Salivary Gland Surgery Before Radiation Therapy in Preventing Radiation-Caused Xerostomia in Patients With Head and Neck Cancer: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Salivary Gland Surgery Before Radiation Therapy in Preventing Radiation-Caused Xerostomia in Patients With Head and Neck Cancer (NCT00068237), a na phase 2 study. The primary outcome is Number of Patients Scored as Having the Surgical Technique of Submandibular Salivary Gland Transfer Performed "Per Protocol".

2. Clinical Question

3. Trial Design

This was a Phase II, completed, single-group study sponsored by the Radiation Therapy Oncology Group. The registry record gives an enrollment of 49 and identifies the intervention as submandibular salivary gland transfer followed by post-operative radiation therapy. The transfer was performed at the time of surgery for the primary tumor and neck nodes. Allocation is recorded as not applicable, and masking is recorded as none. These design features mean that the study is not a randomized comparison and does not contain a like-for-like control group.

The stated primary population was eligible patients who started study treatment. The primary measure concerned the surgical procedure itself: whether central reviewers scored the transfer as having been performed per protocol prescription. The registry description names the Study Chair and the Radiation Therapy Oncology Group Head and Neck Committee Surgical Chair as the central reviewers. Their agreement was required for the per-protocol classification.

The primary outcome description sets out a decision criterion: if 21 or more of 43 subjects were scored per protocol, the technique would be considered reproducible. It describes the decision rule using Simon's two-stage design, an unacceptable rate of 60%, an acceptable rate of 80%, 80% power, and 5% type I error. Those are design criteria in the outcome description. The registry record does not report the observed number meeting the criterion, whether the criterion was met, the stages actually carried out, or any interim analysis.

The registry lists additional outcomes concerning acute and late xerostomia, transferred-gland function, questionnaire scores, toxicity, facial edema, disease-free survival, and overall survival. It records the study as completed, with a start date of 2003-08 and primary completion in 2008-01. Completion status alone does not show which outcomes were analyzed or what their results were; those results 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:

Analysis population for the primary outcome, as defined in the registry: Eligible patients who started study treatment.

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: All eligible patients who started study treatment.

6. Primary Endpoint

The registry lists the primary outcome as Number of Patients Scored as Having the Surgical Technique of Submandibular Salivary Gland Transfer Performed "Per Protocol", measured over At the time of the submandibular salivary gland transfer.

The primary endpoint is a count: the number of patients whose submandibular salivary gland transfer was scored as performed per protocol prescription. It is a measure of procedural fidelity or reproducibility, not a direct measurement of salivary function, dry mouth, cancer control, or treatment benefit. The registry description requires agreement by both central reviewers, the Study Chair and the Radiation Therapy Oncology Group Head and Neck Committee Surgical Chair, for a procedure to receive the per-protocol classification.

This kind of endpoint can address whether a specified surgical technique can be carried out according to its prescription in the study setting. It is relevant to interpreting later clinical outcomes because results from a technique may be difficult to interpret if the technique is not performed as intended. However, a procedure-level classification does not establish that the transfer preserved gland function or prevented xerostomia. Those questions concern separate outcomes listed in the registry.

The outcome description states that a count of 21 or more among 43 subjects would lead to the technique being considered reproducible, under the stated Simon two-stage design criteria. That threshold is a planned decision rule, not the observed result. The actual primary count, the number assessed, and the conclusion based on the observed count are not reported in the registry record. Accordingly, the endpoint's definition and decision rule can be described, but the primary finding cannot be reconstructed from this record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is a participant count, classified by whether the surgical technique met a prespecified procedural standard. The registry calls the outcome the number of patients scored as having the transfer performed per protocol. It further specifies that both central reviewers must classify the surgery as per protocol prescription. Requiring agreement makes the endpoint depend on a common classification rule rather than on a single reviewer's judgment. The registry record does not describe reviewer training, procedures for resolving disagreement, or the criteria used to decide whether an individual operation met the prescription beyond the stated requirement for agreement.

A count endpoint is naturally interpreted as the number of participants who meet a defined condition in the population assessed. In a single-group study, the count can describe how often that condition was observed within the group. It is not by itself a comparison of outcomes between treatment strategies. The primary outcome description supplies a threshold of 21 or more of 43 subjects. That threshold is part of a decision rule for judging reproducibility; it is not the observed count. The observed count, and whether it crossed the threshold, are not reported in the registry record.

The description refers to Simon's two-stage design and states unacceptable and acceptable rates of 60% and 80%, respectively, with 80% power and 5% type I error. In general, a two-stage design evaluates accumulating evidence at planned stages and can allow a study to stop according to prespecified rules. The design description gives the overall framework and the stated operating characteristics, but the registry record does not report the stage-specific rules, the number assessed at each stage, whether an early stopping boundary was used, or the decisions made during conduct. Those details should not be inferred from the name of the design alone.

Power is a property of a design under specified assumptions about the outcome rate and decision rule. It describes the chance that the design will reach a specified conclusion under those assumptions. It is not a measure of how persuasive an observed result is, and it cannot be read as the probability that the technique is reproducible. The stated 80% power belongs to the design description. It is not observed power calculated from the study's results. Since the observed primary count is absent, the record does not permit evaluation of how the study's finding relates to the prespecified decision rule.

Type I error describes the design's risk of making a particular positive decision when the unacceptable-rate condition holds, according to the design's assumptions. Here, the registry states 5% type I error and gives the unacceptable and acceptable rates. These features explain how the decision rule was intended to distinguish between rates considered unacceptable and acceptable. They do not demonstrate that the trial reached either underlying rate, and they do not replace reporting the observed data.

The design is single-group, with allocation recorded as not applicable and masking as none. General statistical interpretation of a single-group result differs from interpretation of a randomized comparison: it can describe outcomes in the treated group, but it does not isolate a treatment contrast from other influences. The registry record does not describe a comparator arm, a randomized allocation procedure, or a masked outcome assessment. The central reviewers' role in primary outcome scoring is stated, but masking of those reviewers is not reported in the registry record.

The registry also lists outcomes that would address clinical and functional questions rather than procedural reproducibility. These include the percentage of patients with acute xerostomia, the percentage with a normally functioning transferred gland, change from baseline to one year in the total score on the modified University of Washington Head and Neck Symptom Questionnaire, facial edema, acute and late grade 3-4 toxicity, and disease-free and overall survival rates at 2 years. These outcomes represent different event types and time horizons. The record does not provide their numerical results or the analyses used to estimate them.

Planning calculations are distinct from the analysis of observed trial outcomes. The stated sample-size assumptions describe an illustration based on a fraction of an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The stated convention is participants per arm for non-time-to-event outcomes and total events for time-to-event outcomes. These assumptions describe planning illustrations, not the single-group design recorded for this trial, and do not establish that this trial used those assumptions. Such calculations are not observed power. No calculated planning values are needed to interpret the registry's primary endpoint, and the primary result remains unreported.

For binary outcomes, general statistical interpretation depends on both the event count and the number of participants assessed. The denominator matters because the same count can have different meaning in groups of different sizes. When outcomes are followed over time, timing and censoring also matter; a survival rate is not interchangeable with a simple event count. The registry lists time horizons for several outcomes, but does not report the analysis details, handling of incomplete follow-up, or estimates for those outcomes. These omissions limit what can be concluded from the record.

In general, confidence intervals express the precision of an estimate by giving a range of values compatible with the data under the method's assumptions. A narrow interval indicates greater precision than a wide interval, while neither guarantees freedom from bias. No confidence interval for the primary outcome is reported in the registry record. Nor are the statistical methods for the secondary outcomes, model specifications, or adjusted estimates reported. It would therefore be inappropriate to invent an interval, infer a model, or treat the planned design characteristics as a substitute for an outcome 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("Surgery + Transfer + Radiation")
n      <- c(44)
events <- c(34)
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  Surgery + Transfer + Radiation  44  34  77.3  62.2  88.5  63.0  87.2  62.9  87.1

11. Multiplicity, Missing Data and Analysis Populations

The registry lists a range of secondary outcomes covering xerostomia, transferred-gland function, questionnaire scores, facial edema, acute and late toxicity, disease-free survival, and overall survival. These outcomes address different aspects of the intervention and use different follow-up horizons. When multiple outcomes are examined, general statistical interpretation must consider that looking for findings across several measures can increase the chance of a seemingly notable result arising by chance. Whether and how that concern was addressed depends on the prespecified analysis plan. A multiplicity adjustment or hierarchy of outcomes is not reported in the registry record.

The record identifies the primary population as eligible patients who started study treatment. It does not report how many participants were included in the primary analysis, whether all eligible treatment starters were evaluated, or how participants with incomplete assessments were handled. An intention-to-treat population, a per-protocol analysis population, and other analysis-population definitions are not reported in the registry record. The per-protocol wording in the endpoint refers to the surgical technique's classification; it should not be read as a complete description of the analysis population.

Missing-data methods, rules for excluding participants, and procedures for handling unavailable follow-up are not reported in the registry record. This matters because the primary measure requires reviewer scoring, while the listed secondary outcomes include measures at specified follow-up times. Without the number assessed and the missing-data approach, the completeness and potential selection effects of outcome reporting cannot be evaluated.

The registry records 0 analyses. It therefore does not provide inferential results, estimates, or uncertainty measures for the outcomes in the record. The design description includes a decision threshold and operating characteristics for the primary question, but those do not reveal the observed outcome or resolve missing-data and multiplicity questions.

12. Safety Results

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

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: acute surgical complication: bleeding/hematoma (4.5%), acute surgical complication: wound infection (4.5%), anorexia (2.3%), confusion (2.3%), apnoea (2.3%).

The safety summary identifies the Surgery + Transfer + Radiation group and reports 44 participants at risk in each of the serious and other adverse event categories. It records 2 participants affected by a serious adverse event and 38 affected by an other adverse event. These counts describe the registry's posted safety summary. They should not be read as comparative risks because the study has no concurrent control group, and the summary does not establish whether an event was caused by the procedure, radiation therapy, chemotherapy, the underlying cancer, or another factor.

The listed serious-event terms include acute surgical complication: bleeding/hematoma at 4.5%, acute surgical complication: wound infection at 4.5%, anorexia at 2.3%, confusion at 2.3%, apnoea at 2.3%, and acute surgical complication: cerebral embolism/CVA at 2.3%. These are the terms and percentages appearing in the registry summary. The percentages should be interpreted as reported, without assuming a denominator or a relationship between each term and the overall count unless that relationship is specified. A participant may have more than one event in general safety reporting, so event terms should not automatically be treated as mutually exclusive categories of people.

The registry field for deaths contains no reported count. The duration of safety surveillance and the detailed attribution procedures are not reported in the registry record. The summary therefore supports a description of the posted counts and terms, not a causal or comparative conclusion about safety.

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

The main statistical question was whether the transfer procedure could be scored as having been performed per protocol often enough to meet the study's stated reproducibility criterion. The registry defines the endpoint and gives a decision rule based on 21 or more of 43 subjects, with unacceptable and acceptable rates of 60% and 80%. Those details describe what the investigators intended to evaluate. The record does not give the observed primary count or state whether the decision rule was met.

Even a reported result meeting that procedural criterion would answer a narrower question than whether transfer preserves function or reduces xerostomia. Procedural fidelity can support interpretation of clinical outcomes, but it is not itself proof of clinical benefit. The record lists outcomes for acute xerostomia, normal function of the transferred gland, symptom questionnaire change, toxicity, facial edema, and survival. Their results are not reported in the registry record, so no conclusion about those outcomes follows from the primary endpoint description.

The design also limits causal interpretation. This is a single-group study without a concurrent control arm. Outcomes observed among participants receiving transfer and radiation would describe that group, but would not by themselves establish what would have happened under a different strategy. The registry record does not report a randomized comparison or an alternative comparative estimate.

The safety information is similarly descriptive. The counts and listed event terms indicate what the registry reports for the treated group, but they do not show whether the intervention increased or decreased adverse events compared with another group. A completed trial status indicates that the study is marked completed in the registry; it does not indicate that every result is available in the record.

Accordingly, the record supports a careful account of the research question, trial structure, endpoint definition, decision criteria, and posted safety counts. It does not support a conclusion about whether the technique met the reproducibility criterion, whether xerostomia or gland function changed, or whether treatment affected survival. The absence of reported estimates also means that precision cannot be assessed for those outcomes. Separating the planned criterion from the observed result is essential to avoid treating a protocol description as a finding.

14. Why This Trial Matters Statistically

This trial illustrates why identifying the exact estimand matters. The primary endpoint concerns whether a surgical technique was performed according to protocol, not whether a patient experienced less dry mouth or had better gland function. These questions may be related in the scientific rationale, but they are not interchangeable statistical outcomes. Clear interpretation starts by distinguishing the process measure from patient outcomes.

The record also illustrates the difference between a planned decision rule and an observed result. The threshold of 21 or more of 43 subjects, along with the stated acceptable and unacceptable rates and design operating characteristics, describes how reproducibility was to be judged. Without the observed count, readers cannot determine the study's conclusion from that rule. A design's intended power cannot fill this reporting gap.

Design structure shapes the strength of the conclusions. In a single-group study, the primary count can be used to assess procedural feasibility or consistency within the treated group, but there is no concurrent randomized control for estimating a treatment contrast. This distinction is especially important when the broader rationale concerns preventing radiation-related xerostomia: a procedural outcome alone cannot establish prevention, and a single-group outcome would not provide the same causal comparison as a randomized trial.

Finally, registry completeness affects statistical appraisal. The record lists multiple clinical outcomes and safety summaries, but does not report outcome analyses, missing-data procedures, multiplicity handling, or the primary result. Statistical transparency requires more than a study status and an endpoint definition; it requires the observed data and methods needed to understand the estimate and its uncertainty. The record is useful for understanding the intended question and design, while leaving the principal empirical conclusion unresolved.

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 important trial-specific limitation in the registry record is the absence of the observed primary endpoint result. Although the record defines the reviewer-based classification and the threshold for considering the technique reproducible, it does not report the count of procedures classified per protocol or whether the threshold was reached. The completion status cannot resolve this omission.

The single-group design has no concurrent control. It therefore cannot provide a direct randomized comparison of transfer with another strategy. This is relevant to the stated rationale of preventing radiation-induced xerostomia: the primary endpoint measures surgical-procedure fidelity, while xerostomia and gland function are separate outcomes. The registry lists those clinical outcomes but does not report their estimates.

The enrollment is 49, while the primary decision rule refers to 43 subjects. The registry record does not explain the relationship between those figures, identify how many participants were eligible and started treatment, or state how many had primary endpoint assessments. No reconciliation should be inferred. The primary population is described as eligible patients who started study treatment, but exclusions and analysis-population details are not reported in the registry record.

Further limitations for appraisal include the absence of reported results for the listed secondary outcomes, missing-data methods, multiplicity procedures, confidence intervals, and detailed analysis methods. The record does not describe the stage-specific conduct of the stated two-stage design or report any interim decisions. Its safety summary is descriptive and lacks a concurrent comparison group; the deaths count is not reported in the registry record. These gaps constrain both the assessment of precision and the interpretation of clinical or safety effects.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Salivary Gland Surgery Before Radiation Therapy in Preventing Radiation-Caused Xerostomia in Patients With Head and Neck Cancer — NCT00068237.
• Registry record last updated 2019-02-05; status last verified 2019-01.
• Results first posted 2014-01-31.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

The registry record describes a completed Phase II, single-group study sponsored by the Radiation Therapy Oncology Group, with enrollment of 49. The intervention was submandibular salivary gland transfer at surgery for the primary tumor and neck nodes, followed by post-operative radiation therapy. Allocation is recorded as not applicable and masking as none.

The primary endpoint was the number of patients whose procedure both central reviewers scored as per protocol prescription. The description gives a threshold of 21 or more of 43 subjects and states a Simon two-stage design with unacceptable and acceptable rates of 60% and 80%, 80% power, and 5% type I error. The observed primary result is not reported in the registry record. Listed secondary outcomes include xerostomia, gland function, questionnaire change, toxicity, facial edema, and survival; their results are not reported in the registry record.

The safety summary reports 2 participants with serious adverse events and 38 with other adverse events, with 44 at risk in each category. The study is marked completed, but the record does not report the primary finding or analyses needed to assess clinical outcomes.