Atezolizumab Before Surgery for the Treatment of Regionally Metastatic Head and Neck Squamous Cell Cancer With an Unknown or Historic Primary Site: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Atezolizumab Before Surgery for the Treatment of Regionally Metastatic Head and Neck Squamous Cell Cancer With an Unknown or Historic Primary Site (NCT05110781), a na phase 2 study. The primary outcome is Pathologic Complete Response (pCR).

2. Clinical Question

This is a window trial: atezolizumab is given before definitive surgery, allowing the primary endpoint to assess tumor pathology at resection. The clinical question is whether pCR is observed after this treatment sequence, not whether atezolizumab is superior to a control regimen. Because the record lists enrollment of 1, any interpretation must be especially attentive to the small amount of participant-level information. The registry does not report a numerical pCR count or rate, so the endpoint cannot be summarized as an observed response from this record.

3. Trial Design

The registry describes a phase II, single-group trial sponsored by the University of California, Davis. Allocation is listed as not applicable and masking as none. The study concerns regionally metastatic head and neck cutaneous squamous cell carcinoma with an unknown or historic primary site. Its stated objective is to test atezolizumab before surgery, with pathologic complete response assessed at resection as the primary endpoint.

The treatment description specifies atezolizumab by intravenous infusion over 30-60 minutes on day 1, with treatment repeated every 21 days for 2 cycles in the absence of disease progression or unacceptable toxicity. Patients then undergo standard-of-care surgery. The record states that patients with residual disease undergo standard treatment beginning 6 weeks after surgery, but the description is incomplete after that point. The listed interventions also include radiation therapy and therapeutic conventional surgery.

The registry lists enrollment of 1. The study start date is 2021-12-07, the primary completion date is 2022-05-02, and the status is terminated. The record does not state why the trial was terminated, whether the listed participant completed treatment or surgery, or whether the planned treatment sequence was delivered as written. Those details are not reported in the registry record.

Because this is a single-group design, outcomes cannot be contrasted with outcomes under a concurrent control condition. The record also does not report a statistical analysis plan, a justification for the enrollment target, or details of any interim monitoring. Those absences limit assessment of how the planned analyses were intended to address uncertainty and bias. A single-group phase II study can describe what was observed among participants treated under its protocol, but this design alone cannot distinguish treatment effects from other explanations for an 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.

Before assignment: Not applicable; only one participant was enrolled and the enrolled participant received study treatment.

Overall 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 Pathologic Complete Response (pCR), measured over At time of surgery (up to 10 weeks from time of enrollment).

The primary endpoint is pathologic complete response, or pCR, measured at the time of surgery, within up to 10 weeks from enrollment. The registry defines pCR as having no residual invasive squamous cell carcinoma within the primary tumor and all resected lymph nodes, as assessed by the pathologist at primary resection. The planned summary is a count of participants meeting that definition and a rate expressed as the proportion of patients demonstrating pCR.

Pathology at surgery is used because it directly assesses whether invasive tumor remains in the tissue removed during the operation. It differs from an imaging-based response assessment: the definition depends on the pathologist’s examination of the resected primary tumor and lymph nodes. This endpoint is clinically relevant to a pre-surgical treatment sequence because it evaluates tumor status at definitive resection.

The registry record does not report the observed pCR count or rate. It therefore does not establish whether any participant met the definition. A defined endpoint is not itself an outcome result. The record also does not report the number of participants with evaluable surgical pathology or how missing pathology, if any, would be handled.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a single-group phase II study with no masking and no allocation to comparison arms. These design features determine what statistical conclusions could be drawn. A single-group analysis can report counts or proportions within the treated group, but it cannot estimate a randomized between-group contrast when no comparator group exists. The registry does not report a statistical analysis plan, so the exact planned methods for summarizing the primary endpoint are not reported in the registry record.

What does a count or proportion describe?

The primary endpoint is a binary participant-level outcome: a participant either meets the registry’s pCR definition or does not. A count records the number meeting that definition. A proportion relates that count to the number of participants included in the analysis. These summaries answer different practical questions: the count reports how many participants had the outcome, while the proportion describes its frequency in the analyzed group. The registry gives the endpoint definition but does not report the pCR count, proportion, or analysis population.

In general, a confidence interval describes uncertainty around an estimated quantity under the assumptions of the method used. It is not a guarantee that the true value lies within the interval, and it does not account automatically for biases caused by missing outcomes, selection, or study design. With very little information, estimates are imprecise. In this trial, a numerical pCR estimate and interval are not reported in the registry record, so there is no posted interval to interpret.

Why does the single-group design matter?

A randomized comparison is designed to assess differences between assigned treatment strategies. Here, allocation is listed as not applicable and the model is single group. Therefore, the study has no control-arm result against which to compare pCR, recurrence, response, or adverse events. A within-group outcome cannot establish what would have happened to the same participants under a different treatment strategy. This is a limitation of the design, not a problem that can be corrected by a particular statistical test.

Masking is listed as none. In general, masking can reduce the influence of knowledge of treatment assignment on subjective decisions, measurement, or outcome assessment. The primary endpoint is based on pathology, but the registry does not report further details about pathology review, independent assessment, or blinding of those assessing specimens. Those procedures are not reported in the registry record.

How should planning illustrations be read?

Any sample-size values associated with planning illustrations should be understood as hypothetical planning quantities, not as outcomes observed in this trial. The stated assumptions describe a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect expressed as a fraction of the observed effect. These assumptions do not describe the actual single-group design, which has no two-arm allocation. The illustrations are not the trial’s own design justification, and they are not observed power.

In general, a sample-size calculation asks how much information a hypothetical design would need to detect a specified effect under stated assumptions. Its answer depends on the chosen effect, error rate, allocation, outcome type, and analysis method. A planning calculation cannot make a small or incomplete study more informative after the fact. It also cannot substitute for a reported endpoint result. The registry does not report the trial’s own sample-size justification, and the listed enrollment is 1.

The stated normal approximation is a simplifying method used in some planning calculations. For binary outcomes with sparse observations, approximations may be unreliable because the data can be far from the conditions under which the approximation behaves well. In general, exact or other methods may be considered for small samples, but the registry does not report which inferential method, if any, was planned for this trial’s primary outcome. No method should be attributed to the investigators without that information.

What can the secondary outcomes add?

The registry lists secondary outcomes that span pathology, recurrence or progression, imaging, overall response, plasma exosome levels, and adverse events. In general, multiple outcomes provide different kinds of information, but interpreting many results raises questions about which outcomes are primary, how comparisons are prioritized, and whether chance findings are controlled. The registry does not report a multiplicity procedure, an outcome hierarchy, or numerical analyses for these outcomes. The count of 0 analyses indicates that analysis results are not listed in the registry record.

The registry record also does not state whether interim analyses were planned or conducted. Without a reported analysis plan, readers cannot determine the prespecified approach to endpoint coding, missing observations, confidence intervals, or statistical testing. General statistical methods can explain how such choices affect interpretation, but they cannot fill in methods that are not reported for 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("Treatment (Atezolizumab, Surgery, Radiation Therap")
n      <- c(1)
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  Treatment (Atezolizumab, Surgery, Radiation Therap  1  0  0.0  0.0  97.5  0.0  79.3  1.3  84.2

11. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary outcome and six secondary outcomes, including major pathologic response, recurrence or disease progression, imaging-based standardized uptake value, overall response, plasma exosome levels, and adverse events. Considering multiple outcomes can broaden the description of a study, but it also creates a multiplicity issue: if many outcomes are tested, the chance of at least one apparently noteworthy result can increase. General approaches include prespecifying an outcome hierarchy or adjusting statistical tests, but the registry does not report whether either approach was used.

The record lists 0 analyses and does not provide numerical outcome results. It is therefore not possible to assess how outcomes were analyzed, whether any tests were conducted, or whether multiplicity was addressed. A hierarchy among the secondary outcomes, or a plan for interpreting them in relation to the primary endpoint, is not reported in the registry record.

Information about missing data is also absent. The registry does not report whether the participant had evaluable pathology, whether any outcome observations were missing, or what rules would be used to include participants in each analysis. The analysis populations, including any intention-to-treat or evaluable population, are not reported in the registry record. These omissions matter because the denominator used for an outcome proportion and the handling of participants without an assessment can affect interpretation.

The record lists enrollment of 1, but enrollment alone does not establish whether that participant received treatment, underwent surgery, had endpoint assessment, or completed follow-up. Those details are not reported in the registry record. Without them, the relationship between the enrollment listing and any outcome analysis cannot be evaluated.

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 registry’s adverse-event summary lists 1 participant at risk for serious adverse events and 0 affected. It also lists 1 participant at risk for other adverse events and 1 affected. The death count is 0. These are counts in the registry record; the numerical descriptions do not include event terms, timing, severity details, or a fuller account of event ascertainment.

The serious adverse event term list is empty. This means no serious event terms are listed in the record; it does not provide a detailed account of monitoring or establish that no safety concerns arose outside the information reported. The registry does not identify the other adverse event, so its nature and clinical significance are not reported in the registry record.

Safety counts from a group with enrollment listed as 1 are descriptive and cannot characterize the range or frequency of adverse events in a broader population. The record also does not state whether the listed participant received all planned treatment. These figures should therefore be read as limited registry-reported counts, not as a comprehensive assessment of safety.

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

The registry record establishes that a phase II, single-group trial was designed to evaluate atezolizumab before surgery and that pCR was the primary endpoint. It also lists enrollment of 1, a terminated status, and a treatment sequence involving atezolizumab followed by surgery. The pCR definition and its timing are specified. These details describe the study’s question and design.

The record does not report a numerical primary endpoint result. It therefore cannot establish whether pCR occurred, how often it occurred, or how precise an estimated pCR rate might be. Nor does it report numerical results for the listed secondary outcomes. A study’s endpoint definition and outcome list should not be mistaken for evidence that an outcome was achieved or measured in a particular way.

The single-group design does not include a randomized comparator. Even if an outcome were reported, it would describe the participants in this treatment sequence rather than quantify a causal difference against another strategy. The enrollment listing of 1 also means the record contains very little participant-level information for estimating outcome frequency or variability. These design and information limits are separate: having a comparator would address a different question from having enough observations for a precise estimate.

The record does not state why the trial was terminated, whether the participant completed treatment, or whether surgery and follow-up occurred. These details are not reported in the registry record and should not be inferred from the status field. The safety summary lists no serious adverse events and no deaths, alongside 1 participant with another adverse event, but gives no event term for that other event. These figures are limited to what the registry lists.

Accordingly, the posted information is useful for understanding the intended clinical question, treatment sequence, primary endpoint, and the constraints of the design. It does not establish that atezolizumab does or does not produce a particular clinical outcome, and it does not support a comparative treatment conclusion.

14. Why This Trial Matters Statistically

This trial illustrates why a registry entry needs to be read at two levels: what the study intended to measure and what results are actually reported. The primary endpoint is clearly defined as pathologic complete response at surgery, but a numerical pCR result is not reported in the registry record. Without that result, statistical interpretation cannot move from endpoint definition to an estimate of response.

The design also demonstrates the distinction between describing an outcome and estimating a treatment contrast. A single-group study can describe outcomes among participants in its treatment sequence, but it has no concurrent randomized control group for estimating a difference between strategies. That distinction remains even if an outcome appears clinically meaningful.

The enrollment listing of 1 makes precision a central concern. In general, estimates from very small samples are sensitive to individual observations and provide limited information about variability. A planning illustration cannot resolve that limitation: hypothetical calculations are not observed evidence and do not replace reported outcomes. The record’s stated planning assumptions involve two-arm allocation, unlike the listed single-group model, so they should not be read as a description of the trial’s actual comparison.

Finally, a terminated status and sparse outcome reporting make transparency about missing information especially important. The reason for termination, evaluability of the primary endpoint, analysis populations, missing-data approach, and multiplicity plan are not reported in the registry record. Naming these unknowns is statistically important because they determine what can be concluded—and just as importantly, what remains uncertain—from the posted information.

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 immediate limitation is the lack of a reported numerical pCR result. The registry defines the endpoint but does not give the number of participants who met it or an analyzed denominator. The listed enrollment is 1, and the record does not establish whether that participant completed treatment, underwent surgery, or had assessable pathology.

The study is single group, with allocation listed as not applicable and masking listed as none. It has no concurrent control arm for a comparative estimate. Consequently, the design cannot distinguish an outcome associated with the treatment sequence from what might have occurred under another strategy. The registry also does not report details of pathology review or whether outcome assessment was blinded.

The trial status is terminated, but the reason for termination is not reported in the registry record. The record does not explain whether termination was related to recruitment, feasibility, safety, scientific considerations, or another reason. The stated treatment description is incomplete after the reference to standard treatment for residual disease beginning 6 weeks after surgery, so the remainder of that care pathway is not reported in the registry record.

Additional limitations concern analysis transparency. The registry lists 0 analyses and does not report a statistical analysis plan, sample-size justification, interim-analysis approach, missing-data rules, analysis populations, or multiplicity strategy. Numerical results for the secondary outcomes are not reported. These omissions prevent evaluation of how outcomes were summarized and how uncertainty or incomplete observations were handled.

These constraints are specific to the information in the registry record. They do not establish that unreported procedures or results did not exist; they mean those details are not reported in the registry record and cannot be evaluated from it.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Atezolizumab Before Surgery for the Treatment of Regionally Metastatic Head and Neck Squamous Cell Cancer With an Unknown or Historic Primary Site — NCT05110781.
• Registry record last updated 2026-06-05; status last verified 2026-05.
• Results first posted 2023-09-05.
• 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.

19. Record Summary

This phase II trial, sponsored by the University of California, Davis, evaluates atezolizumab before surgery for regionally metastatic head and neck cutaneous squamous cell carcinoma with an unknown or historic primary site. The design is single group, with no masking and no comparator arm. The registry lists enrollment of 1 and identifies the study as terminated.

Atezolizumab is described as an intravenous treatment on day 1, repeated every 21 days for 2 cycles, followed by standard-of-care surgery. The primary endpoint is pathologic complete response at surgery, defined by the absence of residual invasive squamous cell carcinoma in the primary tumor and all resected lymph nodes.

The registry record does not report a numerical pCR result or numerical results for the listed secondary outcomes. The reason for termination, analysis populations, missing-data handling, and statistical analysis plan are not reported in the registry record. The safety summary lists 0 serious adverse events, 1 participant with another adverse event, and 0 deaths.