Treosulfan and Fludarabine in Treating Younger Patients Who Are Undergoing a Donor Stem Cell Transplant for Acute Myeloid Leukemia, Acute Lymphoblastic Leukemia, or Myelodysplastic Syndrome: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Treosulfan and Fludarabine in Treating Younger Patients Who Are Undergoing a Donor Stem Cell Transplant for Acute Myeloid Leukemia, Acute Lymphoblastic Leukemia, or Myelodysplastic Syndrome (NCT00253513), a non-randomized phase 1, phase 2 study. The primary outcome is Number of Patients Experiencing Regimen-related Toxicity Events in Study Population.

2. Clinical Question

The clinical question is about toxicity in the setting of a particular conditioning regimen and donor transplant. It is not a randomized comparison of treosulfan and fludarabine against another regimen, nor does the record provide a control group receiving transplantation without these drugs. As a result, the registered design can describe outcomes in the treated study population, but cannot by itself isolate the regimen's effect relative to an alternative.

The record also lists being without disease at one year as a secondary outcome related to disease-free survival. That is a separate clinical question from the primary toxicity outcome. Its result is not reported in the registry record. The study purpose mentions assessing how well the regimen works, but the posted information does not include efficacy results that would answer that question.

The record names acute myeloid leukemia, acute lymphoblastic leukemia, and myelodysplastic syndrome as the conditions of interest. It does not report how participants were distributed among those diagnoses, nor does it specify the study population's age range in the information available for this analysis. Those omissions limit how narrowly the population can be characterized.

3. Trial Design

This completed study is registered as phase 1 and phase 2, with non-randomized allocation, no masking, and a single-group model. The registry lists enrollment of 60. Participants received a conditioning regimen of treosulfan and fludarabine in the context of allogeneic blood or bone marrow transplantation. The sponsor is OHSU Knight Cancer Institute.

A single-group design observes outcomes in participants who receive the study regimen; it does not provide a concurrent control group. Non-randomized allocation means there was no random assignment to competing treatment strategies in this registered study. With no comparator, outcomes cannot be interpreted as a direct estimate of how the regimen differs from another conditioning approach. Differences in patient characteristics, transplant circumstances, or other care could not be separated from treatment effects through a randomized comparison in this design.

No masking was registered. The registry record does not describe whether outcome assessment used independent reviewers or other procedures to reduce the influence of knowledge about treatment. It also does not report detailed eligibility criteria, the planned regimen schedule, the transplant donor criteria, or a sample-size justification. These details should not be inferred from the trial title or general study purpose.

The primary outcome is described as the number of participants experiencing regimen-related toxicity in major organ systems. Its description specifies assessment from day minus 6 to day 28, while the listed timeframe reads “34 days and 2 years.” The record does not clarify the relationship between those timeframe statements. A secondary outcome concerns participants without disease at one year as an indicator of disease-free survival.

The registry marks the study completed and lists 60 as enrollment. Completion status and enrollment do not establish that all planned outcomes were measured or reported. The registry record lists four outcome measures, but no outcome analyses are reported. Detailed results for the primary endpoint and the secondary disease-free outcome are not reported in the registry record.

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

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 Experiencing Regimen-related Toxicity Events in Study Population, measured over 34 days and 2 years.

The primary outcome is the number of participants experiencing regimen-related toxicity affecting major organ systems. The registry description names cardiac, bladder/renal, pulmonary, hepatic, neurologic, and gastrointestinal systems, and describes toxicity assessment from day minus 6 to day 28. The listed timeframe is “34 days and 2 years”; the record does not explain how that timeframe relates to the specified assessment window. The outcome title also refers to “34 days and 2 years,” so the intended timing should be read with that ambiguity in mind.

The registry describes the outcome as a count of participants and a proportion. A count communicates how many participants met the toxicity definition; a proportion relates that count to the population assessed. These summaries can help readers understand the observed burden of a defined toxicity outcome in the study group. They do not, on their own, show whether the regimen caused the events or how the risk compares with another regimen.

Organ toxicity is relevant to a conditioning regimen because the outcome concerns harms affecting major systems during the transplant treatment period. However, interpretation depends on how toxicity was defined, graded, collected, and attributed to the regimen. Those operational details are not reported in the registry record beyond the named systems and assessment window. Most importantly, the registry record does not report a primary endpoint result, so the occurrence of this outcome cannot be quantified from the posted information.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a single-group study estimate?

In general, a single-group clinical study describes outcomes among participants who receive the study intervention. Its event count or proportion can characterize what was observed in that group, provided the outcome definition and denominator are clear. Without a comparator group, the estimate does not directly measure a difference between treatment strategies. It cannot separate the effect of the regimen from the natural course of disease, transplantation, participant characteristics, or other care.

This distinction matters for the current record. The study is registered as single-group and non-randomized, with no masking. The posted safety fields are observations in the treosulfan and fludarabine conditioning group. They are not a randomized contrast, and the record does not provide an alternative regimen's event count. A within-group summary should not be described as proof of benefit or harm relative to another treatment.

What does a count or proportion communicate?

In general, a count gives the number of participants meeting an outcome definition. A proportion places that count in relation to the number assessed, which helps contextualize how common the outcome was in the observed group. Interpretation relies on a clearly defined population, event rule, and assessment period. If participants have incomplete assessments or different follow-up, the denominator and handling of missing observations also matter.

The registry describes the primary measure as a number of participants and a proportion, and names regimen-related toxicity in major organ systems. It does not report the primary result, an analysis population, or how missing assessments were handled. The safety fields separately report participants at risk and participants affected. Those safety summaries should be read according to their own labels, not assumed to be interchangeable with the primary endpoint.

Why is the assessment window important?

In general, an outcome's time window determines which events are eligible to count. A toxicity measure collected during a specified period answers a different question from an outcome accumulated across longer follow-up. A time-to-event outcome also requires a definition of when follow-up begins, how events and censoring are handled, and when observation ends. Without those details, readers cannot determine how the reported timeframe maps to each participant's observation.

Here, the primary outcome description specifies major-organ toxicity from day minus 6 to day 28, while its listed timeframe is “34 days and 2 years.” The registry does not clarify that wording. The record also gives one year as the timing for a secondary disease-free outcome. These details should not be blended into a single follow-up period or used to infer an analysis method that is not stated.

What role does randomization play?

In general, random assignment helps balance measured and unmeasured participant characteristics across treatment groups, on average. That makes a between-group comparison more informative about treatment effects than a comparison of separately selected groups, although randomization does not resolve every design or measurement concern. Non-randomized studies may still provide useful descriptive information, but treatment selection and participant characteristics can be entangled with outcomes.

The registered study is non-randomized and has a single group, so it does not estimate a randomized treatment contrast. No masking was registered. Masking can reduce some forms of influence in treatment delivery or outcome assessment, depending on what is masked and how outcomes are measured. The registry record does not describe additional safeguards or independent outcome adjudication, so none should be assumed.

How should uncertainty be understood?

In general, an estimate from a sample is subject to uncertainty. A confidence interval expresses that uncertainty under the assumptions of the analysis; it is not a guarantee that the true value falls within the interval. The width reflects both the amount of information and the variability of the outcome, as well as the chosen method. A point estimate without an interval can hide substantial uncertainty, particularly for uncommon events.

No confidence interval or primary endpoint analysis is reported in the registry record. Thus, the precision of the primary toxicity estimate cannot be evaluated. The adverse-event fields include counts, but the record does not provide uncertainty intervals for them. Their descriptive character should not be expanded into claims about comparative risk or certainty.

Why can over-dispersion matter?

In general, over-dispersion occurs when observed variability in count data is greater than a statistical model expects. If ignored, a model may understate uncertainty and make estimates appear more precise than warranted. Appropriate approaches depend on the outcome structure, the source of extra variation, and the study design. This is a general statistical consideration, not a method reported for this trial. The registry record does not describe an over-dispersion assessment or count-model analysis.

The primary outcome is described as participants with an event, rather than a repeated-event rate or event count per person. The record does not report enough detail to determine whether events were counted once per participant, how multiple organ toxicities were treated, or what model was planned. Those details should not be inferred from the outcome title.

What do planning calculations mean?

In general, sample-size calculations are planning exercises based on assumptions about a target effect, variability, significance level, allocation, and analysis method. They describe the sample size that a hypothetical future design might require under those assumptions. They are not observed power and do not show that the completed study had a particular probability of detecting an effect.

The registry record does not report a sample-size justification or the trial's original design assumptions. Any planning illustration associated with the posted results is explicitly separate from the trial's own design. Its assumptions include a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect defined as a stated fraction of the observed effect. Such an illustration does not change the fact that this trial was single-group and non-randomized, and should not be read as an analysis of its observed outcomes.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists four outcome measures and identifies regimen-related toxicity as the primary outcome. It also lists being without disease at one year as a secondary outcome. No outcome analyses are reported. The record does not describe a statistical analysis plan, a hierarchy of secondary outcomes, or an adjustment for testing multiple outcomes. Whether any multiplicity procedure was planned is not reported in the registry record.

In general, multiplicity arises when several outcomes, time points, subgroups, or statistical tests are examined. Looking across many tests can increase the chance of a seemingly notable finding arising by chance. Prespecifying a primary outcome and an analysis hierarchy, or using an appropriate adjustment, can help readers understand how the study addresses that issue. The registry information does not establish what approach, if any, was used.

Missing-data handling is also not described. The record does not report how participants with incomplete toxicity assessments, unavailable follow-up, or missing disease-status assessments were treated. It does not report analysis populations, such as whether outcomes were evaluated among all enrolled participants or a defined subset. The enrollment figure should not be assumed to be the denominator for every outcome.

In general, missingness can affect both the estimated event frequency and its uncertainty. The impact depends on why information is missing and how analysis handles it. Without participant flow, outcome-specific denominators, and a stated missing-data method, readers cannot assess that impact for the primary or secondary outcome. These analysis details are not reported in the registry record.

11. 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

Serious events with the highest arm-level rate: death - cgvhd (3.3%), death - fungal infection (3.3%), grade 4 mucositis (1.7%), death - intracranial hemmorrage (1.7%).

The serious adverse event fields for the Treosulfan and Fludarabine Conditioning group list 60 participants at risk and 5 affected. The other adverse event fields list 60 at risk and 0 affected. These are the registry's safety summaries; they should not be confused with the primary endpoint, whose result is not reported. The record does not clarify whether the safety definitions and follow-up match the primary toxicity measure.

The listed serious terms are “Death - cGVHD” at 3.3%, “Death - fungal infection” at 3.3%, “Grade 4 mucositis” at 1.7%, and “Death - intracranial hemmorrage” at 1.7%. These terms and percentages should be read as the specific entries recorded, not as a complete account of every event or as a comparative risk estimate. In general, event terms may not be mutually exclusive, so their percentages should not be added to create a total.

The separate deaths field is not reported in the registry record. Although some listed terms refer to death, the record does not provide further details about attribution, timing, adjudication, or overlap among terms. No causal conclusion about the conditioning regimen follows from these entries alone. The single-group design provides no control-group rate for comparison.

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

The registry record documents a completed, single-group study of treosulfan and fludarabine conditioning in the setting of allogeneic transplantation for acute leukemia or myelodysplastic syndrome. It identifies regimen-related toxicity in major organ systems as the primary outcome and includes limited adverse-event summaries. The serious adverse event fields record 5 affected participants, and the other adverse event fields record 0 affected participants; the listed serious terms include the percentages reported in the record.

Those observations do not answer the primary endpoint question because its result is not reported in the registry record. They also do not establish how the listed safety fields relate to the primary outcome's definition and assessment window. The one-year disease-free outcome is listed as secondary, but its result is not reported. The study's stated purpose is not a substitute for outcome data.

The design cannot support a direct comparison with another conditioning regimen. It has no control group, and participants were not randomly allocated between treatment strategies. Consequently, the event summaries cannot show whether the regimen caused a particular event, increased or reduced risk relative to another approach, or changed disease-free status. Such conclusions require suitable comparative data and a defined analysis.

In general, interpreting clinical results also requires information about eligibility, participant flow, outcome definitions, follow-up, analysis populations, missing data, and uncertainty. Important details of these kinds are not reported in the registry record. The record's enrollment and completion status do not fill those gaps or establish that every planned assessment was completed.

The appropriate reading is therefore bounded: the registry identifies the regimen, design, outcomes, and certain safety entries, but does not provide the primary or secondary outcome analyses needed to assess the study's clinical results. These data can be used to understand what the study was designed to examine and what safety entries were recorded; they cannot establish treatment efficacy or comparative safety.

13. Why This Trial Matters Statistically

This trial is statistically informative as an example of the distinction between a study's objective and the results needed to answer it. The registry identifies a primary toxicity outcome with named organ systems and an assessment period, but does not report the primary result or an analysis. A clearly stated endpoint is necessary for interpretation, yet endpoint definition alone cannot establish the observed event frequency or its precision.

The design also makes the limits of descriptive evidence visible. A single-group, non-randomized study can report what occurred among participants receiving a regimen. It cannot provide the same comparative evidence as a randomized study with a suitable control group. This distinction is especially important when a study purpose uses broad language about how well a treatment works: without the relevant outcome results and a comparison strategy, that purpose remains a question rather than a conclusion.

The safety entries illustrate why event summaries need context. Counts and listed terms can describe recorded events, but readers also need the outcome definitions, follow-up, attribution procedures, denominator rules, and handling of missing information. Without those elements, the data cannot be interpreted as a complete risk profile or compared reliably with another treatment.

Finally, the record highlights the value of transparent reporting. Analysis populations, statistical methods, multiplicity handling, uncertainty intervals, and missing-data procedures are not reported in the registry record. Their absence limits assessment of precision and robustness, regardless of whether the study itself was completed. For biostatisticians and clinical researchers, the key lesson is to distinguish design, outcomes, and reported analyses, and to avoid treating the first two as a substitute for the third.

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.

The principal limitation for interpreting this trial record is the absence of a reported primary outcome analysis. The registry identifies regimen-related toxicity as the primary measure but does not report how many participants met that endpoint or provide an estimate of its precision. The listed safety fields are not established as equivalent to that endpoint.

The design is single-group and non-randomized, with no masking. There is no concurrent comparator for estimating relative safety or efficacy, and no random allocation to balance participant characteristics across treatment strategies. These features limit causal and comparative interpretation even if descriptive results are available.

Several details needed to understand the outcomes are not reported in the registry record. These include detailed eligibility criteria and age range, outcome definitions beyond the named organ systems, the method for attributing toxicity to the regimen, outcome-specific denominators, analysis populations, participant flow, and missing-data handling. The primary outcome description specifies day minus 6 to day 28, while the listed timeframe is “34 days and 2 years”; the record does not clarify this discrepancy in wording.

The registry does not report a statistical analysis plan, a sample-size justification, inferential analyses, confidence intervals, or an approach to multiplicity. The one-year disease-free outcome is listed but its result is not reported. The separate deaths field is also not reported in the registry record, despite death-related terms appearing in the serious adverse event entries.

These gaps mean the posted information cannot establish the complete safety experience, the precision of the primary outcome, or the efficacy of the regimen. They should not be filled by assumptions about customary transplant practice or methods used in similar studies.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Treosulfan and Fludarabine in Treating Younger Patients Who Are Undergoing a Donor Stem Cell Transplant for Acute Myeloid Leukemia, Acute Lymphoblastic Leukemia, or Myelodysplastic Syndrome — NCT00253513.
• Registry record last updated 2012-06-01; status last verified 2011-02.
• Results first posted 2011-02-11.
• 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.

18. Record Summary

NCT00253513 is a completed phase 1 and phase 2, non-randomized, unmasked, single-group study sponsored by OHSU Knight Cancer Institute. The registry lists enrollment of 60. The intervention combines treosulfan and fludarabine conditioning with allogeneic blood or bone marrow transplantation for patients with acute myeloid leukemia, acute lymphoblastic leukemia, or myelodysplastic syndrome.

The primary outcome concerns the number of participants experiencing regimen-related toxicity in major organ systems. The description specifies day minus 6 through day 28, while the listed timeframe is “34 days and 2 years.” The record also lists a secondary outcome of being without disease at one year.

The registry does not report outcome analyses or the primary and secondary results. Safety fields list 5 participants affected by serious adverse events and 0 affected by other adverse events, with serious terms and percentages recorded separately. The single-group design does not provide a randomized comparison, and the posted information does not establish treatment efficacy or comparative safety.