Collection of Transplant Stem Cells for Plasma Cell Myeloma: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Collection of Transplant Stem Cells for Plasma Cell Myeloma (NCT01547806), a na phase 2 study. The primary outcome is Percentage of Patients Achieving at Least 2 x 10^6 Cluster of Differentiation 34 (CD34) Cells Per Kg Recipient Body Weight on Day 1 of Apheresis.

2. Clinical Question

This is a collection-outcome question rather than a comparative treatment-effect question. The record describes an intended clinical process and a threshold for cell collection, but the posted information does not establish how often that threshold was reached or whether collection outcomes differed across participant subgroups.

3. Trial Design

This was a phase 2, single-group study of mobilization and collection of autologous stem cells for transplantation in plasma cell myeloma. The registry record lists the study as completed, with enrollment of 49. The recorded study start was 2012-02-22 and primary completion was 2014-06-17. The sponsor was the National Cancer Institute.

There was no randomized allocation, no masking, and no concurrent comparison arm in the recorded design. The arm description concerns hematopoietic progenitor cells collected by apheresis for subsequent use in clinical protocols. The study therefore describes collection in the participants enrolled rather than estimating a difference between assigned treatment groups.

After screening, including physical examination, medical history, and blood and urine collection, participants were to receive filgrastim injections for 5 days before apheresis. The registry summary says that participants needing additional apheresis procedures to collect cells would receive filgrastim and a dose of plerixafor. This conditional use means the record describes a collection pathway in which the additional agent was reserved for participants who needed further collection; it does not establish how many participants followed that pathway.

The main outcome concerned reaching a CD34 cell collection threshold on Day 1 of apheresis. The registry also lists outcomes concerning adverse events, use of plerixafor with granulocyte-colony stimulating factor, other CD34 collection thresholds, and tumor-cell contamination in the final product. Numerical results for these outcomes are not reported in the registry record.

The design can describe whether the collection goal was achieved among observed participants if the outcome data are available. Without a comparison group, however, it cannot separate the contribution of individual components of the collection process from other influences, or support a direct randomized comparison of strategies.

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: Our study was a relatively small pilot study, with the primary emphasis being on expanding standard stem cell therapy options for patients with multiple myeloma. The plerixafor plus G-CSF combination is used relatively ubiquitously, and several larger studies relating to plerixafor have been performed at large centers that treat multiple myeloma.

Overall Study

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 Patients Achieving at Least 2 x 10^6 Cluster of Differentiation 34 (CD34) Cells Per Kg Recipient Body Weight on Day 1 of Apheresis, measured over Day 1 of apheresis.

The primary endpoint is the percentage of patients achieving at least 2 x 10^6 CD34 cells per kilogram of recipient body weight on Day 1 of apheresis. CD34 cells are progenitor cells identified in the registry description by flow cytometry. The threshold represents the stated minimum dose goal following apheresis.

This endpoint turns a continuous collection quantity into a threshold outcome: each participant either reaches the specified minimum on the first day or does not. Reporting the percentage would describe how often the collection process met that prespecified clinical target in the study group. It is distinct from reporting the average number of cells collected, which could conceal variation in the proportion who reached the minimum.

As a general statistical point, a threshold outcome is easy to interpret against a stated target, but it discards information about how far participants fall above or below that threshold. The endpoint also concerns Day 1 specifically; it should not be read as a measure of the final total collection after any additional apheresis procedures.

The registry record states the endpoint and its timeframe, but does not report its observed percentage, numerator, denominator used in the analysis, or a confidence interval. Consequently, the frequency of reaching the collection target and the precision of that frequency are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a single-group study and a binary primary outcome: reaching the stated CD34 collection threshold on Day 1, or not reaching it. For a binary outcome, a natural descriptive estimate is the proportion of participants with the event among those included in the endpoint analysis. The record gives the endpoint definition and enrollment, but does not report the analyzed numerator or denominator or the resulting percentage. The endpoint estimate therefore cannot be reconstructed from the recorded information.

What would a confidence interval add?

As a general statistical explanation, a confidence interval expresses the uncertainty around an estimated quantity. For a proportion, an interval helps distinguish a relatively precise estimate from one that is compatible with a wider range of underlying values. It does not make the observed data more representative, and it does not remove design limitations. No confidence interval for the primary endpoint is reported in the registry record, so its precision cannot be assessed from the posted results.

The size of an interval depends in part on how many participants contribute outcome data and on the observed proportion. The enrollment figure is not necessarily the endpoint analysis denominator: some participants could lack an evaluable endpoint, and the record does not state whether that occurred. It would be inappropriate to assume that all enrolled participants were included in the endpoint analysis without the relevant analysis details.

What does a single-group result estimate?

In general, an observed proportion in a single-group study describes the frequency of the outcome in that study group under the recorded study conditions. It is not a treatment contrast. A randomized comparison can support estimation of differences between assigned groups because the allocation process is intended to make groups comparable; that feature is absent. The record does not support a direct estimate of the difference between filgrastim alone and filgrastim with plerixafor.

The conditional use of plerixafor also matters when interpreting any subgroup comparison. Participants receiving additional treatment are selected because further collection was needed, according to the study description. A simple comparison between those who did and did not receive plerixafor would therefore not automatically isolate the effect of plerixafor: the groups may differ in the circumstances that led to additional collection. The registry record does not report such a comparison or a method for adjusting it.

Why can a threshold hide useful detail?

As a general point, converting a measured quantity into a yes-or-no threshold makes the result straightforward to relate to a minimum target, but it loses information about the actual cell yield. Participants just below the cutoff and those with a much lower yield are grouped together, as are participants just above the cutoff and those with a much higher yield. The registry record separately lists outcomes involving other CD34 thresholds, but does not report their numerical results. The primary outcome is specifically about Day 1 and should not be interpreted as final total collection after subsequent procedures.

What does the planning note mean?

The registry record includes a planning note describing an illustration based on the observed effect, a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It also states that the effect to detect is a stated fraction of the observed effect. For time-to-event outcomes, the note refers to total events; for other outcomes, it refers to participants per arm. These are generic planning assumptions in the record, not evidence that this single-group study used a two-arm design. Numerical sample-size planning outputs are not reported in the registry record.

As a general statistical principle, sample-size planning asks how much information a future study might need to detect a specified effect under stated assumptions. A planning illustration is not an observed study result and is not observed power. Because this trial has no comparison arm and the primary endpoint result is not reported, no planning illustration should be mistaken for evidence about the collection outcome or a comparison of strategies.

What is not documented about analysis?

The registry record does not report a statistical analysis plan for the primary endpoint, the method used to calculate an interval, handling of missing endpoint data, or any adjustment for covariates. It also does not report interim analyses. These items should be treated as not reported in the registry record rather than inferred from common practice. General methods such as binomial confidence intervals or regression could be used in other settings, but the record does not identify them as methods used in this study.

Over-dispersion is a general concern when observations vary more than a simple model assumes, for example because outcomes cluster or participant risks differ. It can make standard errors too small if ignored. The registry description does not identify a model for the endpoint or provide information that would establish over-dispersion; therefore, it is not possible to say whether this issue arose or how it was handled.

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("Hematopoietic Progenitor Cells (HPC)")
n      <- c(49)
events <- c(48)
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  Hematopoietic Progenitor Cells (HPC)  49  48  98.0  89.1  99.9  89.3  99.6  89.4  99.5

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 13 outcome measures, including the primary collection threshold and several secondary outcomes. When a study evaluates multiple outcomes, there can be more than one opportunity for an apparently notable result to occur by chance. As a general statistical principle, a prespecified hierarchy or multiplicity adjustment can help clarify how multiple tests are interpreted. The registry record does not report a multiplicity strategy, a hierarchy among outcomes beyond identifying the primary endpoint, or a set of hypothesis tests. It is therefore not possible to assess how multiple outcomes were handled analytically.

The record lists 0 analyses. This means analysis entries are not recorded in the registry information available for this analysis; it does not establish that no analyses were conducted. Numerical results for the primary endpoint and the listed secondary measures are not reported in the registry record. The statistical methods for estimating the endpoint are also not reported.

Missing data handling is not reported in the registry record. In particular, the record does not state whether every enrolled participant had an evaluable Day 1 collection outcome, how any unavailable measurements were treated, or whether the endpoint denominator differed from enrollment. These details matter because an estimate among participants with observed data may not describe all enrolled participants if outcome availability is related to collection or health status.

The analysis population is also not reported in the registry record. The record does not specify whether the endpoint was analyzed for all enrolled participants, only those who began apheresis, or another defined group. No assumptions about missing outcomes, exclusions, or analysis populations should be inferred from the study description alone.

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 0% reporting threshold.

Most frequent non-serious adverse event terms

The registry safety record reports 0 participants with serious adverse events among 49 at risk, and 16 participants with non-serious adverse events among 49 at risk. These are participant counts for the study group. They are not comparative rates against another treatment group, because the design has no control arm.

The absence of recorded serious adverse events in this group should be read as a descriptive observation, not as proof that serious harms cannot occur. A study’s observed safety experience is limited to its enrolled participants and recorded follow-up. The registry information does not report serious-event terms, event timing, severity details beyond the serious/non-serious classification, or a comparative safety analysis.

The 16 participants recorded with non-serious adverse events indicate that such events were reported in the study group. The record does not give the specific non-serious event terms in the information available for this analysis. These counts should not be converted into a comparative claim or interpreted as a complete description of all possible risks. The registry record’s safety counts do not replace a broader assessment of adverse-event types, duration, or clinical context.

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

The study addresses an important operational question: whether participants undergoing stem-cell mobilization and collection reached a stated minimum CD34 cell target on Day 1 of apheresis. The registry defines that endpoint and describes the collection pathway, including filgrastim before collection and conditional use of plerixafor when additional apheresis was needed.

What the record does not provide is the observed primary endpoint result. Without the percentage or participant count achieving the target, readers cannot determine how often the Day 1 collection goal was met in this study. The enrollment figure cannot substitute for that outcome, and the study objective cannot be treated as evidence that the target was achieved.

Even if the primary endpoint result were available, the single-group design would answer a descriptive question about this study group rather than establish a comparative advantage of one mobilization strategy over another. There is no randomized comparator in the registry record. Also, plerixafor was described as conditional on need for additional collection, so the record’s design does not support interpreting a simple treated-versus-untreated contrast as an unbiased treatment effect.

The safety counts provide limited descriptive information: no serious adverse events are recorded among participants at risk, while non-serious adverse events are recorded for 16 participants. These figures do not establish safety relative to another approach, and they do not detail the types of events in the available record.

Accordingly, the record supports understanding what was studied and how the primary endpoint was defined, but it does not provide enough outcome reporting to judge the observed frequency of target attainment or the precision of that estimate. This is a limitation of the registry information available, not a conclusion about results that may have been reported elsewhere.

14. Why This Trial Matters Statistically

This trial illustrates the distinction between defining a clinically meaningful endpoint and reporting its result. A threshold such as at least 2 x 10^6 CD34 cells per kilogram on Day 1 gives a clear target for collection, but readers still need the observed proportion, its denominator, and an indication of precision to evaluate how consistently the target was reached.

It also shows why study design determines the kinds of conclusions a result can support. A single-group study can describe collection outcomes in its participants, but it does not provide the direct randomized comparison needed to estimate a contrast between mobilization strategies. This distinction remains important even when a registry lists more than one intervention, because interventions used conditionally within a single treatment pathway do not by themselves create comparable study groups.

The record further illustrates the value of transparent reporting of analysis populations, missing data, statistical methods, and outcome results. Without those details, an endpoint definition and enrollment count cannot be translated into a reliable account of the outcome’s observed frequency or uncertainty. Listing secondary outcomes also does not show whether they were analyzed or how multiple outcomes were interpreted.

For biostatisticians and clinical researchers, the case is a reminder to distinguish registry design information from results and planning assumptions from observed evidence. The record describes a study completed in the setting of stem-cell collection, but the numerical primary endpoint result is not reported in the registry record. Keeping that boundary explicit avoids turning a stated objective into a claimed 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 primary limitation for interpreting this trial from the registry record is that the numerical result for its primary endpoint is not reported. The endpoint definition is available, but the observed percentage, count achieving the target, analysis denominator, and confidence interval are not. As a result, neither the observed collection-goal frequency nor its precision can be assessed.

The single-group design has no concurrent control arm and no randomized allocation. It can describe the experience of participants in the collection protocol but cannot directly estimate a comparative effect. The conditional use of plerixafor further means that participants receiving it were described as needing additional collection; the record does not report an analysis that could account for this selection.

Other outcome-reporting details are also absent from the registry information available for this analysis. The analysis population, missing-data handling, statistical methods, and multiplicity approach are not reported in the registry record. Although the record lists 13 outcome measures, it does not provide numerical results for the primary endpoint or the listed secondary outcomes in the information.

The adverse-event record gives participant counts but does not provide event-specific terms for serious events or a comparative safety assessment. The study description and counts therefore offer a limited account of safety and collection outcomes. These limitations concern the record’s reported information and design; they should not be taken as evidence that unreported analyses or results do not exist elsewhere.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Collection of Transplant Stem Cells for Plasma Cell Myeloma — NCT01547806.
• Registry record last updated 2018-03-07; status last verified 2018-02.
• Results first posted 2017-07-31.
• 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

NCT01547806 is a completed phase 2, single-group study of autologous stem-cell mobilization and collection for transplantation in plasma cell myeloma. The registry reports enrollment of 49 and describes filgrastim before apheresis, with plerixafor planned for participants needing additional collection. The primary endpoint is the percentage achieving at least 2 x 10^6 CD34 cells per kilogram on Day 1 of apheresis.

The numerical primary endpoint result is not reported in the registry record. The safety record lists 0 participants with serious adverse events and 16 with non-serious adverse events among 49 at risk. With no control arm, the study provides no randomized comparison between collection strategies. Analysis methods, missing-data handling, and the analysis population are not reported in the registry record.