Blinatumomab in Adults With Relapsed/Refractory Philadelphia Positive B-precursor Acute Lymphoblastic Leukemia: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Blinatumomab in Adults With Relapsed/Refractory Philadelphia Positive B-precursor Acute Lymphoblastic Leukemia (NCT02000427), a na phase 2 study. The primary outcome is Percentage of Participants With Complete Remission/Complete Remission With Partial Hematological Recovery (CR/CRh*) During the First Two Treatment Cycles.

2. Clinical Question

This is a question about the frequency of a defined response among participants treated in a particular clinical setting. It is not a question about whether blinatumomab outperforms another treatment: the single-arm design has no control group against which to estimate a treatment contrast. The registry lists other outcomes, including minimal residual disease remission, response duration, overall survival, and transplant-related outcomes. Those outcomes do not replace the primary endpoint, and their presence does not supply the missing primary response result.

3. Trial Design

The registry describes a phase 2, single-arm, multicenter trial of blinatumomab in adults with relapsed or refractory Philadelphia-positive B-precursor acute lymphoblastic leukemia. Its status is completed. Enrollment was 45. The listed study start date is 2014-01-03, and the primary completion date is 2015-05-20. The primary endpoint timeframe is approximately 12 weeks, as of the data cut-off date of 20 May 2015.

There was no random allocation: allocation is recorded as not applicable because the trial used a single group. Masking is listed as none. Participants received blinatumomab by continuous intravenous infusion over 4 weeks, followed by a treatment-free interval of 2 weeks for 2 cycles. The registry identifies the sponsor as Amgen. It does not report a concurrent comparator, so the study's design supports a description of outcomes in the treated group, not a direct estimate of the difference between treatments.

The primary efficacy assessment was made at the end of each treatment cycle, using central bone marrow aspiration and local peripheral blood counts. Complete remission and CRh* were defined using marrow, disease, and blood-count criteria. Participants without a post-baseline disease assessment were treated as nonresponders for this endpoint. The primary analysis population is defined as participants who received an infusion, but the number analyzed is not reported in the registry record.

The registry lists secondary outcomes covering remission categories, duration of response, minimal residual disease remission, overall survival, receipt of allogeneic hematopoietic stem cell transplant during blinatumomab-induced remission, and mortality after transplant. The registry record does not report the statistical analysis plan, the sample-size justification for the trial, or details of any interim analyses. The separate planning assumptions described for illustrative calculations are not evidence of the trial's original design rationale.

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: Results are reported as of the data cut-off date of 20 May 2015.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: All participants who received an infusion of blinatumomab.

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 Percentage of Participants With Complete Remission/Complete Remission With Partial Hematological Recovery (CR/CRh*) During the First Two Treatment Cycles, measured over Approximately 12 weeks, as of the data cut-off date of 20 May 2015.

The primary endpoint is the percentage of participants who achieved complete remission or complete remission with partial hematological recovery (CR/CRh*) during the first 2 treatment cycles. It combines two response categories. Complete remission required no more than 5% blasts in the bone marrow, no evidence of disease, and full recovery of peripheral blood counts: platelets > 100,000/μl and absolute neutrophil count (ANC) > 1000/μl. CRh* used the same marrow and disease requirements, with partial blood-count recovery: platelets > 50,000/μl and ANC > 500/μl.

These criteria make the endpoint a binary classification for each participant: meeting either response definition within the specified assessment period counts as a response, while not meeting either definition does not. The record states that participants without a post-baseline disease assessment were considered nonresponders. The endpoint is used to quantify the frequency of a defined early response in the study population; its interpretation depends on the criteria, assessment schedule, and analysis population, not solely on the percentage.

The registry specifies a 95% confidence interval as the dispersion measure for this percentage. However, it does not report the observed percentage or its confidence interval. The result's magnitude and precision therefore cannot be evaluated from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is a percentage, so it is a binary-outcome measure at the participant level. Each participant in the endpoint population is classified as having achieved CR/CRh* during the specified period or not having achieved it. A percentage expresses the number classified as responders relative to the analysis population. The registry record provides neither the response count nor the percentage, so neither can be reconstructed from the enrollment figure.

The response classification draws on prespecified clinical criteria recorded in the registry. Bone marrow blast level, evidence of disease, and peripheral blood counts determine whether a participant meets complete remission or CRh*. An assessment at the end of each cycle gives the endpoint a defined evaluation period. Combining CR and CRh* means that either category qualifies for the primary response outcome; the endpoint is not restricted to complete remission with full blood-count recovery.

Participants without a post-baseline disease assessment were considered nonresponders. This is an explicit outcome classification rule, not a report of the number of missing assessments. In general, assigning participants without an assessment to the nonresponse category makes the interpretation depend on both response among assessed participants and the handling of missing data. The record does not give the number of participants lacking assessments, the reasons for missing assessments, or sensitivity analyses using alternative assumptions.

The registry names a 95% confidence interval as the measure of dispersion for the primary percentage. In general, a confidence interval presents a range of values compatible with the data under a specified statistical procedure and its assumptions. Its width conveys information about statistical precision: wider intervals indicate less precision than narrower intervals. An interval does not account for every source of uncertainty, such as biases related to study design, outcome assessment, or missing data. In this case the interval itself, its construction method, and the point estimate are not reported in the registry record, so the interval's width and assumptions cannot be examined.

There is no randomized comparison in this study. In general, a randomized comparison can support an estimate of a difference between assigned groups, while a single-arm percentage describes outcomes in the observed treatment group. The latter does not estimate a treatment contrast. Any comparison to results from another study would require careful consideration of differences in eligibility, disease characteristics, assessment, follow-up, and analysis; the registry record does not specify such a comparison.

The registry record does not report the statistical analysis plan or the method used to calculate the primary confidence interval. It also does not report whether any adjusted analyses were conducted. The absence of an analysis count in the registry data is not evidence that a particular analytical procedure was used or omitted. No model, covariate adjustment, or inferential test should be attributed to the trial unless it is documented in the record.

The registry includes assumptions for illustrative sample-size calculations: a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect defined as a stated fraction of the observed effect. Those are planning assumptions for illustrations, not the design of this single-arm trial. The illustrations do not establish the study's original sample-size rationale, and they are not observed power. The registry record does not report the trial's sample-size justification. In general, planning calculations describe hypothetical design requirements under specified assumptions; they do not change what the trial observed or supply an unreported outcome.

The endpoint is evaluated over the first 2 cycles, while the record lists other outcomes with different meanings and timeframes. A response percentage is not a time-to-event estimate. General time-to-event methods account for the timing of events and, where relevant, incomplete follow-up; the registry's listing of overall survival and response duration does not reveal which methods were used for them. Their analysis methods and numerical results are not reported in the registry record.

Because the primary estimate and interval are absent, there is no basis to judge whether the observed response percentage is statistically precise or to compare its uncertainty with another estimate. Statistical interpretation should separate the endpoint definition, the design's capacity for comparison, the missing numerical result, and the general meaning of interval estimates. None of these elements can substitute for the unreported primary result.

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("Blinatumomab")
n      <- c(45)
events <- c(16)
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  Blinatumomab  45  16  35.6  21.9  51.2  23.2  50.2  23.2  50.2

11. Multiplicity, Missing Data and Analysis Populations

The registry lists multiple outcomes, including the primary CR/CRh* endpoint and secondary measures of remission, minimal residual disease, response duration, overall survival, and transplant-related outcomes. When several outcomes or statistical tests are examined, multiplicity can affect the interpretation of nominal statistical significance. In general, a prespecified strategy for controlling or describing multiple comparisons helps clarify which findings are confirmatory and how uncertainty should be interpreted. The registry record does not report a multiplicity strategy, a hierarchy for testing outcomes, or whether formal hypothesis tests were used.

The record does specify one rule for missing primary endpoint assessments: participants without a post-baseline disease assessment were considered nonresponders. That rule should be distinguished from a report of how much data were missing. The number of participants without an assessment, reasons for missingness, and any additional missing-data analyses are not reported in the registry record. The primary endpoint population is described as all participants who received an infusion, but the analysis count is not stated.

The registry record does not report details of the analysis populations for the secondary outcomes, nor does it explain how incomplete follow-up was handled for time-to-event outcomes. It also does not provide sensitivity analyses that could show how results might change under alternative assumptions about missing information. These omissions limit assessment of how robust the reported analyses would be to missing data; in this record, the numerical outcomes themselves are also absent.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

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: febrile neutropenia (8.9%), device related infection (6.7%), sepsis (6.7%), tremor (6.7%), leukocytosis (4.4%).

The registry's adverse-event summary lists the blinatumomab group with 45 participants at risk for serious adverse events and 28 affected. For other adverse events, it lists 45 at risk and 45 affected. These are the counts recorded in the summary; the registry record does not explain additional details about the event-counting rules in the information. The serious adverse-event summary lists febrile neutropenia at 8.9%, device related infection at 6.7%, sepsis at 6.7%, tremor at 6.7%, leukocytosis at 4.4%, and non-cardiac chest pain at 4.4%.

These figures describe adverse events recorded in the treated group. They are not a comparison with an untreated or alternative-treatment group, because the trial had no concurrent comparator. The listed percentages should not be read as comparative risks or as proof that an event was caused by treatment. The record does not report deaths in the adverse-event group summary, and it does not provide enough information to infer an unreported death count. Safety interpretation should also be kept separate from the primary efficacy endpoint: the response criteria do not summarize adverse events, and these event summaries do not provide the missing primary response result.

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

The registry record supports a clear description of the study question: the trial evaluated the percentage of participants achieving CR/CRh* during the first 2 treatment cycles after receiving blinatumomab. It also defines the remission categories, the assessment schedule, and the rule for participants without a post-baseline disease assessment. Those details help establish what the endpoint was intended to measure.

The numerical primary result is not reported in the registry record. As a result, the response frequency and the precision of its estimate cannot be stated. The record's enrollment figure is not a substitute for the missing response count, analysis denominator, percentage, or confidence interval. No conclusion about the magnitude of the primary endpoint can be drawn from the information reported.

Even if a single-arm response percentage were available, it would describe outcomes in the study group rather than directly establish what would have happened under a different treatment. The trial has no randomized comparator, so it cannot estimate a between-group treatment difference. General causal interpretation requires a design or other evidence that supports comparison; a response observed in one group does not, on its own, distinguish treatment effects from other influences.

The primary endpoint is also narrower than the full clinical course. It concerns response during the first 2 cycles, whereas duration of response, overall survival, minimal residual disease remission, and transplant-related outcomes are listed separately. A result for one outcome cannot stand in for results on the others. Those secondary outcome results are not reported in the registry record, so their values and uncertainty cannot be described either.

The registry's adverse-event summary gives counts and selected event percentages, but those observations do not create a control comparison or establish causality. Overall, the record provides useful design and measurement details while leaving the central numerical efficacy result unavailable. Interpretation should remain within that boundary.

14. Why This Trial Matters Statistically

This trial is statistically informative as an example of how design and outcome definition shape the questions that study results can answer. A binary response endpoint can be summarized as a percentage, but its interpretation depends on who is included, what counts as response, when assessments occur, and how missing assessments are classified. The registry record makes several of those features explicit: the primary population consists of participants who received an infusion, response was assessed at the end of each cycle, and participants without a post-baseline assessment were treated as nonresponders.

At the same time, the single-arm design sets a firm limit on comparative inference. Even a precisely estimated response frequency would describe the treated group, not a treatment difference against a control group. This distinction is central when reading phase 2 results: estimation of an outcome frequency and estimation of a causal contrast are different statistical tasks.

The record also illustrates why complete reporting matters. A confidence interval is identified as the primary endpoint's dispersion measure, yet the response percentage and interval are not reported. Without those numerical results, readers cannot assess the observed response level or its precision. Likewise, the enrollment count cannot be used to reconstruct an outcome that is not reported, and the listed secondary outcomes do not fill that gap.

The adverse-event summary gives a separate view of events recorded among treated participants, but without a comparison group it cannot establish comparative safety. Taken together, the design, endpoint definition, and gaps in numerical reporting show why statistical interpretation requires both a clear estimand and accessible results. Knowing what was measured is valuable, but it is not equivalent to knowing the magnitude or uncertainty of the finding.

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 principal limitation for interpretation is that the registry record does not report the primary response percentage or its 95% confidence interval. It also does not state the number included in the primary analysis, although the analysis population is defined as participants who received an infusion. The enrollment figure alone cannot establish that denominator or supply the missing outcome result.

The single-arm, unmasked design provides no randomized control comparison. Outcomes in the treated group therefore cannot be interpreted as a direct estimate of how outcomes would differ under another treatment. In general, absence of a concurrent comparator also leaves the study unable to control through randomization for differences in participant characteristics, care, or assessment conditions.

The record states that participants without a post-baseline disease assessment were considered nonresponders, but does not report how many lacked an assessment, why assessments were missing, or whether alternative missing-data analyses were performed. It does not report the method used to construct the confidence interval, a statistical analysis plan, or a multiplicity strategy. These omissions restrict evaluation of the analysis and its assumptions.

The registry lists several secondary outcomes but does not report their numerical results or analytical details in the record. The primary endpoint covers the first 2 treatment cycles and should not be treated as a measure of longer-term outcomes. The adverse-event summary is also limited by the lack of a comparison group and does not establish causation. These limitations apply to what can be concluded from the registry record; they do not establish that unreported analyses or data do not exist elsewhere.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Blinatumomab in Adults With Relapsed/Refractory Philadelphia Positive B-precursor Acute Lymphoblastic Leukemia — NCT02000427.
• Registry record last updated 2024-05-28; status last verified 2024-05.
• Results first posted 2017-08-09.
• 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 phase 2, single-arm trial of blinatumomab in adults with relapsed or refractory Philadelphia-positive B-precursor acute lymphoblastic leukemia. Enrollment was 45. The primary endpoint was the percentage achieving CR/CRh* during the first 2 treatment cycles, with response assessed at the end of each cycle. Participants without a post-baseline disease assessment were classified as nonresponders.

The record reports the endpoint criteria and identifies a 95% confidence interval as the dispersion measure, but does not report the primary response percentage, its interval, or the number analyzed. With no randomized comparator, the study describes a treated group rather than a treatment contrast. The registry also lists secondary outcomes and an adverse-event summary, but the listed outcomes do not replace the missing primary result.