Stereotactic Body Radiotherapy for Head and Neck Tumors: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Stereotactic Body Radiotherapy for Head and Neck Tumors (NCT01344356), a non-randomized phase 4 study. The primary outcome is Local Control Rate.

2. Clinical Question

In statistical terms, the question is descriptive: what local-control and toxicity outcomes were recorded among participants treated in this study? Because the study has no untreated or alternative-treatment control group, its design cannot isolate how outcomes would have differed under another treatment. The posted information also does not establish whether outcomes differed between benign and malignant tumors. The record lists overall survival as a secondary outcome, but does not include an analysis of it.

3. Trial Design

This was a Phase IV, non-randomized, single-group study with no masking. It enrolled 19 participants and is listed as completed. The study started in 2008-07, with primary completion in 2018-05. Mercy Research is named as the sponsor. The registry record describes two treatment groups, Benign Tumors and Malignant Tumors; both received stereotactic body radiotherapy. These groups describe tumor type, not alternative interventions.

The distinction matters when interpreting the tables and plots on this page. A comparison between the benign and malignant groups would not be a randomized comparison. The registry record explicitly cautions that the arms are not a like-for-like control comparison. Differences between the groups could reflect their different tumor types or other differences not described in the record, rather than a treatment contrast. The study therefore cannot serve as a randomized estimate of SBRT versus another treatment.

The stated study purpose was to evaluate local control and acute and late toxicity for SBRT in benign and malignant head and neck tumors. The primary outcome is local control at 5 years. Overall survival is listed as a secondary outcome. The registry record identifies 4 outcome measures, but the posted details do not give a numerical local-control result or an analysis of overall survival.

The record gives an enrollment of 19, but this should not be mistaken for the number with local-control outcome data. It states that 12 patients did not have local-control data reported, with reasons including never being treated, loss to follow-up, and death before data collection. The record does not describe a statistical analysis population or explain how missing outcome information was handled. Thus, the design and enrollment can be summarized, but the available record does not support a complete assessment of the primary outcome.

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: 12 patients did not have local control rate data reported. 3 patients were enrolled but never treated. 6 patients were lost to follow up. 3 patients died before data was collected.

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 Local Control Rate, measured over 5 years.

The primary endpoint is the local control rate, reported as a count of participants, with a 5 years timeframe. The registry description defines local control as complete or partial tumor response, or stable disease. This endpoint is intended to describe whether treated tumors met one of those response or stability categories at the stated assessment period. In general, local-control outcomes are used to summarize tumor status at the treated site, rather than outcomes such as overall survival that concern survival over time.

The endpoint definition alone does not show how many participants met the definition. The registry record does not report a local-control numerator, an analysis denominator, or a numerical rate. It states that 12 patients did not have local-control data reported. It also lists 3 patients as enrolled but never treated, 6 patients as lost to follow up, and 3 patients as having died before data was collected. The record does not explain whether those categories overlap, how each participant was classified, or how missing assessments affected the endpoint analysis.

For that reason, the endpoint can be described but not independently quantified from the registry record. In general, a rate requires both a defined group of participants being assessed and a count meeting the endpoint definition. Without a reported result and analysis population, neither the observed local-control proportion nor its precision can be established from the posted information.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The posted record is enough to identify the broad design and endpoint, but not enough to reconstruct an inferential analysis. General statistical explanations below clarify what common methods would mean; they are not claims that the trial used those methods. The registry record does not report a statistical analysis plan, an estimator for local control, confidence intervals, hypothesis tests, or details of how participant outcomes were analyzed.

What does a participant count describe?

The primary outcome is specified as a count of participants with local control. In general, a count summarizes how many people meet a defined outcome. If that count is divided by a defined analysis population, it can be expressed as a proportion or rate. Those quantities answer related but distinct questions: a count gives the number meeting the definition, while a proportion also makes the size of the assessed group explicit. Here, the registry record supplies the endpoint definition but does not report the count meeting it or the denominator used for analysis. It is therefore not possible to recover a local-control proportion from the record.

The outcome definition combines complete response, partial response, and stable disease. In general, combining categories into one endpoint can make a summary easier to interpret, but it hides how participants were distributed across the included categories. The record does not give category-specific counts, assessment criteria beyond the brief endpoint description, or details of when and how response was assessed.

What would a confidence interval add?

In general, a confidence interval communicates the statistical uncertainty around an estimate. It can help readers distinguish a precisely estimated outcome from one compatible with a broad range of values. An interval does not repair missing information or remove design limitations; it quantifies uncertainty under the assumptions of the analysis. No confidence interval for local control is reported in the registry record, and no estimate is available to interpret for precision.

Likewise, a p-value would address a specified statistical test, not whether an outcome is clinically important or whether a treatment caused it. The record reports no primary-outcome analysis or p-value. It would be inappropriate to infer one from the enrollment, the safety counts, or the study's completed status.

Why does the design affect comparisons?

In general, random allocation can help balance measured and unmeasured characteristics between treatment groups, supporting a more credible treatment comparison. This study is listed as non-randomized and single-group, and the listed benign and malignant groups both received SBRT. The groups are not described as interchangeable controls. A contrast between their outcomes would mix any differences in outcomes with differences associated with tumor type, participant characteristics, or other unreported factors. Thus, even if group-specific results were available, they would be descriptive rather than a randomized treatment-effect comparison.

The lack of masking is also part of the design description. In general, masking can reduce the possibility that knowledge of treatment affects assessment or care. The record says there was no masking, but does not describe outcome-assessment procedures or whether assessments were centrally reviewed. The implications for outcome measurement cannot be determined from the registry record.

How should the planning illustration be read?

The sample-size section uses a planning illustration computed from an observed effect, rather than the trial's own design. Its stated assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is described as a stated fraction of the observed effect. In general, a sample-size calculation asks how many participants might be needed under an assumed effect and analysis framework. It does not tell readers how many participants were actually analyzed or what result the study observed.

The illustration's assumptions do not turn the benign and malignant groups into a controlled comparison. The record specifically says the arms are not a like-for-like control comparison, and the trial itself is not randomized. The planning numbers are not observed power, do not establish that the study had a particular probability of detecting an effect, and should not be read as evidence of efficacy. The registry record does not report the trial's original sample-size justification or its own design calculations.

What is not documented?

The record lists 4 outcome measures and 0 analyses. It does not describe a statistical plan, how missing outcomes were handled, whether any interim analyses occurred, or which analysis population was intended. These omissions prevent a reader from assessing whether results were adjusted for baseline characteristics, whether outcomes were evaluated using a time-to-event method, or whether sensitivity analyses were conducted. These are unknowns, not evidence that a particular method was or was not used.

In general, methods should match the outcome and the question. A fixed-time status endpoint, a count, and a time-to-event outcome such as overall survival may call for different summaries and assumptions. Since the record does not show the specific analyses, readers should avoid attributing a particular estimator, test, or modeling approach to this study.

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("Benign Tumors", "Malignant Tumors")
n      <- c(1, 6)
events <- c(1, 5)
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  Benign Tumors  1  1  100.0  2.5  100.0  20.7  100.0  15.8  98.7
ARM  Malignant Tumors  6  5  83.3  35.9  99.6  43.6  97.0  42.1  96.3

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists 4 outcome measures, including local control as the primary outcome and overall survival as a secondary outcome. It reports 0 analyses. The record does not describe how multiple outcomes were prioritized statistically, whether multiplicity adjustments were planned, or whether any subgroup analyses were intended. The absence of those details means readers cannot determine how the study addressed the possibility of chance findings across multiple outcomes. It does not establish that a particular adjustment was performed or omitted in the analysis.

Missing data also limit interpretation of the primary endpoint. The record states that 12 patients did not have local-control rate data reported and lists 3 enrolled but never treated, 6 lost to follow-up, and 3 who died before data was collected. It does not explain how those cases were handled, whether the reasons overlap, or whether any participants were excluded from an analysis population. There is no reported missing-data method, such as an imputation approach or a sensitivity analysis. The handling of missing data is therefore not reported in the registry record.

The record does not define an intention-to-treat, treated, or evaluable analysis population. Although enrollment is listed as 19, enrollment alone does not establish the endpoint denominator. Without a stated analysis population and missing-data strategy, readers cannot assess how much the local-control result, if reported, would depend on which participants were included. The same caution applies to any comparison between the benign and malignant groups: the record does not describe adjusted analyses or a multiplicity plan for such comparisons.

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 non-serious adverse event terms

The adverse-event figures are counts within the listed benign and malignant tumor groups. In the benign group, 1 participant was at risk for a serious adverse event, and 0 were affected; 1 was at risk for other adverse events, and 1 was affected. In the malignant group, 8 were at risk for a serious adverse event, and 0 were affected; 8 were at risk for other adverse events, and 5 were affected. The table also lists 0 deaths for the benign group and 8 for the malignant group.

These counts should be read as registry entries, not as a comparison of treatment safety between groups. The groups differ by tumor category, and the study was non-randomized. The record does not report event types in the serious-adverse-event listing, follow-up periods for these safety counts, or whether the deaths were considered related to treatment. A death count in an adverse-event table does not, by itself, establish cause or attribution. The counts are also limited in scope and do not provide enough information to characterize the timing, severity, or duration of events. The registry record does not report further detail needed to interpret those aspects.

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

The record supports a description of the study's purpose, design, and endpoint: it evaluated stereotactic body radiotherapy for benign and malignant head and neck tumors, with local control at 5 years as the primary outcome and overall survival as a secondary outcome. It also records some safety counts and explains why local-control data were unavailable for a number of participants. These details are useful for understanding what the investigators set out to study and what the registry currently documents.

However, the registry record does not report a numerical local-control result. It therefore does not establish how many participants met the endpoint definition, the proportion who did so, or the precision of any estimate. The study's completion status and its enrollment of 19 do not substitute for a reported outcome analysis. The recorded missing local-control data further prevent readers from assuming that all enrolled participants contributed an endpoint assessment.

The study also does not answer a randomized comparative question. Both described groups received SBRT, and the benign and malignant groups are not like-for-like controls. Any observed difference between them would not, without appropriate design and analysis, identify an effect of SBRT compared with another treatment. The record does not report a statistical analysis of the primary or secondary outcomes from which such claims could be assessed.

Accordingly, this record should not be interpreted as showing that SBRT does or does not control tumors, or as establishing a treatment effect. It documents an intended evaluation and partial outcome information, not a complete estimate with stated uncertainty. The planning illustrations elsewhere on the page are sample-size exercises based on assumptions; they are not trial findings or observed power. Further interpretation would require outcome results, analysis details, and clearer information about who was included and how missing data were addressed.

14. Why This Trial Matters Statistically

This study is statistically informative because it illustrates the difference between a study's stated objective and the evidence that its registry record makes available. The objective is clearly framed around local control and toxicity after SBRT, and the primary endpoint has a defined timeframe and a brief outcome definition. Yet the record does not report the numerical local-control result. A well-specified question is not the same as a reported estimate.

It also demonstrates why an enrollment figure should not be treated as the endpoint sample size. The record lists 19 enrolled participants, while also stating that 12 did not have local-control data reported. It identifies several reasons for missing outcome information, but does not document the analysis population or missing-data handling. Without those details, readers cannot determine how the outcome denominator was formed or how missingness might affect interpretation.

The design is another important statistical lesson. A non-randomized study with benign and malignant tumor groups does not create a controlled treatment comparison just because the registry lists separate arms. Both groups received the same intervention, and their tumor categories differ. Describing the groups separately can be informative, but it does not estimate a randomized contrast.

Finally, planning calculations must be separated from observed evidence. The sample-size section is explicitly a planning illustration under assumptions, not the study's own design justification and not observed power. Clear separation between estimates, uncertainty, design assumptions, and planning aids helps readers avoid treating an illustration as a result. In this record, the most important statistical conclusion is the boundary of what can be assessed: design and intended outcomes are visible, while a primary outcome estimate and its precision are not reported in the registry record.

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.

Several limitations are specific to the information recorded for this study. The central limitation is that the registry record does not report a numerical result for the primary local-control endpoint. Although the endpoint is described at 5 years, no local-control count, denominator, rate, or confidence interval is given. This prevents readers from evaluating the magnitude or precision of the primary outcome from the record.

The record states that 12 patients did not have local-control data reported and lists 3 who were enrolled but never treated, 6 who were lost to follow-up, and 3 who died before data was collected. It does not explain whether these categories overlap, how missingness was handled, or which participants formed the outcome analysis population. These uncertainties are especially important when the study's total enrollment is 19.

The non-randomized, single-group design has no alternative-treatment control. The two listed groups are based on benign versus malignant tumor type, and both received SBRT. The record cautions that they are not a like-for-like control comparison. Results from those groups, if analyzed separately, could not by themselves establish a causal treatment contrast.

The available registry information also does not report the statistical analysis plan, the endpoint estimator, confidence intervals, hypothesis tests, interim analyses, or the original sample-size justification. It lists 4 outcome measures and 0 analyses. Safety information is limited to event counts without details on event types, timing, or attribution of deaths. Together, these gaps constrain interpretation of local control, survival, and toxicity beyond the descriptive information recorded.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Stereotactic Body Radiotherapy for Head and Neck Tumors — NCT01344356.
• Registry record last updated 2020-04-10; status last verified 2020-03.
• Results first posted 2020-04-10.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

This completed Phase IV study evaluated stereotactic body radiotherapy for benign and malignant head and neck tumors. It was non-randomized, unmasked, and single-group, with 19 participants enrolled. The primary outcome was local control at 5 years, defined as complete or partial tumor response or stable disease; overall survival was listed as a secondary outcome.

The registry record does not report a numerical local-control result or an analysis of overall survival. It states that 12 patients did not have local-control data reported and lists reasons including never being treated, loss to follow-up, and death before data collection. The record includes adverse-event counts for the benign and malignant groups, but does not provide further detail about event types or death attribution. The posted information therefore describes the intended evaluation and some recorded safety data, but does not provide a complete primary-outcome estimate or its statistical precision.