Fludarabine, Rituximab, and Lenalidomide in Minimally Treated/Untreated Patients With Chronic Lymphocytic Leukemia (CLL): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Fludarabine, Rituximab, and Lenalidomide in Minimally Treated/Untreated Patients With Chronic Lymphocytic Leukemia (CLL) (NCT00536341), a na phase 1, phase 2 study. The primary outcome is Number of Adverse Events as a Measure of Safety and Tolerability.

2. Clinical Question

The study was designed as a Phase I/II investigation. Its summary describes a Phase I component followed by a Phase II examination of the regimen’s activity, reflecting uncertainty about the optimal lenalidomide dose and schedule. The registry record does not establish a comparative treatment question: the single-group design cannot directly compare the regimen with another treatment or with usual care.

For the safety question, the posted summaries describe participants affected at each dose level, including serious adverse events. These counts are descriptive. They do not, on their own, estimate how safety would differ under another regimen, and they do not establish that an event was caused by a particular drug. The primary outcome is listed for all treated patients, but a primary-outcome analysis is not reported in the registry record.

3. Trial Design

This is a completed Phase I/II, single-group study of lenalidomide, fludarabine, and rituximab in patients with chronic lymphocytic leukemia. The registry records an enrollment of 64. Allocation is listed as NA, and masking is recorded as none. There is no randomized or masked comparison group, so dose-level summaries should not be interpreted as results from a like-for-like control comparison.

The Phase I description specifies a non-stratified dose-escalation design, with at least 3 patients per dose level. Lenalidomide doses were to be escalated while the fludarabine and rituximab doses remained fixed. Safety and tolerability were to be evaluated every 2 weeks during active treatment. The registry lists results for Dose Level 1 and Dose Level 2, with 10 and 54 participants at risk, respectively. It does not report the dose values or a full account of how participants were assigned to those levels.

The brief summary describes untreated or minimally treated patients, with minimally treated patients included in Phase I only. It also describes a Phase II examination of the regimen’s activity. The description of how the Phase II regimen would be selected is incomplete in the registry record, so the selection procedure and Phase II dosing details are not reported there.

Progression-free survival and overall survival are listed as secondary outcomes. The record identifies 4 outcome measures overall, but no analysis entries are posted. The record does not report a statistical analysis plan, sample-size justification, interim analysis plan, or the detailed criteria used to move between phases or dose levels. The status is completed; completion status does not itself indicate what the results were.

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

Analysis population for the primary outcome, as defined in the registry: All treated patients

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: All enrolled and treated patients

6. Primary Endpoint

The registry lists the primary outcome as Number of Adverse Events as a Measure of Safety and Tolerability, measured over 63 months.

The primary outcome is titled “Number of Adverse Events as a Measure of Safety and Tolerability.” It is listed with participants as the unit and a number-type parameter, and its population is all treated patients. Adverse events were recorded from first treatment until 30 days after the last treatment, with assessment using Common Terminology Criteria for Adverse Events (CTCAE) version 4.0. The outcome timeframe is listed as 63 months.

Adverse-event outcomes are used in early-phase studies to characterize the kinds and frequency of harms observed while a regimen is being given and to support decisions about dose and tolerability. That general purpose does not make a count a causal comparison: without a control group, the record cannot show how the observed safety profile differs from another treatment.

The registry’s wording combines a title about the number of events with a unit of participants. Those are not interchangeable measures: a count of participants affected does not indicate how many separate events each participant experienced. The posted dose-level safety summaries report participants at risk and participants affected, but a primary-outcome analysis is not reported in the registry record. The record therefore does not clarify how the primary title’s event count was analyzed or how it relates to the participant-based safety summaries.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The design determines what statistical conclusions are possible. This trial is listed as single group, with allocation NA and no masking. General statistical principle: random allocation helps balance measured and unmeasured characteristics between treatment groups, while masking can reduce some measurement and management biases. Neither creates a control group after the fact. Here, dose-level summaries describe participants receiving the regimen at different levels; they do not provide a randomized comparison of treatment strategies.

What do the safety counts represent?

The adverse-event summaries give the number at risk and the number affected for each dose level. In general, a participant-based count records whether a person experienced an event, rather than how many event episodes occurred. A person with repeated events may still be represented once in a participant count, depending on the reporting definition. The registry record does not give enough detail to determine the exact counting rules for each summary or whether participants could contribute to multiple event terms.

The primary outcome title refers to a number of adverse events, while its unit is participants. That difference matters because event counts and participant counts answer distinct questions. Event counts can include repeated episodes; participant counts describe how many people were affected. The posted dose-level summaries are explicitly presented in terms of participants at risk and affected. A full primary-outcome analysis clarifying the measure is not reported in the registry record.

Why does the dose-escalation structure matter?

The Phase I description says lenalidomide doses were escalated while fludarabine and rituximab doses remained fixed. General statistical principle: dose-escalation studies are designed to examine safety and tolerability across dose levels, but the groups at different levels may differ in ways that are not controlled by randomization. A comparison between those levels can therefore be affected by the order of enrollment, the rules for escalation, and participant characteristics. The registry record does not describe the escalation algorithm or give the actual dose values, so those features cannot be assessed from the posted information.

The summary says safety and tolerability were evaluated every 2 weeks during active treatment. Regular assessment can support monitoring during treatment, but the record does not report the detailed assessment schedule beyond that statement, the completeness of follow-up, or how adverse events were attributed and graded in the posted summaries. Events were assessed using CTCAE version 4.0, and the stated recording period ran from first treatment until 30 days after last treatment.

How should uncertainty be understood?

General statistical principle: a confidence interval describes a range of values compatible with an estimate under the assumptions of the analysis. Its width reflects statistical precision; it does not remove design limitations or establish causation. No confidence intervals for the posted safety counts are reported in the registry record. The absence of an interval means readers cannot assess the precision of those counts through an interval estimate from this record.

General statistical principle: p-values assess how compatible data are with a specified statistical model and null hypothesis; they are not direct measures of clinical importance or proof that a result is true. No p-values or inferential analyses are posted for the outcomes. The registry record also does not report the statistical model, adjustment strategy, or a prespecified analysis plan. No assumptions about these methods should be inferred from the descriptive counts.

For count outcomes, general statistical methods may need to account for variation that is greater than a simple model expects, often called over-dispersion. That issue is relevant when analyzing event counts, but it cannot be evaluated from participant-level affected counts alone. The registry record does not report a model for the primary event outcome or enough information to assess over-dispersion.

What do the planning illustrations mean?

The planning illustrations are described as hypothetical calculations based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. They use a stated proportion of the observed effect as the target to detect. These are planning assumptions, not features established as the trial’s own design. The illustrations do not describe observed power, and their hypothetical two-arm allocation is not the single-group design recorded for this study. The registry record does not report the trial’s sample-size justification.

In general, a sample-size calculation estimates the enrollment needed under specified assumptions; it does not show that a study had adequate power after the fact. A planning calculation based on an observed effect is especially dependent on that effect estimate and does not replace a prespecified design justification. The registry record does not post the numerical outputs of those calculations in the registry record for interpretation, so no required sample size can be stated.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 4 outcome measures, including the primary safety outcome and the secondary outcomes progression-free survival and overall survival. It does not report analysis entries. Statistical interpretation therefore cannot establish which outcomes were analyzed, whether multiple time points or event definitions were tested, or whether any adjustment for multiple comparisons was used. A multiplicity plan is not reported in the registry record.

General statistical principle: when many outcomes or comparisons are examined, the chance of at least one apparently notable result can increase. Prespecifying primary and secondary outcomes and describing any adjustment helps readers understand how to interpret multiple estimates. The registry identifies a primary outcome and names secondary outcomes, but the inferential analysis details needed to assess multiplicity are not reported in the registry record. No conclusion about adjustment or selective reporting should be inferred from the outcome list alone.

Missing-data methods are also not reported in the registry record. The record does not state how participants who stopped treatment, missed assessments, or had incomplete follow-up were handled in outcome analyses. It also does not give a detailed accounting of the number assessed at each time point for the survival outcomes. Without those details, readers cannot evaluate whether missingness may have affected estimates.

The primary outcome population is described as all treated patients, but the analysis population for each secondary outcome is not reported in the registry record. General statistical principle: an analysis population definition clarifies which participants contribute to each estimate and how protocol deviations or incomplete measurements are handled. The registry’s enrollment of 64 does not by itself establish that every enrolled participant was treated, assessed for every outcome, or included in every analysis.

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

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: abdominal pain (10.0%), infections and infestations - other, pneumonia (10.0%), bronchial infection (3.7%), fever (3.7%), rash (3.7%).

For serious adverse events, the registry lists 2 affected participants among 10 at risk at Dose Level 1 and 16 among 54 at risk at Dose Level 2. For other adverse events, it lists 10 affected among 10 at risk and 54 among 54 at risk. These summaries describe participants affected, not the total number of event episodes, and they do not indicate how many events each participant experienced.

The listed serious-event terms are abdominal pain and infections and infestations - other, pneumonia, each at 10.0%; and bronchial infection, fever, rash, and white blood cell decreased, each at 3.7%. The record does not specify whether a participant could be counted under more than one term or provide a complete term-by-term accounting. The percentages should not be treated as mutually exclusive categories.

The deaths field is not populated in the posted safety summaries; death counts are not reported in the registry record. These figures do not establish that no deaths occurred. Nor do the dose-level counts establish a causal relationship between a specific drug and an event. Because the trial has no randomized control group, the counts cannot quantify excess risk relative to another treatment.

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

The record shows that this Phase I/II study evaluated a three-drug regimen in a single-group design and posted descriptive participant counts for adverse events at two dose levels. It also identifies the primary outcome as adverse events and lists progression-free survival and overall survival as secondary outcomes. The serious adverse-event summaries report 2 affected participants among 10 at risk at Dose Level 1 and 16 among 54 at risk at Dose Level 2.

Those observations do not, by themselves, establish whether the regimen is better or worse than another treatment, or whether it changes disease outcomes. There is no concurrent control group, and no analysis results for the primary outcome or the survival outcomes are reported in the registry record. The record therefore does not support a comparative estimate of benefit or harm.

The participant counts also do not identify the cause of an event. A recorded adverse event may have multiple possible explanations, and the registry summaries do not report an attribution analysis. Similarly, the absence of a posted analysis entry is not evidence that an outcome had no events or that no analysis was conducted; it means those results are not reported in the registry record.

General statistical principle: precision concerns how much uncertainty surrounds an estimate, while validity concerns whether the design and analysis support the intended conclusion. The posted counts are limited in precision because no confidence intervals are reported, and a single-group design limits comparative interpretation regardless of the count size. The record is informative as a description of the reported safety data, but it does not establish a causal treatment effect or a definitive survival result.

13. Why This Trial Matters Statistically

This study is statistically informative because it illustrates the different roles of Phase I and Phase II research. The registry describes dose escalation of lenalidomide with fixed doses of fludarabine and rituximab, followed by a Phase II examination. Early-phase studies can characterize tolerability across dose levels and inform further study, while activity assessments need outcome definitions and analyses that can be interpreted in light of the study design.

The record also illustrates why the denominator and the unit of an outcome matter. Participant-based safety counts answer how many people were affected, whereas an event count can include repeated episodes. The primary outcome title refers to the number of adverse events but lists participants as its unit. Recognizing this distinction prevents the participant counts from being mistaken for total event frequencies.

Another key statistical point is that dose-level summaries are not control-group comparisons. The study is single group, with no random allocation or masking. The two dose-level summaries are useful descriptions of the registry’s safety reporting, but they cannot isolate the effect of dose from other differences among participants or treatment exposure. This is an important distinction when reading early-phase results.

Finally, the registry identifies progression-free survival and overall survival as secondary outcomes but does not post their analyses. A named endpoint is not the same as a reported estimate. Transparent interpretation requires both an outcome definition and the results, methods, and uncertainty needed to judge that result. In this record, the descriptive safety summaries can be discussed, while the unreported analyses cannot be reconstructed or inferred.

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 important limitation is the single-group design. Without a randomized comparator, safety counts cannot show how the regimen compares with another treatment, and they cannot isolate treatment effects from participant characteristics, disease course, or other influences. The registry explicitly notes that the dose-level groups are not a like-for-like control comparison.

The record gives no actual dose values for the listed dose levels and does not fully describe the Phase II regimen selection. The Phase II arm description is incomplete, and the exact composition of each analysis population is not reported. These omissions limit assessment of exposure and of how participants entered the reported groups.

The posted safety summaries do not include confidence intervals, detailed event-level counts, exposure-adjusted rates, or a full account of event attribution. The record does not report death counts in the safety summary, detailed missing-data procedures, or an analysis plan for the primary outcome. It also does not report analyses for progression-free survival or overall survival. These results should not be inferred from the fact that the study is marked completed.

The primary outcome’s wording refers to a number of adverse events, but its unit is participants. The record does not resolve whether or how event episodes were counted in the primary analysis. In addition, the serious adverse-event terms are listed without information about overlap among terms or a full term-specific denominator. These reporting limitations restrict interpretation of the safety summaries beyond the participant counts and percentages explicitly listed.

The registry record does not report a sample-size justification, statistical analysis plan, or interim-analysis plan. The planning illustrations described elsewhere are not the trial’s own design justification and do not establish observed power. Together, these limitations mean the available information is descriptive rather than a complete inferential report.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Fludarabine, Rituximab, and Lenalidomide in Minimally Treated/Untreated Patients With Chronic Lymphocytic Leukemia (CLL) — NCT00536341.
• Registry record last updated 2017-01-16; status last verified 2016-11.
• Results first posted 2016-05-04.
• 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

NCT00536341 is a completed Phase I/II, single-group study of lenalidomide, fludarabine, and rituximab in patients with chronic lymphocytic leukemia. The registry records enrollment of 64, no masking, and allocation listed as NA. Phase I used lenalidomide dose escalation with fixed doses of fludarabine and rituximab.

The primary outcome concerns adverse events as a measure of safety and tolerability, assessed using CTCAE version 4.0 from first treatment until 30 days after the last treatment. The record lists progression-free survival and overall survival as secondary outcomes. It posts participant-based safety counts for two dose levels and selected serious-event terms, but no outcome analysis entries.

Primary and secondary outcome analyses, confidence intervals, p-values, missing-data methods, and a detailed statistical plan are not reported in the registry record. The available results support descriptive reading of the posted safety counts, not a randomized treatment comparison or a causal conclusion.