Combination Chemotherapy With or Without Veliparib in Treating Patients With Stage IV Head and Neck Cancer: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Combination Chemotherapy With or Without Veliparib in Treating Patients With Stage IV Head and Neck Cancer (NCT01711541), a randomized phase 1, phase 2 study. The primary outcome is Dose Limiting Toxicity (Phase I).

2. Clinical Question

3. Trial Design

NCT01711541 is a completed phase I/phase II study with randomized allocation, double masking, and a parallel model. The registry characterizes it as partially randomized: phase I evaluates dose and toxicity, while phase II is described as a randomized comparison of veliparib or placebo alongside combination chemotherapy. The record lists total enrollment of 24 and identifies the National Cancer Institute as sponsor. The study start date is 2012-10-22, and primary completion is recorded as 2018-02-15.

The phase I primary outcome is dose-limiting toxicity, assessed during the first cycle of induction chemotherapy. The posted results are separated by dose level. The listed outcome counts are 0.0 participants at Dose Level 0, 0.0 of 3.0 at Dose Level 0B, 0.0 of 3.0 at Dose Level 1, 0.0 of 3.0 at Dose Level 2, and 1.0 of 6.0 at Dose Level 3. The outcome description notes that Dose Level 0 was excluded from this outcome because of a treatment-regimen change and describes eligibility, cancellation, dosing-error, and cycle-completion issues at other levels.

The phase II secondary outcomes include toxicity, progression-free survival, disease-free survival, time to local or distant progression, disease-specific survival, and overall survival. Although the record lists these outcomes, it does not report outcome analyses for them. Thus, the posted evidence described by this record is chiefly a phase I toxicity summary, not a reported randomized comparison of efficacy outcomes. The registry also lists chemotherapy, radiation, placebo, and laboratory biomarker interventions, but the arm descriptions are truncated in the 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.

Before assignment: The study originally opened at Dose Level 0 with a treatment of Docetaxel, cisplatin and flouricil (TPF) in combination with ABT-888 (veliparib). With a concern for the feasibility of this regimen in other reported studies, this study was suspended and re-opened with a treatment of Carboplatin and Paclitaxel in combination with ABT-888.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Dose Level 0 was not included in this outcome due to a change in treatment regimen. On Dose Level 0B, 1 patient was ineligible based on protocol criteria. On dose level 2, 1 patient cancelled prior to treatment, 1 had a dosing error and 1 pt did not complete cycle 1. On Dose Level 3, 1 patient cancelled prior to treatment.

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Dose Limiting Toxicity (Phase I), measured over Up to 3 weeks.

The primary endpoint counts participants who report a dose-limiting toxicity during the first cycle of induction chemotherapy, over a timeframe of up to 3 weeks. This is a safety and dose-finding endpoint, rather than a measure of tumor response or survival. In an early-phase study, dose-limiting toxicity counts can inform whether a dose level is tolerable enough to consider in further study. The registry states that the maximum tolerated dose is determined as the highest dose where 1 or fewer out of 6 patients reports a dose-limiting toxicity.

The registry definition includes specified severe blood-count events, febrile neutropenia, dose delays related to recovery or non-hematological toxicity, treatment-related grade 3 or grade 4 non-hematological toxicity subject to listed exclusions, and any drug-related death. For example, the definition includes Grade 4 neutropenia (ANC < 500) lasting more than 14 days, Grade 4 thrombocytopenia, and a dose delay of greater than 3 weeks due to failure to recover counts. It excludes several named symptoms and conditions from one category of non-hematological toxicity. The full definition also describes conditions for certain delays despite supportive measures.

The endpoint is useful for dose selection because it focuses on serious or treatment-limiting events over a defined early treatment period. It does not, by itself, establish comparative safety between randomized groups or describe longer-term harms. The registry record reports dose-level counts but does not give an explicit maximum tolerated dose conclusion.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a dose-limiting toxicity count measure?

A count records how many participants met the endpoint definition during the stated observation period. It is different from a rate, which expresses a count relative to a denominator, and different again from a time-to-event analysis, which accounts for when events occur and how long participants are observed. The registry presents participant counts by dose level and gives denominators for those groups. The reported primary outcome is categorical: a participant either meets the dose-limiting toxicity definition during the specified period or does not.

The endpoint’s definition matters because it determines which events count. Here, the definition includes selected severe hematologic toxicities, specified treatment-related non-hematological toxicities, dose delays under stated circumstances, and any drug-related death. It also lists exceptions for some symptoms and conditions. Applying this definition consistently is essential: a general adverse event is not automatically a dose-limiting toxicity, and the endpoint count cannot be assumed to include every adverse event.

Why use dose levels in an early-phase analysis?

General statistical explanation: early-phase dose-finding studies examine tolerability across dose levels to guide later study. The observed event count at a level is interpreted alongside the prespecified dose-limiting toxicity rule and the cohort size. Such results are inherently imprecise when groups are small. They describe what occurred in the observed cohort; they do not precisely establish the frequency of toxicity in a wider population.

The registry states a decision rule for the maximum tolerated dose: the highest dose where 1 or fewer out of 6 patients reports a dose-limiting toxicity. It reports counts by dose level, but does not report the final dose determination or full dose-escalation rationale. A reader should distinguish the stated rule from a conclusion applying that rule. The count at a particular level alone does not reveal whether it was the highest level studied, whether further escalation was considered, or what dose was selected for subsequent study; those details are not reported in the registry record.

What can a confidence interval add?

General statistical explanation: a confidence interval expresses uncertainty around an estimate under a statistical model. It indicates a range of values compatible with the observed data and method, rather than a guarantee that the true value lies in that range. For an event proportion, an interval can communicate that a small cohort leaves substantial uncertainty even when the observed count is low. The registry does not report confidence intervals for the primary dose-level counts, so no interval-based precision claim can be made from this record.

General statistical explanation: when a result is based on few observations, the estimate can change meaningfully if the event status of a participant differs. This is why a zero count should not be described as evidence that an event cannot happen. In this study, the posted count of zero at some dose levels is a descriptive observation, not a precise estimate of the underlying probability of a dose-limiting toxicity.

Why is a two-arm comparison not available?

The trial includes a randomized phase II comparison in its design description, but the posted primary outcome is grouped by dose level and pertains to phase I dose-limiting toxicity. The registry record says values are missing or not estimable for a two-arm comparison for this binary endpoint. It reports no phase II analysis from which to estimate a contrast between veliparib and placebo with chemotherapy. A randomized design does not itself produce a reported treatment effect; an analysis of the relevant outcomes and groups is needed.

General statistical explanation: an unadjusted comparison of two groups would summarize observed outcomes without accounting for other variables. Such a calculation would only be meaningful if the necessary group-specific results were available and the populations and endpoint definitions were aligned. The record does not report a recalculated two-arm estimate for this endpoint. There is therefore no treatment contrast, uncertainty interval, or p-value to interpret for the primary outcome.

How should planning calculations be understood?

General statistical explanation: sample-size planning illustrations ask how many participants might be needed under stated assumptions to detect a chosen effect with a chosen power and significance level. They are prospective planning exercises based on assumptions; they are not measurements of the trial’s actual power and do not establish what the trial demonstrated. The assumptions described for planning illustrations include a two-sided significance level of 0.05, equal allocation, a normal approximation, and an effect defined as a fraction of the observed effect. Time-to-event illustrations use total events, while other illustrations use participants per arm.

These planning assumptions do not substitute for the trial’s own design rationale. The sample-size justification, planned interim analyses, and full statistical analysis plan are not reported in the registry record. Since the record does not provide an estimable two-arm result for this binary endpoint, a planning illustration should not be read as an observed comparative result or as evidence of observed power.

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("Dose Level 0B", "Dose Level 1", "Dose Level 2", "Dose Level 3")
n      <- c(3, 3, 3, 6)
events <- c(0, 0, 0, 1)
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  Dose Level 0B  3  0  0.0  0.0  70.8  0.0  56.1  0.6  60.2
ARM  Dose Level 1  3  0  0.0  0.0  70.8  0.0  56.1  0.6  60.2
ARM  Dose Level 2  3  0  0.0  0.0  70.8  0.0  56.1  0.6  60.2
ARM  Dose Level 3  6  1  16.7  0.4  64.1  3.0  56.4  3.7  57.9

11. Multiplicity, Missing Data and Analysis Populations

The registry lists multiple secondary outcomes: toxicity, progression-free survival, disease-free survival, time to local or distant progression, disease-specific survival, and overall survival. It reports no analyses for these outcomes. The record therefore does not provide results from which to assess the direction, magnitude, or precision of any phase II effects.

When a study evaluates multiple outcomes, the chance of at least one apparently notable finding can rise if each is tested without accounting for multiplicity. General statistical explanation: multiplicity methods can control or describe that issue, depending on the analysis goals. The registry’s approach to multiplicity, including any hierarchy of outcomes or adjustment procedure, is not reported in the registry record. No claim about adjusted or unadjusted phase II findings can be made because those analyses are not posted.

The primary outcome description notes exclusions and treatment-related changes that affect interpretation of the dose-level counts. It does not fully report the analysis population, explain all denominator differences, or state how missing endpoint assessments were handled. The registry record does not describe an imputation method, a missing-data sensitivity analysis, or a rule for classifying participants without a complete first cycle.

The record also does not report whether analyses followed an intention-to-treat, per-protocol, safety, or other population definition for the randomized phase II comparison. These population definitions can affect the interpretation of a treatment comparison, particularly when treatment is not started or a planned assessment is unavailable. Without those details and posted analyses, the reader cannot establish how the listed phase II outcomes were analyzed or whether missingness could have influenced their estimates.

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 serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: respiratory failure (66.7%), mucositis oral (33.3%), nausea (33.3%), oral pain (33.3%), fever (33.3%).

The registry’s serious adverse event summary lists, by dose level, participants at risk and participants affected. It reports 3 at risk and 3 affected at Dose Level 0; 3 and 0 at Dose Level 0B; 3 and 1 at Dose Level 1; 5 and 0 at Dose Level 2; and 7 and 5 at Dose Level 3. The same safety summary reports 0 deaths for each listed dose level. These are serious adverse event summaries, not the primary dose-limiting toxicity counts.

The other adverse event summary reports all listed participants affected in each dose-level group: 3 of 3 at Dose Level 0, 3 of 3 at Dose Level 0B, 3 of 3 at Dose Level 1, 5 of 5 at Dose Level 2, and 7 of 7 at Dose Level 3. The record does not explain why these safety denominators differ from the primary outcome counts, nor does it define the relationship between each safety summary and the primary endpoint population.

Serious-event terms listed include respiratory failure at 66.7%, and mucositis oral, nausea, oral pain, fever, and lung infection at 33.3% each. The denominator and calculation basis for these term percentages are not reported in the registry record. These summaries describe events recorded in the study; they do not establish that an event was caused by a particular intervention or permit a randomized comparison of safety.

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

The posted primary result describes dose-limiting toxicity counts during the first cycle of induction chemotherapy across phase I dose levels. It shows no reported dose-limiting toxicity at Dose Levels 0B, 1, and 2, and 1.0 at Dose Level 3 among 6.0 participants. The record separately lists Dose Level 0 as 0.0 while explaining that the level was excluded from the outcome after a treatment-regimen change. These are limited descriptive observations in dose-level groups.

The results do not establish a precise toxicity probability at any dose level. The cohorts are small, the registry does not provide confidence intervals for these counts, and the record notes eligibility and treatment-completion issues. Nor does the posted count alone identify a recommended or maximum tolerated dose: the record states a rule for determining the maximum tolerated dose but does not report its final determination.

The results also do not answer the phase II comparative question. Although the study design describes veliparib versus placebo with combination chemotherapy, the registry record does not post analyses for the listed phase II outcomes. There are no reported comparative results for progression-free survival, disease-free survival, local or distant progression, disease-specific survival, or overall survival. The primary dose-level counts should not be interpreted as evidence for or against a difference between randomized treatments.

General statistical explanation: statistical evidence describes data and uncertainty under specified methods; it does not by itself establish clinical importance or causation. A descriptive event count is not a complete benefit-risk assessment, and the safety summaries do not provide comparative estimates. The posted information is useful for understanding what the registry records for early-phase tolerability, but it is insufficient to quantify comparative efficacy or fully characterize the safety profile of the phase II approaches.

14. Why This Trial Matters Statistically

This study illustrates a common distinction in clinical trial reporting: a trial can have a randomized phase and a planned comparative question while the posted result available for interpretation concerns a different phase and endpoint. Here, the registry describes a partially randomized phase I/phase II design, but the primary outcome data are phase I dose-limiting toxicity counts arranged by dose level. The record does not report analyses for the phase II outcomes.

That distinction matters statistically because design labels do not replace outcome-specific analyses. A randomized comparison requires results from the randomized groups, with clear outcome definitions, analysis populations, and uncertainty estimates. The phase I counts answer a narrower descriptive question about observed toxicities at dose levels. They cannot be substituted for a comparative estimate of the effect of veliparib versus placebo.

The record also demonstrates why denominators and analysis populations need careful attention. Its primary outcome description identifies ineligibility, cancellation, dosing error, non-completion of cycle 1, and a treatment-regimen change. Its safety summaries list group sizes that differ from the primary outcome. Without a complete account of how these participants entered each analysis, apparently similar counts can refer to different populations or outcomes.

Finally, a stated dose-finding threshold should not be mistaken for a reported dose recommendation. The registry describes the criterion used to determine a maximum tolerated dose, but does not report the conclusion. Keeping observed counts, decision rules, and final interpretations separate is essential for transparent statistical reading. The missing phase II analyses and unreported analysis details limit the conclusions available from this 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.

The primary outcome population description is truncated after beginning to describe a cancellation at Dose Level 3. It also mentions exclusions and treatment issues at other dose levels without fully specifying how each affected the denominator or analysis. The primary result therefore cannot be reconciled completely with all enrollment and evaluability details from the registry record.

The safety summaries use denominators that differ from the posted primary outcome group counts, including at Dose Level 0, which the primary outcome description says was not included because of a regimen change. The record does not explain the discrepancy or establish whether the safety and primary endpoint summaries use the same participants or assessment rules. Serious-event term percentages are listed, but their denominator and calculation basis are not reported.

The registry does not post a final maximum tolerated dose determination, the dose-escalation rationale, or the statistical analysis plan. It does not report confidence intervals for the dose-limiting toxicity counts. The phase II outcome analyses, including comparative estimates and uncertainty measures, are also not reported. The record does not describe handling of missing outcomes, analysis populations, or multiplicity procedures.

These limits are specific to the information recorded for this trial and restrict interpretation to the posted descriptive counts and safety summaries. They prevent a full assessment of the phase II comparison and a complete reconstruction of the dose-finding analysis.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Combination Chemotherapy With or Without Veliparib in Treating Patients With Stage IV Head and Neck Cancer — NCT01711541.
• Registry record last updated 2023-06-07; status last verified 2023-06.
• Results first posted 2019-06-05.
• 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

NCT01711541 is a completed, partially randomized phase I/phase II trial sponsored by the National Cancer Institute. It enrolled 24 participants and studied veliparib or placebo with combination chemotherapy in patients with stage IV head and neck cancer.

The posted primary outcome is phase I dose-limiting toxicity during the first cycle of induction chemotherapy, with a timeframe of up to 3 weeks. The registry reports dose-level counts and states a maximum tolerated dose rule, but does not report an explicit dose determination. Serious and other adverse event summaries are also listed by dose level.

Six phase II secondary outcomes are listed, but analyses for them are not reported in the registry record. The posted results therefore do not provide a randomized estimate of the comparative effects of veliparib and placebo with chemotherapy.