Alteration in Timing of Plerixafor Administration: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Alteration in Timing of Plerixafor Administration (NCT01149863), a non-randomized phase 2 study. The primary outcome is Number of Patients Who Collected ≥ 6 x 10^6 CD34+ Cells by Day 5 (4 Apheresis Sessions) With Plerixafor Administration at 1500..

2. Clinical Question

The motivating question was whether changing administration time from the usual evening timing described in the registry to 17 hours before apheresis could be evaluated for CD34+ cell mobilization and safety. The brief summary presents the earlier timing as potentially more convenient because it would occur during normal clinic hours. That rationale is not itself an outcome measure.

The registered primary outcome counts participants reaching a specified collection threshold within a defined period. A secondary outcome counts participants who collected more than 10 x 10^6 CD34+ cells/kg on Day 1. The registry record does not report the observed result for either outcome, so the extent to which participants reached these targets cannot be determined from the record.

3. Trial Design

The registry identifies this as a phase 2 study with non-randomized allocation, no masking, and a single-group model. It lists Emory University as the sponsor, autologous transplantation as the condition, and 34 as the enrollment. The study status is completed. Its recorded start was 2010-06, and its primary completion was 2011-12.

The intervention was plerixafor administered 17 hours before apheresis; the arm description specifies a 3PM (1500 hours) dose. The study title and brief summary describe plerixafor in combination with G-CSF. The record does not give further dosing details in the information reported for this analysis.

The study was designed to examine cell mobilization and safety after altering the timing of plerixafor administration. Its primary outcome concerns reaching a CD34+ cell collection target by Day 5, with a maximum of 4 apheresis sessions specified in the outcome title. The secondary outcome concerns a higher collection threshold on Day 1.

The brief summary says these outcomes would be compared with results from previous studies in which plerixafor was administered 11 hours before apheresis. That is a historical comparison, not a randomized, concurrent control group. The study's non-randomized, single-group structure means that any contrast with prior results may also reflect differences between the studies, their participants, or their conduct. Details needed to assess the comparability of those prior studies are not reported in the registry record.

The registry record does not report a statistical analysis plan, a sample-size justification, or the methods used to conduct a historical comparison. Those omissions limit assessment of how the investigators intended to estimate or formally compare outcomes.

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.

Overall Study

Reasons for not completing this period:

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 Number of Patients Who Collected ≥ 6 x 10^6 CD34+ Cells by Day 5 (4 Apheresis Sessions) With Plerixafor Administration at 1500., measured over Within the first 5 days following plerixafor initiation.

The primary endpoint counts participants who collected at least 6 x 10^6 CD34+ cells by Day 5, within the first 5 days following plerixafor initiation and over 4 apheresis sessions. It is a participant count, not a measurement of average cell yield. The endpoint is intended to capture whether a specified collection target was reached during the stated period.

A threshold-based outcome can be clinically interpretable because it distinguishes reaching a predefined target from not reaching it. However, the count alone does not describe how far above or below the threshold individual collections were, or the distribution of total CD34+ cell yields. Those details are not reported in the registry record.

The endpoint title also specifies plerixafor administration at 1500. This ties the outcome to the altered timing under study. The secondary outcome uses a different threshold and time point: the number of participants who collected more than 10 x 10^6 CD34+ cells/kg on Day 1 after dosing at 1500.

The record names the primary endpoint but does not report its observed count or the proportion of participants reaching the target. It also does not report uncertainty estimates for that result. Consequently, the endpoint's definition is available, but its observed magnitude and precision 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 represent? The primary outcome is a count of participants who met a collection threshold by a specified time, not a continuous summary of all cell yields. In general, a binary outcome classifies each participant according to whether a defined event occurred. Counts can be straightforward to interpret, but they do not show how close participants who did not meet the threshold came to it, or how much participants who met it exceeded it.

The registry defines the event as collecting at least 6 x 10^6 CD34+ cells by Day 5, across 4 apheresis sessions. That definition specifies a threshold and an observation window. It does not, by itself, provide the observed count, denominator, or uncertainty. The outcome result is not reported in the registry record, and neither a confidence interval nor another precision estimate is reported for it.

What would a confidence interval add? In general, a confidence interval describes the range of estimates compatible with the data under a stated statistical method. It helps readers distinguish a precise estimate from one with substantial uncertainty. It does not correct for bias in study design, and its interpretation depends on the analysis assumptions. No confidence interval for the primary endpoint is reported in the registry record, so its precision cannot be evaluated from the available outcome information.

What does the study design permit? This is a single-group, non-randomized study with no masking. Its brief summary describes comparison with previous studies using an 11-hour interval. Historical comparisons can provide context, but the earlier group is not a concurrently randomized control. In general, differences between studies can arise from population characteristics, collection procedures, or outcome measurement as well as from the intervention timing. The record does not give the prior-study results or enough detail to assess their comparability.

Randomization is useful in general because it can balance measured and unmeasured prognostic factors between concurrent groups, on average. That protection does not apply to a historical contrast in the same way. The record's design classification should therefore guide interpretation: it documents an evaluation of the 17-hour timing in a single group, not a randomized estimate of the difference between 17-hour and 11-hour dosing.

How should the planning illustrations be read? The stated planning assumptions describe illustrations based on an observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The assumptions say that the effect to detect is a stated fraction of the observed effect. They also distinguish total events for time-to-event calculations from participants per arm for other calculations. These are planning conventions, not observed trial findings. They are not the trial's own design justification, and they should not be read as observed power. The registry record does not report a sample-size justification for the trial. No numerical planning estimates or observed primary effect are reported in the information, so no specific planning conclusion can be drawn.

In general, a planning calculation asks what sample size might be needed under specified assumptions about an effect and statistical procedure. It does not show that a completed study had a particular probability of detecting an effect after the results are known. Such a calculation also cannot replace an estimate and confidence interval for the outcome actually observed. The registry record does not report the trial's inferential analysis of the primary endpoint.

Why can variation matter? In general, over-dispersion occurs when outcome variability is greater than a statistical model assumes. If ignored, standard errors and confidence intervals may be too optimistic. This is a general consideration for count data, but the registry record does not report a fitted model, an over-dispersion assessment, or a model-based primary analysis. It would therefore be inappropriate to attribute any particular method or diagnostic to this study.

For a binary endpoint, an analysis could report a participant count and a proportion, with an uncertainty interval, or compare groups using a stated statistical model. These choices depend on the design and analysis plan. The registry record names a participant count as the primary measure but does not report an analysis method or a comparative estimate. No unreported statistical test, adjustment, or model can be assumed.

The key distinction is between a registered outcome definition and a reported outcome result. The former tells readers what was meant to be measured; the latter is needed to estimate what occurred and how uncertain that estimate is. For this trial, the endpoint definition and some safety counts are present, while the primary endpoint result and its inferential analysis are not reported in the registry record.

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("Plerixafor 17 Hours Prior to Apheresis")
n      <- c(31)
events <- c(31)
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  Plerixafor 17 Hours Prior to Apheresis  31  31  100.0  88.8  100.0  89.0  100.0  89.1  99.9

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 2 outcome measures. The primary outcome is the number of participants who collected at least 6 x 10^6 CD34+ cells by Day 5, while the secondary outcome is the number who collected more than 10 x 10^6 CD34+ cells/kg on Day 1. These outcomes use different thresholds and time points, so they address related but non-identical aspects of collection.

When a study evaluates multiple outcomes, multiplicity can matter because testing more hypotheses can increase the chance of at least one apparently unusual result. In general, investigators may identify a primary outcome in advance and specify how secondary outcomes will be interpreted or adjusted. The registry identifies a primary outcome, but multiplicity procedures and a prespecified statistical analysis plan are not reported in the registry record. The record also lists 0 analyses, so it does not provide inferential results for these outcomes.

The registry record does not report the number of participants with missing primary endpoint data, the reasons for any missing data, or the method used to handle missingness. It also does not report whether the primary analysis used all enrolled participants or a defined analysis population. The enrollment figure of 34 therefore cannot be assumed to be the denominator for the primary endpoint.

In general, missing outcome data can affect an estimate if participants with unavailable measurements differ from those with observed measurements. The direction and extent of that effect depend on why data are missing and on the analysis approach. With no missing-data description or analysis population reported, the potential impact cannot be evaluated for this study.

Information about interim analyses, multiplicity adjustments, and sensitivity analyses is not reported in the registry record. Their absence from the record should not be interpreted as evidence that a particular procedure was or was not used.

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 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: hypokalemia (3.2%), bone pain (3.2%).

The safety record lists 31 participants at risk for serious adverse events and 2 affected participants. It separately lists 31 participants at risk for other adverse events and 26 affected participants. These are counts recorded for the study group; they are not a comparison with an untreated group or a randomized control group.

Hypokalemia and bone pain are listed as the top serious adverse event terms, each with a reported frequency of 3.2%. The registry record does not provide additional detail about event severity beyond the serious-event classification, timing, duration, management, or attribution. The figures should therefore be read as registry-recorded safety information rather than proof that plerixafor or its administration time caused an event.

The deaths field is not reported in the registry record. That is different from a reported count of zero. The record also does not provide enough information to determine whether participants could contribute more than one event, so event terms should not be interpreted as mutually exclusive participant categories.

These safety counts offer a description of events recorded in the group, but the study's single-group, non-randomized design limits causal interpretation. The registry record does not report a formal comparison of safety between the 17-hour timing and the timing used in previous studies.

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

The record identifies a phase 2 evaluation of plerixafor given 17 hours before apheresis, with CD34+ cell collection and safety as its focus. It specifies the primary collection threshold, the time window, and the planned number of apheresis sessions in the outcome definition. It also records safety counts for the study group. These details make the study question and some aspects of the reported safety experience clear.

However, the primary endpoint result is not reported in the registry record. The record therefore does not show how many participants reached the collection target, what proportion did so, or how uncertain any estimate would be. The secondary outcome result is also not reported. Without these results, the registry information cannot establish the observed level of CD34+ cell collection under the studied timing.

The study is single-group and non-randomized. Its brief summary proposes comparison with previous studies that used plerixafor 11 hours before apheresis, but the registry record does not include those studies' outcome values or a formal comparison. Any historical contrast would need to be interpreted cautiously because differences between studies can affect apparent outcomes.

The recorded safety counts describe events among participants listed at risk. They do not establish causation, and they do not offer a concurrent control comparison. The registry record does not report deaths in the available information, which should not be read as a zero count.

In general, a study's design and the completeness of its results determine what conclusions its data can support. Here, the registry record supports describing the intervention timing, outcome definitions, design, and listed safety counts. It does not support estimating the primary collection outcome or its precision, nor does it permit a reliable estimate of a difference from the earlier timing.

14. Why This Trial Matters Statistically

This study addresses a question about when to administer plerixafor in relation to apheresis, rather than whether to use the drug at all. The registry describes 17-hour timing and identifies comparison with previous studies using 11-hour timing as the intended context. Separating a timing question from a treatment-versus-no-treatment question is important when interpreting the design and the scope of any result.

The study also illustrates why a clearly defined endpoint is not the same as an available endpoint result. The primary outcome specifies a collection threshold, a time window, and a number of apheresis sessions. Those features help define the question. But without the observed count, denominator, and an estimate of uncertainty, readers cannot assess the magnitude or precision of the outcome.

Its non-randomized, single-group design is another statistical consideration. A comparison to historical results can be informative as context, but it is less able to separate timing effects from differences between studies than a concurrent randomized comparison. The registry record does not report the earlier results or a formal comparative analysis, leaving that contrast unquantified.

The safety data also demonstrate the distinction between recording events and attributing them. Counts of serious and other adverse events describe what was recorded among participants at risk. They do not, without an appropriate comparison and further clinical assessment, identify the cause of those events.

Finally, the study record makes clear that completion status and enrollment are not substitutes for outcome reporting. The record is marked completed and lists 34 enrolled, but the primary outcome result and its analysis are not reported. For statistical interpretation, transparent outcome estimates, denominators, and uncertainty measures are essential to move from a study question to an evidence-based description of what was observed.

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 interpreting efficacy-related findings is that the registry record does not report the observed primary endpoint result. It also does not report the secondary outcome result, an endpoint denominator, or an uncertainty estimate. Thus, the collection outcomes cannot be quantified from the recorded information.

The design is non-randomized and single-group, with no masking. The comparison described in the brief summary is with previous studies using 11 hours before apheresis, not a concurrent randomized group. The registry record does not provide those historical outcome values or details sufficient to assess how comparable the studies were. Any contrast would be vulnerable to differences between studies as well as to the timing being evaluated.

The registry lists 34 enrolled, but does not report how many participants contributed primary endpoint data or the reasons for any unavailable data. Analysis populations and missing-data handling are not reported in the registry record. The enrollment number should therefore not be treated as the endpoint denominator.

The record identifies 2 outcome measures but does not report a statistical analysis plan, multiplicity procedures, interim analyses, or sensitivity analyses. It also does not report inferential analyses for the primary endpoint. Consequently, the planned handling of multiple outcomes and robustness of estimates cannot be assessed.

Safety information is limited to the listed counts and serious-event terms. The record does not report deaths in the available information, and it provides no concurrent control group for comparison. These limitations mean that the safety entries are descriptive and do not establish causation.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Alteration in Timing of Plerixafor Administration — NCT01149863.
• Registry record last updated 2013-12-13; status last verified 2013-05.
• Results first posted 2013-07-08.
• 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 identifies a completed phase 2, non-randomized, single-group study sponsored by Emory University, with 34 participants enrolled. It evaluates plerixafor administered 17 hours before apheresis, alongside G-CSF, with dosing specified at 3PM (1500 hours).

The primary outcome is the number of participants collecting at least 6 x 10^6 CD34+ cells by Day 5, within 4 apheresis sessions. The secondary outcome concerns collecting more than 10 x 10^6 CD34+ cells/kg on Day 1. Neither outcome result is reported in the registry record. The brief summary describes comparison with previous studies using an 11-hour interval, rather than a randomized concurrent control.

The safety record lists serious and other adverse event counts, including hypokalemia and bone pain as top serious terms. The registry does not report a primary endpoint analysis, its denominator, or an uncertainty estimate. The design and missing outcome results limit conclusions about collection outcomes and historical differences.