This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for A Reduced Toxicity Allogeneic Unrelated Donor Stem Cell Transplantation (SCT) for Severe Sickle Cell Disease (NCT01279616), a na phase 2 study. The primary outcome is Event-free Survival.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01279616 |
| Phase | Phase 2 |
| Condition | Sickle Cell Disease |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 8 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Nationwide Children's Hospital |
| Results posted | Yes |
2. Clinical Question
Population
The study was intended for patients <21 years old with severe complications from sickle cell disease who did not have a matched sibling donor. The registry record lists 8 participants enrolled.
Intervention
Participants were to receive unrelated-donor allogeneic hematopoietic stem cell transplantation after protocol therapy. The listed drugs are fludarabine monophosphate, rituximab, busulfan, ATG, cyclophosphamide, mycophenolate mofetil, and tacrolimus. The arm description specifies stem cell infusion on Day 0.
Comparator
No comparison group is listed. The registry describes a single-group study, with allocation recorded as NA and masking as none. Its design does not support a like-for-like comparison between treatments.
Primary question
The stated aim was to estimate the safety of a reduced-toxicity immunosuppressive and myeloablative preparative regimen for unrelated-donor transplantation. The primary endpoint was event-free survival at 1 year. No endpoint result is available in the registry record, so the study's posted results do not answer that question.
3. Trial Design
This was a phase 2, single-group study sponsored by Nationwide Children's Hospital. Its title describes a reduced-toxicity unrelated-donor stem cell transplantation study for severe sickle cell disease. The official title describes a pilot study of an immunosuppressive and myeloablative preparative regimen. The registry lists 8 participants enrolled.
The record lists no random allocation and no masking. It describes a single hematopoietic stem cell transplant group, with stem cell infusion on Day 0. No control arm is listed, so outcomes cannot be compared within this study against outcomes under another assigned treatment. The planned donor source was unrelated donors or unrelated cord blood units selected from the NMDP database, as described in the study summary.
The registry records a start date of 2010-09 and a primary completion date of 2015-01. The study status is terminated. The primary outcome measure is event-free survival, with a timeframe of 1 year. The record lists one outcome measure and no analyses. It states that the study was terminated and the principal investigator left the institution; efforts to contact the investigator were unsuccessful. No outcome measure data is available.
The registry record does not report why the study was terminated, how many participants completed follow-up, or whether the intended follow-up was completed for any participant. It also does not report a control-group plan, a randomized allocation procedure, or masking procedures. The absence of a control group is a feature of the recorded single-group design, not evidence of a treatment comparison that was conducted but omitted.
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
| Stage | Hematopoietic Stem Cell Transplant |
|---|---|
| STARTED | 8 |
| COMPLETED | 1 |
| NOT COMPLETED | 7 |
Reasons for not completing this period:
| Reason | Hematopoietic Stem Cell Transplant |
|---|---|
| donor could not be located | 5 |
| no signs of sickle cell disease | 2 |
Analysis population for the primary outcome, as defined in the registry: The study was terminated and the PI has left the institution. Efforts were made to contact the PI but unsuccessful. No outcome measure data is available for the 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.
Population: No baseline data are available for this study as the study was terminated. The PI has left the institution and cannot be contacted.
| Characteristic | Unit | Hematopoietic Stem Cell Transplant |
|---|---|---|
| Participants analysed | 0 | |
| Age, Categorical: <=18 years | — | |
| Age, Categorical: Between 18 and 65 years | — | |
| Age, Categorical: >=65 years | — | |
| Sex: Female, Male: Female | — | |
| Sex: Female, Male: Male | — | |
| Region of Enrollment: United States | participants | — |
6. Primary Endpoint
The registry lists the primary outcome as Event-free Survival, measured over 1 year.
| Element | Registry entry |
|---|---|
| Result type | N/A |
| Measure of spread | not applicable |
| Unit | not stated |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is event-free survival at 1 year. In general, event-free survival describes whether participants remain free of a defined event over a specified follow-up period. It can be useful when a study seeks to characterize a broad outcome that matters to its research question, rather than reporting only a single clinical event. That general description does not establish which events counted in this study.
The registry record gives the endpoint name and timeframe but does not define the events included, explain how events were identified, or describe how follow-up time was handled. It also contains no event-free survival result, estimate, uncertainty interval, or analysis. Therefore, the endpoint cannot be interpreted as a reported rate or estimate of participants' outcomes. The record's lack of endpoint data should not be read as evidence that every participant experienced an event or that none did.
For a time-to-event endpoint, the definition of an event and the handling of participants without a recorded event are important to interpretation. In general, participants may have different lengths of follow-up, and some observations may be incomplete or censored. Those concepts matter only when the endpoint definition and analysis are known. The registry record does not say how such matters were addressed for this study, nor does it give enough information to reconstruct the endpoint.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The central interpretive fact is that the registry record has no outcome measure data for the primary endpoint. Although event-free survival at 1 year is listed, no estimate is posted. There is consequently no result from which to describe the observed event-free survival, its precision, or how many participants experienced an endpoint event. No statistical analysis results are listed.
This is different from a finding of no events, and it is different from a finding that all participants experienced an event. Neither conclusion follows from an unavailable outcome measure. The record also does not report a confidence interval, a p-value, or any other estimate of uncertainty for event-free survival. Without an estimate and its uncertainty, the precision of the intended endpoint assessment cannot be judged.
The registry lists 8 participants enrolled, but enrollment alone does not establish how many contributed endpoint data or completed the planned follow-up. The record says that the study was terminated and that the principal investigator left the institution. It further says that efforts to contact the investigator were unsuccessful and that no outcome measure data is available. It does not report whether data were collected but not entered, whether follow-up was incomplete, or what happened to individual participants. Those possibilities cannot be distinguished using the posted record.
The design also limits what any observed result could establish. This is a single-group study without a listed comparator. In general, observations from a single group can describe outcomes among enrolled participants, but they do not by themselves establish how those outcomes compare with a different treatment or with outcomes that would have occurred without the study regimen. No such comparative result is posted in any case.
The registry's serious adverse event record lists 8 participants at risk and 0 affected, alongside 0 deaths. These are registry entries, not a substitute for the absent primary endpoint result. The record identifies no serious adverse event terms and labels the group “No Arm Analyzed: N/A.” The sparse safety entries warrant cautious description; they do not establish that all safety outcomes were fully captured or that risks were absent.
Overall, the posted information documents the study's intended question, design, enrollment, endpoint, and termination status, but it does not provide results that answer the intended endpoint question. The appropriate interpretation is therefore about the limits of the available record, not about whether the transplantation regimen produced a particular outcome.
9. Statistical Methods Explained
The registry record identifies a single-group phase 2 study, with no random allocation and no masking. It lists 8 participants enrolled and no analyses. The record does not report a statistical analysis plan, a sample-size justification for the trial, or the methods used to analyze the primary endpoint. The statistical concepts below are general; they should not be taken as methods used in this study unless the registry record states that they were.
What can a single-group design estimate?
In general, a single-group study can describe outcomes observed among participants who received the study intervention. It cannot, on its own, separate an intervention's effect from other explanations for the observed outcomes. Those explanations can include participant characteristics, the course of the condition, other care, and the way outcomes are recorded. A concurrent comparison group can help address some questions about relative outcomes, but none is listed in this record. The study's stated aim was to estimate safety, while the listed primary endpoint was event-free survival at 1 year. No results are posted for either a comparative or descriptive analysis.
What does a time-to-event endpoint require?
In general, time-to-event analysis uses information about whether an event occurred and when it occurred. It also needs an operational definition of the event, a starting point for measuring time, and rules for handling participants whose event status or follow-up is incomplete. Some participants may not have an observed event before their follow-up ends; methods can account for such incomplete observation, but the interpretation depends on how it is handled. The registry record names event-free survival and gives a 1-year timeframe, but it does not define the endpoint events, report event times, describe follow-up completeness, or state an analysis method. No survival estimate can be reconstructed from the posted information.
How should uncertainty be understood?
In general, a confidence interval describes a range of values compatible with an estimate under the assumptions of the analysis. A narrow interval indicates greater statistical precision than a wide interval, while neither interval alone resolves issues of study design or data quality. The registry record contains no primary endpoint estimate or confidence interval, so neither the direction nor the precision of an endpoint result can be assessed. There is also no posted p-value or analysis result to interpret.
What do the planning assumptions mean?
The registry record describes a sample-size planning illustration using a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect to detect expressed as a stated fraction of an observed effect. For time-to-event planning, it says the calculation is based on the total number of events; other planning results are expressed as participants per arm for 80% power or another specified power level. These are planning conventions, not observed trial findings and not observed power.
Those planning assumptions do not match the recorded study design in important respects: this trial is listed as single-group, while the illustration assumes equal allocation between two arms. The registry record does not report that the illustration was the trial's own design justification or that a two-arm allocation was planned. In addition, no primary endpoint estimate is posted from which a reader could independently assess the stated observed-effect basis. No planning result should be treated as evidence about the trial's outcomes or as a description of the number of participants actually enrolled.
Over-dispersion is a general statistical concern when outcome variability is greater than a model assumes; if ignored, uncertainty can be understated. The registry record does not identify an over-dispersion model or report a statistical model for the primary endpoint. This concept therefore cannot be used to explain or adjust any result in this record. Similarly, the record does not report adjustments for baseline characteristics, an interim analysis, or a model-based sensitivity analysis.
No recalculated estimate is available to compare with a sponsor analysis. The registry record lists no analyses and no endpoint values, so there is no posted summary statistic from which to make a simple unadjusted recalculation. Any sample-size figures associated with planning should be understood as illustrations under their stated assumptions, not as evidence that the study had a particular probability of detecting an effect.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists event-free survival at 1 year as the primary outcome measure and lists no analyses. It does not report a multiplicity strategy, such as a procedure for controlling the chance of a false positive when testing multiple outcomes or hypotheses. Because no statistical results are posted, there is no reported set of tests from which to assess whether multiplicity affected interpretation.
The record does not report how missing outcome data were handled. It states that the study was terminated, the principal investigator left the institution, contact efforts were unsuccessful, and no outcome measure data is available. This explains why the registry lacks results, but it does not establish whether participant-level measurements were missing, whether follow-up ended early, or whether any data were collected but not entered. The number of participants contributing endpoint data is not reported in the registry record.
The record also does not define an analysis population, such as a group based on enrollment, treatment receipt, or completed follow-up. Enrollment is listed as 8, but the number enrolled should not be assumed to equal the number analyzed. The record lists no analyses, so there is no information about exclusions, deviations from the planned treatment, or how participants were handled in an analysis set.
In general, missing-data methods depend on why data are unavailable and on the outcome and analysis being used. Those reasons and methods are not reported in the registry record, so no missing-data assumption can be evaluated. The lack of posted endpoint data prevents assessment of the primary question and also prevents a meaningful check of sensitivity to alternative assumptions.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| No Arm Analyzed: N/A | 0 | 8 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| No Arm Analyzed: N/A | 0 of 0 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| No Arm Analyzed: N/A | 0 of 0 |
The registry's adverse-event record labels the group “No Arm Analyzed: N/A,” lists 8 participants at risk for serious adverse events, 0 affected by serious adverse events, and 0 deaths. It lists 0 participants at risk for other adverse events and 0 affected in that category. No serious adverse event terms are listed.
These entries should be read as registry counts, not as proof that no adverse events occurred during the study. The record does not explain the “No Arm Analyzed” label, provide event-level details, or clarify the scope and completeness of adverse-event reporting. The zero count for participants affected by serious adverse events is also not the primary endpoint result; event-free survival is a separate listed outcome with no data available.
In general, safety counts need context about the population monitored, the period of observation, event definitions, and the completeness of reporting. Those details are not reported in the registry record. The listed counts can be described as posted, but they do not support a broader conclusion about the safety profile of the regimen.
12. What the Result Does, and Does Not, Mean
The record establishes that a phase 2, single-group study of unrelated-donor transplantation for severe sickle cell disease was registered, that 8 participants were enrolled, and that the study was terminated. It also identifies event-free survival at 1 year as the primary endpoint and describes the intended use of an immunosuppressive and myeloablative preparative regimen. These details characterize the study's question and design.
The record does not establish the participants' 1-year event-free survival outcome. No endpoint measure data, analysis, estimate, or uncertainty interval is posted. Accordingly, the record does not show whether participants remained event-free, how often endpoint events occurred, or how precisely an estimate could be made. Missing results are not evidence of a favorable or unfavorable outcome.
The serious adverse event entries list 0 affected participants and 0 deaths among a group with 8 at risk, but the record offers limited context and no serious event terms. Those entries should not be expanded into a claim that the intervention had no adverse effects. They do not supply the missing primary endpoint data, and they do not establish that safety follow-up was complete.
More generally, a single-group study can provide descriptive information about participants who received an intervention, but it does not provide a direct comparison with an alternative treatment or no intervention. Since the registry has no outcome data, even a descriptive estimate is unavailable. The posted record therefore documents a research effort and its recorded status, not a result establishing benefit, harm, or comparative effectiveness.
13. Why This Trial Matters Statistically
This study is statistically important to read with a clear distinction between a registered research question and an analyzable result. The registry identifies a clinically focused objective and a primary endpoint, but it contains no outcome measure data. A named endpoint is not itself an estimate, and enrollment information cannot substitute for outcome information. Keeping those distinctions explicit prevents the intended question from being mistaken for a result.
The single-group design is also central to interpretation. Without a listed comparator, the study was not structured as a randomized, like-for-like treatment comparison. In general, single-group observations and comparative effects answer different questions. Even if an outcome estimate had been available, it would need to be described as an outcome observed in the study group rather than as a comparison attributable to treatment assignment.
The registry status and missing results matter for transparency. It records termination and explains that the principal investigator left the institution and could not be reached, while also stating that no outcome measure data is available. This makes the limits of the public record visible, but leaves unresolved whether data were collected, how complete follow-up was, and why the study ended. Those gaps prevent a statistical assessment of the planned endpoint.
Finally, the planning illustration has assumptions that differ from the recorded single-group design, including equal allocation between two arms. Treating such planning assumptions as if they described the actual trial would confuse a calculation framework with the design that the registry records. The statistical lesson is to keep design, planning, observed data, and analysis distinct: the record supplies design and status information, but it does not supply the endpoint observations needed for inference.
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.
Several limitations specific to this record constrain interpretation. The study is listed as terminated, and its stated reason for the absence of outcome data is that the principal investigator left the institution and could not be contacted. No explanation for the termination itself is reported in the registry record. It is also not reported whether the study stopped before planned follow-up was complete, whether participants continued to be monitored, or whether outcome data exist outside the registry.
The primary endpoint is named but not operationally defined. The record does not specify which events count toward event-free survival, how the endpoint was assessed, or how incomplete follow-up was handled. Without these details and without outcome values, the result cannot be reconstructed or independently checked. The number of participants with evaluable endpoint data is not reported.
The single-group design offers no listed comparison group, and the record reports no random allocation or masking. Those features limit comparative interpretation even if descriptive outcome data were available. In this record, the absence of outcome data is an additional barrier: there is no estimate to interpret in the first place.
The registry lists 8 participants enrolled and sparse adverse-event counts, but it does not report the duration or completeness of safety monitoring, detailed event terms, or the meaning of the “No Arm Analyzed: N/A” label. The sample-size planning assumptions are also not documented as the trial's own justification and include equal allocation between two arms, unlike the recorded single-group design. These limits make it important to distinguish what the registry records from what remains unknown.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: A Reduced Toxicity Allogeneic Unrelated Donor Stem Cell Transplantation (SCT) for Severe Sickle Cell Disease — NCT01279616.
- Registry record last updated 2019-04-03; status last verified 2019-04.
- Results first posted 2019-04-03.
- 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.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
18. Record Summary
The registry record describes a phase 2, single-group study of unrelated-donor allogeneic stem cell transplantation for severe sickle cell disease. It lists 8 participants enrolled, no random allocation, no masking, and event-free survival at 1 year as the primary outcome measure. The study is recorded as terminated, with a start date of 2010-09 and a primary completion date of 2015-01.
No outcome measure data or analysis results are available. The record states that the principal investigator left the institution and that contact efforts were unsuccessful. Serious adverse event entries list 8 participants at risk, 0 affected, and 0 deaths, but no serious event terms. The available record therefore describes the study's design and status but does not provide results for its primary endpoint.