Phase III B in Acute Lymphoblastic Leukemia: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Phase III B in Acute Lymphoblastic Leukemia (NCT03123939), a na phase 3 study. The primary outcome is Number of Participants With Treatment-Emergent Adverse Events (TEAEs).

2. Clinical Question

3. Trial Design

This was a Phase IIIb, single-group, open-label, multicenter study of CTL019 in pediatric and young adult patients with relapsed or refractory B-cell acute lymphoblastic leukemia. The record describes the study as intended to determine safety and efficacy. Its title identifies a Phase III B study, while the phase classification is Phase 3. The study is marked completed. Its recorded start date is 2017-04-24, and its primary completion date is 2020-10-13.

Because the design was single-group, participants were not allocated between CTL019 and a control treatment. Allocation is listed as not applicable, and masking is listed as none. These features matter when interpreting outcomes: reported events in the treated group can describe what occurred during follow-up, but without a concurrent control they do not establish how outcomes would have differed under another treatment or no treatment.

The intervention is described as a single dose of autologous CTL019-transduced viable T cells. The registry gives a dose range of 0.2 to 5.0 × 10^6 cells per kg for patients weighing ≤ 50 kg and 0.1 to 2.5 × 10^8 cells for patients weighing > 50 kg. The record does not explain how a dose within the range was selected for an individual participant.

Enrollment is listed as 69. The safety population is defined as all participants who received an infusion, and the adverse-event group lists 69 participants at risk. The registry record does not report further details about participant flow, exclusions, follow-up completeness, or how many participants contributed to each secondary outcome. Although the study is described as multicenter, the number or locations of centers 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.

Before assignment: This was a single arm study.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: The Safety Set (SAF) comprised of all the participants who received an infusion of CTL019

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: Full Analysis Set (FAS) comprised of all the participants who received an infusion of CTL019

6. Primary Endpoint

The registry lists the primary outcome as Number of Participants With Treatment-Emergent Adverse Events (TEAEs), measured over From CTL019 infusion until end of study, up to 12 months.

The primary outcome is the number of participants with treatment-emergent adverse events (TEAEs). The registry defines the collection period as starting at CTL019 infusion and continuing until the end of the study, up to 12 months. It specifies the Safety Set as the analysis population: participants who received an infusion of CTL019.

A participant count is a way to describe how many people in the safety population experienced an event during the specified observation period. It is distinct from an event count, which could count repeated events in the same person. The registry names the unit as participants, so the intended summary concerns people with TEAEs, rather than the total number of individual event episodes.

Safety outcomes are used to characterize events observed during treatment and follow-up. A time window helps define which events are counted, and a stated analysis population clarifies who is included in the denominator. Neither feature alone determines whether an event was caused by treatment. “Treatment-emergent” identifies an event collected after treatment begins; the registry description does not state that every such event was judged treatment-related.

The registry record does not report the primary TEAE count or a corresponding estimate of uncertainty. It does list serious and other adverse-event summaries, but those should not be assumed to be interchangeable with the named primary outcome without a reported definition linking them. The detailed criteria for classifying TEAEs are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a participant count describe?

A participant count reports how many people met an outcome definition within the specified population and follow-up period. For a safety outcome, this differs from counting every event episode: one participant may experience more than one event, while a person-level count records that participant as having experienced the outcome. The primary outcome is explicitly named as a count of participants with TEAEs. The registry record does not report the observed value for that primary outcome.

To interpret a count, readers also need a clear population, event definition, and observation period. The record defines the Safety Set as all participants who received a CTL019 infusion and describes TEAE collection from infusion through the end of study, up to 12 months. It also presents adverse-event group counts with participants at risk. A denominator helps place a count in context, but does not by itself convey uncertainty or establish a causal relationship. Details about event grading, coding, adjudication, and attribution are not reported in the registry record.

What would an interval estimate add?

General statistical explanation: a confidence interval expresses the uncertainty around an estimate under a specified statistical model. For a participant-level event proportion, an interval can show a range of values compatible with the observed data and the chosen method. It is not a guarantee that the true value falls inside that range, and it does not correct limitations such as incomplete follow-up, outcome misclassification, or lack of a comparison group.

No confidence interval for the primary TEAE outcome is reported in the registry record, and no primary count is given from which to assess one. The record also does not report a statistical method for constructing intervals. Thus, uncertainty around the primary safety result cannot be assessed from the posted information. The same limitation applies to the listed secondary outcomes, for which results and uncertainty estimates are not reported.

Why does the single-group design matter?

General statistical explanation: a concurrent control group can help distinguish outcomes associated with an intervention from outcomes that might have occurred over the same period for other reasons. Random allocation, when used, can reduce systematic differences between groups, although it does not eliminate every source of uncertainty. In a single-group study, the observed outcomes describe participants receiving the intervention; there is no randomized comparison in the record to estimate a relative effect.

This study is classified as single-group, with allocation not applicable and no masking. Those design features mean that observed events cannot be interpreted as a randomized contrast. The results may provide descriptive information about events recorded during treatment and follow-up, but they do not show what would have happened to comparable participants under a different condition. The registry record does not report an external or historical comparator analysis.

What analyses are reported?

The registry lists 24 outcome measures and 0 analyses. Those entries do not supply inferential results for the primary endpoint or the secondary outcomes. In particular, the record contains no posted hypothesis-test results, effect estimates, confidence intervals, or adjusted analyses to evaluate. Statistical analysis methods, including any planned modeling, are not reported in the registry record.

The record includes sample-size planning assumptions for an illustration based on an observed effect: a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. These are planning assumptions, not evidence that the single-group study used a two-arm design. The registry record does not report the trial’s own sample-size justification or identify a trial-design calculation. Sample-size illustrations should be understood as planning scenarios, not observed power or proof that an effect was detected.

General statistical explanation: power is a design concept describing the chance that a planned test will reject a specified null hypothesis under assumed conditions. It is not a property that can be inferred from whether a result is statistically significant, and a post hoc calculation based on an observed effect does not establish the probability that a finding is true. The assumptions and calculations used for the trial’s original planning are not reported in the registry record.

What can be learned from serious-event summaries?

Serious and other adverse-event summaries provide descriptive information about event reporting in the treated group. The listed group includes participants at risk and participants affected, while the record also names selected serious-event terms and percentages. Such summaries do not automatically provide the primary endpoint result: the primary outcome is defined as participants with TEAEs, and the registry does not report how its separate serious and other event categories map to that definition.

General statistical explanation: over-dispersion matters when variability in count data is greater than a simple model assumes. In such settings, a model that assumes less variability can understate uncertainty and produce intervals that are too narrow. Whether over-dispersion is relevant depends on the outcome, data structure, and statistical model. The registry record does not report a count model, a dispersion estimate, or a model-based analysis for the adverse-event outcomes, so no conclusion about over-dispersion or an appropriate adjustment can be drawn.

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("CTL019")
n      <- c(69)
events <- c(69)
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  CTL019  69  69  100.0  94.8  100.0  94.7  100.0  94.9  100.0

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 24 outcome measures, including the primary TEAE outcome and secondary outcomes covering remission, response, transplantation, and survival. Reporting many outcomes raises a general statistical consideration: when multiple hypotheses are tested, the chance of at least one apparently unusual result can increase unless the analysis plan addresses multiplicity. Whether and how that issue was handled in this study is not reported in the registry record. The record lists 0 analyses, so it does not provide a set of reported tests or adjusted results to assess.

The registry record does not report a statistical analysis plan, a hierarchy among secondary outcomes, multiplicity adjustments, interim analyses, or rules for selecting which outcomes to emphasize. These matters should not be inferred from the list of outcomes alone. The stated sample-size planning assumptions do not establish that the trial used a two-arm analysis or explain how multiple outcomes were addressed.

Missing-data methods are also not reported in the registry record. The safety population is defined as all participants who received an infusion, but the record does not describe loss to follow-up, missing outcome assessments, censoring rules, or whether all participants were observed for the full stated period. The record also does not explain how missing data were handled for remission or time-to-event outcomes.

These omissions limit interpretation of both the completeness and the statistical reliability of outcome summaries. A defined analysis population is useful, but it does not answer whether outcome data were available for every participant or how incomplete observations were treated. No assumptions about missingness, imputation, or sensitivity analyses can be made from the registry information.

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: cytokine release syndrome (40.6%), pyrexia (15.9%), herpes zoster (4.3%), sepsis (4.3%), acute lymphocytic leukaemia recurrent (4.3%).

The serious adverse-event group lists 69 participants at risk and 50 participants affected. The other adverse-event group lists 69 at risk and 66 affected. The record also lists 9 deaths. These are reported group counts; the registry information does not explain whether the deaths were attributed to treatment, the disease, or another cause. The timing and circumstances of the deaths are not reported in the registry record.

Among the listed serious-event terms, the registry reports cytokine release syndrome at 40.6%, pyrexia at 15.9%, herpes zoster at 4.3%, sepsis at 4.3%, acute lymphocytic leukaemia recurrent at 4.3%, and bone marrow failure at 2.9%. The denominator and calculation method for these percentages are not reported in the registry record, so they should be quoted as displayed rather than treated as independently calculated risks.

General statistical explanation: a serious-event count is not necessarily the same measure as the count of all treatment-emergent adverse events. Nor does the word “serious” establish that an event was caused by treatment. The primary outcome is a participant count for TEAEs, but its result is not reported. The registry record does not provide enough detail to reconcile the serious and other event summaries with that primary endpoint.

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

The record establishes that this was a completed, single-group, open-label Phase IIIb study of CTL019 in pediatric and young adult patients with relapsed or refractory B-cell acute lymphoblastic leukemia. It identifies treatment-emergent adverse events as the primary outcome and gives the intended collection period and safety population. It also reports adverse-event group counts, selected serious-event terms, and deaths. These registry entries describe the study’s design and some of its posted safety information.

However, the registry record does not report the result count for the primary TEAE outcome. It also does not report results for the listed remission, response, transplantation, or survival outcomes. The absence of these results means the registry information cannot quantify those outcomes or their precision. It is not evidence that an outcome did or did not occur; it is a limitation of what is reported in the record.

The single-group design also matters. Without a concurrent control group, outcomes in the CTL019 group cannot be interpreted as a randomized comparison with another treatment or with no treatment. The adverse-event summaries are descriptive, and the record does not establish that listed events or deaths were caused by CTL019. The displayed percentages for serious-event terms lack a reported denominator or calculation method in the registry information.

General statistical explanation: efficacy conclusions usually require defined outcome results, an analysis appropriate to the design, and a clear account of uncertainty and missing data. A study’s stated purpose is not itself evidence of a particular outcome. Here, the registry describes an intent to assess safety and efficacy, but the absence of reported primary and secondary results prevents a full statistical assessment of either.

Accordingly, the record supports a description of the study design and the adverse-event entries it lists. It does not provide enough outcome information to estimate the primary safety result, evaluate secondary efficacy results, or make a comparative causal claim. Those conclusions would require information not reported in the registry record.

14. Why This Trial Matters Statistically

This study illustrates why a registered clinical question and a reportable result are different things. The record names a specific primary safety outcome, defines the safety population, and specifies the period during which TEAEs were collected. Those elements help identify what was intended to be measured. Yet the primary result itself is not reported, so readers cannot assess its magnitude or precision from this record.

Its single-group design is also important statistically. A treated-group description can document events in the study population, but a control group would be needed for a concurrent comparison. Without one, differences from an imagined alternative cannot be estimated from the trial record. This is especially relevant when interpreting outcomes that may reflect the disease course or other factors in addition to treatment.

The registry lists a broad set of secondary outcomes, but no analyses are reported. This makes the distinction between outcome registration and outcome evidence particularly clear. A list of intended endpoints does not show that each endpoint was measured completely, analyzed, or reported with uncertainty. The record does not provide enough information to assess multiplicity, missing data, or analysis choices.

For statistical readers, the study therefore highlights the value of transparent reporting of participant flow, endpoint definitions, denominators, analysis methods, and estimates with uncertainty. The available adverse-event summaries are relevant descriptive information, but they do not fill the gap in the primary endpoint result or substitute for a comparative analysis. The registry record supports careful description, while leaving important inferential questions unresolved.

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 main limitation of the registry information is the absence of the primary outcome count. Although the primary TEAE outcome, its collection window, and its safety population are specified, the result and any measure of uncertainty are not reported in the registry record. This prevents a quantitative interpretation of the primary endpoint.

The secondary outcomes are named but their results are not reported. Consequently, remission, response duration, relapse-free survival, event-free survival, overall survival, and transplantation outcomes cannot be described quantitatively from this record. The number of outcome measures is reported, but details of the analysis and reporting for those outcomes are not available.

The single-group, open-label design has no concurrent comparator, so the study cannot provide a randomized estimate of treatment differences. The record also does not report participant flow beyond enrollment and the safety population description, follow-up completeness, missing-data handling, or outcome-specific denominators. It is therefore unclear whether the available follow-up was complete for all outcomes.

The serious-event percentages are listed without a reported denominator or calculation method in the registry information. The record does not supply enough detail to determine how those entries relate to the primary TEAE definition. Deaths are listed, but timing and attribution are not reported. These limitations do not negate the posted event summaries; they constrain how precisely and causally they can be interpreted.

Finally, statistical methods, analysis plans, multiplicity handling, and the trial’s sample-size justification are not reported in the registry record. The presence of planning assumptions for an illustration does not establish the study’s own design calculations or analysis strategy.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Phase III B in Acute Lymphoblastic Leukemia — NCT03123939.
• Registry record last updated 2021-07-21; status last verified 2021-06.
• Results first posted 2021-07-21.
• 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 record describes a completed, multicenter, open-label, single-group Phase IIIb study of CTL019 for pediatric and young adult patients with relapsed or refractory B-cell acute lymphoblastic leukemia. Enrollment is listed as 69. CTL019 was administered as a single dose, with different stated dose ranges according to body weight.

The primary outcome is the number of participants with treatment-emergent adverse events, collected from infusion through the end of study, up to 12 months. The safety population comprises participants who received an infusion. The primary outcome count is not reported in the registry record.

Adverse-event summaries list 50 affected participants among 69 at risk for serious events, 66 affected among 69 at risk for other events, and 9 deaths. The record lists selected serious-event terms with percentages but does not report their denominator or calculation method. Secondary outcomes are named, but their results and statistical analyses are not reported. The single-group design provides no concurrent randomized comparison.