Acetylcysteine Rinse in Reducing Saliva Thickness and Mucositis in Patients With Head and Neck Cancer Undergoing Radiation Therapy: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Acetylcysteine Rinse in Reducing Saliva Thickness and Mucositis in Patients With Head and Neck Cancer Undergoing Radiation Therapy (NCT02123511), a randomized phase 2 study. The primary outcome is Groningen Radiotherapy-Induced Xerostomia (GRIX) Sticky Saliva Total Score Area Under the Curve (AUC).

2. Clinical Question

3. Trial Design

This was a randomized, double-blind, parallel-group phase 2 pilot trial sponsored by Mayo Clinic. Enrollment was 34, and the registry status is completed. The listed start was 2014-04, and primary completion was 2016-03-22. Participants were assigned to an oral rinse described in the study plan as acetylcysteine or to placebo. Both arms had the same reported administration schedule, beginning within 3 days of radiotherapy initiation and continuing until 14 days after radiotherapy completion.

The registered treatment description and the outcome labels are not fully aligned: the study description names acetylcysteine, while the posted result arm is called Rincinol. The registry record does not explain this naming difference, so the posted outcome comparisons are described using the result-arm labels when discussing the numerical results. The placebo result arm is labelled Arm A; the other result arm is labelled Arm B.

The primary outcome was the GRIX sticky-saliva total-score area under the curve, measured up to two weeks following radiotherapy. The record describes an evaluable primary-endpoint population, with 16 participants in the placebo arm and 12 in the Rincinol-labelled arm contributing to the posted primary result. The enrollment total therefore should not be treated as the sample size for every outcome. The safety summaries report 17 participants at risk in the placebo group and 16 in the Rincinol group.

The registry lists 10 outcome measures and 10 analyses. Several secondary measures concern sticky saliva, xerostomia, pain, and swallowing, including measures assessed up to 90 days after radiation therapy. Details of the original sample-size justification, allocation procedure, concealment procedures, and any interim analyses are not reported in the registry record. The details of the protocol’s planned analysis beyond the primary endpoint description are also 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:

Analysis population for the primary outcome, as defined in the registry: evaluable for Primary Endpoint (AUC for GRIX Sticky Saliva Total Score)

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: Eligible patients are included in this participant flow.

6. Primary Endpoint

The registry lists the primary outcome as Groningen Radiotherapy-Induced Xerostomia (GRIX) Sticky Saliva Total Score Area Under the Curve (AUC), measured over Up to 2 weeks following radiotherapy.

The primary endpoint was the GRIX sticky-saliva total-score area under the curve, with results reported as a mean score and standard deviation. GRIX is described as a 14-item questionnaire with four subscales on 0-100 scales; higher scores indicate worse symptoms. For the primary endpoint, the area under the curve was calculated for each participant from baseline to two weeks following radiotherapy, using assessments across the treatment period. The registry describes averaging the areas for available assessment periods to obtain a participant-level summary.

An area-under-the-curve measure can represent symptom experience across a span of assessments, rather than relying on one measurement alone. This can be useful when symptoms change during treatment. As a general statistical point, an average across a time course can summarize both symptom levels and their persistence, although the interpretation depends on how assessments are collected and how incomplete observations are handled. Those missing-data details are not reported in the registry record.

The endpoint is relevant to the trial’s stated question because sticky saliva is one of the symptoms the intervention was intended to address. The registry’s description says higher scores represent worse symptoms. The primary comparison used the arm-level mean scores, with a t-test described as assuming equal variance. The endpoint’s score scale and area-under-the-curve construction should be kept in mind when interpreting the reported mean difference: it is a difference in the summarized score, not a count of participants with an improvement or a direct measure of treatment adherence.

7. Results Posted in the Registry

• Arm B (Rincinol): mean 27.20 versus 40.90 on control; difference -13.70 (95% CI -30.31 to 2.91), standardized effect d = -0.61; z-test p = 0.106.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Groningen Radiotherapy-Induced Xerostomia (GRIX) Sticky Saliva Daytime Area Under the Curve (AUC)

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Arm B (Rincinol): mean 26.10 versus 45.20 on control; difference -19.10 (95% CI -35.81 to -2.39), standardized effect d = -0.81; z-test p = 0.025.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Arm B (Rincinol) than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Groningen Radiotherapy-Induced Xerostomia (GRIX) Sticky Saliva Nighttime Area Under the Curve (AUC).

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Arm B (Rincinol): mean 29.10 versus 34.50 on control; difference -5.40 (95% CI -24.01 to 13.21), standardized effect d = -0.22; z-test p = 0.569.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Arm B (Rincinol) and the control. The interval gives the range of effects that remain compatible with the data.

GRIX Xerostomia Daytime AUC

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Arm B (Rincinol): mean 27.30 versus 44.10 on control; difference -16.80 (95% CI -30.57 to -3.03), standardized effect d = -0.94; z-test p = 0.017.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Arm B (Rincinol) than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

The secondary measures cover sticky saliva at daytime and nighttime, xerostomia, pain, swallowing, and quality of life. Across the numerical results available for three secondary outcomes, the estimated directions and precision are not uniform. Some comparisons have intervals that exclude zero, while another has an interval spanning zero. This mixture suggests that the secondary results should be treated as outcome-specific observations rather than as one consistent signal across all symptom domains.

The daytime sticky-saliva and xerostomia summaries are directionally consistent with lower average scores in the Rincinol-labelled group, whereas the nighttime sticky-saliva summary is less precise and does not exclude zero. These secondary comparisons may add context to the primary sticky-saliva endpoint, but they do not replace it. The primary endpoint remains the prespecified focus identified in the registry record, and its recalculated interval includes zero.

The registry lists nine secondary outcomes, but numerical information in the record is not equally detailed across all of them. Statistical methods for secondary analyses, missing-data handling, and the analysis population for each outcome are not fully reported. Results from multiple secondary tests also raise a multiplicity concern: the more comparisons considered, the greater the chance that some may look unusual by chance alone. The registry record does not report whether secondary hypotheses were adjusted for multiplicity or designated as confirmatory versus exploratory.

Accordingly, the secondary findings are best regarded as contextual and hypothesis-generating. They can help identify which symptom domains warrant careful evaluation in future research, but the posted record does not support treating an isolated secondary p-value as independent confirmation of the primary finding. The variety of outcomes, their differing precision, and unreported multiplicity procedures all limit the strength of cross-outcome conclusions.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Groningen Radiotherapy-Induced Xerostomia (GRIX) Sticky Saliva Daytime Area Under the Curve (AUC)
• Groningen Radiotherapy-Induced Xerostomia (GRIX) Sticky Saliva Nighttime Area Under the Curve (AUC).
• GRIX Xerostomia Daytime AUC
• GRIX Xerostomia Nighttime AUC
• GRIX Xerostiomia Total Score AUC
• EORTC Quality of Life Questionnaire (QLQ) H&N Pain AUC
• EORTC Quality of Life Questionnaire (QLQ) Swallowing
• EORTC Quality of Life Questionnaire (QLQ) H&N Sticky Saliva AUC

9. Statistical Interpretation

10. Statistical Methods Explained

What does a mean difference describe?

The primary endpoint is continuous, so each arm is summarized by a mean and a standard deviation. The mean describes the average observed score in the group. The standard deviation describes how spread out individual scores were around that group mean; it is not the uncertainty in the mean itself. The recalculated comparison expresses the mean in the Rincinol-labelled arm minus the mean in the placebo arm. A negative value therefore corresponds to a lower observed mean in the Rincinol-labelled group.

As a general statistical explanation, a difference in means gives a concise estimate of the contrast between groups on the outcome’s measurement scale. It does not show how many individual participants improved, whether every participant had a similar experience, or whether a difference is important to patients. Those questions require additional data or context that are not reported in the registry record.

Why use a t-test?

The primary outcome description specifies a t-test with equal variance. A t-test compares group means while accounting for the amount of variation and the number of observations in each group. The equal-variance version assumes that the outcome variability is sufficiently similar across the groups for a pooled estimate of variance to be appropriate. The observed standard deviations are 23.7 and 21.0, but those estimates come from small groups and do not establish whether the assumption is adequate.

As a general statistical point, assumptions are simplifications used to obtain an estimate and its uncertainty. If the underlying assumptions are poorly matched to the data, the reported uncertainty may not behave as intended. The registry record does not report diagnostic checks, a justification for the equal-variance assumption, or a sensitivity analysis using another model.

What does the recalculation add?

The recalculated mean difference and interval are unadjusted calculations based on the posted summary statistics. They make the direction, estimated magnitude, and uncertainty of the primary contrast explicit. The recalculated p-value is also unadjusted. It should be read alongside the estimate and interval, rather than as a standalone verdict. The sponsor’s posted analysis uses a one-sided t-test and reports p = 0.123; the recalculated comparison is not the same analysis specification.

A p-value describes how compatible the observed data are with a specified null model under the assumptions of the test. It is not the probability that the null hypothesis is true, nor does it measure the size or clinical importance of an effect. A confidence interval conveys a set of effect values that are reasonably compatible with the data under its method and confidence level. The confidence level for the interval is not reported in the registry record, so no level should be attributed to it from this record alone.

Why does variability matter?

Greater variability generally makes a group mean less precisely estimated when sample size is held fixed. A small study can therefore have a point estimate that appears notable while still having a wide interval. In the primary comparison, each arm has a modest number of evaluable participants, and the interval includes zero. That is a statement about precision and compatibility, not proof that the true effect is zero.

As a general concept, over-dispersion means that observed variability exceeds what a chosen statistical model expects. It can make standard errors too small if the model fails to account for the extra variation. The primary outcome is a continuous score, and the registry does not report an over-dispersion analysis or a diagnosis of this issue. It should not be assumed that over-dispersion occurred.

How do the secondary analyses fit?

The registry lists 10 outcome measures and 10 analyses, including several secondary symptom and quality-of-life outcomes. The numerical secondary results should be interpreted as exploratory context unless the analysis plan and multiplicity procedures are known. When many outcomes are tested, the chance of finding at least one apparently unusual result can increase. As a general statistical safeguard, prespecification and adjustment procedures can help manage that issue, but the registry record does not report a multiplicity plan.

The available record describes the primary endpoint test as equal-variance and the sponsor’s posted primary analysis as a one-sided t-test. The method for all secondary analyses, any covariate adjustment, the handling of repeated measurements, and the exact analysis populations are not reported in the registry record. Consequently, the posted group summaries support descriptive comparisons, but they do not allow a full reconstruction of the original analysis strategy.

11. Confidence Intervals and Precision

The primary recalculated mean difference is -13.7, with a confidence interval from -30.31 to 2.914. The interval extends across zero. This means that the observed data do not pin down a single precise value for the difference: values below zero and values above zero remain compatible with the interval. The estimate points toward a lower mean score in the Rincinol-labelled arm, but the interval does not rule out no difference or a difference in the opposite direction.

As a general explanation, a confidence interval is a way to express uncertainty around an estimated effect. A narrower interval indicates greater precision, while a wider interval indicates that the estimate is less precise. The interval’s interpretation depends on the statistical method and its confidence level. The registry record does not report the confidence level associated with the recalculated interval; therefore, it is described only by its reported endpoints rather than assigned a confidence percentage.

The primary analysis includes 16 placebo participants and 12 participants in the Rincinol-labelled arm. A small sample can yield imprecise estimates, particularly when individual scores vary. The group standard deviations, 23.7 and 21.0, describe appreciable spread in the observed scores, but the registry does not provide individual participant data or report precision for the group means separately.

The sponsor’s reported one-sided p-value is 0.123, while the recalculated unadjusted p-value is 0.106. These values arise from analysis presentations that are not identical; the registry describes the sponsor result as a one-sided t-test and the primary endpoint description specifies a t-test assuming equal variance. A p-value does not replace the interval: it does not convey the full range of plausible effect sizes or resolve the uncertainty about magnitude. The sponsor’s own analysis takes precedence when characterizing the sponsor-reported test, while the recalculation remains a separate summary-statistic comparison.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The sample-size figures are planning illustrations based on the observed effect, not the trial’s original design calculations. For this continuous outcome, the figures are participants per arm, not total events. The stated assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The assumed effect to detect is a stated fraction of the observed effect. The original design assumptions and sample-size justification are not reported in the registry record.

The 80% power column gives the illustrative number of participants per arm associated with an 80% chance of detecting the specified effect under the planning assumptions, if that effect and the assumptions were true. The 90% power column uses a higher target chance of detection under those same assumptions. These are prospective planning quantities, not a description of what happened in the trial. This is not observed power.

The planning rows consider 100%, 75%, and 50% of the observed effect. As the assumed effect becomes smaller, more participants are needed to distinguish it from random variation at the stated significance level and target power. This general relationship explains why the planning requirements rise in the rows using a smaller fraction of the observed effect. The illustration is especially sensitive to the observed effect in a pilot sample: an effect estimated from a small study may not be stable, and using it as a planning value does not guarantee that a later study will see the same magnitude.

These values do not demonstrate that the trial was adequately powered, nor do they explain how the actual enrollment target was chosen. They are not a substitute for the unreported original design rationale. The posted calculations also do not account for information about missing outcomes, adherence, or other design features beyond the stated planning assumptions.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = -13.700; pooled standard deviation σ = 22.597.
2. n = 2 × (1.96 + 0.842)² × 22.597² / -13.700² = 42.7, rounded up to 43 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- -13.7                      # observed difference in means
sigma <- 22.59709817994                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(2123511)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 43 (80% power), 58 (90% power)
 75% of observed effect: n per arm = 76 (80% power), 102 (90% power)
 50% of observed effect: n per arm = 171 (80% power), 229 (90% power)
power.t.test: 43.7 
Simulated power at n = 43 per arm: 0.789 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Analyses Reported by the Sponsor

The registry reports the sponsor’s primary analysis as a one-sided t-test, with p = 0.123. It does not post a sponsor mean-difference estimate or confidence interval for that analysis. Separately, the recalculation from the posted group summaries gives a mean difference of -13.7, a confidence interval from -30.31 to 2.914, and an unadjusted p-value of 0.106. The two results should not be conflated: the sponsor’s analysis and the recalculation have different reported test specifications.

The sponsor’s own analysis takes precedence when describing the sponsor-reported result. The recalculation is useful for making a simple, unadjusted contrast from the posted means, standard deviations, and group sizes, but it is not a correction to or replacement for the sponsor’s analysis. The registry describes the primary endpoint comparison as a t-test assuming equal variance, while the sponsor-analysis entry identifies a one-sided t-test. Why these specifications differ, whether there were additional details in the full analysis plan, and whether any adjustment or alternative analysis was used are not reported in the registry record.

Both presentations should be read in the context of the small evaluable primary sample and the uncertainty in the estimated difference. Neither p-value describes the probability that the treatment has a particular effect. The posted sponsor p-value alone also does not indicate the magnitude of the observed contrast, because the sponsor’s estimated effect and interval are not reported.

15. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary endpoint and multiple secondary outcomes, including measures of sticky saliva, xerostomia, pain, swallowing, and quality of life. Testing several outcomes can increase the chance of at least one apparently strong result arising from random variation. As a general statistical principle, multiplicity can be addressed through prespecified testing hierarchies or statistical adjustments, but the registry record does not report a multiplicity procedure, a hierarchy among secondary outcomes, or whether secondary tests were intended as confirmatory or exploratory.

Missing data are also relevant because the primary results describe an evaluable endpoint population. The posted primary arm sizes are 16 and 12, whereas overall enrollment was 34. The registry does not explain the reasons participants were not included in that primary analysis, how many observations were missing at each assessment, or whether missingness was related to symptoms, treatment exposure, or other factors. The handling of incomplete questionnaires and the method used to calculate areas under the curve when assessments were unavailable are not reported in the registry record.

The record does not state whether the primary analysis followed an intention-to-treat principle, a per-protocol principle, or another population definition beyond the phrase “evaluable for Primary Endpoint.” The population for each secondary outcome is likewise not fully specified in the posted information. Without those details, the effect of exclusions or incomplete follow-up on the estimates cannot be assessed.

As a general explanation, missing-data methods rely on assumptions about why observations are missing. Different assumptions can lead to different estimates, especially when the amount or pattern of missingness differs between groups. No missing-data sensitivity analyses are reported in the registry record. Details of interim analyses, analysis-plan deviations, and adjustments for repeated measures are also not reported. These omissions limit the ability to reconstruct the full statistical plan or assess how robust the reported results are to analytical choices.

16. 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 (5.9%), nausea (5.9%), oral hemorrhage (5.9%), oral pain (5.9%), lung infection (5.9%).

The safety summary reports serious adverse events among 5 of 17 participants at risk in the placebo group and 0 of 16 in the Rincinol group. Other, non-serious adverse events are reported among 15 of 17 and 14 of 16, respectively. The registry reports zero deaths in both groups. These are descriptive counts from the safety summaries; the record does not provide a comparative statistical test or an adjusted estimate of between-group risk.

The listed serious-event terms are dysphagia, nausea, oral hemorrhage, oral pain, lung infection, and white blood cell decreased, each reported at 5.9%. The registry does not provide enough detail in this summary to attribute each listed term to a particular participant or to establish whether any participant experienced more than one event. These terms should therefore be read as reported event categories, not as a complete account of each participant’s experience.

As a general statistical point, safety counts in small groups can be unstable, and a difference in observed counts does not by itself establish a causal difference between treatments. Interpretation also depends on event definitions, follow-up, attribution, and completeness of reporting. Those details are not reported in the registry record. The figures describe what was posted, not a definitive comparison of safety between the arms.

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

The posted primary summaries show a lower mean GRIX sticky-saliva total-score area under the curve in the arm labelled Rincinol than in the placebo arm. The recalculated mean difference is -13.7, and the interval from -30.31 to 2.914 includes zero. The data therefore leave uncertainty about the size and direction of the underlying mean difference. The sponsor’s own primary analysis reports a one-sided p-value of 0.123; the registry does not post its corresponding effect estimate or interval.

This result does not establish that acetylcysteine does or does not reduce sticky-saliva symptoms. A point estimate is not a guarantee that the same difference would occur in another sample, and an interval spanning zero is not proof that the groups are identical. It indicates that the trial’s primary summary does not determine the effect precisely enough to exclude a range that includes no difference. The record also does not report a threshold for a clinically important change on this endpoint, limiting interpretation of the score difference’s practical meaning.

The study was a pilot with 34 enrolled participants and fewer participants contributing to the primary evaluable analysis. Its results can describe the observed sample and provide context for future study planning, but they do not establish a definitive effect. The planning figures are illustrations based on the observed effect and should not be mistaken for evidence of the probability that the trial detected a real effect.

The secondary outcomes and safety counts add context, but their interpretation is constrained by the number of measures, variable precision, incomplete reporting of analysis methods, and unknown missing-data handling. The record does not resolve the difference between the intervention name in the study description and the Rincinol label in the posted results. Taken together, the record supports a cautious statistical reading: there is an observed difference in the primary sample, accompanied by substantial uncertainty and limitations in the available analysis details.

18. Why This Trial Matters Statistically

This trial illustrates why an estimated effect should be read together with its uncertainty. The primary point estimate is negative, but the confidence interval spans zero. A reader focused only on the direction or size of the point estimate could overstate what the data establish; a reader focused only on a p-value could miss the range of effects compatible with the estimate. Considering both the estimate and interval makes the limited precision more visible.

The study also shows how a pilot trial’s observed effect can be used for planning without implying that the effect is stable. The listed participant requirements change substantially when the assumed target is a smaller fraction of the observed effect. This is a general feature of planning: detecting a smaller difference usually requires more information. The planning illustration does not reveal the trial’s original design rationale, which is not reported in the registry record, and it is not observed power.

Multiplicity is another important statistical issue. The registry includes a primary endpoint and several secondary symptom and quality-of-life outcomes. Without a reported multiplicity strategy, secondary p-values are more appropriately considered exploratory context than independent confirmation. Missing-data and analysis-population details also matter because the primary result is based on an evaluable subset, and the registry does not explain exclusions or incomplete assessments.

Finally, the differences in how the primary analysis is described—the endpoint text’s equal-variance t-test and the sponsor result’s one-sided t-test—show why the analysis method must accompany the numerical result. The posted record supports a transparent reading of the observed means, uncertainty, and sponsor-reported test, while leaving important design and analysis details unresolved. These are core statistical considerations in interpreting small clinical trials, regardless of the specific intervention.

19. 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 result is based on 16 placebo participants and 12 participants in the arm labelled Rincinol, within a pilot trial that enrolled 34 participants. These modest endpoint groups limit precision, as reflected by the recalculated interval extending from -30.31 to 2.914. The registry does not report the reasons that enrolled participants were not included in the primary evaluable population or provide a missing-data analysis.

There is a naming ambiguity in the record: the intervention description identifies acetylcysteine, while the posted outcome arm is labelled Rincinol. The relationship between those names is not explained. This makes it important to preserve the distinction between the registered treatment description and the labels attached to the numerical outcomes rather than assume the record has resolved it.

The sponsor reports a one-sided t-test, while the primary endpoint description specifies a t-test assuming equal variance. The registry does not explain this difference or report a sponsor effect estimate and interval. The confidence level for the recalculated interval is also not stated in the record. Further details about the original sample-size justification, allocation and concealment procedures, multiplicity, interim analyses, and protocol deviations are not reported in the registry record.

The registry lists multiple secondary outcomes, but the method and analysis population for each are not fully described. The posted safety summary gives event counts but not a comparative statistical analysis or detailed event-level attribution. Finally, the primary outcome’s score difference is not linked in the record to a threshold for clinical importance. These limitations constrain conclusions about precision, robustness, and clinical meaning.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: Acetylcysteine Rinse in Reducing Saliva Thickness and Mucositis in Patients With Head and Neck Cancer Undergoing Radiation Therapy — NCT02123511.
• Registry record last updated 2019-04-30; status last verified 2018-12.
• Results first posted 2019-04-05.
• 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.

23. Record Summary

NCT02123511 is a completed randomized, double-blind, parallel-group phase 2 pilot trial sponsored by Mayo Clinic. It enrolled 34 participants with head and neck cancer undergoing radiation therapy. The registered study compared an acetylcysteine oral rinse with placebo, administered five times per day from within 3 days of radiotherapy initiation through 14 days after radiotherapy completion.

The primary endpoint was the GRIX sticky-saliva total-score area under the curve, assessed through two weeks following radiotherapy. The posted primary summaries include 16 placebo participants and 12 participants in the arm labelled Rincinol. The recalculated mean difference is -13.7, with an interval from -30.31 to 2.914; the sponsor’s posted one-sided test reports p = 0.123. The registry record does not resolve the naming difference between the intervention description and outcome label.

The study also lists secondary symptom and quality-of-life outcomes and reports safety counts. Multiplicity handling, missing-data methods, and several aspects of the original statistical plan are not reported in the registry record. The primary estimate should therefore be interpreted with attention to its uncertainty and the limited analysis details.