Study Evaluating The Role of ClO2 on Mucositis for Pt. Undergoing Head/Neck Radiotherapy: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Study Evaluating The Role of ClO2 on Mucositis for Pt. Undergoing Head/Neck Radiotherapy (NCT03602066), a randomized phase 2 study. The primary outcome is Incidence of Severe Oral Mucositis (OM) (>= World Health Organization [WHO] Mucositis Scale Grade 3).

2. Clinical Question

The question is framed around the occurrence of severe oral mucositis, rather than any mouth soreness or mucositis at any grade. In the registry's scale description, grade 3 is characterized by oral ulcers and a liquid-only diet; grade 4 is described as a situation in which oral alimentation is impossible. The primary endpoint groups grade 3 and higher together.

The registry describes a randomized, double-masked, parallel-group pilot phase II study. Its stated aim was to compare severe oral mucositis between the chlorine dioxide and placebo arms. The record reports no grade 3 or higher cases in either arm and says no differences were observed. That is a description of the posted outcome, not evidence that the two treatments have identical effects. The arm counts are small, and the registry does not report an estimable between-arm comparison for this binary endpoint.

Other study questions concerned when severe mucositis began, how long it lasted, patient-reported outcomes on the Oral Mucositis Weekly Questionnaire, and radiotherapy interruptions. Those are secondary outcomes; their results are not reported in the record presented.

3. Trial Design

This was a randomized, double-masked, parallel-group phase II pilot study sponsored by the University of Arizona. The registry record lists enrollment of 14 and describes two arms: chlorine dioxide sterilization oral rinse and placebo oral rinse. The posted primary outcome counts are 6 participants in the chlorine dioxide arm and 8 in the placebo arm.

The rinse schedules were described in parallel. Participants in each arm were to use the assigned oral rinse over 30 seconds twice daily, beginning at the start of radiotherapy and continuing through the evening before the one-month radiotherapy follow-up appointment. The record lists laboratory biomarker analysis as another intervention, but does not describe its procedures or report biomarker findings.

The study start date is 2019-02-14, and the primary completion date is 2022-11-07. The registry status is terminated. The reason for termination, the timing of the decision, and whether all planned study activities were completed are not reported in the registry record. Termination alone does not explain why the study stopped or establish how it affected the results.

The primary endpoint was the incidence of severe oral mucositis, defined as World Health Organization mucositis grade 3 or higher, assessed up to 30 days after radiotherapy. The record identifies four secondary outcomes: time to onset of severe mucositis, duration of severe mucositis, patient-reported outcomes measured with the Oral Mucositis Weekly Questionnaire, and rates of radiotherapy interruption. Results for these secondary outcomes are not reported in the registry record.

Randomization and masking describe intended features of the comparison, but the record does not report details such as the randomization procedure, how masking was maintained, or whether masking was assessed. The protocol's sample-size justification and the reasons for selecting the planned enrollment 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 Incidence of Severe Oral Mucositis (OM) (>= World Health Organization [WHO] Mucositis Scale Grade 3), measured over Up to 30 days post radiotherapy.

The primary endpoint is the incidence of severe oral mucositis: the number of participants who developed World Health Organization mucositis grade 3 or higher, considered in relation to the participants in each arm. The assessment window was up to 30 days after radiotherapy. The registry's scale description characterizes grade 3 as oral ulcers with a liquid-only diet, and grade 4 as oral alimentation being impossible.

This endpoint focuses on a clinically substantial level of mucositis, rather than counting any symptom or mild oral change as a primary event. A binary endpoint records whether each participant did or did not meet the specified threshold during the assessment window. Such an endpoint can be summarized as a proportion within each arm and compared across arms, subject to the amount and quality of the available outcome data.

The registry states that the planned analysis would estimate a proportion for each group with an exact 95% binomial confidence interval and use a chi-square test for the comparison, with Fisher's Exact Test as an alternative if the minimum expected value was < 5. These are the planned methods described in the outcome record. The posted results report no grade 3 or higher cases in either arm and state that no differences were observed. They do not provide the planned confidence intervals or an estimable two-arm comparison.

The endpoint is therefore useful for describing whether severe mucositis was recorded in this study, but the zero counts do not by themselves establish that the underlying risks are the same across treatments. The endpoint also does not capture the full range of mucositis severity, timing, duration, patient experience, or treatment interruption; those topics were designated as secondary outcomes.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a binary primary outcome: whether a participant experienced severe oral mucositis, defined as World Health Organization grade 3 or higher, up to 30 days after radiotherapy. A binary outcome places each participant into an event or no-event category for the specified threshold and period. The outcome record reports no events in either study arm.

What does a proportion describe?

A proportion summarizes the frequency of an event within an arm relative to the participants assessed for that outcome. Here, the posted counts are 0 of 6 in the chlorine dioxide arm and 0 of 8 in the placebo arm. These counts describe what was recorded in this trial; they are not, by themselves, precise estimates of the event rates that would occur in a broader population. The registry does not report confidence intervals for these arm-specific results.

A confidence interval is a statistical range intended to express uncertainty in an estimate under the assumptions of the method used. It is not a guarantee that the true value lies inside a particular interval. The outcome description says exact 95% binomial confidence intervals were planned for each group separately. Exact methods are often used for proportions when event counts are sparse, because approximations designed for larger samples can behave poorly in sparse data. The record does not post the resulting intervals, so their numerical bounds cannot be described.

How was a comparison planned?

The registry says that a chi-square test would be used to compare the arms. A chi-square test assesses whether the observed distribution across categories is inconsistent with a null model of no association between group and outcome. Its usual approximation depends on adequate expected cell counts. The registry therefore describes Fisher's Exact Test as an alternative if the minimum expected value was < 5. Fisher's Exact Test calculates probabilities using the observed table margins and is commonly considered when data are sparse.

Over-dispersion is a concern in some data settings when the variability exceeds what a chosen model expects; it can make standard errors too small and statistical evidence appear stronger than warranted. That is a general issue, not a reported feature of this trial. For this primary binary endpoint, the immediate limitation is that no events were observed in either arm and the registry does not provide a test result or an estimable two-arm comparison. It would be inappropriate to invent a p-value or infer one from the posted counts.

Why are zero events not proof of no effect?

When both groups have zero observed events, the observed counts do not distinguish the arms. But a lack of observed events is not the same as evidence that the underlying probabilities are equal. With limited observations, other event patterns may remain compatible with the data-generating process even though none appeared in this trial. Formal uncertainty estimates can help convey that limitation, but the planned intervals are not reported in the registry record.

A non-significant test, if one had been reported, would not by itself demonstrate equivalence. Equivalence requires a defined margin and an analysis designed to assess whether the treatment difference is sufficiently small relative to that margin. A non-inferiority question likewise requires a prespecified margin and an appropriate analysis. Such margins and analyses are not reported in the registry record. The posted statement that no differences were observed should therefore be read as a description, not as a conclusion of equivalence.

What is the distinction between planning and observed power?

Sample-size calculations are planning tools: they explore how many participants might be needed under selected assumptions about an effect, significance level, allocation, and statistical method. They do not describe the probability that a completed study's result is correct, and they do not repair uncertainty after the data have been observed. The registry's planning assumptions describe a two-sided significance level of 0.05, equal allocation, a normal approximation, and effects expressed as fractions of the observed effect. These are planning illustrations, not the study's own design justification. The protocol's sample-size justification is not reported in the registry record.

Because the primary record says no events occurred in either arm and marks the two-arm binary comparison as not estimable, an observed between-arm effect is not available for interpretation from the posted primary results. No sample-size planning output should be treated as observed power. The registry does not report whether alternative assumptions or methods were used in the original study design.

What can be said about the analysis that was performed?

The outcome description identifies planned methods, but the record reports no posted analyses. It does not include a primary p-value, a confidence interval, or a numerical treatment-effect estimate. It also does not report whether the chi-square or Fisher's Exact Test was ultimately selected. The primary results support a descriptive statement about the recorded event counts, not a reconstruction of an inferential analysis.

In general, a complete account of a randomized comparison would clarify which participants were included, how missing outcomes were handled, and whether the analysis followed the assigned groups. Those details are not reported in the registry record. The result should therefore be interpreted alongside the limited information about analysis populations and missing data, rather than assuming that every enrolled participant contributed a complete endpoint assessment.

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("Arm I (Chlorine Dioxide Sterilization)", "Arm II (Placebo)")
n      <- c(6, 8)
events <- c(0, 0)
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  Arm I (Chlorine Dioxide Sterilization)  6  0  0.0  0.0  45.9  0.0  39.0  0.4  41.0
ARM  Arm II (Placebo)  8  0  0.0  0.0  36.9  0.0  32.4  0.3  33.6

11. Multiplicity, Missing Data and Analysis Populations

The registry identifies four secondary outcomes: time to onset of severe oral mucositis, duration of severe oral mucositis, patient-reported outcomes measured by the Oral Mucositis Weekly Questionnaire, and rates of radiotherapy interruption. Although the record lists seven outcome measures, results for the secondary outcomes are not reported in the registry record.

When a study assesses multiple outcomes or performs multiple statistical tests, the chance of at least one apparently notable result can increase. Statistical approaches to multiplicity can adjust interpretation or testing, but the appropriate approach depends on the study's aims and prespecified analysis plan. Any multiplicity strategy, hierarchy among outcomes, or adjustment is not reported in the registry record. Without the secondary results and analysis details, it is not possible to assess how those outcomes were analyzed or how multiple comparisons were handled.

The record does not describe missing outcome data, reasons for missingness, imputation, or sensitivity analyses. It also does not report analysis populations, such as whether the primary analysis included all randomized participants or a different defined group. The registry enrollment and primary outcome arm counts are reported, but those counts alone do not establish that every randomized participant completed follow-up or that missingness was absent.

Details about participant flow, adherence to the rinse schedule, protocol deviations, and the handling of participants who did not complete radiotherapy are not reported in the registry record. These omissions limit assessment of how closely the analyzed groups correspond to the randomized groups and whether the outcome window was assessed consistently. The reason the trial was terminated is also not reported. These are reporting gaps, not evidence that a particular form of missingness, deviation, or selective analysis occurred.

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: dysphagia (12.5%).

The registry reports serious adverse events for each arm. In the chlorine dioxide arm, 0 of 6 participants were reported as having a serious adverse event; in the placebo arm, 1 of 8 participants was reported as having a serious adverse event. The record lists dysphagia at 12.5% among the top serious-event terms. It does not identify the arm associated with that term in the information, so the term should not be attributed to a particular arm.

The record reports other adverse events in 6 of 6 participants in the chlorine dioxide arm and 8 of 8 participants in the placebo arm. Deaths were reported for 0 participants in each arm. These are counts from this study; they do not establish whether an event was caused by the assigned rinse, radiotherapy, the underlying condition, or another factor. The registry information does not provide event-level timing, severity beyond the serious-event classification, or a causal assessment.

Serious adverse event counts and other adverse event counts are distinct summaries. A serious-event count does not describe every adverse effect, and a count of participants with other events does not indicate how many events each participant experienced. The arm counts are limited, so the observed figures should be read descriptively rather than as a precise comparison of safety risks. The registry record does not report a formal statistical comparison of adverse events.

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

The primary result establishes what was recorded in this study: no grade 3 or higher oral mucositis was reported in either the chlorine dioxide or placebo arm during the stated period, up to 30 days after radiotherapy. The registry says no differences were observed. The posted arm counts are 6 in the chlorine dioxide group and 8 in the placebo group.

That finding does not show that the treatments have equal effects. Zero events in both groups leave the observed counts without a between-arm separation, and the registry does not report confidence intervals or an estimable comparative result for this binary outcome. The absence of a reported difference is not proof of equivalence, and the record does not describe an equivalence or non-inferiority design.

The result is limited to severe mucositis, defined as grade 3 or higher, and to the stated follow-up window. It does not describe the incidence of lower grades of mucositis. It also does not answer whether the arms differed in onset, duration, patient-reported oral symptoms, or radiotherapy interruptions; these were secondary outcomes, but their results are not reported in the registry record.

The trial's design and status provide context but do not resolve the uncertainty. It was a randomized, double-masked pilot phase II study and is listed as terminated. The reason for termination, the sample-size justification, missing-data handling, and analysis populations are not reported. These gaps prevent a fuller assessment of how the observed counts relate to the planned study and its intended analysis.

Accordingly, the defensible interpretation is descriptive: no severe oral mucositis events were posted for either arm, and no difference in the counts was observed. The result does not establish a treatment benefit, lack of benefit, or equal risk. It also should not be generalized beyond the outcome definition, follow-up window, and participants represented in the registry record.

14. Why This Trial Matters Statistically

This trial illustrates a central issue in clinical statistics: a zero-event result can be clinically understandable but statistically difficult to compare. The primary outcome was clearly defined as severe oral mucositis at grade 3 or higher, and the record reports zero cases in both arms. Because the observed counts are the same, they offer no direct separation between the groups.

At the same time, identical observed counts do not mean that the underlying event rates are known to be identical. The arm counts are 6 and 8, and the record does not report the planned exact confidence intervals or an estimable comparative analysis. Readers therefore cannot gauge the precision of the arm-specific estimates or the uncertainty around a treatment contrast from the posted primary results.

The trial is also a reminder to distinguish a planned method from a reported analysis. The registry describes exact binomial intervals and a chi-square test, with Fisher's Exact Test if the minimum expected value was < 5. However, no primary test result or interval is reported. Statistical methods in an outcome description do not substitute for the corresponding results.

Finally, the trial's pilot phase II designation and terminated status matter as context, but neither supplies an explanation for the zero-event outcome. The reason for termination and the protocol's sample-size justification are not reported in the registry record. The result is most useful as a transparent record of what was observed and as an illustration of why sparse binary outcomes need careful treatment: no observed events can coexist with substantial uncertainty about comparative effects.

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 primary outcome information is sparse. The registry reports zero severe oral mucositis events in both arms and states that no differences were observed, but it does not report arm-specific exact confidence intervals, a p-value, or a numerical comparative estimate. The two-arm comparison is not estimable in the posted results. This prevents a quantitative assessment of the uncertainty around the treatment contrast.

The outcome window is specified as up to 30 days post radiotherapy, but details of assessment timing, completeness of follow-up, and outcome ascertainment are not reported in the registry record. The record also does not describe the analysis population, missing-data methods, participant flow, adherence, or protocol deviations. These omissions mean that the relationship between enrollment, follow-up, and the posted endpoint counts cannot be fully assessed.

Four secondary outcomes are named, but their results are not reported. The record therefore does not describe onset or duration of severe mucositis, patient-reported outcomes, or radiotherapy interruptions. It also does not report multiplicity procedures, if any. The reason for termination and the original sample-size justification are not reported, limiting context for interpreting the study's completion and statistical planning.

The primary endpoint focuses on grade 3 or higher mucositis. It does not summarize lower-grade symptoms or all aspects of oral health during treatment. The serious adverse event summary is also limited: the record gives arm-level counts and a top serious-event term but does not provide a causal assessment or identify the arm for the listed dysphagia term. These limitations are specific to the reported record and do not establish that unreported events or analyses did or did not occur.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Study Evaluating The Role of ClO2 on Mucositis for Pt. Undergoing Head/Neck Radiotherapy — NCT03602066.
• Registry record last updated 2024-03-20; status last verified 2024-02.
• Results first posted 2024-03-20.
• 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

NCT03602066 is a randomized, double-masked, parallel-group pilot phase II study sponsored by the University of Arizona. It compared chlorine dioxide sterilization oral rinse with placebo among patients with stage I–IV head and neck cancer undergoing radiotherapy. The record lists enrollment of 14, a start date of 2019-02-14, a primary completion date of 2022-11-07, and a status of terminated.

The primary outcome was incidence of World Health Organization grade 3 or higher oral mucositis, assessed up to 30 days post radiotherapy. No cases were reported in either arm: 0 of 6 for chlorine dioxide and 0 of 8 for placebo. The registry states that no differences were observed, but provides no estimable two-arm comparison or confidence intervals.

Four secondary outcomes are listed, but their results are not reported in the registry record. The reason for termination, missing-data methods, analysis populations, and sample-size justification are also not reported. The primary result is descriptive and does not establish equal treatment effects.