Clinical Study to Evaluate CryoBalloon™ Full and Swipe Ablation Systems for Ablation of Human Esophageal Epithelium: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Clinical Study to Evaluate CryoBalloon™ Full and Swipe Ablation Systems for Ablation of Human Esophageal Epithelium (NCT02729753), a non-randomized na study. The primary outcome is Safety of the CryoBalloon™ Full and Swipe Ablation System.

2. Clinical Question

The registry describes a human-esophageal-epithelium ablation study in people already scheduled for esophagectomy, rather than a trial designed to compare clinical outcomes between treatments. The primary safety outcome is specifically phrased around serious, device-related adverse events after Swipe treatment. The safety record also gives counts for the Full system, but this does not turn the study into a randomized comparison of the systems.

The record lists device performance outcomes for average procedure time and ease of deployment. Their values are not reported in the registry record. The clinical question is therefore narrow: the posted safety counts describe events in the recorded groups over the stated follow-up, not broader comparative effectiveness or longer-term clinical outcomes.

3. Trial Design

This was a completed study with enrollment of 10. The registry lists the phase as NA, allocation as nonrandomized, masking as none, and the model as single group. It also names both the CryoBalloon™ Full Ablation System and the CryoBalloon™ Swipe Ablation System and provides group-specific safety counts. These design features should be read together: the record contains information on two devices, but does not describe randomized assignment or a like-for-like control comparison.

Participants were scheduled to undergo esophagectomy for reasons unrelated to the study objective. The Full system was described as ablating 360 degrees of human esophageal epithelium, while the Swipe system was described as ablating 90 degrees. How participants were assigned to a device, whether any participant received both systems, and the order or specific conduct of procedures are not reported in the registry record.

The primary completion date is 2016-10-24, and the status is completed. The primary safety timeframe is 2 weeks. The registry identifies average procedure time and ease of deployment as secondary device-performance outcomes, but their measurement definitions, analysis results, and handling are not reported in the registry record. Likewise, a detailed protocol, eligibility criteria, and sample-size justification are not reported in the registry record.

Nonrandomized allocation means that observed groups may differ in ways not captured in the posted counts. With no described control condition, group differences cannot be interpreted as unbiased estimates of a device effect. The safety counts are descriptive records for the participants at risk in each group, not evidence from a controlled comparison.

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 Safety of the CryoBalloon™ Full and Swipe Ablation System, measured over 2 weeks.

The primary endpoint is the number of participants with serious, device-related adverse events after treatment with the CryoBalloon™ Swipe Ablation System, assessed over 2 weeks. It is a participant count: a person contributes to the endpoint if they meet the recorded event definition during the specified follow-up. The registry’s primary-outcome wording does not give a more detailed event definition or describe how device relationship and seriousness were adjudicated; those details are not reported in the registry record.

A short-term safety endpoint is used to describe whether serious events were recorded after the procedure. A count is direct and clinically interpretable, but on its own it does not convey the range or timing of event types, the certainty of classification, or the possibility of events outside the follow-up window. The registry record gives no longer-term primary safety timeframe.

The posted safety information lists zero serious affected participants for the Swipe group, with 6 at risk. It also lists zero for the Full group, with 3 at risk. These are descriptive observations from the recorded groups. The registry does not report an inferential analysis, confidence interval, or adjusted estimate for this endpoint, so the counts should not be read as a precise estimate of the event frequency beyond the observed participants and timeframe.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is a binary participant-level measure: each participant either meets the endpoint definition during the stated follow-up or does not. The registry presents this outcome as a count of participants, rather than as a time-to-event estimate or a continuous measurement. Its event definition includes seriousness and device relationship, and the timeframe is 2 weeks. The method used to assess seriousness or device relationship is not reported in the registry record.

What a participant count conveys

A count is straightforward to read, especially when the clinical question concerns whether any qualifying event was observed. Its interpretation depends on the denominator: a count without the number of participants at risk does not show how many people were observed for the outcome. The record gives group-specific denominators alongside affected-participant counts. Those denominators are the appropriate basis for describing the posted observations, but they do not by themselves resolve how participants entered each safety group or whether follow-up was complete.

General statistical explanation: an event proportion is often accompanied by an uncertainty interval. The interval indicates how much uncertainty remains about the underlying event frequency, given the observed data and the method used. When events are rare or absent, the observed count alone can give an overly reassuring impression of certainty. No interval estimates are reported in the registry record, so the precision of the event-rate estimates is not quantified there.

Why design affects interpretation

The study is listed as nonrandomized, unmasked, and single group, while the record separately names two devices and provides group-specific safety counts. Random assignment, if used, can help balance measured and unmeasured prognostic characteristics between groups. The registry does not describe random assignment. Differences between the device groups could therefore reflect participant selection, procedure circumstances, or other factors as well as the device. The record does not report enough information to adjust for such differences, and it reports no comparative analysis.

General statistical explanation: an unmasked study can also be vulnerable to differences in how outcomes are noticed, classified, or recorded. This matters especially for outcomes requiring judgment, such as seriousness or device relationship. It does not show that any classification was incorrect; it means the record’s absence of masking and lack of adjudication details should be kept in mind when interpreting the event counts.

What analysis is reported

The registry lists 4 outcome measures and 0 analyses. It identifies average procedure time and ease of deployment as secondary outcomes, but does not report their results in the record described. No p-values, confidence intervals, adjusted models, or hypothesis tests are reported. Thus, the available interpretation is descriptive. There is no reported basis for declaring a difference statistically significant, estimating an adjusted device effect, or quantifying uncertainty around a comparison.

General statistical explanation: a p-value, when reported, measures how compatible data are with a specified statistical model and null hypothesis; it is not a measure of the probability that a treatment works. A confidence interval conveys a range of values compatible with the data and the method’s assumptions. Neither can be reconstructed responsibly without the required analysis choices and data. No such inferential results are reported in the registry record.

How to read the planning illustration

The sample-size assumptions describe a planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation; the effect to detect is a stated fraction of the observed effect. The assumptions also specify that non-time-to-event illustrations are expressed as participants per arm. Such a calculation is a planning exercise, not an observed outcome and not evidence of the study’s achieved power.

The registry does not report that these assumptions were used to design the study, and a sample-size justification is not reported in the registry record. The record does not provide the numerical illustration values or describe the effect definition underlying it in sufficient detail. Any planning estimate should therefore be distinguished from the actual enrollment and observed event counts. Planning illustrations do not alter the descriptive nature of the posted safety results.

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("CryoBalloon™ Swipe Ablation System", "CryoBalloon™ Full Ablation System")
n      <- c(6, 3)
events <- c(0, 0)
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  CryoBalloon™ Swipe Ablation System  6  0  0.0  0.0  45.9  0.0  39.0  0.4  41.0
ARM  CryoBalloon™ Full Ablation System  3  0  0.0  0.0  70.8  0.0  56.1  0.6  60.2

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 4 outcome measures, including the primary safety outcome and secondary outcomes for average procedure time and ease of deployment. It reports 0 analyses. Results for the named secondary performance outcomes are not reported in the registry record. The record does not describe a hierarchy of hypotheses, a family of confirmatory tests, or an adjustment for multiple comparisons; these details are not reported in the registry record.

General statistical explanation: when several outcomes or statistical tests are examined, the chance of obtaining at least one apparently unusual result can increase if each test is interpreted separately. A prespecified hierarchy or multiplicity adjustment can help control that issue. Because no inferential analyses are listed, there is no reported multiplicity-adjusted or unadjusted testing result to interpret for this study.

The registry gives safety denominators for each device group, but does not explain the relationship between the group denominators and total enrollment of 10. Participant flow, exclusions from each analysis, loss to follow-up, and missing outcome data are not reported in the registry record. The record also does not specify an intention-to-treat, per-protocol, or other analysis population, or describe imputation or other missing-data methods. These omissions limit assessment of whether the recorded participants represent everyone enrolled and whether all participants were observed for the full timeframe.

These limitations should not be converted into assumptions that data were missing, that a particular analysis population was used, or that multiplicity was handled in a particular way. The registry record does not report those procedures. The available counts should be read as posted, with their stated denominators, rather than as results from an undocumented inferential plan.

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 non-serious adverse event terms

For serious adverse events, the record lists 0 affected participants among 3 at risk for the CryoBalloon™ Full Ablation System and 0 among 6 at risk for the CryoBalloon™ Swipe Ablation System. The primary outcome specifically concerns serious, device-related events after Swipe treatment within 2 weeks. These counts report what was recorded in the stated groups; they do not establish that serious events cannot occur.

The record lists 1 participant with an other adverse event among 3 at risk in the Full group and 0 among 6 at risk in the Swipe group. It does not describe those other events in the record described. Deaths are listed as 0 for both groups, and no serious-event terms are listed. The counts do not identify timing, duration, resolution, or individual clinical circumstances.

Because the study was nonrandomized and the denominators differ, these figures are not a controlled comparison of safety between devices. They are also limited to the recorded follow-up; the primary timeframe is 2 weeks. No confidence intervals or statistical comparisons are reported in the registry record. The safest statistical reading is therefore descriptive: report the counts and denominators as recorded, and avoid treating zero observed events as proof of zero underlying risk.

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

The record documents a small completed study of two ablation systems in patients scheduled for esophagectomy for reasons unrelated to the study objective. It reports zero serious affected participants in each device group and gives the corresponding group-specific denominators. For the primary Swipe safety outcome, the stated observation window is 2 weeks. The record also lists other adverse events and deaths by group.

These observations do not establish that either system is free of serious risk. A zero count among the participants observed is not the same as proof that the underlying event frequency is zero. The short stated timeframe also cannot answer questions about events occurring later. The registry does not report a confidence interval or other inferential estimate that would quantify uncertainty around the counts.

Nor does the record establish that one system is safer or performs better than the other. Allocation was nonrandomized, masking was absent, and the registry does not describe a like-for-like control comparison. The group-specific counts are descriptive; differences in group composition or circumstances could affect them. Results for average procedure time and ease of deployment are not reported in the registry record, so safety counts should not be mistaken for evidence on those performance measures.

The study population is defined by planned esophagectomy, and the registry describes ablation of human esophageal epithelium. The record does not establish whether observations generalize to other populations, settings, or longer-term outcomes. In statistical terms, the posted results answer a limited question about events recorded in the observed participants over the stated follow-up. They do not provide a broad comparative estimate or a definitive statement about clinical benefit or harm.

14. Why This Trial Matters Statistically

This study illustrates why design labels and denominators matter when reading clinical safety results. The registry identifies the study as nonrandomized and single group, yet gives safety counts separately for the Full and Swipe systems. A reader must distinguish these descriptive group summaries from a randomized comparison: the record does not establish that the groups were comparable at baseline or that any difference arose from the device alone.

The endpoint also shows the importance of specifying what is counted. The primary measure is the number of participants with serious, device-related adverse events after Swipe treatment during 2 weeks. That is narrower than a count of all adverse events, and it differs from device-performance outcomes such as procedure time or ease of deployment. Clear separation of these outcomes prevents one type of result from being used as a substitute for another.

Zero events can be clinically salient, but statistical interpretation still depends on the number observed, the follow-up period, event definitions, and uncertainty. Here, the safety denominators are small and no interval estimate or inferential analysis is reported. The posted counts are useful as a transparent record of what was observed, but they do not by themselves establish a precise underlying event rate.

The registry also highlights the value of complete reporting. Information about assignment, participant flow, missing data, event adjudication, and the analysis population is not reported in the registry record. Without these details, readers cannot fully assess selection, outcome classification, or completeness. Recognizing those limits is part of sound biostatistical interpretation, not a reason to discard the counts.

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.

Several trial-specific limitations constrain interpretation. The study is nonrandomized and unmasked, and the registry lists a single-group model. Although safety results are separated by device, assignment methods and the rationale for group membership are not reported in the registry record. The two groups therefore cannot be treated as randomized or exchangeable controls.

The registry reports enrollment of 10, while the adverse-event record gives 3 at risk for the Full system and 6 at risk for the Swipe system. The relationship between enrollment and these denominators is not explained in the registry record. Participant flow, the number completing follow-up, and any exclusions from the safety counts are not reported. Missing outcomes and their handling are likewise not reported in the registry record.

The primary follow-up timeframe is 2 weeks, limiting interpretation to the stated short-term window. Event definitions, seriousness assessment procedures, and device-relatedness adjudication are not described in the registry record. No serious-event terms are listed, and the other adverse events are not characterized by type in the information reported.

The record lists 4 outcome measures but no analyses. Results for the named secondary outcomes of average procedure time and ease of deployment are not reported in the registry record. No inferential estimates, confidence intervals, or sample-size justification are reported in the registry record. The planning assumptions are not evidence that the trial was designed or powered to answer a particular question. These reporting gaps mean that conclusions should remain descriptive and limited to the posted counts.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Clinical Study to Evaluate CryoBalloon™ Full and Swipe Ablation Systems for Ablation of Human Esophageal Epithelium — NCT02729753.
• Registry record last updated 2022-04-22; status last verified 2018-09.
• Results first posted 2018-10-12.
• 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 describes a completed, nonrandomized study of the CryoBalloon™ Full and Swipe Ablation Systems in patients scheduled for esophagectomy for reasons unrelated to the study objective. Enrollment was 10; the primary safety timeframe was 2 weeks. The primary outcome was the number of participants with serious, device-related adverse events after Swipe treatment.

The safety record lists 0 serious affected participants among 3 at risk in the Full group and 0 among 6 at risk in the Swipe group. Other adverse events are listed for 1 participant in the Full group and 0 in the Swipe group; deaths are listed as 0 in both groups. The registry lists no analyses. Secondary performance results, assignment details, missing-data procedures, and a sample-size justification are not reported in the registry record. The counts are descriptive and do not support a randomized comparison between devices.