This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Polar Wand Carbon Dioxide Cryotherapy for Barrett's Esophagus (NCT01477177), a na na study. The primary outcome is Reduction in Barrett's Histology Grade, Using the Modified Vienna Classification.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01477177 |
| Phase | NA |
| Condition | Barrett's Esophagus |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 4 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Mayo Clinic |
| Results posted | Yes |
2. Clinical Question
Population
People with Barrett’s esophagus and low-grade or high-grade dysplasia were the intended population. The registry describes the study as a pilot involving a small number of patients. It records enrollment of 4. Further participant characteristics and the number with each dysplasia grade are not reported in the registry record.
Intervention
The intervention was Polar Wand carbon dioxide cryotherapy, recorded as a device. The arm description characterizes it as a cryotherapy device using carbon dioxide described as room-temperature gas to treat gastrointestinal neoplasia. The registry’s brief summary frames the study as an initial assessment of feasibility, safety, and efficacy.
Comparator
There was no recorded comparison arm. The study is identified as a single-group model, with allocation listed as not applicable. It is therefore not a randomized, like-for-like comparison of cryotherapy with another treatment or with no treatment. Any change observed over time would not, by itself, isolate the effect of the device from other influences.
Primary question
The primary outcome was reduction in Barrett’s histology grade using the Modified Vienna Classification, with a 12-month timeframe. The registry description says reduction in Barrett’s segment length and histology classification would be measured at 12 months. The central question was whether the intervention could be assessed for feasibility, safety, and potential efficacy in a pilot study; the registry record does not report outcome analyses that answer those questions.
3. Trial Design
This was a pilot study of Polar Wand carbon dioxide cryotherapy for Barrett’s esophagus with low-grade and high-grade dysplasia. The registry lists Mayo Clinic as the sponsor, the study model as single group, and the phase and allocation as not applicable. Masking is listed as none. Enrollment was 4. The intervention was recorded as a device, and the treatment arm was called Polar Wand Treatment.
The registry lists a start date of 2011-08 and a primary completion date of 2014-04. Its status is terminated. The stated reason is that enrollment was much slower than anticipated and there were funding issues. These registry entries describe the study’s conduct and status; they do not establish why any individual participant did or did not complete follow-up. Participant flow, follow-up completeness, and reasons for withdrawal are not reported in the registry record.
The study’s stated purpose was an initial assessment of feasibility, safety, and efficacy in a small number of patients, intended to inform whether development of a full-scale trial was supported. This is a different purpose from a definitive comparison designed to estimate a treatment effect against a concurrent control. With no comparator arm, changes over time cannot be separated from the natural course of the condition, measurement variability, or other influences. The registry does not report a protocol-level statistical plan, a sample-size justification, or a planned control condition.
The registry lists five outcome measures and no analyses. It identifies reduction in Barrett’s histology grade using the Modified Vienna Classification as the primary outcome, with a timeframe of 12 months. Other listed outcomes concern segment length, complications, post-ablation symptoms, and histology grade. Results for these outcomes are not reported in the registry record.
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
| Stage | Polar Wand Treatment |
|---|---|
| STARTED | 4 |
| COMPLETED | 4 |
| NOT COMPLETED | 0 |
Analysis population for the primary outcome, as defined in the registry: Terminated study. Enrollment much slower than anticipated and funding issues.
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.
| Characteristic | Unit | Polar Wand Treatment |
|---|---|---|
| Participants analysed | 4 | |
| Age, Continuous | years | 66 (61 to 71) |
| Sex: Female, Male: Female | Participants | 0 |
| Sex: Female, Male: Male | Participants | 4 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 |
| Race (NIH/OMB): Asian | Participants | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 |
| Race (NIH/OMB): Black or African American | Participants | 0 |
| Race (NIH/OMB): White | Participants | 4 |
| Race (NIH/OMB): More than one race | Participants | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 |
| Region of Enrollment: United States | participants | 4 |
6. Primary Endpoint
The registry lists the primary outcome as Reduction in Barrett's Histology Grade, Using the Modified Vienna Classification, measured over 12 months.
| Element | Registry entry |
|---|---|
| Result type | N/A |
| Measure of spread | not applicable |
| Unit | not stated |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is titled reduction in Barrett’s histology grade, assessed using the Modified Vienna Classification, at 12 months. The registry description adds that Barrett’s segment length and histology classification would be measured at that time. It does not specify a numerical scoring rule, a threshold that would count as a reduction, or how results would be summarized. Those details are not reported in the registry record.
In general, a histology classification describes findings in tissue samples. Tracking a classification over time can be used to describe whether the recorded grade changes, stays the same, or moves in the other direction. The value of a classification-based endpoint depends on clear rules for sampling, assessment, and interpretation. General statistical considerations include whether the measure is ordinal, how categories are handled, and whether the same procedures are used at each assessment. The registry record does not provide these details, so the endpoint’s exact operational definition cannot be reconstructed from the record.
The endpoint is relevant to the study’s stated focus on Barrett’s dysplasia, but no post-treatment histology values or change summaries are reported. Consequently, the registry record does not show the magnitude, direction, or precision of any histology change. It also does not provide the endpoint’s analysis population or explain how missing 12-month assessments would be handled.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies a pilot study with enrollment of 4, a single-group design, and terminated status. It records a primary outcome of reduction in Barrett’s histology grade using the Modified Vienna Classification at 12 months, but reports no analyses. As a result, there is no posted estimate of histology change, no uncertainty interval, and no statistical test to interpret. The record therefore does not establish whether the endpoint changed, by how much it may have changed, or how precisely any change was estimated.
The termination reason recorded is enrollment much slower than anticipated and funding issues. This explains the status as given in the registry, but does not supply information about endpoint results. Slow enrollment and funding constraints can limit the amount of evidence generated; they should not be interpreted as evidence for or against an intervention effect. The registry describes the work as a pilot intended to provide an initial assessment and inform the development of a full-scale trial.
The absence of a comparator is important to interpretation. In a single-group study, a before-and-after difference, if reported, would describe change among observed participants. It could not, on its own, distinguish an intervention effect from changes that might occur over time for other reasons. General statistical reasoning also cautions that very small studies tend to produce uncertain estimates, even when an estimate can be calculated. Here, there is no outcome estimate in the registry record to assess for magnitude or precision.
The safety record lists 4 participants at risk in the treatment group, 0 with serious adverse events, 0 with other adverse events, and 0 deaths. These are event counts as recorded, not comparative safety estimates. The registry does not provide the duration or completeness of safety follow-up, event definitions beyond the serious and other categories, or further detail on how events were collected. Zero recorded events in this small study cannot establish that the risk of an event is absent.
The sample-size assumptions describe an illustrative planning framework based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The study itself was single-group, and no observed outcome effect or analysis is reported. Thus, any such planning illustration is hypothetical rather than evidence from this study, and it is not observed power. The record does not report an actual sample-size justification for the pilot.
9. Statistical Methods Explained
What can be inferred from the design?
The registry identifies a single-group study with no masking and no applicable allocation. These design features mean the record does not describe a randomized comparison or a concurrent control group. In general, random allocation can help balance measured and unmeasured prognostic factors between groups, while a control group can help distinguish an intervention-associated difference from changes that occur over time for other reasons. Those protections are not part of the design. This does not make a pilot study meaningless; it defines the kinds of conclusions its data could support.
A single-group pilot can be used to describe whether study procedures were feasible and to collect preliminary observations. The registry’s stated aim was an initial assessment of feasibility, safety, and efficacy to inform whether a full-scale trial should be developed. A pilot’s preliminary observations are not equivalent to a controlled estimate of treatment effect. The registry record does not report a formal feasibility measure, a threshold for success, or a statistical plan for assessing it.
What would an endpoint estimate mean?
In general, an endpoint estimate is a numerical summary of the observed outcome for the defined analysis population. For a change endpoint, the summary depends on which measurements are compared and how the change is represented. The registry names reduction in histology grade as the primary outcome and gives a 12-month timeframe, but does not state the scoring rule, the baseline comparison, or the summary measure. No endpoint estimate is reported, so there is no quantity whose magnitude can be assessed.
A confidence interval, in general, describes the uncertainty around an estimated quantity under the assumptions of the statistical method used. A narrow interval indicates greater precision than a wide interval, but neither interval width nor statistical significance alone establishes clinical importance. No confidence interval is reported in the registry record. Nor is a p-value or other inferential result reported. No statistical conclusion about the primary endpoint can therefore be drawn from the posted results.
Why does the absence of a comparator matter?
General interpretation of change over time requires care. Participants may change for reasons unrelated to the intervention, and outcome measurements may vary. Without a concurrent comparison group, observed change cannot separate those possibilities from an intervention-associated change. Even if individual pre-treatment and post-treatment values were available, they would not create a randomized comparison. The record reports no outcome analyses or individual measurements, so this limitation is conceptual as well as practical.
For a comparative trial, a treatment contrast is typically defined between groups. Here, the registry describes one treatment group and no control group. The sample-size assumptions mention equal allocation between two arms, but that is an illustration for planning rather than the design recorded for this study. The assumptions do not turn this pilot into a two-arm comparison and do not provide an observed treatment contrast.
How should sample-size illustrations be read?
General sample-size planning asks how much information a future study might need to detect a specified effect under stated assumptions. The assumptions in the record describe a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. They also refer to planning for a stated fraction of an observed effect. These are planning assumptions, not outcomes from the pilot. The record does not report a usable observed effect or analyses from which to judge such planning. Sample-size illustrations should not be described as observed power: power is a design property under specified assumptions, and a planning calculation does not show what this study found.
The record’s general note distinguishes time-to-event planning, which uses a total number of events, from other planning illustrations, which use participants per arm. This study’s listed primary endpoint is histology grade rather than a time-to-event outcome. No numerical planning result is reported in the registry record, and no sample-size justification for the actual single-group pilot is reported.
What is not available for statistical appraisal?
The registry lists five outcome measures and zero analyses. It does not report outcome distributions, estimates, uncertainty intervals, or hypothesis tests. The registry record also does not report a protocol-level statistical analysis plan, interim analyses, the approach to missing data, or the analysis populations. Without these details, it is not possible to assess whether analyses followed a prespecified plan, whether all enrolled participants contributed to each outcome, or whether incomplete follow-up could have affected interpretation.
In general, statistical methods are most interpretable when the endpoint, analysis population, handling of missing observations, and analysis approach are defined before results are known. That general principle does not establish what this study planned: those specifics are not reported in the registry record. The appropriate reading is therefore descriptive and bounded by the information recorded, without filling in unreported methods or results.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists five outcome measures. The primary outcome is reduction in Barrett’s histology grade using the Modified Vienna Classification at 12 months. The listed secondary outcomes concern Barrett’s segment length, complications, post-ablation symptoms, and histology grade. The record reports zero analyses, so it does not provide results for the primary or secondary outcomes.
In general, testing many outcomes can increase the chance of finding an apparently notable result by chance if each is tested separately. Statistical plans can address this through outcome hierarchies, adjusted testing procedures, or an explicitly exploratory interpretation. The registry record does not report whether multiplicity was considered, whether any adjustment was planned, or how the outcomes were prioritized beyond identifying the primary outcome. No adjustment method should be inferred.
Missing-data handling is also not reported in the registry record. The record does not state how many participants had an evaluable 12-month histology assessment, whether any measurements were missing, or whether missingness was addressed by exclusion, imputation, or another method. It also does not identify the analysis population, such as a population defined by enrollment, treatment received, or outcome availability. These omissions prevent assessment of how the reported enrollment relates to any endpoint analysis.
The reason for termination is recorded as enrollment much slower than anticipated and funding issues. That statement does not establish how many participants completed follow-up or whether missing outcomes occurred. No interim analyses, stopping rules, or prespecified statistical analysis plan are reported in the registry record. In the absence of results and these methods details, multiplicity and missing-data concerns remain unresolved rather than quantifiable.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Polar Wand Treatment | 0 | 4 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Polar Wand Treatment | 0 of 4 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Polar Wand Treatment | 0 of 4 |
The registry records 4 participants at risk in the Polar Wand Treatment group. It reports 0 serious adverse events, 0 other adverse events, and 0 deaths. These are descriptive counts for the group; the record does not provide a comparative safety estimate because there is no control group.
In general, a count of zero means that no event in that category was recorded among the participants represented in the available record. It does not prove that the event cannot occur, nor does it precisely establish the rate of an event in a wider population. The amount of information in a zero count depends on how many people were observed and how completely and for how long events were monitored. Follow-up duration for safety, event-collection methods, and additional event definitions are not reported in the registry record.
The small enrollment and absence of a comparator limit what can be learned about uncommon harms or differences in risk. The figures should be read as the registry’s reported counts, not as evidence that the intervention is free of serious or other adverse events. The record does not report detailed event narratives or a separate safety analysis.
12. What the Result Does, and Does Not, Mean
The registry record establishes that a small pilot study of Polar Wand carbon dioxide cryotherapy was conducted as a single-group study and later terminated. It records enrollment of 4 and gives slow enrollment and funding issues as the reasons for termination. It also identifies reduction in Barrett’s histology grade at 12 months as the primary outcome. These are useful details about the study’s purpose, design, and status.
The record does not report an analysis of the primary endpoint or any other outcome. It therefore does not show whether histology grade or segment length changed, how participants’ symptoms changed, or what complications occurred beyond the posted adverse-event counts. There is no reported estimate of effect, confidence interval, or statistical test. The absence of those results is not evidence that an outcome did or did not change.
The design also limits what an outcome change could establish, even if a change estimate were available. Because there was no comparison group, an observed within-group change would not distinguish the intervention from other causes of change over time. A pilot’s stated purpose is preliminary assessment and support for decisions about further study; it is not, by itself, a controlled estimate of comparative benefit or harm.
The safety counts are 0 serious adverse events, 0 other adverse events, and 0 deaths among 4 at risk. They describe what the registry records for this group, but do not demonstrate that risk is absent. The record does not describe safety follow-up duration or completeness, so the scope of those counts cannot be fully assessed.
Overall, the registry record documents an early, terminated investigation with no posted outcome analyses. It can inform readers about the intended question and the limits of the available evidence, but it cannot answer whether the intervention changed the measured outcomes or establish a causal treatment effect.
13. Why This Trial Matters Statistically
This study matters statistically because its stated purpose and design are clearly preliminary. The registry describes an initial assessment of feasibility, safety, and efficacy intended to inform whether a full-scale trial should be developed. That purpose calls for a distinction between collecting preliminary observations and estimating a reliable comparative treatment effect. The record identifies a single-group design, so the study does not provide a concurrent control for interpreting change over time.
The small enrollment of 4 and terminated status also make transparency about uncertainty especially important. The record attributes termination to slower-than-anticipated enrollment and funding issues. It reports no analyses, so readers cannot assess the size or precision of an outcome estimate. Statistical interpretation must not substitute a planning calculation for evidence: the sample-size assumptions described in the record are a planning illustration, not an analysis of observed results or evidence of observed power.
The study also illustrates why registry outcomes and analysis details matter. The primary endpoint is named, but the registry does not report the scoring rule, the analysis population, missing-data handling, or statistical plan. Without those details and results, the endpoint cannot be independently interpreted as a quantitative change. This is particularly important when a study lists several outcome measures and when follow-up is described at a specific time point.
These limitations do not erase the value of a pilot’s stated aim. They define what the record contributes: documentation of a planned preliminary assessment, its design, its termination reason, and limited safety counts. They also make clear why any next study intended to estimate comparative effects would need a design and analysis plan appropriate to that question. The registry record does not report whether such a study was subsequently conducted.
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.
The central limitation is that the registry reports no outcome analyses. There is no posted primary-endpoint estimate, no reported histology result at 12 months, and no outcome-specific measure of uncertainty. The listed secondary outcomes likewise have no analyses reported. Thus, the record cannot support a quantitative assessment of changes in histology grade, Barrett’s segment length, complications, or post-ablation symptoms.
The study was single group, with no comparator, and was unmasked. These design features constrain causal interpretation. Any change over time, if measured, could not be separated from other influences by a randomized control comparison. The enrollment was 4, and the study was terminated because enrollment was much slower than anticipated and funding issues arose. The registry does not report participant flow, completion of follow-up, or the number assessed for each outcome.
Important endpoint details are also absent. The primary outcome is named and has a 12-month timeframe, but the registry does not report a scoring rule, a threshold for reduction, or how histology assessments were conducted and summarized. Its description mentions both segment length and histology classification at 12 months, while segment length is also listed as a secondary outcome. The record does not clarify the analysis relationship between these measures.
Further limitations include unreported missing-data methods, analysis populations, multiplicity procedures, interim analyses, and a protocol-level statistical plan. Safety follow-up duration and event-collection details are not reported. The record’s planning assumptions do not supply a sample-size justification for the actual single-group pilot, and no observed effect is available for interpretation. These gaps limit the conclusions that can be drawn from the registry record.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Polar Wand Carbon Dioxide Cryotherapy for Barrett's Esophagus — NCT01477177.
- Registry record last updated 2019-05-15; status last verified 2019-04.
- Results first posted 2019-05-15.
- 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.
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18. Record Summary
NCT01477177 is a Mayo Clinic-sponsored pilot study titled Polar Wand Carbon Dioxide Cryotherapy for Barrett’s Esophagus. It studied Polar Wand carbon dioxide cryotherapy in a single group, with no masking and no applicable allocation or phase. Enrollment was 4. The registry lists a start date of 2011-08, a primary completion date of 2014-04, and terminated status. The recorded reason for termination is enrollment much slower than anticipated and funding issues.
The primary outcome was reduction in Barrett’s histology grade using the Modified Vienna Classification, with a 12-month timeframe. The registry lists five outcome measures and zero analyses. It reports 0 serious adverse events, 0 other adverse events, and 0 deaths among 4 at risk. No outcome estimates or statistical analyses are reported in the registry record, so the primary question about histology change cannot be answered from the posted results.