Pembrolizumab in Combination With CRT for LA-SCCHN: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Pembrolizumab in Combination With CRT for LA-SCCHN (NCT02586207), a na phase 1 study. The primary outcome is Adverse Events Will be Assessed and Graded Using CTCAE 4.0. Occurrences With Max Grade and Percentage/Number of Participants Affected by AEs Will be Provided..

2. Clinical Question

3. Trial Design

This was a Phase Ib, single-group, open-label, multi-site trial. The registry identifies no allocation to competing study arms and no masking. Participants received pembrolizumab in combination with cisplatin-based definitive chemoradiotherapy; there was no randomized control group. The registry lists enrollment of 59 and reports a completed study. The brief summary's anticipated enrollment was approximately 39, which differs from the registry enrollment figure; a reason for that difference is not reported in the registry record.

The treatment schedule began with pembrolizumab 200 mg intravenously 7 days before chemoradiotherapy. Chemoradiotherapy began on day 1 and included cisplatin 40 mg/m2 intravenously weekly and radiation at 70 Gy, fractionated at 2 Gy once daily over 35 days. The summary says chemoradiotherapy was expected to end on approximately day 46-50. Pembrolizumab 200 mg intravenously was then scheduled from day 57 for five additional doses, as tolerated, through day 141. Participants were to be evaluated for response following treatment.

The primary objective was safety and tolerability in people with treatment-naive Stage III-IVB squamous cell carcinoma of the head and neck. The primary outcome description specifies adverse events graded with CTCAE 4.0, with counts and percentages of affected participants reported by grade. Its assessment timeframe extends through day 240, described as allowing capture of adverse events up to 90 days after treatment completion. The registry lists complete response at treatment end, Day 150, as a secondary outcome. Further details about the protocol's rationale, eligibility criteria, site count, and conduct 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: Number of participants who experience an Adverse Event.

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 Adverse Events Will be Assessed and Graded Using CTCAE 4.0. Occurrences With Max Grade and Percentage/Number of Participants Affected by AEs Will be Provided., measured over through day 240 (this time frame allows capturing of AEs that occurred up to 90 days after completion of treatment).

The primary endpoint concerns the number of participants who experienced adverse events during the stated safety follow-up. The registry describes grading adverse events using CTCAE 4.0 and reporting the maximum grade and the number and percentage of participants affected. The timeframe is through day 240, intended to capture events occurring up to 90 days after treatment completion. The description also says safety and tolerability were assessed by clinical review of relevant parameters, including adverse events, laboratory tests, and vital signs.

As a general statistical concept, counting participants with at least one event gives a participant-level measure of how many people were affected; it does not by itself describe how many separate events occurred in each person, how long events lasted, or the full pattern of severity. Grade-specific counts can help describe severity, but detailed grade-specific results are not reported in the registry record. Counts are also dependent on the defined observation period and on which participants have outcome information available.

Safety outcomes are appropriate for a Phase Ib combination study because they describe observed harms and tolerability during treatment and follow-up. They do not, without a comparator and suitable analyses, establish whether events were caused by a particular component of the combination or whether their frequency differs from another treatment. The registry's primary outcome description gives the intended assessment, while the posted adverse-event summary gives selected event counts and terms. A complete grade-by-grade account of the primary endpoint is not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The principal statistical feature is the single-group design. Every participant received the combination described in the registry; there was no randomized comparator and no masking. As a general concept, random allocation can help balance measured and unmeasured characteristics between treatment groups, while a control group provides a contemporaneous reference. Without those features, this trial can describe outcomes in its enrolled group, but it cannot make a direct treatment-effect comparison. Differences from historical expectations would require a defined external comparison and assumptions that are not reported in the registry record.

What does a participant count represent?

The primary outcome concerns participants affected by adverse events. A participant count is different from a count of event episodes: one participant may experience more than one event, while the participant-level outcome may count that person only once within a given category. The registry describes counts and percentages by grade, but does not report the full grade-level results in the record summarized. Thus, the posted summary counts should not be treated as a complete event inventory, and counts in different categories should not be added together to infer a total number of unique people.

As a general statistical concept, a percentage is easier to interpret when its denominator and outcome definition are clear. The serious and other adverse-event summaries each identify 59 participants at risk, and the serious-event terms are posted as percentages. The record does not supply all event-specific denominators or explain in detail how event terms were grouped for this summary. The percentages should therefore be quoted as recorded rather than independently reconstructed.

What can an interval estimate tell a reader?

A confidence interval is a statistical range intended to express the uncertainty around an estimate under specified assumptions. For a single-group event proportion, an interval can indicate that the observed proportion is not a perfectly precise estimate of the rate that might occur in a broader population. As a general concept, interval width is affected by the amount of information and by the statistical method used. The registry record does not report confidence intervals for the adverse-event counts, so numerical precision beyond the displayed counts and percentages cannot be assessed from the record.

Likewise, a p-value addresses compatibility between observed data and a defined statistical null model; it is not a measure of clinical importance or the probability that a hypothesis is true. No p-value or comparative hypothesis test is reported in the registry record. In a single-arm study, a p-value would also require a specified reference or model. That reference and any confirmatory testing plan are not reported in the registry record.

Why does the treatment combination matter for attribution?

Participants received pembrolizumab together with cisplatin and radiation. An event observed during follow-up could reflect the disease, one or more treatment components, the combined regimen, or factors not captured in the summary. Attribution requires clinical assessment and prespecified definitions; those event-level attribution details are not reported in the registry record. The design also does not separate component effects because there are no groups receiving different components.

Open-label conduct means treatment assignment was not masked. As a general concept, knowledge of treatment can affect reporting or assessment, particularly for outcomes involving clinical judgment. The registry identifies the study as open-label but does not report procedures used to reduce assessment bias. This does not establish that bias occurred; it identifies a design feature relevant to interpretation.

How should planning calculations be read?

Planning illustrations based on observed effects are not observed power and are not the trial's original sample-size justification. The stated illustration assumptions include a two-sided significance level of 0.05, equal allocation between two hypothetical arms, and a normal approximation. Those assumptions do not describe the actual single-group trial design. The registry record does not report the trial's sample-size justification, target power, or the rationale behind the planned enrollment. Any hypothetical two-arm planning scenario should therefore be kept separate from the observed single-group results and should not be interpreted as a feature of the trial's protocol.

Over-dispersion is a general issue when variation in count outcomes exceeds what a chosen model assumes. A model that understates variation may produce intervals that are too narrow or tests that overstate precision. The reported primary outcome is a participant count rather than a detailed repeated-event count analysis, and no model for over-dispersion is reported in the registry record. This concept is relevant when evaluating count models generally, but the posted results do not permit assessment of whether such a model was needed or used.

Finally, the record lists two outcome measures and no analyses. The specific analysis populations, handling of incomplete follow-up, prespecified statistical methods, and any interim analyses are not reported in the registry record. Without those details, the reader cannot evaluate whether the posted summaries follow a prespecified analysis plan or how sensitive they are to missing outcome data.

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("Single Arm")
n      <- c(57)
events <- c(57)
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  Single Arm  57  57  100.0  93.7  100.0  93.7  100.0  93.8  100.0

11. Multiplicity, Missing Data and Analysis Populations

The registry lists two outcome measures: the primary safety and tolerability assessment and a secondary complete response outcome at treatment end, Day 150. When a study examines multiple outcomes or multiple comparisons, the chance of at least one apparently notable finding can increase. As a general statistical concept, multiplicity procedures can address that issue when formal hypothesis tests are planned. A multiplicity adjustment or testing hierarchy is not reported in the registry record. No analysis results or p-values are reported, so the impact of multiplicity on statistical conclusions cannot be assessed.

Missing data can affect both safety and response summaries. For example, incomplete follow-up could mean that some events are not observed, while missing response assessments could affect the number of participants with an evaluable outcome. This is a general concern, not evidence that missingness occurred in this trial. The registry record does not report missing-data counts, reasons for missingness, imputation methods, sensitivity analyses, or rules for determining evaluability.

The registry identifies 59 participants enrolled, but the analysis populations for each outcome are not reported in the registry record. It is therefore not possible to determine whether the same set of participants contributed to every reported safety or efficacy measure, or whether any participants were excluded from an analysis. Definitions of the safety population and response-evaluable population are also not reported.

These omissions limit assessment of how complete and comparable the outcome data are. They do not justify assuming that data were missing or that a particular analysis population was used. The enrollment and event counts can be described as posted, while the handling of missing results and the multiplicity strategy remain unreported.

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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: dehydration (11.9%), dysphagia (6.8%), aspiratoin pneumonia (5.1%), fever (5.1%), vomiting (5.1%).

The registry's adverse-event summary records 28 participants affected in the serious-event category among 59 at risk. In the other adverse-event category, it records 59 affected among 59 at risk. The record also lists 10 deaths. These figures describe what is entered in the registry; they do not establish the timing, cause, or treatment attribution of each event or death. The record does not give a detailed account of how the death count relates to adverse-event categories or the specific follow-up time for those deaths.

The listed serious adverse-event terms and percentages are Dehydration, 11.9%; Dysphagia, 6.8%; Aspiratoin Pneumonia, 5.1%; Fever, 5.1%; Vomiting, 5.1%; and Hyponatrimia, 3.4%. These terms are reported as written in the registry. They are not a full account of every serious event, and the record does not provide event-specific counts in this summary.

As a general principle, serious-event status and event severity grade are distinct concepts. A serious event is not automatically the highest grade, and a grade alone does not establish seriousness. The registry's primary endpoint description refers to CTCAE 4.0 grading and maximum grades, but grade-specific results are not reported in the registry record. Without detailed case information or a control group, the counts should not be used to infer causation or comparative risk.

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

The posted results describe a safety experience in a single group treated with pembrolizumab and cisplatin-based chemoradiotherapy. The record reports adverse-event counts, a set of serious-event terms with percentages, and a death count. These observations are relevant to describing what was recorded during the trial, but they are not a randomized comparison and do not quantify how outcomes would differ under another treatment strategy.

The study cannot isolate the effect of pembrolizumab from the effects of cisplatin, radiation, or their combination. Disease-related events and other factors may also contribute to what is observed. Because no control group was included, comparisons with another population would require additional information and assumptions not reported in the registry record. The record also does not establish whether individual events were judged related to a particular treatment component.

The registry identifies complete response at treatment end, Day 150, as a secondary outcome, but does not report a result for that outcome. Accordingly, the posted record does not allow assessment of the response outcome. It also does not report confidence intervals or inferential tests for the safety summaries, and the precision of the findings cannot be characterized beyond the presented counts and percentages.

As a general distinction, an outcome being listed as an endpoint is not the same as having a numerical result available for interpretation. Similarly, the absence of a reported efficacy result is not evidence of a positive or negative result. The appropriate reading is limited to the information actually recorded: the trial design, treatment schedule, enrollment, and posted adverse-event summary.

These data should not be treated as advice for individual care or as proof that the combination is beneficial or harmful. They are descriptive observations from the participants enrolled in this trial. More complete outcome reporting, analysis details, and a suitable comparator would be needed to answer comparative questions or to characterize uncertainty and attribution more fully.

14. Why This Trial Matters Statistically

This trial is statistically notable for the distinction between a safety-focused early-phase question and a comparative treatment-effect question. The primary objective was to assess safety and tolerability of a multi-component treatment in treatment-naive Stage III-IVB squamous cell carcinoma of the head and neck. A single-group design can provide descriptive information about events observed during treatment and follow-up. It does not, by itself, estimate the difference in outcomes between the combination and another regimen.

The combination design also raises an attribution issue. Pembrolizumab, cisplatin, and radiation were delivered as parts of one treatment strategy. Without groups that differ in treatment components, observed events cannot be separated statistically by component based on this trial alone. This limitation is inherent in the design and should be distinguished from the question of whether the event counts were recorded correctly.

The registry reports enrollment of 59, while the brief summary anticipated approximately 39 patients. The reason for this difference is not reported in the registry record. The contrast underscores why planned enrollment, actual enrollment, and the analysis population are separate quantities. The record does not report a sample-size justification or the population included in each outcome analysis.

Statistical interpretation also depends on complete outcome reporting. The registry identifies both safety and complete response outcomes, but the detailed grades and secondary response result are not reported. Without those results and analysis methods, readers cannot evaluate precision, missing-data sensitivity, or formal statistical evidence. These limitations do not invalidate the descriptive counts; they define the scope of what can be concluded from them.

For clinical researchers, the trial illustrates the importance of distinguishing an early-phase safety description from confirmatory evidence. Counts can describe observed events, but causal and comparative conclusions require appropriate design features, outcome reporting, and analysis. The registry record supports the former more than the latter.

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 design limitation is the absence of a comparator. Since all participants received the combination, the registry results cannot directly compare it with chemoradiotherapy alone or another strategy. The open-label design is another consideration. As a general concept, awareness of treatment can affect reporting and assessment, although the registry record does not establish that this occurred or describe specific safeguards.

The reported safety information is incomplete relative to the primary outcome description. The endpoint calls for adverse events by grade and percentage, and describes review of laboratory tests and vital signs. The registry summary does not report a complete grade-specific account or detailed results for laboratory tests and vital signs. The serious-event terms and percentages are selected terms, not a full event listing in the available record.

The secondary complete response outcome at Day 150 has no result reported in the registry record. The analysis populations, missing-data handling, confidence intervals, hypothesis tests, and prespecified statistical plan are also not reported. These gaps prevent assessment of the precision of estimates, the completeness of follow-up, and the robustness of any outcome interpretation.

The brief summary anticipated approximately 39 patients, whereas registry enrollment is 59. A reason for the difference is not reported in the registry record, and the target enrollment or sample-size justification is not reported. The registry indicates completion, but completion alone does not supply the missing analysis details or outcome results.

Finally, findings from a multi-component regimen cannot identify which treatment element contributed to any event. The record does not report event-by-event attribution or provide an untreated or alternative-treatment reference. These limitations constrain causal interpretation; they do not alter the descriptive counts as recorded.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Pembrolizumab in Combination With CRT for LA-SCCHN — NCT02586207.
• Registry record last updated 2025-10-07; status last verified 2025-09.
• Results first posted 2021-01-15.
• 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 identifies NCT02586207 as a completed Phase Ib, open-label, single-group, multi-site study of pembrolizumab with cisplatin-based definitive chemoradiotherapy for locally advanced squamous cell carcinoma of the head and neck. Enrollment was 59. The study started in 2015-11, and primary completion was 2020-09-29.

The primary outcome concerned adverse events assessed and graded using CTCAE 4.0 through day 240, with counts and percentages by grade intended for reporting. The registry lists complete response at treatment end, Day 150, as a secondary outcome. The adverse-event summary records 28 participants affected in the serious-event category, 59 in the other-event category, and 10 deaths; the complete response result and detailed grade-specific safety results are not reported in the registry record.

The single-group design supports descriptive reporting but not a direct randomized comparison. Statistical analysis methods, missing-data handling, analysis populations, and a sample-size justification are not reported in the registry record.