Preoperative Chemo and Chemoradiotherapy for Adenocarcinoma of the Stomach and Gastroesophageal Junction (GEJ): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Preoperative Chemo and Chemoradiotherapy for Adenocarcinoma of the Stomach and Gastroesophageal Junction (GEJ) (NCT00525785), a na phase 2 study. The primary outcome is Complete Pathologic Response Rate.

2. Clinical Question

The registry describes a phase II study sponsored by M.D. Anderson Cancer Center. Its brief summary frames the research as an assessment of a chemotherapy combination given with radiation therapy before surgery, including study of safety. It does not state a comparative question about whether this regimen performs better than another treatment.

The primary endpoint is a proportion rather than a time-to-event outcome: it concerns whether a participant meets the stated pathologic response definition at restaging and surgical resection. That assessment is timed at 4-6 weeks after chemoradiotherapy, approximately at 16 weeks into treatment. The record does not report the observed number of participants with pathologic complete response, the response percentage, or the confidence interval. Consequently, the central efficacy question cannot be answered from the posted outcome data.

3. Trial Design

This is a phase II, completed, single-group clinical trial. The registry lists enrollment of 58 and identifies 5-fluorouracil, folinic acid, oxaliplatin, radiotherapy and surgery among the interventions. Allocation is recorded as NA, and masking is listed as none. There is no randomized control group in the registry record, so the study is not a randomized comparison of treatments.

The stated clinical setting is potentially resectable adenocarcinoma of the stomach or gastroesophageal junction. The trial title and summary describe chemotherapy and chemoradiotherapy before surgery, with surgery to remove the cancer if possible. The arm description specifies preoperative chemotherapy with oxaliplatin, folinic acid and infusional 5-FU, identified as FOLFOX-48, and describes 2 cycles. The record also names radiotherapy and surgery, but a full schedule for those interventions is not reported in the registry record.

The primary outcome is the complete pathologic response rate. The assessment timeframe is restaging and surgical resection at 4-6 weeks after completion of chemoradiotherapy, approximately at 16 weeks into treatment. The endpoint description states that all registered participants are used as the denominator. The record defines pathologic complete response as absence of tumor cells in the surgical specimen; its response-assessment text also includes 95% or more necrosis of the cancer. It separately describes complete clinical response using endoscopy, biopsy, cytology, or both.

The registry lists 1 outcome measure and no analysis entries. It gives the status as completed, with a start date of 2004-01 and primary completion date of 2016-01. The protocol details, including a statistical analysis plan and any sample-size justification, are not reported in the registry record. No actual primary endpoint estimate is posted, so the design can be described but its primary efficacy result cannot be evaluated from this 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

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 Complete Pathologic Response Rate, measured over Restaging and surgical resection at 4-6 weeks after completion of chemoradiotherapy, approximately at 16 weeks into treatment.

The primary endpoint is the complete pathologic response rate, expressed as a percentage of participants. It asks whether tumor cells were absent from the surgical specimen after preoperative treatment. The endpoint description specifies that all registered participants are included in the denominator, rather than restricting the denominator to participants who underwent surgery or had an assessable specimen. This distinction matters because a response proportion depends on both its numerator and its chosen denominator.

The registry says that conventional response criteria cannot be applied to primary gastric carcinoma because it is not measurable by those usual criteria. A pathologic endpoint instead assesses tissue obtained at surgery. The record defines pathologic complete response as absence of tumor cells in the surgical specimen and also gives a response-assessment criterion of 95% or more necrosis of the cancer. It describes complete clinical response separately, based on absence of tumor on endoscopy, biopsy, cytology, or both. These are distinct assessment concepts; the registry does not report a clinical response result.

The planned assessment is at restaging and surgical resection at 4-6 weeks after completion of chemoradiotherapy, approximately at 16 weeks into treatment. The record does not report how many participants met the pathologic complete response definition, the resulting percentage, or its 95% confidence interval. Thus, although the endpoint and its intended timing are described, the posted results do not permit an estimate of the observed response rate or its precision.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

A complete pathologic response is a binary outcome at the participant level: a participant either meets the stated definition or does not. A response rate expresses the number meeting that definition relative to a specified denominator. The registry endpoint description explicitly sets the denominator as all registered participants. The numerator and resulting rate are not reported in the registry record, so no estimate can be interpreted.

What does a confidence interval convey?

A confidence interval communicates uncertainty around an estimated quantity. For a response proportion, it reflects that the observed rate is based on a finite group and that another group of similar participants could produce a different estimate. A narrower interval indicates greater statistical precision, while a wider interval indicates less precision. It does not describe the range of individual participant outcomes, and it does not account automatically for bias, measurement problems, or limitations of the study design.

The endpoint specifies a 95% confidence interval, but the interval itself is not reported in the registry record. Without the response count and estimate, there is no basis for assessing its width or the precision of the primary result. The stated confidence level describes the intended uncertainty summary; it does not make an absent result interpretable.

Why does the denominator matter?

For a binary endpoint, the denominator determines which participants contribute to the response proportion. This record states that all registered participants are used. That intention is important because a denominator limited to participants with surgery or an available specimen could yield a different proportion. The record does not say how participants without an assessable surgical specimen were handled in the reported analysis, and it does not post such an analysis. The endpoint definition therefore gives a planned denominator, but the missing result prevents checking its implementation.

What does a single-group design allow?

A single-group study describes outcomes among participants receiving the study regimen. It does not supply a concurrent comparison group. Random allocation, when used in a comparative trial, can help balance known and unknown participant characteristics between groups; this record lists allocation as NA and describes a single-group model. Therefore, a response rate in this study would be descriptive and would not establish how outcomes would have differed under another treatment or under no study treatment.

The study is unmasked. For a tissue-based endpoint, the registry record does not report whether specimen assessment was conducted by reviewers unaware of treatment or whether any independent review process was used. That assessment procedure is not reported in the registry record. No assumption about blinding of pathologic review should be made from the masking entry alone.

How should safety counts be read?

Adverse-event figures describe participants recorded as affected within the study group. The record lists 4 participants affected by serious adverse events and 42 affected by other adverse events, with 58 at risk for each category. Serious and other adverse events are separate registry categories. A count of affected participants is not the same as an event count: a participant may experience more than one event, and the record does not report the number of events per participant. The listed serious-event terms are descriptive labels with percentages; their overlap and coding rules are not reported.

Statistical methods for comparing event rates would require an appropriate comparison group and a defined analysis. No such comparative safety analysis is reported. Likewise, no adjusted or recalculated efficacy analysis is reported, so no recalculated estimate or comparison should be inferred.

What are planning calculations?

Sample-size planning calculations, where available, are illustrations of how many participants per arm might be needed under specified assumptions. They are not observed results and do not show the trial's achieved power. The general planning information for this record describes a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and effects defined as fractions of an observed effect. Those assumptions concern a hypothetical two-arm planning exercise and do not change the actual single-group design. A planning justification used by the investigators is not reported in the registry record.

Over-dispersion is a general statistical issue when outcome variability exceeds what a simple model assumes. For a binary outcome, model-based uncertainty can be affected by clustering or other dependence among observations; if observations are not independent, a basic calculation may understate uncertainty. The registry does not report a model for the primary endpoint, clustering, or an over-dispersion adjustment. This general point should not be mistaken for evidence that over-dispersion occurred in this trial.

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("5-Fluorouracil + Folinic Acid + Oxaliplatin")
n      <- c(58)
events <- c(8)
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  5-Fluorouracil + Folinic Acid + Oxaliplatin  58  8  13.8  6.1  25.4  7.2  24.9  7.2  25.0

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 1 outcome measure and 0 analysis entries. Although a primary outcome is identified, the primary response estimate and confidence interval are not reported in the registry record. No secondary outcome results are listed in the available record. The multiplicity plan—how the study would account for testing more than one endpoint, time point, or subgroup—is not reported in the registry record.

Multiplicity is a general concern when several statistical claims are tested. As the number of tested claims grows, the chance of at least one apparently noteworthy result can increase unless the analysis plan addresses that issue. The registry record does not describe a testing hierarchy, adjustment procedure, or prespecified subgroup analysis. It is therefore not possible to assess how multiplicity was handled, or whether it was relevant to any analyses that may have been conducted outside the registry record.

The endpoint definition says all registered participants are used in the denominator. However, missing endpoint data, participants without resection, and the handling of specimens that could not be assessed are not reported in the registry record. The record does not describe an imputation method, a missing-data sensitivity analysis, or an analysis population separate from the stated all-registered denominator. These details matter because excluding participants with unavailable outcomes or assigning them a particular outcome can alter a binary response estimate.

The protocol's statistical analysis plan, interim analyses, and sample-size justification are not reported in the registry record. No assumptions should be made about whether interim monitoring occurred or how any analyses were selected. With no posted response estimate and no analysis entries, neither missing-data handling nor multiplicity can be evaluated from the registry results.

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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: hemorrhage, gi-stomach (6.9%), gi bleed (6.9%), dehydration (5.2%), nausea vomiting (3.4%), nausea (3.4%).

The safety record lists 4 participants affected by serious adverse events among 58 at risk. It lists 42 participants affected by other adverse events among 58 at risk, and records 0 deaths. These are counts for the single study group. They are not comparative estimates and do not show how the same participants would have fared under another regimen.

The serious adverse-event terms listed include Hemorrhage, GI-Stomach and GI Bleed, each at 6.9%; Dehydration at 5.2%; and Nausea Vomiting, Nausea, and Vomiting, each at 3.4%. These labels describe reported event categories. The registry does not report whether a participant could appear under more than one term, whether related terms were coded separately, or how event severity and attribution were assessed. The percentages for terms should not be added or treated as mutually exclusive participant groups.

Serious adverse events and other adverse events are distinct categories in the record. The information does not provide event duration, timing, severity grades beyond the serious classification, or a comparison of risks between treatment groups. Those details are not reported in the registry record. The counts are therefore useful as descriptive safety reporting, but do not establish a comparative safety profile or a causal relationship for any listed event.

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

The record describes a phase II investigation of preoperative chemotherapy and chemoradiotherapy for potentially resectable stomach or gastroesophageal junction adenocarcinoma. Its primary endpoint is a pathologic response proportion assessed around surgery. The outcome definition and timing are stated, and the registry posts descriptive safety counts. However, the primary response count, percentage, and 95% confidence interval are not reported in the registry record.

That missing endpoint result is consequential: the central efficacy question cannot be answered from the posted results. The registry's enrollment figure does not reveal how many participants had a complete pathologic response. Nor does the completed status supply information about the size or precision of that response rate. The endpoint description's all-registered denominator does not fill in the missing numerator or establish how unavailable assessments were handled.

Even if an observed response proportion were reported, a single-group design would describe outcomes in the enrolled study group rather than provide a controlled estimate of comparative treatment effect. There is no randomized comparator in this record. Differences between this group and people treated in another setting could reflect differences in participant characteristics, care, or assessment, as well as treatment. No claim that the regimen works or does not work follows from the posted information.

The safety entries indicate that serious and other adverse events were recorded in the group, and the record lists 0 deaths. The term-level percentages provide descriptive detail but do not establish comparative risk, event causality, or the degree to which categories overlap. A complete interpretation of safety would also require context about ascertainment, severity, timing, and follow-up, which is not reported in the registry record.

Accordingly, the record is informative about the planned clinical question, study structure, response definition and selected safety counts. It is insufficient for estimating the primary response result, judging its precision, comparing treatment strategies, or resolving uncertainty about missing outcome data and analysis methods.

14. Why This Trial Matters Statistically

This study illustrates why a clearly stated endpoint is not the same as a reported result. The registry defines complete pathologic response, identifies its intended denominator, and specifies an assessment timeframe around restaging and surgery. Those details help readers understand what the primary outcome was meant to measure. Yet the response count, proportion and confidence interval are not reported in the registry record, so the endpoint cannot be quantified from the posted results.

The denominator statement is especially relevant for a surgical pathology outcome. Using all registered participants makes the intended population explicit, while the absence of information about participants without an assessable specimen leaves a practical analysis question unresolved. Readers need both the response count and the accounting of participants who could not contribute an assessment to understand how the planned denominator was applied.

The single-group design also shows the distinction between describing an outcome and estimating a treatment contrast. A response proportion could characterize the enrolled group, but without a comparator it would not establish how outcomes differ under another approach. This limitation is separate from statistical precision: even a narrowly estimated proportion would not, on its own, resolve the absence of a control group.

Finally, the safety record demonstrates why participant counts and event categories need careful interpretation. Serious and other adverse events are reported separately, and the record lists specific serious-event terms. Without information on overlap, attribution, timing and comparative data, these entries remain descriptive. In combination, the endpoint and safety reporting make the record useful for understanding what was intended and what was recorded, while also showing how absent analysis results constrain statistical interpretation.

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 direct limitation is that the registry record does not report the primary complete pathologic response count, percentage, or 95% confidence interval. It therefore does not allow assessment of the observed response magnitude or precision. Although the endpoint description specifies all registered participants as the denominator, the record does not report the numerator or explain how participants without an assessable surgical specimen were treated.

The single-group design has no concurrent control arm, and allocation is listed as NA. It cannot provide a like-for-like comparison with another regimen. The record lists masking as none; whether pathologic reviewers were independently or blindly assessing specimens is not reported in the registry record.

The response-assessment description includes absence of tumor cells in the surgical specimen and also states 95% or more necrosis of the cancer. The record does not clarify how those statements were operationalized together for the primary endpoint. It also does not report the number of participants who reached surgery or had specimens available for assessment. These gaps make it difficult to evaluate endpoint ascertainment and completeness.

The registry contains no analysis entries. The statistical analysis plan, sample-size justification, multiplicity handling, interim analyses, missing-data methods and analysis populations are not reported in the registry record. Safety reporting is descriptive: event overlap, attribution, timing and severity details beyond the serious classification are not reported. These limitations restrict both efficacy and safety interpretation, even though the study status is completed.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Preoperative Chemo and Chemoradiotherapy for Adenocarcinoma of the Stomach and Gastroesophageal Junction (GEJ) — NCT00525785.
• Registry record last updated 2020-02-10; status last verified 2020-01.
• Results first posted 2020-02-10.
• 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

NCT00525785 is a completed phase II, single-group study sponsored by M.D. Anderson Cancer Center. It enrolled 58 participants and concerns preoperative chemotherapy and chemoradiotherapy for potentially resectable adenocarcinoma of the stomach or gastroesophageal junction. The named drugs are 5-fluorouracil, folinic acid and oxaliplatin; radiotherapy and surgery are also listed.

The primary outcome is complete pathologic response, assessed at restaging and surgical resection at 4-6 weeks after chemoradiotherapy, approximately at 16 weeks into treatment. The endpoint definition specifies all registered participants as the denominator. The registry record does not report the response count, percentage, or confidence interval, and contains no analysis entries.

Safety entries list 4 participants affected by serious adverse events, 42 affected by other adverse events, and 0 deaths. The record does not provide a control-group comparison. Its statistical plan, missing-data handling and other analysis details are not reported in the registry record.