Carvedilol in Preventing Heart Failure in Childhood Cancer Survivors: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Carvedilol in Preventing Heart Failure in Childhood Cancer Survivors (NCT02717507), a randomized phase 2 study. The primary outcome is Average Left-Ventricular Wall Thickness-Dimension Ratio Z-score (LVWT/Dz).

2. Clinical Question

The trial addresses whether a medication might alter a cardiac measurement in survivors with prior high-dose anthracycline exposure. Its primary endpoint is a continuous echocardiographic measure, not a direct count of heart-failure diagnoses or cardiovascular events. The registry’s study summary describes heart failure as a concern for this population, while the specified primary outcome tracks a structural or functional measurement over time.

This distinction matters when reading the results. A change in an echocardiographic measure would describe that measure; by itself, it would not establish a change in heart-failure incidence, symptoms, or other clinical outcomes. The registry lists several secondary cardiac measures, including ventricular dimensions, volumes, mass, fractional shortening, and ejection fraction, but numerical results for those measures are not reported in the registry record.

3. Trial Design

This was a phase 2b randomized, double-masked, parallel-group, placebo-controlled trial. The registry names the Children’s Oncology Group as sponsor and records enrollment of 196 participants. The study status is completed. The recorded start date is 2016-04-04, and the primary completion date is 2022-06-30.

Participants were assigned to one of two arms: low-dose carvedilol or placebo. Both were taken by mouth once or twice daily for 24 months. Randomization supports a comparison between assigned groups, while masking is intended to reduce the influence of treatment knowledge on participant or study assessments. The registry does not report the specific allocation procedure, who was masked, how masking was maintained, or whether it was assessed.

The primary endpoint was measured before treatment and at 6, 12, 18, and 24 months after treatment initiation. It is described as a mean continuous outcome, with standard errors reported by arm at each time point. The endpoint description says that 31 participants without a second echocardiography assessment were excluded, leaving 151 analyzable participants. The record does not explain the handling of other missing assessments or provide a fuller accounting of participants included at each time point.

Although the registry identifies the study as phase 2b, it does not report a sample-size justification, a target enrollment rationale, or the statistical analysis plan. It also does not report details of treatment adherence, changes in treatment, or follow-up beyond the stated outcome time frame. Those details should not be inferred from the randomized, masked design alone. The available record establishes the broad comparison and measurement schedule, but not every operational or analytical choice used in the trial.

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: 196 pts were enrolled (109 pts enrolled with Childrens Oncology Group (COG) and 87 pts enrolled on a pilot study at City of Hope (COH) 182 of those pts started tx (14 excluded: 6 ineligible and 8 pts started tx). (The (109) enrollment number in the protocol section reflects the number of pts enrolled on the COG portion of the study. Per Section 9.2 of the protocol (pt accrual and expected duration of the trial), 87 pts had already been accrued through a different mechanism the pilot study)

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: We excluded 31 participants who did not have a second time point assessment of echocardiography, resulting in 151 analyzable participants.

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 Average Left-Ventricular Wall Thickness-Dimension Ratio Z-score (LVWT/Dz), measured over Baseline before treatment, 6 months, 12 months, 18 months, 24 months after treatment initiation.

The primary endpoint is the average left-ventricular wall thickness-dimension ratio Z-score, abbreviated LVWT/Dz in the registry. It is a continuous echocardiographic measure. The ratio compares the left-ventricular posterior wall dimension in systole with the internal left-ventricular dimension in diastole. For each participant, the ratio is converted to a Z-score by subtracting the reference healthy population mean and dividing by the reference population standard deviation.

A Z-score expresses how far a measurement is from the reference mean in standard-deviation units. The registry states that a negative Z-score indicates a worse outcome. This reference-standardized scale can make measurements interpretable relative to a healthy population, rather than only in the original measurement units. It does not, by itself, describe the probability of a clinical event or diagnose heart failure.

The mean is reported by treatment arm at baseline before treatment and at 6, 12, 18, and 24 months after initiation, with corresponding standard errors. Repeated assessments can describe how the measure changes over time and allow comparison of the patterns between randomized groups. The registry gives the endpoint definition and timing, but arm means, standard errors, and a numerical treatment comparison are not reported in the registry record.

The trial also lists secondary cardiac measures, including ventricular dimensions and volumes, left-ventricular mass, fractional shortening, and ejection fraction. These measures provide related cardiac information, but they are distinct outcomes and should not be treated as substitutes for the defined primary endpoint.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical methods determine how measurements are summarized, compared, and interpreted. The registry identifies a continuous primary endpoint, repeated measurements over time, and arm-level means with standard errors. It does not report the full analysis plan or the numerical primary comparison. The explanations below are general unless they restate a specific feature of the registry record.

What does the mean describe?

For a continuous outcome, the mean is the arithmetic average of participant measurements in a group. Reporting a mean at each scheduled time point can describe the group’s average trajectory. Comparing such trajectories requires an analysis that accounts for the repeated observations and specifies the treatment contrast of interest. The registry record does not report which model or comparison procedure was used for the primary analysis.

A mean can conceal variation among participants. Two groups can have similar averages but different distributions, or different averages with substantial overlap among individuals. The registry identifies standard errors as the dispersion measure accompanying the arm means. A standard error concerns uncertainty in an estimated mean; it is not the same as a standard deviation, which describes variation among individual observations. Individual-level distributions are not reported in the registry record.

What does a Z-score mean?

General explanation: a Z-score expresses a value in standard-deviation units relative to a reference distribution. In this trial, the registry defines the score using a healthy population reference mean and standard deviation. It also specifies that negative values indicate a worse outcome. A Z-score’s interpretation depends on that stated definition and should not be confused with a statistical test statistic or a probability. The registry does not report the reference population’s numerical characteristics.

How do repeated assessments affect analysis?

The primary outcome was scheduled before treatment and at 6, 12, 18, and 24 months after initiation. Repeated measurements from the same participant are generally related; treating them as independent observations can misrepresent uncertainty. General approaches can model time, treatment, and how the treatment contrast changes over time, while accounting for within-participant correlation. The registry record does not identify the approach used, the primary time point for a treatment contrast, or whether the analysis focused on a trajectory or a particular assessment.

There are several possible ways to summarize repeated data, and they answer somewhat different questions. Comparing groups at one time point asks about the between-arm contrast at that time. Comparing change from baseline asks about a contrast in change. A model of all available repeated observations can use the pattern across time, subject to its assumptions. These are general distinctions, not claims about the trial’s analysis. The actual analysis choices are not reported in the registry record.

What does a standard error or confidence interval communicate?

General explanation: a standard error indicates the sampling uncertainty around an estimate under the analysis used. A confidence interval presents a range of estimates compatible with the data and method at a stated confidence level. The interval can help readers assess both the direction and precision of an estimated contrast. It is not a guarantee that the true effect lies within its limits. The registry’s endpoint description says standard errors accompany arm means, but numerical standard errors and a primary treatment-effect confidence interval are not reported in the registry record.

A p-value, when reported, measures how incompatible the observed data are with a specified null model, subject to the analysis assumptions. It does not measure the size or clinical importance of an effect. The registry information does not report a primary p-value, a significance threshold for the primary analysis, or whether the reported comparison was adjusted for covariates.

Why can over-dispersion matter?

General explanation: over-dispersion occurs when the observed variability is greater than a statistical model expects. If a model underestimates variability, standard errors can be too small and intervals can appear too narrow. Methods that allow for extra variation may be appropriate in some settings. The primary outcome is described as a continuous measure, and the registry does not report that over-dispersion was evaluated or that a particular model required an adjustment. This general issue should not be read as evidence that over-dispersion occurred in this trial.

How should planning calculations be understood?

General explanation: a sample-size calculation estimates how many participants might be needed under stated assumptions about an effect, variability, allocation, and statistical method. The record describes planning illustrations based on a fraction of the observed effect, using a two-sided significance level of 0.05, equal allocation, and a normal approximation. Such calculations are planning illustrations, not observed power and not evidence that the trial detected an effect. Their interpretation depends on assumptions, and the registry’s sample-size justification for the original trial is not reported in the registry record.

The record’s planning description distinguishes participants per arm for non-time-to-event outcomes from total events for time-to-event outcomes. The primary endpoint is continuous, not a time-to-event outcome. Numerical planning estimates are not reported in the registry information used for this explanation. No new sample-size value can be inferred from the assumptions alone.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 20 outcome measures and 17 analyses, including the primary endpoint and several secondary cardiac measures. Testing or estimating many outcomes can raise multiplicity concerns: when multiple hypotheses are evaluated, the chance of at least one apparently notable finding can increase. General statistical practice may address this through a prespecified hierarchy, adjustment, or careful emphasis on estimation. The registry record does not report a multiplicity strategy, a hierarchy among secondary outcomes, or which analyses were prespecified.

The primary endpoint was assessed at baseline and at 6, 12, 18, and 24 months after treatment initiation. Multiple time points can also create choices about which comparison is primary and how repeated measures are modeled. The registry does not report whether one follow-up time point was designated as the main treatment contrast, whether an overall longitudinal test was used, or how any multiple time-point comparisons were handled.

For the primary outcome, the record states that 31 participants without a second echocardiography time-point assessment were excluded, leaving 151 analyzable participants. This is the available description of the primary analysis population. The record does not report the reasons for missing assessments, missingness by treatment arm, the number contributing data at each later time point, or whether sensitivity analyses addressed missing data. It also does not report whether participants were analyzed according to randomized assignment in an intention-to-treat analysis.

Missing data can affect interpretation if participants with absent assessments differ from those with observed assessments. General explanation: methods for incomplete repeated measurements rely on assumptions about the relationship between missingness and observed or unobserved outcomes. Without the trial’s analysis details, those assumptions and their impact cannot be evaluated. The reported exclusion and analyzable population should therefore be distinguished from a complete account of all participants randomized or followed.

11. 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 reports no serious adverse events among participants at risk in either arm: 0 affected among 89 at risk in the carvedilol arm and 0 affected among 93 at risk in the placebo arm. It reports other adverse events affecting 2 of 89 participants at risk in the carvedilol arm and 0 of 93 at risk in the placebo arm. Deaths are reported as 0 in each arm.

These are registry counts, not a complete description of every possible safety outcome. The record does not list serious adverse-event terms, and it does not provide detail about the two other adverse events in the carvedilol arm. It also does not state the observation period or provide further information about event severity, timing, attribution, or whether a participant could contribute more than one event. The number of participants at risk is the denominator reported for these figures.

Zero reported events does not establish that an event is impossible or that no event occurred outside the registry’s reporting definitions or period. The counts should be read as the adverse-event figures recorded for the trial, without inferring a broader safety profile or making a treatment recommendation.

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

The registry describes a randomized, double-masked comparison of carvedilol and placebo in childhood cancer survivors exposed to high-dose anthracyclines. It specifies a primary echocardiographic measure and repeated assessment schedule. However, numerical results for the primary endpoint and a treatment comparison are not reported in the registry record. As a result, the record does not permit a quantitative conclusion about the difference between the assigned groups on that measure.

The endpoint is a Z-score derived from a left-ventricular wall thickness-dimension ratio, with negative values defined as worse. This gives the outcome a reference-based interpretation, but it remains a cardiac measurement rather than a direct measure of heart-failure incidence. Even if numerical endpoint results were available, interpreting what they mean for clinical outcomes would require evidence about the relationship between this measure and those outcomes. That relationship is not reported in the registry record.

The adverse-event entries report no serious adverse events or deaths in either arm and two other adverse events in the carvedilol arm, compared with none in the placebo arm. These counts are limited to the registry’s recorded categories and do not supply detailed event descriptions or broader safety context.

The trial’s completed status does not fill in missing outcome estimates. Nor does the planned sample-size description establish the observed effect, the precision of an estimate, or whether a particular result was statistically detectable. A planning calculation is not observed power. The registry record’s available information supports describing the study design, endpoint, analysis population statement, and recorded adverse-event counts, but not a claim that carvedilol did or did not alter the primary outcome or prevent heart failure.

13. Why This Trial Matters Statistically

This trial is statistically notable for combining random allocation and masking with a repeated, continuous cardiac endpoint. Randomization provides a basis for comparing assigned groups, while masking can help limit influences tied to treatment knowledge. Repeated echocardiographic assessments can describe whether average measurements follow different patterns over the treatment period. Those design features are important, but their value for interpretation depends on the analysis and results being reported.

The primary measure is standardized against a healthy reference population. That allows a reader to interpret a score in relation to a reference mean, while the repeated schedule offers more information than a single endpoint assessment. At the same time, a standardized surrogate measurement is not interchangeable with a clinical event. Statistical significance, even if reported, would not alone establish the clinical importance of a difference.

The registry also makes the analysis population issue visible: it states that participants without a second echocardiography assessment were excluded from the primary outcome analysis. Transparent reporting of how many participants contribute to each time point, why data are missing, and how missingness is addressed is important in longitudinal research. Those further details are not reported in the registry record.

Finally, the record illustrates the distinction between a completed trial and a fully interpretable result. It records enrollment, study status, outcome definitions, and limited adverse-event counts, but numerical primary outcome estimates and the analysis plan are not reported. Without those elements, readers cannot judge the magnitude or precision of the primary comparison. Statistical interpretation depends not only on a trial’s design, but also on clear reporting of estimates, uncertainty, and analysis choices.

14. 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 central limitation for interpreting this registry record is that numerical primary-outcome results are not reported. The endpoint definition and schedule are available, but arm means, standard errors, a treatment contrast, a confidence interval, and a primary test result are not reported in the registry record. The same applies to numerical results for the listed secondary cardiac outcomes.

The analysis description is limited. The record does not report the statistical model, the exact primary contrast, the covariates used, the handling of repeated measurements, or whether the analysis followed randomized assignment. It also does not report the prespecified analysis plan, sample-size justification, or multiplicity approach. These omissions prevent assessment of whether the reported analysis, if any, matched an intended plan.

The primary-outcome description states that 31 participants lacking a second echocardiography assessment were excluded, resulting in 151 analyzable participants. Reasons for missing assessments and the distribution of missing data across arms and time points are not reported in the registry record. The record also does not describe sensitivity analyses or other missing-data methods. The analysis population statement therefore does not resolve the potential influence of incomplete follow-up.

Safety information is also limited: there are no serious adverse-event terms listed, and details of the other adverse events are not reported. The record does not provide event timing, severity, attribution, or a fuller account of ascertainment. Finally, the intervention is described as low-dose carvedilol taken once or twice daily, but the dose and schedule-selection details are not reported. These limits should be kept in view when interpreting the study’s design and recorded counts.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Carvedilol in Preventing Heart Failure in Childhood Cancer Survivors — NCT02717507.
• Registry record last updated 2025-04-23; status last verified 2025-04.
• Results first posted 2023-09-29.
• 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.

18. Record Summary

The registry identifies NCT02717507 as a completed, randomized, double-masked, parallel, placebo-controlled phase 2b trial sponsored by the Children’s Oncology Group. Enrollment was 196. The study began on 2016-04-04, with primary completion on 2022-06-30.

Participants received low-dose carvedilol or placebo by mouth once or twice daily for 24 months. The primary outcome was the average left-ventricular wall thickness-dimension ratio Z-score, assessed before treatment and at 6, 12, 18, and 24 months. The outcome description reports 151 analyzable participants after exclusion of 31 without a second echocardiography assessment.

Numerical primary-outcome results and a treatment-effect estimate are not reported in the registry record. Serious adverse events and deaths are recorded as 0 in each arm; other adverse events are recorded for 2 participants in the carvedilol arm and 0 in the placebo arm.