Assessing the da Vinci® Robotic Surgical System for Surgery of the Upper Aerodigestive Tract: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Assessing the da Vinci® Robotic Surgical System for Surgery of the Upper Aerodigestive Tract (NCT00721539), a na na study. The primary outcome is Overall Complication Rate (Intraoperative and Postoperative).

2. Clinical Question

The clinical question is principally one of feasibility and short-term safety in a pilot setting, rather than comparative effectiveness. The listed secondary outcomes include whether the planned diagnostic or therapeutic procedure could be performed, average blood loss and average operative time. Those measures could describe whether the procedure was carried out as intended and some features of the operation, but their results are not reported in the registry record.

The record does not give a detailed breakdown of lesion sites, benign versus malignant cases, or the procedures planned for individual participants. It therefore does not establish how broadly the findings, if reported elsewhere, would apply across the range of oral and laryngopharyngeal lesions. With no control group and no posted primary endpoint result, the clinical question remains descriptive: the record identifies what the pilot intended to assess, but does not supply enough outcome information to judge the observed complication experience.

3. Trial Design

This is a pilot study registered as a single-group study of transoral robotic surgery using the da Vinci Surgical Robot Platform. The arm description states that the platform was used to access neoplastic disease of the upper aerodigestive tract. The registry lists the allocation as NA and masking as NONE; phase is also recorded as NA. These entries do not describe a randomized or masked comparison.

The enrollment is 9. The record gives a study start of 2010-09 and a primary completion date of 2012-09, and lists the status as TERMINATED. A reason for termination is not reported in the registry record. The record names Stanford University as sponsor. It does not report a protocol-level explanation of the study design, eligibility criteria, or rationale for the planned enrollment.

The primary outcome is overall complication rate, defined to include intraoperative and postoperative complications through six weeks. Secondary outcomes are feasibility, average blood loss and average operative time. Feasibility is defined as the ability to perform the planned diagnostic or therapeutic procedure. The registry record reports four outcome measures, but it does not provide results for the primary endpoint or the listed secondary outcomes in the registry record described for this analysis.

Because this is a single-group pilot, the design can describe outcomes among participants undergoing the procedure but cannot isolate a treatment effect relative to an alternative. The absence of a comparator also means that any event rate would need to be interpreted as an observed experience in this enrolled group, not as evidence that the procedure changes risk compared with another approach. The record reports no statistical analyses. It also does not report the sample-size justification or a detailed statistical analysis plan.

The registry's sample-size assumptions describe a planning illustration based on an observed effect, not the trial's own design. The stated illustration uses a two-sided significance level of 0.05, equal allocation between two arms and a normal approximation; it frames the effect to detect as a stated fraction of the observed effect. Those hypothetical assumptions do not convert this single-group pilot into a two-arm study, and should not be read as the protocol's enrollment rationale or as observed power.

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.

Before assignment: Exclusion criteria include unexplained fever, active infection, pregnancy, anatomic parameters which preclude surgery including trismus, limited range of neck motion, poor dentition, and physical features such as redundant hypopharyngeal tissues which prevent adequate exposure of tumor.

Overall Study

Analysis population for the primary outcome, as defined in the registry: Subjects enrolled in this pilot study.

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 Overall Complication Rate (Intraoperative and Postoperative), measured over Six weeks.

The primary endpoint is the overall complication rate during the period from surgery through six weeks postoperatively. Its description includes complications encountered during the operation or up to six weeks afterward, with examples of patient injury, hemorrhage, lacerations and readmission following surgery. The outcome is expressed in participants, so it concerns how many participants experienced a complication rather than a tally of every separate complication event.

A short-term complication endpoint is used to characterize immediate procedural safety and the burden of events associated in time with the operation. Including both intraoperative and postoperative events gives the endpoint a broader scope than an outcome limited to the operating room. A defined follow-up window also clarifies which events are intended to count. However, the endpoint description alone does not tell readers how events were identified, adjudicated, or classified when several complications occurred in the same participant; those details are not reported in the registry record.

The registry record does not report the number of participants with a primary-endpoint complication, the denominator assessed for this endpoint, or an estimated rate. The adverse-event figures should not be substituted for this endpoint result: the record presents them separately, and the primary endpoint's stated definition is not shown to be identical to the adverse-event categories. Consequently, the endpoint's intended meaning can be described, but its observed result cannot be assessed from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a single-group design estimate?

In a single-group study, outcomes are described among participants who received the intervention. The central statistical quantity for a binary outcome such as whether a participant had a complication is a proportion: participants with the event divided by participants assessed for that outcome. That estimate describes the observed study group. Without a comparison group, it does not estimate a difference attributable to the intervention, because there is no concurrent group to represent outcomes under another approach.

For this study, the intended primary outcome is a participant-level complication measure through six weeks. The registry record does not report its event count or assessed denominator. Although the adverse-event information includes a risk denominator, it is a separate reporting category and cannot be assumed to supply the missing primary endpoint data. Keeping outcome definitions separate prevents an apparently available count from being misread as the result for a different endpoint.

Why does precision matter?

A point estimate is the observed rate or other summary calculated from study data. A confidence interval expresses the uncertainty associated with that estimate under the statistical method used. In general, intervals are wider when information is limited and narrower when the data are more informative. A wide interval can encompass a broad range of plausible values, even when the point estimate appears reassuring. A narrow interval indicates greater precision, but does not by itself establish clinical importance or freedom from bias.

No confidence interval for the primary outcome or adverse-event figures is reported in the registry record. Thus, readers cannot use a reported interval to judge the precision of an estimated complication rate. The enrollment and adverse-event risk set also do not establish that every participant had complete follow-up for the primary outcome. Follow-up completeness for that endpoint is not reported.

What does zero observed events mean?

When no participants in a category are recorded as affected, the observed count is zero for that category. This is not the same as proving that the event is impossible or that the population risk is zero. Sampling variability remains, and the underlying risk could be nonzero even when no event appears in a limited study group. Formal uncertainty estimates can help communicate this distinction, but none is reported. It is also important to distinguish zero from missing information: a zero is an observed count, whereas a null entry for deaths does not give a numerical observation.

These distinctions apply to the adverse-event record: 0 participants are listed as affected by serious adverse events and 0 by other adverse events among 9 at risk in the transoral robotic surgery group. The deaths entry is null. These entries do not give the primary complication result, and the record does not identify the serious adverse event terms. They also do not describe how events were attributed to the procedure.

How should the listed planning assumptions be read?

The registry's sample-size assumptions describe an illustration for planning based on an observed effect, rather than the design of this pilot. The stated approach uses a two-sided significance level of 0.05, equal allocation between two arms and a normal approximation. It considers detecting a stated fraction of the observed effect. In general, a sample-size calculation asks how much information a planned study would need to detect a specified effect under chosen assumptions. Its answer depends on those assumptions, including the effect being targeted and the statistical method.

Here, those assumptions should not be mistaken for actual enrollment planning. The registered study is single-group, whereas equal allocation between two arms belongs to a hypothetical comparison. Nor is a planning calculation an observed power calculation. Observed power is not a useful replacement for an uncertainty interval around results, and the assumptions do not establish that the study had adequate power for its primary outcome. The registry record does not report the trial's own sample-size justification, a prespecified effect size, or its statistical analysis plan.

What can be inferred from missing analyses?

The registry record reports no analyses. This means no inferential test, adjusted estimate, or reported confidence interval is available in the analysis information. It does not establish why analyses are absent or whether analyses were performed outside the registry. No p-value should be inferred from the event counts. A statistical test would also not solve the design's lack of a comparator or replace missing outcome reporting.

For a pilot, descriptive summaries can be useful for characterizing feasibility and identifying procedural outcomes that warrant further study. Such summaries remain exploratory unless supported by a prespecified analysis and adequate information. A binary outcome can be summarized with a participant count and denominator, while continuous measures such as blood loss and operative time generally require a stated summary and a clear account of the observations included. The registry lists average blood loss and average operative time, but their values and distributional details are not reported.

In general, continuous outcomes may be skewed, and an average can be sensitive to unusually high or low observations. Binary outcomes can be sparse, especially in a pilot, which makes conventional approximations less reliable. Appropriate analysis depends on the endpoint, study design, completeness of follow-up and assumptions that are not fully specified in the registry record. Accordingly, the posted information supports cautious descriptive interpretation, not a reconstructed 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("Transoral Robotic Surgery")
n      <- c(9)
events <- c(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  Transoral Robotic Surgery  9  0  0.0  0.0  33.6  -0.0  29.9  0.3  30.8

11. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary outcome and secondary outcomes for feasibility, average blood loss and average operative time. Considering several outcomes can raise a multiplicity issue: the more statistical questions tested, the greater the chance that at least one result appears noteworthy by chance if tests are interpreted without accounting for the number of comparisons. An analysis plan may designate one outcome as primary and specify how secondary outcomes will be handled. Such a plan is not reported in the registry record, and no analyses are reported, so the handling of multiplicity cannot be assessed.

Missing-data methods and analysis populations are also not described. The record does not state how participants with incomplete follow-up would be handled for the six-week complication endpoint, whether all enrolled participants were included in each outcome analysis, or whether any participants were excluded from an analysis. The adverse-event risk set is reported as 9, but that does not establish complete follow-up for the distinct primary outcome.

The record does not report imputation, sensitivity analyses, or rules for handling unavailable measurements. For continuous secondary outcomes, it does not describe whether the reported average would be based on all enrolled participants or only those with an observed measurement; in fact, values are not reported. Without these details, readers cannot evaluate potential bias from missing observations or determine whether outcome-specific populations differed.

These are reporting gaps, not evidence that data were missing or that a particular method was used. The registry record does not explain the absence of analysis details, so no reason should be inferred.

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.

The adverse-event record lists the transoral robotic surgery group with 9 participants at risk. It records 0 participants affected by serious adverse events and 0 affected by other adverse events. The record's outcome meaning is participants with an event, so these figures describe participant counts in the listed categories rather than the number of separate events.

Deaths are recorded as null. Null is not a numerical count and should not be read as zero. The serious adverse event terms are also not listed, so the record does not identify particular event types. It does not give event-level descriptions, timing, severity details beyond the serious versus other categories, or attribution to the procedure or device.

These safety figures should be kept distinct from the primary endpoint, which is overall complications during and through six weeks after surgery. The primary endpoint result is not reported in the registry record. The adverse-event categories may not capture all complications as defined for that endpoint, and the record does not state that they are equivalent.

Zero recorded affected participants in these categories is a descriptive result for the reported group, not a guarantee of no risk. The small pilot enrollment and lack of a reported uncertainty estimate limit how precisely these counts characterize safety beyond the participants recorded. They also cannot establish comparative safety because the study has no control group.

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

The result that can be read directly from the record is limited. For the adverse-event categories, 0 participants are recorded as affected by serious adverse events and 0 by other adverse events, among 9 at risk in the transoral robotic surgery group. The deaths entry is null, and serious adverse event terms are not listed. The primary endpoint result and the listed secondary outcome results are not reported in the registry record.

That is not the same as a complete evaluation of the intervention. A zero adverse-event count in this group does not demonstrate zero underlying risk, and it does not mean that the primary complication endpoint had zero events. The endpoint definitions and reporting categories are distinct unless the record establishes that they match; it does not. Without a reported primary endpoint count, readers cannot calculate or interpret an overall complication rate from this record.

The study's single-group design also means it cannot estimate how outcomes compare with another procedure or with no robotic platform. It cannot determine whether any event was caused by the procedure, the device, the underlying disease, or other circumstances. Even a fully reported descriptive result would characterize this enrolled pilot group, not establish a causal effect by itself.

The record does not report inferential analyses, confidence intervals, or the statistical plan. It therefore does not quantify uncertainty around the posted adverse-event counts or show whether the study was designed to test a particular hypothesis. The sample-size assumptions listed for a planning illustration are not the trial's own design and should not be treated as evidence of observed power.

The appropriate interpretation is therefore cautious and specific: the record documents a terminated pilot study of transoral robotic surgery and reports no affected participants in its listed serious or other adverse-event categories. It does not supply the primary complication result needed to address the stated primary question, nor results for feasibility, blood loss or operative time. No conclusion about comparative benefit, efficacy or safety follows from the available record.

14. Why This Trial Matters Statistically

This trial is statistically important as an example of the difference between a registered clinical question and a result that can be evaluated. The registry defines a clinically meaningful primary endpoint—complications during surgery and through six weeks—but does not report its event count or denominator. Without those values, the main endpoint cannot be summarized as an observed rate, and its precision cannot be assessed.

The record also illustrates why safety summaries must be matched to their definitions. The adverse-event figures are participant counts in serious and other categories, while the primary outcome is overall complications with a specified time window and examples. Treating those categories as interchangeable would produce a misleading interpretation. Null deaths data likewise cannot be converted into a zero count.

The single-group pilot design is suited to describing experience and exploring feasibility, but it does not provide a randomized or concurrent comparison. Statistical methods cannot create that missing comparison after the fact. Even a precise event estimate from a single group would not, by itself, show that the procedure caused better or worse outcomes than an alternative.

The record's planning assumptions add another useful distinction. Hypothetical sample-size calculations can help illustrate what a future comparison might require under chosen assumptions, but they do not establish how this pilot was planned or how much information it actually produced. They are not a substitute for reporting observed outcomes and uncertainty.

For clinical research readers, the key lesson is to separate study purpose, outcome definition, observed data and inferential claims. This record identifies the intended outcomes and gives limited adverse-event counts, but leaves the primary result and analyses unavailable. Recognizing that boundary prevents a descriptive safety entry from being overstated as a complete answer to the study's clinical question.

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 consequential trial-specific limitation is that the registry record does not report the primary overall complication result, despite defining a six-week endpoint. The secondary outcome results for feasibility, average blood loss and average operative time are also not reported. As a result, the stated objectives cannot be evaluated from the outcome information available in the record.

The study is a single-group pilot with enrollment of 9 and no comparator. Its results, even if fully reported, would be descriptive and would not establish how outcomes differ from another surgical approach. The record does not report detailed eligibility criteria, the number assessed for each outcome, the completeness of follow-up, or the handling of missing observations. It also does not give a reason for the TERMINATED status.

Safety reporting is limited to participant counts in serious and other adverse-event categories. Serious adverse event terms are not listed, and deaths are null rather than numerically reported. The record does not describe event attribution, ascertainment procedures, or how adverse events relate to the primary complication definition. Therefore, the available safety entries do not provide a complete characterization of postoperative complications.

Finally, no analyses or statistical analysis plan are reported. The registry does not provide uncertainty intervals, multiplicity procedures, outcome-specific analysis populations, or a sample-size justification for the pilot. These gaps prevent assessment of precision and analysis choices. They should be understood as limitations of the record's reported information; they do not establish why the information is absent or what analyses may have been conducted elsewhere.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Assessing the da Vinci® Robotic Surgical System for Surgery of the Upper Aerodigestive Tract — NCT00721539.
• Registry record last updated 2016-11-03; status last verified 2016-11.
• Results first posted 2016-11-03.
• 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 record describes a pilot study assessing transoral robotic surgery with the da Vinci Surgical Robot Platform for benign and malignant lesions of the oral cavity and laryngopharynx. It is registered as a single-group study with enrollment of 9, masking listed as NONE, phase listed as NA and status TERMINATED. The recorded study start is 2010-09, and the primary completion date is 2012-09.

The primary outcome is overall complications during surgery and up to six weeks postoperatively. Secondary outcomes are feasibility, average blood loss and average operative time. The primary and secondary outcome results are not reported in the registry record. The adverse-event record lists 0 participants affected by serious adverse events and 0 affected by other adverse events among 9 at risk; deaths are null, and serious event terms are not listed. No analyses are reported. The reason for termination, sample-size justification, missing-data methods and detailed statistical plan are not reported in the registry record.