control group, an inferential analysis, confidence intervals, analysis populations, or detailed missing-data and multiplicity methods.