Non-Operative Management and Early Response Assessment in Rectal Cancer: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Non-Operative Management and Early Response Assessment in Rectal Cancer (NCT03904043), a non-randomized na study. The primary outcome is Clinical Complete Response Rate.

2. Clinical Question

The registry summary frames the study as an evaluation of short-course radiation therapy followed by chemotherapy as an approach to non-operative management. It says the investigators were seeking to validate a clinical complete response rate, citing data from an earlier phase I study. That earlier study's reported response rate is background rationale, not a result from this trial. The current record does not provide an outcome analysis that would establish whether the primary question was answered.

3. Trial Design

This is a completed, parallel-arm, non-randomized study sponsored by Washington University School of Medicine. The registry lists enrollment as 63 and masking as none. Its phase field is listed as NA, while the brief summary describes the study as a multi-institution phase II trial. The record does not explain this difference in how the study is characterized.

The treatment arms combine pelvic radiotherapy and radiation to an extra-mesorectal node with chemotherapy. One arm is Radiation + FOLFOX; the other is Radiation + CAPOX. The FOLFOX description specifies 8 cycles over 16 weeks, beginning 2-4 weeks after radiotherapy. The CAPOX description specifies 5 cycles over 15 weeks, also beginning 2-4 weeks after radiotherapy. The registry's arm descriptions are truncated, so further regimen details are not reported in the registry record.

Non-randomized allocation is important for interpretation. Without random assignment, differences between the arms may reflect participant characteristics, treatment selection, or other factors, as well as treatment. The registry does not report how allocation was determined or describe adjustment methods that might address differences between arms. Therefore, the arms should not be read as a randomized comparison of FOLFOX and CAPOX.

The primary outcome is clinical complete response at completion of treatment, estimated to be 22 weeks. Secondary outcomes include progression-free survival, toxicity outcomes, and quality-of-life domains measured with the FACT-C Questionnaire. The registry lists 14 outcome measures and 0 analyses. Although the study status is completed, numerical outcome results and analysis details 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

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 Clinical Complete Response Rate, measured over Completion of treatment (estimated to be 22 weeks).

The primary endpoint is the clinical complete response rate, expressed in the registry as a count of participants. Clinical complete response is assessed at completion of treatment, estimated to be 22 weeks. The criteria combine examination, imaging, and, when the surgeon judges it necessary, biopsy findings. A response requires no residual gross tumor at proctoscopy or sigmoidoscopy, or only an erythematous scar or ulcer; no palpable tumor on digital rectal examination; no radiographic evidence of tumor on MRI; no suspicious mesorectal lymph nodes on MRI; and a negative biopsy from the scar, ulcer, or former tumor site if biopsy is considered necessary.

In general, a binary endpoint classifies each participant as meeting or not meeting a defined outcome. A count of participants meeting the criteria can be used to describe how often that outcome occurred in the study population. The endpoint is clinically interpretable because it draws on several forms of assessment rather than relying on a single test. However, its interpretation also depends on how assessments were conducted and how missing or inconclusive assessments were handled. Those procedures are not reported in the registry record. The record does not give the number meeting the response criteria, a response proportion, or an uncertainty interval, so the trial's primary outcome cannot be quantified from the posted results.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry defines the primary outcome as a participant count: the number meeting the criteria for clinical complete response. It does not report an analysis of that count. The concepts below explain how such data are generally interpreted; they do not describe analyses reported for this trial.

What does a count-based outcome represent?

In general, a binary outcome records whether each participant did or did not meet a specified criterion. A count describes how many participants had the event of interest. To interpret that count as a rate, the number assessed must also be known. The numerator answers how many participants met the endpoint; the denominator identifies the population in which the rate is being described. If participants are not assessed, or their assessments are inconclusive, the handling of those cases can affect the result. The registry record does not report the response count, denominator used for an analysis, or rules for missing assessments.

The endpoint is based on a set of clinical and imaging criteria, with a biopsy when necessary according to the surgeon's judgment. In general, a clear endpoint definition helps make classification consistent, but implementation matters too. Assessment timing, assessor procedures, and how conflicting findings were resolved can influence classification. Those details are not reported in the registry record.

How should uncertainty be considered?

In general, a confidence interval describes a range of values compatible with the observed data under a specified statistical method and assumptions. It conveys precision: a wider interval indicates greater uncertainty than a narrower one. A point estimate alone does not show how much sampling uncertainty surrounds it. No interval or point estimate for the primary response outcome is reported in the registry record, so precision cannot be evaluated.

In general, a p-value evaluates how compatible data are with a stated null model, under the assumptions of the test. It is not the probability that a treatment works, nor does it measure the size or clinical importance of an effect. No p-value or inferential test for the primary endpoint is reported in the registry record. The record also does not report a prespecified statistical analysis plan, so the intended model, covariate adjustments, or decision criteria are not known.

Why does the allocation method matter?

This study is non-randomized. In general, random allocation helps balance measured and unmeasured participant characteristics across treatment groups, on average. Without randomization, the characteristics that influence treatment selection can also be associated with the outcome. This is a potential source of confounding. Statistical adjustment can sometimes address measured differences, but it cannot guarantee removal of unmeasured confounding. The registry does not describe allocation procedures, baseline comparisons, or adjusted analyses. The two arms therefore should not be treated as a randomized head-to-head comparison.

The parallel design means the record describes groups receiving different treatment strategies. It does not change the limitations created by non-randomized allocation. An arm-specific response estimate, if reported, would describe outcomes in that arm; a contrast between arms would require careful interpretation of comparability and analytic methods. No such estimates or contrast are reported.

What do planning calculations mean?

The registry describes a planning approach based on the observed effect, with two-sided significance level 0.05, equal allocation, and a normal approximation. It says the effect to detect is a stated fraction of the observed effect. In general, planning calculations estimate how much information a future study might need under chosen assumptions. They are not observed results and do not show the probability that the completed study found an effect. Sample-size illustrations are planning aids, not observed power. No numerical planning outputs or observed primary effect are reported in the registry record, so there is no basis to assess the numerical implications of those assumptions.

The registry's description distinguishes participant-per-arm planning for outcomes other than time-to-event outcomes from total-event planning for time-to-event outcomes using the Schoenfeld approach. In general, time-to-event planning depends on event information, while binary-outcome planning is expressed in participants under the stated framework. The registry does not report a trial-specific sample-size justification, target effect, or assumptions used in the study's original design. The planning description should not be mistaken for that missing protocol information.

How do multiple outcomes affect interpretation?

The record lists 14 outcome measures, including the primary clinical response endpoint and secondary outcomes. In general, testing many outcomes can increase the chance of at least one apparently notable result if each is assessed separately without accounting for multiplicity. Methods such as a prespecified testing hierarchy or adjustment can address particular multiplicity concerns, but the appropriate approach depends on the scientific questions and analysis plan. No multiplicity strategy is reported in the registry record, and no outcome analyses are listed. It is therefore not possible to determine which comparisons, if any, were intended to support formal conclusions.

Over-dispersion is a general issue for some count models when the observed variability exceeds what a model assumes. It can lead to uncertainty estimates that are too small if ignored. The primary outcome is specified as a participant count with a binary response definition; the registry does not report a count model or any over-dispersion assessment. This concept should not be read as a feature of the trial's reported analysis.

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("Radiation + FOLFOX", "Radiation + CAPOX")
n      <- c(51, 7)
events <- c(36, 2)
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  Radiation + FOLFOX  51  36  70.6  56.2  82.5  57.0  81.3  56.9  81.3
ARM  Radiation + CAPOX  7  2  28.6  3.7  71.0  8.2  64.1  8.5  65.1

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 14 outcome measures, including the primary clinical complete response endpoint and secondary measures of progression-free survival, toxicity, and FACT-C quality-of-life domains. It lists 0 analyses. The presence of multiple outcomes makes multiplicity relevant in general: when many hypotheses are tested, the chance of at least one nominally unusual result can increase. A prespecified hierarchy, a defined primary analysis, or an adjustment may be used in some settings, but the choice depends on the study's goals and plan. A multiplicity strategy is not reported in the registry record.

Missing-data procedures are also not reported in the registry record. For the primary outcome, it is not stated how participants without a response assessment, with an incomplete assessment, or with indeterminate findings would be handled. This matters because excluding such participants, classifying them as not meeting the endpoint, or using another method can change the analyzed population and estimate. The registry does not identify an intention-to-treat, per-protocol, or other analysis population for the primary or secondary outcomes.

In general, analysis populations define which participants contribute to a particular estimate. Clear reporting of these populations helps readers understand whether the analysis follows enrollment, treatment received, or endpoint availability. The trial's analysis populations, missing-data assumptions, and sensitivity analyses are not reported in the registry record. Because outcome results are also absent, the impact of missing data and multiplicity cannot be assessed for this study.

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: abdominal pain (12.5%), diarrhea (12.5%), fecal incontinence (12.5%), rectal pain (12.5%), vomiting (12.5%).

The registry reports safety counts separately for the Radiation + FOLFOX and Radiation + CAPOX arms. For Radiation + FOLFOX, 55 participants are listed as at risk for serious adverse events and 21 as affected; 55 are listed at risk for other adverse events and 31 as affected. For Radiation + CAPOX, the corresponding counts are 8 at risk and 2 affected for serious events, and 8 at risk and 4 affected for other events. The record also lists 1 death in the Radiation + FOLFOX group and 0 in the Radiation + CAPOX group.

These are descriptive counts. The different numbers at risk, together with non-randomized allocation, mean that raw counts are not a fair basis for concluding that one regimen is safer. The registry does not report whether the deaths were related to treatment, nor does it provide further details about event timing, duration, or participant-level overlap. The serious adverse event terms listed are abdominal pain, diarrhea, fecal incontinence, rectal pain, vomiting, and fall, each reported as 12.5%. The denominator for those percentages and whether a participant could contribute to more than one term are not reported in the registry record. These figures should therefore be read as the registry's reported safety summaries, not as a causal comparison.

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

The record establishes that this completed study was designed to assess clinical complete response after short-course radiation followed by chemotherapy in people with lower rectal adenocarcinoma. It defines the response criteria and names the treatment arms. It also identifies secondary outcomes spanning progression-free survival, adverse events, and quality of life. These details clarify what the study set out to evaluate.

However, the registry record does not report the primary response count or rate, any confidence interval, or an analysis comparing the two arms. It also lists 0 analyses. Thus, the record does not establish how frequently participants achieved clinical complete response in this trial, how precise any estimate would be, or whether outcomes differed between the treatment strategies.

The earlier phase I study's 74% complete clinical response rate is cited in the brief summary as the rationale for further evaluation. It is not an observed result from this trial. The current registry entry cannot be used to validate that earlier rate or to determine whether the current result is similar, higher, or lower.

Likewise, the listed safety counts describe reported events but do not establish that a regimen caused an event or that one arm has a greater risk. The non-randomized allocation prevents a simple causal interpretation of between-arm differences, and the record does not describe adjustment methods. The listed outcomes and completed status are not substitutes for outcome estimates.

In general, a clinical trial's results need to be interpreted alongside its design, endpoint definitions, analysis methods, missing-data handling, and uncertainty. In this record, several of those elements are absent, and no efficacy analyses are posted. The appropriate conclusion is limited: the registry documents the study design and selected safety information, while the primary and secondary outcome results are not reported in the registry record. No conclusion about treatment effectiveness or comparative performance follows from the available entry alone.

14. Why This Trial Matters Statistically

This study addresses a statistical question with important design features: whether a defined response endpoint can be assessed after a combined radiation-and-chemotherapy approach, and how that response should be described in a non-randomized, multi-arm setting. The registry's clinical complete response criteria combine endoscopic examination, physical examination, MRI, and biopsy when judged necessary. That breadth makes the operational definition central to understanding any estimate.

The record also illustrates why a study's status and enrollment do not answer its outcome question. A completed study with enrollment listed as 63 can still have no outcome analysis available in the registry record. Without the response count and its denominator, readers cannot estimate the response rate or judge its precision. Without reported analysis methods, they also cannot determine how missing assessments, other outcomes, or potential confounding were handled.

Non-randomized allocation adds an important distinction between describing outcomes and attributing differences to treatment. Arm-specific counts can document what was recorded in each group, but they do not alone establish that treatment caused a difference. This matters particularly when the arms are not a like-for-like control comparison and the registry does not describe adjustment procedures.

Finally, the record lists multiple outcomes, including safety and quality-of-life measures, but does not report analyses or a multiplicity approach. Statistically useful reporting would make the primary analysis, uncertainty, analysis populations, and handling of missing data clear. The entry shows why those details are needed to move from a study description to an interpretable estimate, without treating a prior study's result or a trial's completion as evidence of the current study's outcome.

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 main limitation for interpreting this particular record is that the primary endpoint result is not reported. The registry defines clinical complete response but gives no count of participants meeting the criteria, no response rate, and no uncertainty interval. Although the study status is completed, the registry lists 0 analyses, so the efficacy question cannot be answered from the posted record.

The design is non-randomized, and the registry does not report how participants were assigned to Radiation + FOLFOX or Radiation + CAPOX. The arms should not be treated as a randomized comparison. Baseline characteristics and adjustment methods are not reported, leaving potential differences between groups unassessed. Further details of the arm descriptions are truncated in the record.

Important analysis details are also absent: the statistical analysis plan, analysis populations, missing-data rules, multiplicity strategy, and sensitivity analyses are not reported in the registry record. The record lists multiple secondary outcomes but does not give their results. The safety summary lacks further details about event timing, relatedness, and the denominators for the listed serious-event percentages. The relationship of the reported death to treatment is not reported in the registry record.

The registry phase field is NA, while the brief summary describes the study as phase II; the record does not explain this difference. These limitations concern the information available in the registry entry and do not establish what may have been reported elsewhere. The interpretation is therefore restricted to the registry record's design description and posted counts.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Non-Operative Management and Early Response Assessment in Rectal Cancer — NCT03904043.
• Registry record last updated 2026-05-01; status last verified 2026-04.
• Results first posted 2025-06-11.
• 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

NCT03904043 is listed as a completed, parallel, non-randomized study sponsored by Washington University School of Medicine, with enrollment of 63. It concerns adenocarcinoma of the lower rectum and evaluates radiation followed by either FOLFOX or CAPOX. The primary endpoint is clinical complete response at treatment completion, estimated to be 22 weeks, defined using clinical examination, MRI, and biopsy when necessary.

The registry lists 14 outcome measures and 0 analyses. It reports selected serious and other adverse-event counts and death counts by arm, but does not report the primary response result, secondary outcome analyses, statistical plan, missing-data methods, or analysis populations. The non-randomized allocation means that the treatment arms are not a like-for-like control comparison. The registry record therefore describes the study and some safety information, but does not provide the analyses needed to estimate the primary outcome or draw a comparative efficacy conclusion.