Cytosponge™ for Post-Chemoradiation Surveillance of Oesophageal Cancer: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Cytosponge™ for Post-Chemoradiation Surveillance of Oesophageal Cancer (NCT03529669), a na na study. The primary outcome is Completion Rate.

2. Clinical Question

3. Trial Design

This was a completed, single-group feasibility study of the Cytosponge™ device for post-chemoradiotherapy surveillance in people with oesophageal cancer. The registry lists an enrollment of 41 and identifies the University of Oxford as sponsor. The recorded start date is 2018-04-18, and the primary completion date is 2020-01-30. These dates and enrollment describe the registry record; they do not establish how many participants contributed to each outcome analysis.

The study plan described one Cytosponge™ procedure for each participant, at one time-point within 4-16 weeks after completion of chemoradiotherapy. Eligible participants had known oesophageal cancer and had received pre-operative or definitive chemoradiotherapy. The intervention is classified as a device. The registry identifies no masking and no allocation scheme, and the study model is single-group. There was no control arm for a like-for-like comparison.

The primary outcome was completion rate, described as the percentage of consented, evaluable patients who successfully underwent the procedure. The registry also lists secondary outcomes concerning serious adverse events related to the device procedure, biomarker analysis, acceptance, and willingness to repeat the procedure. These are outcome topics, not reported results: numerical results for them are not reported in the registry record. The record contains no posted analyses. Consequently, the design can be described, but the measured completion rate and the results of the other outcomes cannot be assessed from 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

Analysis population for the primary outcome, as defined in the registry: Individuals who attempted to carry out the Cytosponge procedure.

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 Completion Rate, measured over Day 1 following intervention.

The primary endpoint is Completion Rate, defined in the registry as the percentage of consented, evaluable patients successfully undergoing the Cytosponge™ procedure. Its stated timeframe is Day 1 following intervention. The endpoint is intended to describe whether participants could complete the procedure, making it relevant to feasibility rather than a comparison of clinical effectiveness.

The registry's population description refers to individuals who attempted the procedure, while the endpoint description specifies consented, evaluable patients. Those phrases do not provide a numerical denominator or clarify how participants who were not evaluable would be handled. The number who successfully completed the procedure, the denominator used, and the resulting percentage are not reported in the registry record. Therefore, the endpoint's definition is available, but its observed value and precision cannot be characterized from that record.

In general, a completion outcome can be represented as a participant-level success or non-success and summarized as a proportion. Such a summary is useful for describing whether a procedure was carried out in a study setting. It does not, by itself, establish diagnostic accuracy, the ability to detect recurrence, or a benefit compared with another surveillance method. Those questions require outcomes and comparisons beyond the primary endpoint.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The statistical approach that can be described from the registry is limited by the absence of posted outcome analyses. The primary outcome is a participant count summarized as a completion percentage, but the numerator, denominator, estimate, and uncertainty are not reported in the registry record. The study's design and endpoint definition nevertheless illustrate several important statistical distinctions.

What a completion percentage represents

In general, a binary outcome places each participant into one of two categories for the outcome being assessed, such as successful completion or non-completion. A proportion is the number meeting the defined outcome divided by the number included in the analysis. For this study, the registry describes the completion endpoint as the percentage of consented, evaluable patients who successfully undergo the procedure. It separately describes the population as individuals who attempted the procedure. Since the registry does not report the analyzed denominator or explain the relation between those descriptions, the calculation cannot be reconstructed from the record.

The choice of denominator matters. A rate among all consented participants answers a different descriptive question from a rate among only those who attempted the procedure or those deemed evaluable. A reader needs the analysis population and the handling of participants with missing or incomplete outcome information to interpret the estimate. Those details are not reported in the registry record. No percentage can be calculated from enrollment alone, and no unreported denominator should be assumed.

How uncertainty would be interpreted

In general, a confidence interval expresses statistical uncertainty around an estimate under a specified model and analysis. For a proportion, the interval's width depends in part on the amount of outcome information and on the observed proportion. A narrow interval indicates greater statistical precision than a wide one, but neither interval width nor an estimate alone establishes that a procedure is clinically useful. In this study, the registry record does not report a completion estimate or confidence interval. Therefore, the precision of the primary result cannot be judged.

A p-value is commonly used to assess how compatible data are with a specified null model, given the statistical assumptions. It does not measure the size or importance of an effect. This registry record does not report posted analyses or a primary p-value. More fundamentally, the primary endpoint is a single-group completion description, and no between-group contrast is defined. It would not be appropriate to invent a test or treat the study as a randomized comparison.

Single-group design and comparisons

In general, a single-group study can describe outcomes observed among its participants, subject to how those participants were selected and how outcomes were recorded. It cannot, on its own, separate the effect of an intervention from differences that would have occurred under another approach. Here, allocation is listed as NA, masking as none, and the model as single-group. The record also flags that the arms are not a like-for-like control comparison. There is no control arm in this study from which to estimate a comparative effect.

This does not make a feasibility outcome meaningless: completion can be a descriptive measure of whether the procedure was carried out. It does mean that interpretation should stay within that scope. Procedure completion is distinct from the accuracy of a biomarker result, the detection of disease, and patient outcomes. The listed secondary outcomes address some additional topics, but numerical results for them are not reported in the registry record.

Planning calculations are not observed power

In general, sample-size planning calculations estimate how much information a future study might need for a chosen statistical objective under stated assumptions. The planning illustration associated with this analysis is described as using the observed effect, a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; its target effect is a stated fraction of the observed effect. These are planning assumptions, not a description of the actual single-group design. The registry does not report that they were the trial's own design assumptions or sample-size justification.

Such planning numbers are hypothetical requirements under their assumptions, not observed power. Observed power is not a substitute for an estimate and its uncertainty, and a sample-size illustration cannot establish what happened in the trial. The record does not report the observed primary effect needed to evaluate the illustrative target, nor does it report the trial's own sample-size justification. The planning illustration should therefore be understood as separate from the study's observed completion result.

Why model assumptions matter

In general, statistical methods depend on assumptions about the data and the way observations were collected. For a participant-level binary endpoint, the outcome definition and analysis population are central: ambiguous eligibility or missing outcomes can alter the interpretation of a proportion. An analysis also needs to state how uncertainty was calculated. No such primary analysis details are reported in the registry record. Since no estimate is posted, there is no basis to assess whether a particular statistical model fitted the observed results or whether alternative methods would materially change the interpretation.

For a two-arm planning illustration, equal allocation and a normal approximation are assumptions about the hypothetical design and calculation. They do not describe this single-group feasibility study. The distinction between planning methods and the trial's recorded design is essential: calculations built around two arms cannot create a comparator that the study did not have.

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("Cytosponge™")
n      <- c(41)
events <- c(39)
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  Cytosponge™  41  39  95.1  83.5  99.4  83.9  98.7  83.8  98.5

11. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary outcome and several secondary outcomes, including procedure-related serious adverse events, biomarker positivity, acceptance, and willingness to repeat the procedure. When several outcomes are assessed, multiplicity can arise if multiple statistical tests are used to support claims. In general, adjusting for multiplicity can help control the chance of false-positive findings across a family of tests, while a prespecified hierarchy can clarify which outcomes are confirmatory and which are exploratory. Whether any multiplicity adjustment or testing hierarchy was planned is not reported in the registry record.

The registry record contains no posted analyses. It does not report outcome estimates, tests, or a multiplicity strategy, so it is not possible to determine whether adjustments were needed or used. The listed outcomes should not be treated as evidence that each was analyzed or that any statistical claim was made.

Missing-data procedures and the number of participants included in each outcome analysis are not reported in the registry record. For the primary endpoint, the registry describes the outcome denominator as consented, evaluable patients and the population as individuals who attempted the procedure. It does not state how participants with incomplete assessments, unsuccessful attempts, or unavailable endpoint information were classified. These details matter because the analysis population determines the question answered by a completion percentage.

In general, an analysis population should be defined before results are interpreted, and the handling of missing observations should be made explicit. No primary analysis population beyond the endpoint wording is described in sufficient detail to establish the denominator. The enrollment of 41 should not be assumed to be the number analyzed for every outcome. Without denominators and missing-data information, the completeness and comparability of the outcome summaries cannot be assessed.

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: acute cholecystitis (2.6%), pneumonia (2.6%).

The adverse-event record for the Cytosponge™ group lists 39 participants at risk for serious adverse events and 1 affected, and 39 at risk for other adverse events and 3 affected. It also lists 3 deaths. Acute cholecystitis and pneumonia appear among the serious adverse-event terms, each listed at 2.6%. These are the registry's recorded figures; the record does not report a fuller account of timing, clinical context, or event-level overlap.

The secondary outcome is specifically described as the number of serious adverse events related to the device procedure. The adverse-event figures alone do not establish that a serious event or death was caused by the procedure. The registry record does not provide enough detail to make that attribution, and the listed death count should not be interpreted as procedure-related mortality.

In general, adverse-event counts are interpreted in relation to the participants assessed, the period of observation, and the rules used to define and attribute events. Counts do not by themselves measure comparative risk, particularly in a single-group study without a control arm. The record does not report a comparative safety estimate or enough detail to determine how the adverse-event observation period relates to the procedure timeframe. These figures should therefore be read as recorded event counts and terms, not as proof of causation or a comparison with another approach.

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

The registry record establishes that a single-group feasibility study evaluated Cytosponge™ after chemoradiotherapy for oesophageal cancer. Its primary question was whether consented, evaluable patients could successfully undergo the procedure. However, the registry record does not report the completion-rate result. It therefore cannot support a numerical conclusion about the observed proportion completing the procedure or the precision of that estimate.

The record also does not report numerical results for the secondary outcomes concerning biomarker findings, acceptance, or willingness to repeat the procedure. These outcomes are relevant to the topics the study set out to examine, but their inclusion in the registry is not a result. The adverse-event fields contain counts and terms, which can be described, but they do not establish that events were caused by the device procedure.

The single-group design answers a descriptive feasibility question rather than a comparative one. Without a comparator group, it cannot estimate how outcomes would differ under another surveillance approach. Completion is also not equivalent to a test's ability to identify disease or to evidence that a surveillance strategy changes clinical outcomes. Those interpretations require results and comparisons not reported in this record.

In general, results are most interpretable when the outcome definition, analyzed population, denominator, estimate, and uncertainty are all reported. Here, enrollment is recorded as 41, but the number assessed for the primary endpoint and the primary estimate are not reported. The registry does not state how missing or non-evaluable observations were handled. Thus, even the intended descriptive outcome cannot be quantitatively evaluated from the registry record.

The appropriate reading is limited: the record documents the study's purpose, design, and named outcomes, along with some adverse-event information. It does not establish the magnitude or precision of the primary endpoint, a comparative advantage, diagnostic performance, or clinical benefit. Those claims should not be inferred from the completed status or from the study's feasibility rationale.

14. Why This Trial Matters Statistically

Feasibility studies address practical questions that arise before a larger evaluation can be interpreted: whether an intervention can be delivered as intended and whether participants can complete the procedure. This study framed completion of Cytosponge™ after chemoradiotherapy as its primary endpoint. That focus makes the definition of success, the eligible analysis population, and the denominator especially important statistical details.

The record also illustrates why design and outcome reporting need to be read together. A single-group study can provide a descriptive account of its participants, but it cannot estimate a comparative effect against an unobserved control group. A completion percentage, even if reported, would answer a narrower question than whether the device identifies disease accurately or changes clinical outcomes. Keeping these questions separate prevents a feasibility measure from being interpreted as evidence for a different claim.

Several outcomes are named, spanning completion, safety, biomarker analysis, acceptance, and willingness to repeat the procedure. Their presence shows the range of issues the study aimed to consider, but absent numerical results and analysis details they cannot be weighed statistically. In general, transparent reporting of denominators, uncertainty, missing-data handling, and analysis populations is necessary to judge how stable and interpretable estimates are.

The registry record is statistically informative about the study structure and intended questions, while also showing the limits of what can be concluded without posted outcome analyses. That distinction is valuable for clinical researchers: a registered outcome is not the same as a reported estimate, and a planning illustration is not evidence of an observed result. The design and the available reporting determine which conclusions the data can support.

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 immediate limitation for interpreting this trial is that the primary completion-rate result is not reported in the registry record. The number of participants who completed the procedure, the endpoint denominator, and any estimate of uncertainty are also not reported. Although enrollment is listed as 41, the record does not establish how many participants were included in the primary analysis or in each secondary outcome analysis.

The endpoint descriptions use different population wording: the primary outcome is described as a percentage among consented, evaluable patients, while the population is described as individuals who attempted the procedure. The registry does not clarify how these groups relate or how participants without an evaluable outcome were handled. Missing-data procedures and analysis populations are not reported in the registry record.

The single-group design has no comparator and no masking. As a result, the study cannot provide a like-for-like comparison with another surveillance approach. The record also does not report numerical results for the listed biomarker, acceptance, or repeat-procedure outcomes. Adverse-event counts are available, but event attribution, context, and overlap are not detailed enough in the registry record to determine causality.

The registry does not report the trial's own sample-size justification, a detailed statistical analysis plan, or whether multiplicity procedures were planned. The separate planning assumptions described for illustrative calculations should not be mistaken for the study protocol. Together, these gaps limit assessment of the primary result, its precision, and the scope of any statistical conclusions that could be drawn from the study.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Cytosponge™ for Post-Chemoradiation Surveillance of Oesophageal Cancer — NCT03529669.
• Registry record last updated 2022-07-25; status last verified 2022-03.
• Results first posted 2022-07-25.
• 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

NCT03529669 is a completed, single-group feasibility study sponsored by the University of Oxford. It evaluated one Cytosponge™ procedure, planned within 4-16 weeks after chemoradiotherapy, in people with oesophageal cancer. The registry lists enrollment of 41, a start date of 2018-04-18, and a primary completion date of 2020-01-30.

The primary endpoint was the percentage of consented, evaluable patients successfully undergoing the procedure, with a timeframe of Day 1 following intervention. Secondary outcomes concerned device-procedure-related serious adverse events, biomarker results, acceptance, and willingness to repeat the procedure. The registry record does not report the primary completion result or numerical results for those secondary outcomes. It lists adverse-event counts and serious-event terms, but does not establish that events were caused by the procedure. With no comparator group, the study's design supports a feasibility question rather than a comparative treatment or surveillance claim.