Veliparib, Radiation Therapy, and Temozolomide in Treating Younger Patients With Newly Diagnosed Diffuse Pontine Gliomas: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Veliparib, Radiation Therapy, and Temozolomide in Treating Younger Patients With Newly Diagnosed Diffuse Pontine Gliomas (NCT01514201), a na phase 1, phase 2 study. The primary outcome is Percentage of Participants Observed to Have Unacceptable Toxicity During the Intra-patient Dose Escalation of Temozolomide During Maintenance Therapy (Feasibility Analysis Population).

2. Clinical Question

The broader clinical question described in the registry is whether this combination could be studied for side effects, dose selection, and tumor-related outcomes in younger patients with newly diagnosed diffuse pontine gliomas. The registry's brief summary gives a biological rationale for combining a PARP inhibitor with radiation and chemotherapy, but that rationale is not evidence of a treatment effect. The study's design does not include a control group that would allow outcomes under the combination to be compared directly with outcomes under another treatment or usual care.

The primary endpoint is narrower than overall clinical benefit: it focuses on unacceptable toxicity during maintenance dose escalation. Progression-free survival and pseudo-progression are listed as secondary outcomes, along with pharmacokinetic measures for veliparib. Their presence does not establish what those outcomes showed. Results for the primary endpoint, as well as detailed results for the secondary outcomes, are not reported in the registry record.

3. Trial Design

This completed study was registered as phase I/II and used a single-group design. The registry lists enrollment of 66 participants, no allocation, and no masking. Its sponsor was the National Cancer Institute. The recorded start date is 2012-02-01, and the primary completion date is 2018-03-28. These design features describe the overall study, but do not establish how many enrolled participants contributed to each outcome analysis.

The phase I description includes dose escalation during concurrent treatment with veliparib and radiation. Participants received veliparib by mouth twice daily, 5 days a week for 6-7 weeks, alongside daily radiation, 5 days a week for 6-7 weeks. The radiation approaches listed are 3-dimensional conformal radiation therapy and intensity-modulated radiation therapy. The record also lists laboratory biomarker analysis and a pharmacological study, in addition to the drugs and radiation interventions.

Maintenance therapy was described as starting 3-4 weeks later. Its initial doses were 25 mg/m2 of veliparib and 135 mg/m2 of temozolomide. The protocol description allowed temozolomide escalation to 175 mg/m2 and 200 mg/m2 in courses 2 and 3, respectively, if unacceptable toxicity had not occurred at the dose levels being tested. Intra-patient escalation was to follow rules used in 3+3 designs. The record says this escalation was halted early during phase I because it was not well tolerated.

The primary endpoint description says patients were combined across dose levels because they received the same maintenance therapy. Although the endpoint was intended for all patients, only the first 12 enrolled were included because dose escalation stopped early; 1 of those participants did not start maintenance. The remainder of the endpoint population and the final endpoint result are not reported in the registry record. The record also does not report a randomized treatment comparison, a control arm, or details that would support causal comparisons between dose groups.

Sixteen outcome measures and one analysis are listed in the registry information. The exact analysis methods, analysis-population definitions beyond the primary endpoint description, and any additional outcome-specific denominators are not reported in the registry record. The posted enrollment total should therefore not be assumed to be the denominator for every result.

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: Of the 66 patients enrolled, 1 phase II patient was deemed ineligible due to an elevated alanine aminotransferase (ALT). Of note, the 6 phase I patients who were treated at the established maximum tolerated dose (MTD) during the phase I portion of the trial were also counted as phase II patients in analyses of phase II objectives.

PHASE I: Veliparib + Radiation Therapy

Reasons for not completing this period:

PHASE I: Maintenance With Veliparib/TMZ

Reasons for not completing this period:

PHASE II: Veliparib + Radiation Therapy

Reasons for not completing this period:

PHASE II: Maintenance With Veliparib/TMZ

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: The first 18 patients enrolled on the study were phase I patients used to determine the maximum tolerated dose or the recommended phase II dose and to address other objectives of the phase I component of this trial.

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.

Population: The one ineligible patient enrolled on the protocol was excluded. Summary statistics for baseline characteristics are shown for eligible patients only (n=65).

6. Primary Endpoint

The registry lists the primary outcome as Percentage of Participants Observed to Have Unacceptable Toxicity During the Intra-patient Dose Escalation of Temozolomide During Maintenance Therapy (Feasibility Analysis Population), measured over 28 days per treatment cycle.

The primary endpoint measures the percentage of participants observed to have unacceptable toxicity during intra-patient temozolomide dose escalation in maintenance therapy. It is described as a feasibility analysis, meaning it addresses whether the planned escalation could be carried out within the study's toxicity rules. It is not, by itself, a measure of tumor response or a comparison of clinical benefit between treatments.

The registry defines unacceptable toxicity as events at least possibly attributable to veliparib and temozolomide. Examples include any grade 4 non-hematologic toxicity; specified grade 3 non-hematologic toxicities, with exceptions such as grade 3 nausea or vomiting lasting <5 days and grade 3 fever or infection lasting <5 days; grade 3 or higher thrombocytopenia; grade 4 neutropenia; and a delay >14 days in starting a subsequent cycle due to neutrophil <1,000/mm3 or platelets <100,000/mm3.

Escalation was planned from 135 mg/m2 of temozolomide toward 175 mg/m2 and 200 mg/m2 in subsequent courses, conditional on avoiding unacceptable toxicity at the tested dose levels. The record states that dose escalation stopped early because the approach was not well tolerated. That statement explains why the planned assessment was curtailed; it does not provide the endpoint's observed percentage or the number meeting the toxicity definition.

The endpoint description identifies the feasibility analysis population as the first 12 enrolled participants. One did not start maintenance. The result, the numerator, and a confidence interval are not reported in the registry record. Without those quantities, the observed frequency and its precision cannot be assessed from this record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical methods turn observations into estimates while making clear what population and comparison the estimates address. In this trial, the primary question is a percentage: the share of participants in the feasibility analysis population who experienced toxicity meeting the registry's definition. A percentage is meaningful only alongside its numerator, denominator, and definition of who was assessed. The registry describes a planned population of the first 12 enrolled participants, notes that one did not start maintenance, and says escalation stopped early. It does not report the observed percentage or enough detail to establish the final denominator and numerator.

What does a percentage estimate?

For a binary outcome such as whether a participant met a toxicity definition, each participant is classified as having or not having the event, under the stated assessment rules. The resulting percentage estimates the frequency of that event in the analysis population and observation period. It is not a measure of how severe every participant's experience was, nor does it by itself establish that the treatment caused the event. In this trial, attribution was described as at least possibly related to veliparib and temozolomide, and the record lists specific toxicity thresholds and exceptions.

A confidence interval is a range of values reflecting the uncertainty associated with an estimate under a statistical method. A narrower interval generally indicates greater precision, while a wider interval indicates less precision. Its interpretation depends on the analysis assumptions and the population being estimated. No confidence interval for the primary endpoint is reported in the registry record, and one cannot be inferred from the enrollment total alone.

What does the design allow?

A single-group study can describe outcomes among participants who received the regimen, but it does not create a concurrent randomized counterfactual. Random allocation, when used, helps balance known and unknown participant characteristics on average across treatment groups. This registry reports no allocation and a single-group model. Therefore the phase I dose levels and phase II group are not equivalent to randomized arms. Any observed difference between those groups could have explanations other than dose, and the record does not report a comparative analysis that accounts for such differences.

Masking concerns whether participants, investigators, or assessors are kept unaware of treatment assignment. The registry reports no masking. Because there is no separate randomized treatment assignment, the record does not describe a blinded comparison. The absence of masking can matter for outcomes influenced by observation or judgment; toxicity criteria can be more standardized than subjective judgments, but the record does not specify adjudication procedures or independent review.

How should the escalation be understood?

The protocol description says temozolomide dose escalation was planned within participants, conditional on not experiencing unacceptable toxicity at the tested dose levels. It also says rules employed in 3+3 designs were used and that escalation stopped early because it was not well tolerated. These details describe dose-finding and feasibility intent, not a statistical estimate of efficacy. Stopping escalation early changes which planned dose levels could be assessed and limits conclusions about higher planned levels. The registry record does not report the complete decision sequence, dose-specific endpoint results, or a formal dose-toxicity model.

General explanation: dose-escalation designs use observed toxicities to guide whether further dose increases are permitted. A 3+3 approach is a rule-based method in which decisions depend on toxicity observations among small groups at dose levels. The exact operating characteristics of a particular implementation depend on its rules and stopping decisions; they should not be assumed from the design label alone. Here, the registry describes the use of such rules but does not give the detailed protocol or complete dose-level results.

What do planning calculations mean?

The sample-size illustrations are described as planning illustrations computed from an observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The target effect is a stated fraction of the observed effect. For time-to-event outcomes, the illustration gives a total number of events using the Schoenfeld approach; for other outcomes it gives participants per arm. These are hypothetical planning quantities under stated assumptions, not the number actually enrolled, not an analysis of the trial's observed design, and not observed power.

General explanation: a planning calculation asks how much information a future comparison might need to detect a chosen effect under specified assumptions. Its answer depends on the chosen effect, error rate, allocation, outcome type, and method. It does not show that the current trial had that power, especially when the current study has a single-group design and no randomized two-arm comparison. The illustrations' numerical results and effect fractions are not reported in the registry information, so no planning count can be stated.

The registry record reports one analysis but does not provide the statistical analysis plan, model specifications, hypothesis tests, handling of missing observations, or multiplicity strategy. General explanation: multiplicity arises when several outcomes or statistical tests are considered; without a prespecified strategy, the chance of at least one apparently notable result can be difficult to interpret. A missing-data method also matters because participants without an outcome assessment may differ from those assessed. Neither issue can be resolved from a list of outcomes alone.

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 1 (135 mg/m2)", "Dose Level 2 (175 mg/m2)", "Dose Level 3 (200 mg/m2)")
n      <- c(11, 5, 3)
events <- c(1, 2, 2)
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 1 (135 mg/m2)  11  1  9.1  0.2  41.3  1.6  37.7  2.1  38.5
ARM  Dose Level 2 (175 mg/m2)  5  2  40.0  5.3  85.3  11.8  76.9  11.8  77.7
ARM  Dose Level 3 (200 mg/m2)  3  2  66.7  9.4  99.2  20.8  93.9  19.4  93.2

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 16 outcome measures and one analysis. The listed secondary outcomes include progression-free survival, percentage of patients with pseudo-progression, and pharmacokinetic measures such as veliparib maximum concentration, apparent clearance, apparent volume of distribution, terminal half-life, and trough. A list of multiple outcomes raises questions about which analyses were primary, whether additional hypotheses were tested, and how any multiplicity was handled. The statistical analysis plan and any adjustment strategy are not reported in the registry record.

Multiplicity is a general statistical issue: when several outcomes or tests are examined, the chance of observing a seemingly unusual result by chance can increase. An analysis plan may address this by identifying a primary outcome and specifying whether and how secondary outcomes are interpreted. The registry identifies a primary endpoint and secondary outcome names, but does not report a testing hierarchy, adjustment method, or details of analyses for the outcomes.

The primary endpoint description identifies the first 12 enrolled participants as the intended feasibility analysis population because escalation stopped early. It also states that one of those participants did not start maintenance. The record does not specify how this participant was handled in the endpoint calculation, whether any other endpoint observations were missing, or how missing data were treated. Thus, the endpoint denominator and analysis rules cannot be reconstructed from the registry record.

Analysis populations matter because estimates apply to the participants included under a defined rule. The total enrollment of 66 should not be assumed to be the denominator for every outcome. Outcome-specific analysis populations, participant flow, and missing-data methods are not reported in the registry record. The record also does not report interim analyses or stopping boundaries beyond noting that intra-patient dose escalation was halted early. The reason given is that the escalation was not well tolerated; further details on the decision process are not reported.

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: hydrocephalus (50.0%), platelet count decreased (33.3%), depressed level of consciousness (33.3%), headache (16.7%), hearing impaired (16.7%).

The registry lists adverse-event groups for phase I dose levels and phase II, with counts at risk, counts affected by serious adverse events, counts affected by other adverse events, and deaths. For phase I, dose level 1 (50 mg/m2) lists 5 of 6 participants with serious events, 6 of 6 with other adverse events, and 6 deaths. Dose level 2 (65 mg/m2) lists 2 of 6 with serious events, 6 of 6 with other adverse events, and 5 deaths. Dose level 3 (85 mg/m2) lists 2 of 6 with serious events, 6 of 6 with other adverse events, and 6 deaths. The phase II group (MTD) lists 19 of 47 with serious events, 46 of 47 with other adverse events, and 40 deaths.

These are counts within the registry's listed groups, not results of a randomized comparison. They should be read with the group sizes and endpoint definitions, not as estimates that can be compared causally across dose levels. The registry also lists hydrocephalus at 50.0%; platelet count decreased and depressed level of consciousness at 33.3% each; and headache, hearing impaired, and hematuria at 16.7% each among the top serious-event terms.

The record does not report exposure-adjusted event rates, detailed event timing, or a comparative safety analysis alongside these figures. The reported deaths should not be assumed to be caused by treatment; the registry information does not establish attribution. Serious-event counts and the primary endpoint's unacceptable-toxicity definition are distinct descriptions and should not be treated as interchangeable.

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

The registry record establishes that a phase I/II, single-group study evaluated veliparib with radiation therapy followed by maintenance veliparib and temozolomide in younger patients with newly diagnosed diffuse pontine gliomas. It describes dose escalation, toxicity criteria, an intended feasibility population, and selected adverse-event counts. It also states that the intra-patient dose escalation stopped early because it was not well tolerated. These are meaningful details about study design and conduct.

The record does not provide the primary endpoint result. It is therefore not possible to report the percentage with unacceptable toxicity, quantify the uncertainty around that percentage, or determine from the endpoint estimate how frequently the specified toxicity occurred in the intended analysis population. The statement that escalation stopped early does not supply those missing quantities. Nor does it establish the safety profile of every planned dose level, because the escalation did not proceed as initially intended.

The trial has no randomized comparator. Outcomes observed among treated participants cannot be used on their own to estimate what would have happened under another regimen. The phase I dose groups and phase II group are study cohorts, not randomized arms. The adverse-event counts provide a descriptive account, but differences among those groups cannot establish comparative effects. Likewise, the registry's background explanation of how veliparib, radiation, and temozolomide may act is a rationale, not a finding that the combination improves an outcome.

Progression-free survival, pseudo-progression, and pharmacokinetic measures appear among the listed outcomes, but their results are not reported in the registry record. No claim about efficacy, survival, tumor response, or drug exposure can be drawn from the outcome names alone. The record also does not state the sample-size justification, detailed analysis methods, missing-data approach, or multiplicity plan. General statistical interpretation requires those details to understand how estimates were constructed and how much confidence to place in them.

Accordingly, the posted information supports describing the study's intended question, its single-group design, its early-terminated dose escalation, and the safety counts it lists. It does not support a treatment-effect estimate or a conclusion that the regimen is more or less effective than an alternative. The absence of a reported primary result is a limitation of what can be concluded from the registry record, not evidence of a particular result.

14. Why This Trial Matters Statistically

This trial illustrates why the endpoint, analysis population, and study design must be read together. The primary endpoint focuses on unacceptable toxicity during an intra-patient dose-escalation process, while the total enrollment is 66 and the intended feasibility analysis population is described as the first 12 enrolled. The registry notes that escalation stopped early and that one of the first 12 did not start maintenance. Those details make the denominator and participant flow central to interpretation, yet the endpoint result and complete analysis details are not reported.

It also demonstrates the distinction between a dose-finding or feasibility question and a treatment-effect question. The design sought to study side effects and dose selection, and the record describes toxicity-driven stopping of escalation. A single-group design can document what occurred in the treated cohort, but it cannot provide a randomized comparison against another treatment. This distinction is especially important when dose groups are discussed: different groups in a phase I/II study are not automatically comparable groups for causal inference.

The safety information shows why counts need context. Group sizes differ, and the registry presents both serious and other adverse-event counts, along with selected terms. Without outcome-specific definitions, exposure time, participant flow, and comparative methods, these figures are descriptive rather than a complete comparative safety analysis. The registry's list of other outcomes likewise does not replace outcome estimates and uncertainty intervals.

Finally, planning illustrations should not be confused with the actual design or with observed power. The described assumptions involve equal allocation between two arms, while this trial is single-group. Their role is to illustrate hypothetical planning under assumptions, not to validate this study's sample size. Separating design details, observed results, and hypothetical calculations is essential for a statistically responsible reading of the 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 most direct limitation is that the registry record does not report the primary endpoint value, its numerator and denominator, or a confidence interval. Although the endpoint is defined in detail and the intended analysis population is described, the percentage of participants with unacceptable toxicity cannot be assessed from the record. The note that escalation stopped early because it was not well tolerated gives context but does not substitute for a quantitative endpoint result.

The primary assessment was restricted to the first 12 enrolled after early stopping of escalation, and one participant did not start maintenance. The registry does not provide a complete participant-flow account or explain how that participant was handled in the analysis. Therefore the endpoint population's final size and missing-outcome handling are unclear. Total enrollment of 66 is not necessarily the denominator for this outcome or for other outcomes.

The design is single-group, with no allocation and no masking. It does not provide a randomized comparator for estimating relative effects. The phase I dose-level groups and phase II group may differ in ways that the registry information does not describe or adjust for. The planned dose escalation also stopped early, limiting the conclusions that can be drawn about the intended escalation sequence and higher planned temozolomide doses.

Additional limitations include the absence of detailed statistical methods, sample-size justification, interim-analysis information, and a multiplicity plan in the registry record. Results for the listed secondary outcomes are not reported in the information describing the trial. The safety counts do not include exposure-adjusted rates or a reported comparative analysis, and the registry information does not establish treatment attribution for deaths. Eligibility details and a complete account of outcome-specific analysis populations are also not reported.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Veliparib, Radiation Therapy, and Temozolomide in Treating Younger Patients With Newly Diagnosed Diffuse Pontine Gliomas — NCT01514201.
• Registry record last updated 2019-08-13; status last verified 2019-07.
• Results first posted 2019-08-13.
• 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

NCT01514201 is a completed phase I/II, single-group study sponsored by the National Cancer Institute. It enrolled 66 participants and evaluated veliparib with radiation therapy, followed by maintenance veliparib and temozolomide, in younger patients with newly diagnosed diffuse pontine gliomas. The recorded start date is 2012-02-01 and the primary completion date is 2018-03-28.

The primary endpoint was the percentage of participants observed to have unacceptable toxicity during intra-patient temozolomide dose escalation in maintenance therapy. The registry says escalation stopped early during phase I because it was not well tolerated; only the first 12 enrolled were included in the intended feasibility analysis, and one did not start maintenance. The endpoint result is not reported in the registry record.

The registry lists progression-free survival, pseudo-progression, pharmacokinetic outcomes, and adverse-event summaries. It reports no randomized comparator and does not report detailed statistical methods, missing-data handling, multiplicity strategy, or sample-size justification. The posted information supports a description of design and selected safety counts, but does not provide a numerical primary endpoint estimate or a comparative treatment-effect estimate.