Combined Kidney and Bone Marrow Transplantation to Prevent Kidney Transplant Rejection: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Combined Kidney and Bone Marrow Transplantation to Prevent Kidney Transplant Rejection (NCT00801632), a na phase 2 study. The primary outcome is Number of Participants Successfully Withdrawn Off of Immunosuppressant Medication for 104 Weeks.

2. Clinical Question

3. Trial Design

This is a completed phase 2, single-group trial, NCT00801632, with an enrollment of 5. The registry lists kidney transplantation and chronic kidney failure among its conditions. Its arm description identifies one group, Kidney and Marrow Recipients, who received combined kidney and bone marrow transplantation. Allocation is recorded as not applicable, and masking as none; the record therefore does not describe a randomized, masked comparison.

The listed interventions include kidney transplantation and bone marrow transplantation, along with MEDI-507, cyclophosphamide, rituximab, tacrolimus, corticosteroids, and thymic irradiation. The record does not report the detailed protocol, timing, doses, or participant-level exposure to these interventions. Those details should not be inferred from the intervention list alone.

The study started in 2008-12, reached primary completion in 2014-04, and is marked completed. The primary outcome is the number of participants successfully withdrawn from immunosuppressant medication according to a prespecified duration and follow-up definition. The registry also lists secondary outcomes involving acute rejection, renal function, graft survival, participant survival, blood-cell recovery, and clinically significant invasive or resistant opportunistic infection. The timeframe specified for the primary outcome is 48 months post-transplant; several secondary outcomes refer to 156 weeks.

Because there is no control group, the design can describe what happened among the enrolled participants but cannot establish a comparative treatment effect. Small enrollment also means that participant-level outcomes can have substantial influence on any group summary. The registry record does not report a protocol rationale for the design or enrollment target, so the reasons for these choices are not known.

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:

Analysis population for the primary outcome, as defined in the registry: Intent-to-treat

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: Intent-to-treat

6. Primary Endpoint

The registry lists the primary outcome as Number of Participants Successfully Withdrawn Off of Immunosuppressant Medication for 104 Weeks, measured over 48 months post-transplant.

The primary endpoint is the number of participants considered successfully withdrawn from immunosuppressant medication. A participant meets the registry definition if they are off immunosuppressive therapy for 104 consecutive weeks leading up to study week 208, or study termination if that occurs first. The listed timeframe is 48 months post-transplant, and the analysis population is intent-to-treat.

This endpoint focuses on sustained medication withdrawal rather than a brief interruption. Requiring a continuous period makes the outcome a defined clinical status over time, while the cutoff at study termination sets a stopping point for participants whose follow-up ends earlier. The endpoint is a count of participants, not a measure of the duration of medication use for each person or a continuous measure of kidney function.

The endpoint is relevant to the trial’s stated aim of studying whether this transplant approach permits withdrawal of immunosuppressant medication. However, interpreting the endpoint requires the observed count and clarity about follow-up and missing outcomes. The registry record does not report the number who met the success definition, nor does it describe participant-level outcome status. As a result, the primary endpoint’s observed result and its precision are not available in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical interpretation depends on matching the method to the study design and the type of endpoint. This trial is recorded as single-group, with allocation not applicable and masking none. The primary endpoint is a count of participants meeting a binary success definition: either the participant meets the specified medication-withdrawal criterion or does not. The registry labels the primary measure as a number of participants. It does not report an observed count, an interval estimate, a test result, or a detailed statistical analysis plan.

What does a single-group result describe?

In general, a single-group analysis describes outcomes observed among participants enrolled in that group. It does not, on its own, estimate a contrast against a separate control group. A comparison requires an appropriate reference and a method that accounts for how participants entered each group. In a randomized trial, random allocation can support causal interpretation of between-group differences under suitable assumptions. That design is not recorded. Any observed outcome would therefore need to be interpreted as a description of this study group rather than a randomized comparison.

The group received a combined kidney and bone marrow transplant, and the intervention list also includes several drugs and thymic irradiation. When treatments are delivered together, an outcome cannot be attributed to one component using a single-group summary alone. The registry record does not specify treatment sequence, dose, or the exact exposure of each participant, and it does not report analyses separating component effects.

How should a confidence interval be understood?

In general, a confidence interval expresses the uncertainty around an estimate under a statistical model and its assumptions. A narrow interval indicates greater precision under that model; a wide interval indicates less precision. An interval does not guarantee that the estimate is free of bias, and it does not substitute for a suitable comparison design. The registry record does not report a confidence interval for the primary outcome, so its precision cannot be described from the available record.

For a binary outcome, a proportion and its interval may be used to describe the share meeting a definition, while a count reports the number meeting it. The primary measure is recorded as a number of participants. No conversion to a proportion is appropriate without a reported denominator and the relevant observed count. The enrollment is listed as 5, but the record does not state how many participants had evaluable primary outcomes or whether all enrolled participants contributed to a reported result.

What do the planning illustrations mean?

The registry’s planning assumptions describe illustrations based on an observed effect, not the trial’s own design. They specify a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is a stated fraction of the observed effect. Time-to-event illustrations use a total number of events, while other illustrations use participants per arm. These assumptions do not turn this single-group study into a two-arm trial, and any resulting sample-size values are planning illustrations, not observed trial findings.

In general, a sample-size calculation asks how much information a proposed study might need under stated assumptions. It is not a measure of the probability that a completed study’s finding is true. Power calculated from a design is not observed power, and a planning illustration based on an observed effect should not be read as evidence that the study was designed around that effect. The registry record does not report the trial’s own sample-size justification or statistical plan, so those should not be inferred from the planning assumptions.

Why do event counts and event rates need context?

Adverse-event summaries can be expressed as participants affected, events, or percentages. These quantities are not interchangeable: a participant may experience more than one event, and repeated events may contribute to event totals. The registry’s listed adverse-event information includes participants at risk and participants affected, as well as percentages for selected event terms. It does not explain all calculation and coding details, such as whether terms are participant-based or event-based in every summary. General interpretation should therefore distinguish the reported participant counts from the listed term percentages.

Some clinical outcomes, including survival and time to recovery, may be analyzed with time-to-event methods. In general, such methods account for the time until an event and can incorporate participants whose event time is not observed before follow-up ends. The registry lists graft survival, participant survival, and recovery times as secondary outcomes, but does not report their estimates or the methods used to analyze them. It is not possible to determine from the record whether censoring, competing events, or other time-to-event issues were addressed.

Over-dispersion is a general concern when observed variability exceeds the assumptions of a model, which can make standard errors too small and intervals too narrow if ignored. Whether it is relevant depends on the outcome and analysis model. The registry record does not report a model or dispersion estimate for these outcomes, so no conclusion about over-dispersion or its handling can be made.

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("MEDI-507")
n      <- c(5)
events <- c(3)
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  MEDI-507  5  3  60.0  14.7  94.7  23.1  88.2  22.3  88.2

11. Multiplicity, Missing Data and Analysis Populations

The registry lists eight outcome measures and two analyses. The named secondary outcomes include acute rejection, change in renal function, graft survival through 156 weeks, participant survival through 156 weeks, neutrophil recovery, platelet recovery, and clinically significant invasive or resistant opportunistic infection. The primary outcome concerns sustained withdrawal of immunosuppressant medication. Reporting multiple outcomes raises a general multiplicity issue: when many outcomes or analyses are examined, the chance of at least one apparently unusual finding can increase. Whether and how that issue was addressed is not reported in the registry record.

The registry identifies the primary analysis population as intent-to-treat. In general, an intent-to-treat approach aims to analyze participants according to their assigned or enrolled study group, regardless of subsequent treatment changes, according to the protocol’s definitions. In this single-group record, that label identifies the population for the primary outcome but does not resolve how missing endpoint data, treatment discontinuation, or early termination were handled. The specific missing-data rules and analysis procedures are not reported in the registry record.

The primary endpoint definition allows assessment up to study termination when it occurs before the specified study-week cutoff. The record does not say how participants who lacked enough follow-up, withdrew, or had unknown medication status were classified. It also does not provide outcome denominators or a participant flow description. Without those details and the observed outcome count, the extent and possible impact of missing data cannot be assessed.

The registry record does not report a prespecified multiplicity adjustment, interim analyses, imputation method, or sensitivity analysis. These omissions do not show that such procedures were absent from all study documents; they mean they cannot be evaluated from the registry record.

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: engraftment syndrome (100.0%), transplant rejection (40.0%), anaemia (20.0%), thrombotic microangiopathy (20.0%), atrial fibrillation (20.0%).

The adverse-event record is for the MEDI-507 group. It reports 5 participants at risk and 5 affected for serious adverse events, and 5 participants at risk and 5 affected for other adverse events. The serious-event terms listed are Engraftment syndrome, Transplant rejection, Anaemia, Thrombotic microangiopathy, Atrial fibrillation, and Stomatitis. Their listed percentages are 100.0%, 40.0%, and 20.0% for each of the remaining four terms, respectively.

These summaries should be read as reports of events recorded during the study, not as proof that the intervention caused them. The registry record does not report event timing, duration, recurrence, severity grading, or an assessment of causal relationship. A participant may experience more than one event, so listed event terms need not represent separate participants or mutually exclusive categories. The record’s death field is not reported in the registry record.

Adverse-event percentages are most informative when their denominator, event definition, observation period, and coding rules are clear. The record lists participants at risk and affected, but does not provide further detail on these conventions. These safety summaries therefore describe the registry’s reported information; they do not establish a comparative safety profile, especially in a single-group study without a control arm.

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

The study addresses a clinically important research question: whether a combined kidney and bone marrow transplant approach can be followed by sustained withdrawal of immunosuppressant medication. The registry defines success using a continuous period off therapy and a follow-up cutoff. That definition makes the intended primary outcome clear, but the observed number of participants who met it is not reported in the registry record.

Without that outcome result, the record does not support a conclusion about how often withdrawal was achieved, how precisely the outcome was estimated, or how the study group’s experience compares with another approach. The record’s completed status does not fill this gap. A missing result should not be interpreted as either success or failure.

Even if the primary result were available, the single-group design would limit causal interpretation. There is no randomized control arm to distinguish the study group’s outcomes from outcomes that could occur under another treatment approach. The treatment strategy also includes multiple listed interventions, so this design cannot isolate the effect of one component. Any observed outcomes would be descriptive of this group and would require careful consideration of its small enrollment and the completeness of follow-up.

The safety summaries provide information about reported adverse events in the MEDI-507 group, including the event terms and percentages listed in the registry. They do not establish that an event was caused by a study intervention, and they cannot provide a controlled comparison of harms. The registry record also does not report the results for the listed secondary measures of rejection, renal function, survival, recovery, and infection.

The appropriate interpretation is therefore bounded: the record documents the design, the endpoint definition, and selected adverse-event summaries, but it does not report the primary outcome result or the secondary outcome values. It cannot establish effectiveness, comparative benefit, or comparative safety. Further detail on participant outcomes, follow-up, and analysis would be needed to evaluate those questions.

14. Why This Trial Matters Statistically

This trial is statistically notable because its primary question concerns a sustained state over time, while the recorded primary measure is a count of participants meeting a defined withdrawal criterion. The definition specifies both the duration off immunosuppressant medication and the follow-up point at which success is assessed. These details matter: a clear endpoint definition helps readers understand what qualifies as success, even when the result itself is unavailable.

The study also illustrates the limits of evidence from a single-group design. Describing outcomes can be valuable, particularly for an approach involving combined transplantation and multiple listed interventions. But without a control arm, the observed experience cannot be separated from other explanations or directly compared with an alternative. This is a design limitation, not a defect that can be repaired by a statistical test alone.

The enrollment of 5 is important when considering precision and generalizability. In a small group, each participant’s course can have a large influence on descriptive summaries. The registry record does not report a primary outcome estimate or interval, so the actual precision cannot be quantified from the available information. Nor does the record report the trial’s own sample-size justification.

Finally, the registry lists several clinically distinct secondary outcomes and adverse-event terms. Keeping their definitions, denominators, timeframes, and analysis methods clear is central to interpreting results across such domains. Those details are incomplete in the available record. The trial therefore offers a useful case for distinguishing a carefully defined research question from the evidence needed to answer it: design and endpoint information alone do not establish the observed outcome.

15. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The main trial-specific limitation in the registry record is that it does not report the observed primary outcome. Although the success definition and timeframe are stated, the number of participants meeting the definition and any estimate of uncertainty are absent. The record also does not report the results of the listed secondary outcomes, leaving rejection, renal function, graft survival, participant survival, recovery, and infection outcomes unevaluable from this information.

The study has a single group, with no randomized comparator. Consequently, observed outcomes cannot provide a direct estimate of a difference between treatment strategies. The group received a combined kidney and bone marrow transplant, and the intervention list includes additional agents and procedures. The record does not provide enough detail to attribute outcomes to any individual component.

The enrollment is 5, which limits the amount of information available for descriptive interpretation and makes summaries sensitive to individual participant outcomes. The registry does not report detailed participant characteristics, participant flow, outcome-specific denominators, or follow-up completeness. It is therefore not possible to assess how representative the enrolled group was or how missing observations might affect results.

Additional uncertainties include the absence of a reported statistical analysis plan, sample-size justification, missing-data procedures, multiplicity approach, and detailed adverse-event definitions and attribution. The event summaries do not provide timing, recurrence, or severity grading. These limitations concern what can be evaluated from the registry record; they should not be taken as proof that the information is absent from other study documents.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Combined Kidney and Bone Marrow Transplantation to Prevent Kidney Transplant Rejection — NCT00801632.
• Registry record last updated 2015-11-10; status last verified 2015-11.
• Results first posted 2015-05-12.
• 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

NCT00801632 is a completed phase 2, single-group study titled Combined Kidney and Bone Marrow Transplantation to Prevent Kidney Transplant Rejection, with the official title Renal Allograft Tolerance Through Mixed Chimerism. Enrollment is listed as 5. The study started in 2008-12 and reached primary completion in 2014-04.

The sole listed arm received combined kidney and bone marrow transplantation. The primary outcome is the number of participants successfully withdrawn from immunosuppressant medication according to a 104-week definition, assessed through study week 208 or termination, with a listed timeframe of 48 months post-transplant. The record does not report the observed primary outcome.

Secondary outcomes cover rejection, renal function, survival, recovery, and infection. Serious and other adverse-event summaries are listed for the MEDI-507 group. The single-group design does not provide a randomized comparison, and the available record does not include the primary or secondary outcome results needed to assess efficacy or comparative effects.