Staging and Outcome Depending on Surgical Treatment in Adenocarcinomas of the Oesophagogastric Junction: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Staging and Outcome Depending on Surgical Treatment in Adenocarcinomas of the Oesophagogastric Junction (NCT01766986), a registered phase not stated study. The primary outcome is Overall Survival.

2. Clinical Question

The background describes uncertainty about staging and classification before surgery, and says that this uncertainty makes selection of a surgical approach problematic. The study summary says the retrospective analysis examined preoperative and postoperative staging, surgical treatment and outcome using data from a prospectively collected database. This design can describe observed patterns and associations in the recorded patients. It cannot, by itself, establish that differences between surgical groups were caused by the operation or by staging classification.

The registry record does not report how AOG was defined, how staging was assessed, or how misclassification was identified. It also does not explain whether the primary question concerned prognosis, agreement between preoperative and postoperative staging, or a comparison of outcomes between surgical approaches. Those details matter for interpreting the scope of any conclusions, and should not be inferred from the title or summary alone.

3. Trial Design

The record identifies this as a retrospective study of patients with AOG. Its summary says the analysis used data from a prospectively collected database and considered surgical treatment, preoperative and postoperative staging, and outcome. Thus, the data collection described in the summary was prospective, while the stated analysis was retrospective. This distinction does not make the study a randomized trial.

The registry labels the study completed and records an enrollment of 130. The recorded start is 2008-01 and primary completion is 2013-01. The sponsor is Universitätsklinikum Hamburg-Eppendorf. The condition listed is esophageal carcinoma. Further details about recruitment, eligibility, study sites, the database, and the timing of individual assessments are not reported in the registry record.

No randomized allocation is described. The record explicitly notes that allocation is not stated and that the arms are not a like-for-like control comparison. It does not identify the surgical approaches associated with the groups, explain how patients came to receive a particular approach, or describe whether group membership was defined by treatment, staging category, or another characteristic. Without those details, group differences cannot be interpreted as a direct treatment effect.

The registry lists one outcome measure and no analyses. Overall survival is the named primary outcome, described as overall survival after surgery (months), with a timeframe of 36 months. However, no survival value, event count, comparison estimate, confidence interval, or statistical test is posted. The record also does not state a statistical analysis plan or explain how follow-up and censoring were handled.

The enrollment figure is a study-level record, while the adverse-event entries are reported under generic group labels. The record does not explain the relationship between those entries and the study’s surgical or staging groups. No additional design details should be inferred from those labels.

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

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.

Population: Only patients with histologically provenAOG type I or II who had not undergone neoadjuvanttherapy were included in this study. Demographic, clinical,operative and postoperative data were collected for eachpatient

6. Primary Endpoint

The registry lists the primary outcome as Overall Survival, measured over 36 months.

Overall survival is the listed primary outcome. In general, overall survival measures the time from a defined starting point until death from any cause. The registry describes the outcome as overall survival after surgery (months), which identifies surgery as the context, but does not specify the exact time origin, the method for determining death, or how patients without a recorded death were handled.

The stated timeframe is 36 months. A defined follow-up horizon can help make outcome reporting interpretable by clarifying the period to which an estimate refers. The record does not provide an estimate of survival at that horizon, a median survival time, a number of deaths, or any other numerical result for the endpoint. It also does not report whether survival was analyzed as a time-to-event outcome or through another summary.

In general, overall survival is used because it captures death from any cause and can be clinically meaningful as a broad outcome. Time-to-event methods can account for differing follow-up durations when their assumptions and data are appropriate. Those are general properties of the endpoint and methods; the registry record does not establish which method was used in this study.

The endpoint’s title alone does not establish what the observed survival was or whether it differed across staging or surgical groups. Without posted estimates and their uncertainty, the primary outcome cannot support a quantitative conclusion about prognosis or group differences.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record does not report a statistical analysis plan. It lists an outcome measure but no analyses, and it does not give an analysis population, statistical model, adjustment strategy, or method for calculating uncertainty. The following concepts explain how such analyses are commonly interpreted in general; they do not establish which methods this study used.

What does a confidence interval describe?

In general, a confidence interval describes the uncertainty around an estimated quantity under a specified statistical method. A narrow interval indicates greater precision than a wide interval, while an interval spanning a range of plausible values may leave substantial uncertainty about the size or direction of an effect. A confidence interval does not correct for bias in the study design, unmeasured confounding, inaccurate measurement, or selective reporting. No confidence interval for overall survival or a group comparison is reported in the registry record.

How are time-to-event outcomes usually analyzed?

Overall survival is commonly treated as a time-to-event outcome. In general, time-to-event methods use both the time until an event and information from participants whose event time is not observed during follow-up. Those participants may be censored, meaning their follow-up contributes information up to a recorded point without establishing when an event occurred afterward. Appropriate interpretation depends on the time origin, follow-up completeness, censoring rules and assumptions about how censoring relates to the outcome. The registry does not report these details, an event count, or a survival curve.

A survival estimate at a specified horizon and a comparison of survival over follow-up answer related but different questions. A horizon-specific estimate describes survival at that point; a time-to-event comparison can use the pattern of event times across follow-up. The record gives a 36 months timeframe but no estimate or description of the method, so it is not possible to tell which summary was planned or posted.

Why does group formation matter?

For a causal treatment comparison, groups should be comparable in factors that influence both treatment selection and outcome. Random assignment is one way to support comparability, but no randomized allocation is described. The registry explicitly states that allocation is not stated and that the arms are not a like-for-like control comparison. In a retrospective study, measured differences might sometimes be addressed with adjustment or other methods, but such methods cannot guarantee removal of bias from unmeasured or poorly measured factors. The record does not report whether adjustment was performed.

Staging comparisons also depend on clear definitions and consistent measurement. Comparing preoperative with postoperative staging would require information on the staging systems, assessment procedures, and rules for classifying disagreement. Those details are not reported in the registry record. It is therefore not possible to assess the reproducibility of staging or the statistical treatment of misclassification.

What does over-dispersion mean in general?

For count outcomes, over-dispersion occurs when observed variability is greater than a statistical model expects. If ignored, uncertainty estimates can be too small and tests can be misleading. This concept is relevant only when a suitable count outcome and model are used; the registry record does not report a count model or indicate that over-dispersion was assessed. It should not be read as a description of this study’s analysis.

How should planning illustrations be read?

In general, sample-size calculations depend on assumptions about the outcome, effect to detect, variability, significance level and allocation. A planning illustration based on an observed effect is not the study’s original design justification and is not observed power. The record describes an illustration using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; it says the effect to detect is a stated fraction of the observed effect. It also distinguishes total events for time-to-event calculations from participants per arm for other calculations. These assumptions do not demonstrate that the study used that design, nor do they supply an analysis of the posted survival outcome.

Because the registry reports no analysis results, there is no effect estimate to assess for precision and no inferential result to interpret. Statistical methods can clarify how evidence would be summarized, but they cannot replace missing estimates or establish which methods were actually applied.

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("Group 1", "Group 2", "Group 3")
n      <- c(41, 51, 38)
events <- c(12, 11, 13)
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  Group 1  41  12  29.3  16.1  45.5  17.6  44.5  17.6  44.6
ARM  Group 2  51  11  21.6  11.3  35.3  12.5  34.6  12.5  34.7
ARM  Group 3  38  13  34.2  19.6  51.4  21.2  50.1  21.2  50.2

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists one outcome measure and no analyses. It names overall survival as the primary outcome, but does not provide a statistical analysis plan or explain whether other outcomes, staging comparisons, surgical comparisons, or subgroup analyses were planned. The method for controlling the risk of false-positive findings when testing multiple hypotheses is not reported in the registry record.

Multiplicity matters in general when several outcomes, comparisons, time points, or subgroups are examined. The more opportunities there are to identify an apparently notable result, the more important it is to know which analyses were planned and how results were interpreted. Without a prespecified analysis plan, readers cannot distinguish planned analyses from exploratory ones. The registry record does not provide enough detail to assess this issue for the study.

Missing-data procedures are also not reported in the registry record. It does not state whether survival follow-up was complete, how loss to follow-up was handled, how missing staging information was treated, or whether any imputation was used. For time-to-event outcomes, censoring rules and follow-up completeness are particularly relevant to interpretation. No assumptions about missingness or censoring should be inferred.

The record does not define the analysis population or say whether analyses included all enrolled patients, only patients who underwent surgery, or another group. It also does not describe exclusions or the availability of data for each outcome. The enrollment figure alone does not identify the denominator used for any particular analysis.

These omissions limit assessment of both the robustness and scope of the reported evidence. They do not prove that the study had missing data or multiple testing; they mean that the registry record does not report how those issues were addressed.

12. Safety Results

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

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

Serious events with the highest arm-level rate: adverse event (0.0%).

The registry lists serious adverse-event entries under Group 1, Group 2 and Group 3. The respective numbers at risk are 41, 51 and 38, and each group lists zero affected participants for the serious adverse-event entry. The listed top serious term is “Adverse event” at 0.0%.

These are the adverse-event figures reported in the record, not a complete description of safety monitoring. The groups are not clinically identified, and the registry does not explain how they relate to surgical approaches or staging categories. It also does not report the adverse-event definition, collection method, observation period, severity grading, or whether every participant had the same opportunity for events to be recorded.

A zero in a reported entry means no affected participants are recorded for that entry in that group; it does not establish that no events could occur or that safety was comprehensively assessed. The figures should not be interpreted as evidence of comparative safety because the groups are not described as randomized or like-for-like controls. The registry record does not report an analysis comparing adverse-event risks.

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

The record establishes that the study addressed preoperative staging and classification of AOG in relation to surgical treatment and outcome. It describes a retrospective analysis using a prospectively collected database and names overall survival after surgery as the primary outcome, with a 36 months timeframe. This provides context for the research question, but not a quantitative answer to it.

No survival estimate or statistical analysis result is posted. There is no reported estimate of survival, group comparison, confidence interval, p-value, or event count for the primary outcome. Accordingly, the record does not show whether survival differed by surgical treatment, whether preoperative misclassification was related to outcome, or how precisely any association was estimated.

The design also limits what could be concluded from a group comparison. The record does not describe randomized allocation and explicitly says that allocation is not stated and that the arms are not a like-for-like control comparison. In general, retrospective group differences can reflect both treatment and differences in the patients or disease characteristics associated with treatment selection. The registry does not report whether these factors were measured or adjusted for. A causal conclusion about the effect of surgery would therefore not be justified from the record alone.

The serious adverse-event entries report zero affected participants in each listed group, with a top serious term recorded at 0.0%. Those entries do not establish comparative safety, given the absence of group definitions and safety-method details.

The appropriate interpretation is narrow: the registry describes the study purpose, design context, primary outcome label and limited adverse-event entries, but does not report the principal outcome analysis. It neither demonstrates a survival benefit nor demonstrates an absence of a survival difference. Any such claim would require results and methods not reported in the registry record.

14. Why This Trial Matters Statistically

This study’s statistical question sits at the intersection of classification, treatment selection and outcome. The summary identifies controversy about preoperative staging and says that uncertainty complicates the choice of surgical approach. Statistically, that raises questions about how accurately staging represents disease and how patient groups can be compared when treatment is not randomly assigned.

The distinction between a prospectively collected database and a retrospective analysis is important. Prospective data collection may support planned and consistent recording, but retrospective analyses still depend on what was measured, how variables were defined, and which observations were available for analysis. The registry record does not report enough detail to assess those features. Data collection alone does not remove confounding or measurement error.

The record also illustrates why naming a primary endpoint is not the same as reporting evidence about it. Overall survival and a 36 months timeframe are specified, but no survival estimate or analysis result is posted. Without an estimate and a measure of uncertainty, readers cannot evaluate the magnitude, direction or precision of the outcome.

Finally, the warning that the arms are not like-for-like controls is central to interpretation. Comparisons in nonrandomized data may reflect differences in who received each approach as well as any treatment-related differences. Transparent descriptions of group definitions, adjustment methods, follow-up and missing data would help readers judge those comparisons. Their absence in the registry record prevents that assessment, so the statistical importance of the study’s question should be kept separate from conclusions that its posted results do not 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 registry record provides limited detail about the study’s methods and results. It does not describe eligibility criteria, the exact surgical approaches, how the groups were formed, or how preoperative and postoperative staging were defined. Although the summary says the analysis examined misclassification, the operational definition of misclassification and the method used to compare staging assessments are not reported.

The primary outcome is named, but no survival result is posted. The record does not give a death count, survival estimate, confidence interval, comparison estimate, or test result. It also does not explain the time origin for survival, follow-up procedures, censoring rules, or whether the stated timeframe was used for a particular survival summary.

The study is retrospective and no randomized allocation is described. The record itself cautions that allocation is not stated and the arms are not a like-for-like control comparison. It does not report adjustment for differences between groups, so the extent to which confounding was considered cannot be assessed.

The registry does not report missing-data handling, the analysis population, exclusions, or the completeness of follow-up. It does not provide a statistical analysis plan or explain how multiple outcomes or comparisons were handled. These omissions prevent a full assessment of bias, precision and the reproducibility of the analysis.

The safety entries use generic group labels and do not describe event collection or observation. Their zero affected counts should therefore be read as limited registry entries, not as a comprehensive safety evaluation. These are limitations of what the registry record reports; they do not establish what may have been documented elsewhere.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Staging and Outcome Depending on Surgical Treatment in Adenocarcinomas of the Oesophagogastric Junction — NCT01766986.
• Registry record last updated 2021-01-06; status last verified 2020-12.
• Results first posted 2021-01-06.
• 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 record describes a completed retrospective study of adenocarcinomas of the oesophagogastric junction, using data from a prospectively collected database. Its stated focus is preoperative staging, postoperative staging, surgical treatment and outcome. The registry lists enrollment of 130, records the study start as 2008-01 and primary completion as 2013-01, and names Universitätsklinikum Hamburg-Eppendorf as sponsor.

Overall survival after surgery is the primary outcome, with a timeframe of 36 months. No analysis results or survival estimates are reported. The record states that allocation is not stated and that the groups are not like-for-like controls. Serious adverse-event entries list zero affected participants in each of three generic groups, with the top serious term reported at 0.0%. The registry does not provide enough methodological detail to assess comparative effectiveness or safety.