Zidovudine, Interferon Alfa-2b, PEG-Interferon Alfa-2b in Patients With HTLV-I Associated Adult T-Cell Leukemia/Lymphoma: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Zidovudine, Interferon Alfa-2b, PEG-Interferon Alfa-2b in Patients With HTLV-I Associated Adult T-Cell Leukemia/Lymphoma (NCT00854581), a non-randomized phase 4 study. The primary outcome is Number of Patients Achieving Clinical Response to Protocol Therapy Who Lack IRF-4 and/or c-Rel Expression..

2. Clinical Question

3. Trial Design

This is a Phase 4, non-randomized, unmasked, sequential study sponsored by the University of Miami. The registry record lists 13 participants enrolled and gives the study status as terminated. The recorded start is 2007-11, and primary completion is recorded as 2011-06. A reason for termination is not reported in the registry record.

The treatment plan has an induction phase followed, for participants meeting response criteria, by maintenance. The induction description says participants move to maintenance if they achieve CR or PR. It also describes a Day 14 response assessment for participants achieving a clinical CR. Part 1 Maintenance is described as extending from Treatment Day 14 or 21 to the start of Month 3 (Day 60), and eligibility is again tied to CR or PR after induction.

The later maintenance descriptions distinguish participants by disease response and molecular findings. Part 2A is for participants described as achieving CR with undetectable clonal disease. Part 2B is for participants described as achieving CR with minimal residual disease by multiplex PCR or PR in Part 1. The descriptions include zidovudine and PEG-interferon alfa-2b, with valproic acid also listed for Part 2B. The full dosing details for some phases are incomplete in the registry record, so the regimen should not be reconstructed beyond those descriptions.

Because treatment is sequential and not randomized, the maintenance groups are defined by earlier response and disease status. They are not independent treatment arms assigned at baseline. Differences among their reported event counts cannot establish comparative treatment effects. Masking is listed as none. The registry record does not report a control group, a detailed statistical analysis plan, or a reason for the sequential design.

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.

Induction (Up to Day 21)

Reasons for not completing this period:

Part 1 Maintenance (Up to Day 60)

Part 2 Maintenance (Up to 12 Months)

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: All participants who had a treatment response (PR or CR)

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 Achieving Clinical Response to Protocol Therapy Who Lack IRF-4 and/or c-Rel Expression., measured over Up to 12 months post-initiation of protocol therapy.

The primary endpoint is the number of patients who achieved clinical response to protocol therapy and lacked IRF-4 and/or c-Rel expression. Clinical response is defined as CR plus PR, with response assessed according to the adult T-cell leukemia/lymphoma consensus report identified in the record. The record also describes imaging assessment using Cheson criteria. CR requires disappearance of clinical, microscopic, and radiographic evidence of disease; PR requires a reduction in measurable disease and abnormal peripheral-blood lymphocyte count. A response had to persist for at least 4 weeks.

The endpoint is intended to describe a molecular characteristic among clinical responders, rather than to count every enrolled participant as an endpoint event or non-event. This makes the eligible population important: the primary population is participants who had PR or CR. The record specifies an assessment timeframe of up to 12 months after protocol therapy began, but it does not give the observed endpoint count, the number of responders assessed, or an estimate of uncertainty.

In general, pairing clinical response with a biomarker can describe whether a molecular feature is present among people meeting a clinical response definition. It does not by itself show that the biomarker caused response, predicts response in other patients, or distinguishes treatment-sensitive from treatment-resistant disease. The registry record does not report an analysis establishing any such relationship.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

General: what a count endpoint says. The primary endpoint is a count of participants who satisfy two conditions: they had a clinical response, and they lacked IRF-4 and/or c-Rel expression. A count communicates how many participants met the endpoint definition, but its interpretation depends on the population assessed and the number with evaluable biomarker information. In this record, the eligible population is described as participants with CR or PR. The endpoint result and the number assessed are not reported in the registry record.

General: uncertainty around a count. Statistical uncertainty describes how much an estimate might vary across comparable samples. For a binary outcome such as whether a participant meets an endpoint definition, an analysis might report a proportion and a confidence interval. A confidence interval is a range of values compatible with the data and the stated method; it is not a guarantee that the true value lies in that range. No such estimate or interval is reported for the primary endpoint, so its precision cannot be assessed from the registry record.

General: the importance of the denominator. A count alone does not indicate how common an outcome was unless the relevant number assessed is also known. For this endpoint, the denominator would need to reflect the participants meeting the response condition who were evaluated for biomarker expression. The registry record identifies responders as the endpoint population but does not report the number of responders or the number with biomarker assessments. It would be inappropriate to substitute the overall enrollment count for that missing endpoint denominator.

General: selection into sequential phases. In a sequential treatment design, participants may enter later phases based on earlier outcomes. Here, the maintenance descriptions specify eligibility according to CR or PR and, in later phases, molecular disease status. This means that participants in a later phase have already passed through a selection process. A comparison of outcomes between phases would mix treatment differences with differences in who qualified for each phase. Randomization can help balance measured and unmeasured baseline factors between groups; this study is listed as non-randomized and does not provide that protection for phase comparisons.

General: response definitions. Consistent response criteria can make outcome classification more reproducible. The record refers to consensus criteria and to Cheson criteria for imaging. It defines CR and PR and requires a response to persist for at least 4 weeks. Those definitions clarify what constitutes clinical response, but the record does not report the number of participants classified as CR, PR, or non-responders. Nor does it report how response assessments were handled when information was incomplete or not evaluable.

General: biomarker interpretation. A biomarker endpoint can characterize disease biology, but its interpretation depends on assay methods, timing, and the handling of missing or ambiguous measurements. The primary endpoint refers to lack of IRF-4 and/or c-Rel expression. Detailed assay procedures, rules for combining the two markers, and the number of evaluable samples are not reported in the registry record. Without those details and the endpoint result, reproducibility and the precision of the biomarker finding cannot be assessed.

General: descriptive safety counts. Event counts by treatment phase are useful for describing what was recorded in each phase. They are not automatically comparable rates. The number at risk, duration of exposure, event definitions, and participant movement between phases matter when comparing groups. A participant may also contribute to more than one sequential phase. The record gives at-risk counts and affected counts for serious and other events, but does not provide exposure-adjusted analyses or explain whether phase counts overlap at the participant level.

General: power and sample-size planning. A sample-size calculation is a planning exercise based on assumptions about the outcome, effect to detect, significance level, allocation, and statistical method. It is not evidence that a study had a particular probability of detecting an effect after the results are known. The record does not report a trial-specific sample-size justification or analysis plan. Any planning illustration based on an observed effect would be distinct from the original design rationale and should not be described as observed power. No numeric planning estimates are reported in the registry record.

General: analysis transparency. Statistical interpretation usually depends on knowing the analysis population, endpoint handling, model, and uncertainty estimates. The registry record lists no analyses and reports no primary endpoint estimate. It does not report whether analyses were adjusted, whether there were interim analyses, or how missing data were handled. These omissions mean the displayed outcome definitions and event counts cannot be used to reconstruct an inferential analysis.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists seven outcome measures, including the primary clinical-response and biomarker endpoint and the secondary outcomes failure-free survival and overall survival. It reports zero analyses. No multiplicity strategy is reported in the registry record. In general, when several outcomes or repeated statistical tests are evaluated, the chance of at least one apparently notable result can increase; multiplicity methods can address that issue. Without reported analyses or a stated approach, it is not possible to determine whether or how multiplicity was considered.

Missing-data methods are not reported in the registry record. The primary endpoint depends on both clinical response status and biomarker information, so missing response assessments or unevaluable biomarker measurements could affect who is included in the endpoint denominator. The record does not state whether participants with missing measurements were excluded, classified in a particular way, or handled through another method. It also does not report the number with missing or unevaluable data.

The endpoint population is described as all participants who had a treatment response, meaning CR or PR. The record does not report a broader analysis population for the primary endpoint, such as all enrolled participants, or explain how participants without response assessments were treated in analyses. It also does not report whether safety counts include all treated participants or only participants entering each phase beyond the at-risk figures shown in the event record.

In general, an analysis population should be defined before interpreting an estimate because different inclusion rules can produce different results. Here, the listed endpoint population is clear at a broad level, but the actual analyzed population and the handling of missing outcomes are not reported in the registry record. No adjustment for multiple outcomes, missingness, or analysis-population differences can be assumed.

11. 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 serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: infection, catheter-related (50.0%), nausea (50.0%), renal failure (50.0%), sepsis (50.0%), urinary tract infection (50.0%).

The registry record reports adverse-event counts by treatment phase. During Induction Therapy, 2 serious events affected 13 participants at risk, and 12 other events affected 13 at risk; 5 deaths are listed. For Part 1 Maintenance, the corresponding counts are 1 serious event among 7 at risk, 2 other events among 7 at risk, and 2 deaths. For Part 2A Maintenance, they are 1 serious event among 2 at risk, 1 other event among 2 at risk, and 0 deaths. For Part 2B Maintenance, they are 1 serious event among 3 at risk, 3 other events among 3 at risk, and 1 death.

These are descriptive counts, not evidence that treatment caused an event or death. The record does not report causality assessments, exposure-adjusted rates, or enough detail to establish whether participants counted in one phase also contributed to later phases. The groups differ in size and are defined by progression through the treatment sequence, so their counts should not be treated as a randomized safety comparison.

The record lists Infection, Catheter-related; Nausea; Renal failure; Sepsis; Urinary tract infection; and Vomiting among the top serious-event terms, each with 50.0%. The denominator and precise interpretation of these percentages are not reported in the registry record. They should not be read as percentages of all 13 enrolled participants. The event listings describe reported safety information, not an estimate of treatment-attributable risk.

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

The posted results describe a study of zidovudine and interferon-based therapy organized into induction and response-dependent maintenance phases. The primary question is molecular: among participants with a clinical response, how many lacked IRF-4 and/or c-Rel expression? The registry record defines that endpoint and its assessment period, but does not report the observed count, the number assessed, or an uncertainty estimate. Consequently, the endpoint’s magnitude and precision cannot be stated.

The study is non-randomized and sequential. That design can describe treatment delivery and outcomes within the enrolled group, but it does not provide a randomized estimate of comparative treatment effect. In particular, later maintenance groups are selected according to response and molecular disease status. Their outcomes cannot be interpreted as if participants had been assigned to otherwise equivalent groups at the outset.

The safety information consists of phase-specific counts and a list of serious-event terms with associated percentages. These data do not establish that treatment caused the events. Differences among phases may reflect selection, group size, exposure duration, or other factors that are not resolved by the reported counts. The registry record does not report the denominator for the serious-event percentages or an exposure-adjusted analysis.

The record also does not report results for failure-free survival or overall survival, despite listing them as secondary outcomes. It provides no p-values, confidence intervals, or analysis results. Therefore, the available registry information cannot establish whether the regimen improved clinical outcomes, whether the biomarker characteristic is associated with response, or how precise any such association might be.

These limitations do not make the endpoint definitions or safety counts meaningless: they identify what the study intended to assess and what events were recorded by phase. They do set boundaries on interpretation. The registry record supports a description of the study design and reported counts, not a claim of efficacy, lack of efficacy, comparative safety, or validated biomarker prediction.

13. Why This Trial Matters Statistically

This study illustrates why the connection between an endpoint and its analysis population matters. The primary outcome is not simply clinical response: it is the number of clinical responders who also meet a biomarker condition. A clear response definition is useful, but the result still requires the number of responders assessed and the number with evaluable biomarker data. Those outcome counts are not reported in the registry record.

It also highlights a key issue in sequential studies. Later treatment phases are reached only after earlier response and disease-status assessments. That structure can be appropriate for describing a treatment pathway, but it means phase groups are selected rather than exchangeable. Statistical comparisons across them cannot be interpreted like randomized comparisons, and simple counts cannot separate treatment effects from selection or exposure differences.

The safety record provides another practical lesson: event counts need context. At-risk counts differ across phases, and deaths are listed alongside serious and other adverse events. Without event attribution, duration of exposure, and information on participant overlap, these figures should remain descriptive. Percentages for serious-event terms also require a clear denominator to be interpretable as risks.

Finally, the record shows the distinction between an outcome being registered and an outcome being reported with an analysis. The registry lists multiple outcomes, but no analyses and no primary endpoint result. Without estimates and uncertainty measures, readers cannot assess the size or precision of the intended biomarker finding. These are broadly relevant statistical considerations for clinical studies with response-conditioned endpoints, sequential treatment, and incomplete outcome reporting.

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 most direct limitation is that the registry record does not report the primary endpoint result. It also does not give the number of participants who achieved CR or PR, the number with biomarker assessments, or the number included in an analysis. The study enrolled 13 participants overall, but overall enrollment cannot substitute for the endpoint-specific denominator.

The non-randomized sequential design limits causal and comparative interpretation. Eligibility for maintenance depends on earlier response and, for later phases, molecular disease status. Participants in different phases are therefore selected groups. The record does not describe a concurrent randomized comparator, and the treatment arms are not a like-for-like control comparison.

Several elements needed to assess reproducibility and potential bias are not reported in the registry record. These include a detailed statistical analysis plan, the handling of missing or unevaluable endpoint data, the biomarker assay procedures and combination rules, and any interim analyses. The reason for the terminated status is also not reported. The full dosing descriptions for some phases are incomplete in the registry record.

The safety data are presented as phase-specific counts, but the record does not report event attribution, duration of exposure, participant overlap across phases, or exposure-adjusted analyses. The denominators for the listed serious-event percentages are not reported. These limitations prevent direct risk comparisons across phases and prevent interpreting the reported events as treatment-caused.

Although failure-free survival and overall survival are listed as secondary outcomes, their results are not reported. No effect estimates or uncertainty measures are reported for the listed outcomes. These reporting gaps mean that the study’s clinical and molecular findings cannot be evaluated quantitatively from the registry record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Zidovudine, Interferon Alfa-2b, PEG-Interferon Alfa-2b in Patients With HTLV-I Associated Adult T-Cell Leukemia/Lymphoma — NCT00854581.
• Registry record last updated 2018-04-17; status last verified 2017-12.
• Results first posted 2015-01-06.
• 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

NCT00854581 is a Phase 4, non-randomized, unmasked, sequential study sponsored by the University of Miami. The registry record lists 13 participants enrolled, a start of 2007-11, primary completion of 2011-06, and terminated status. The study concerns HTLV-I-associated adult T-cell leukemia/lymphoma and evaluates protocol therapy involving zidovudine and interferon-based treatment, with valproic acid also listed.

The primary endpoint is the number of clinical responders who lack IRF-4 and/or c-Rel expression, assessed up to 12 months after treatment initiation. The registry record defines response but does not report the primary endpoint result or any analyses. Failure-free survival and overall survival are listed as secondary outcomes without reported results. Adverse-event counts are listed by treatment phase, but they do not establish treatment causation or support randomized comparisons.