A Study of Rituximab (MabThera) in Participants With Chronic Lymphocytic Leukemia (CLL): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study of Rituximab (MabThera) in Participants With Chronic Lymphocytic Leukemia (CLL) (NCT02533401), a na phase 2 study. The primary outcome is Percentage of Participants With Death or Disease Progression.

2. Clinical Question

3. Trial Design

This was a phase II, multicenter, single-arm study of rituximab plus fludarabine and cyclophosphamide as first-line treatment in participants with B-cell CLL. The registry lists the study as completed, with an enrollment of 34. The study began in 2006-02, and primary completion is recorded as 2014-12. These dates describe the registry record; they do not by themselves explain how long each participant was followed.

The study has one named treatment arm: Rituximab + Fludarabine + Cyclophosphamide. The arm description gives treatment details for the first cycle, including rituximab on Cycle 1 Day 1 and fludarabine and cyclophosphamide on Days 2 to 4 of Cycle 1. It also describes rituximab dosing in milligrams per meter-squared, administered intravenously. The registry text available for this analysis ends partway through the treatment description, so the complete regimen schedule is not reported in the registry record.

Allocation is listed as not applicable, consistent with the single-group design, and masking is listed as none. There is no randomized control group. The study can describe outcomes and adverse events observed among enrolled participants, but this design does not isolate the treatment’s effect from other explanations for those observations. The registry identifies the study as evaluating efficacy and safety; it does not report a comparison against another treatment.

The primary endpoint was defined as the percentage of participants with death or documented disease progression during follow-up, assessed up to 5 years from baseline. The registry lists the primary population as all participants enrolled. Although the record lists 5 outcome measures, it reports no analysis count and does not give an observed result for the primary endpoint in the information available for this analysis. Details such as the protocol’s sample-size justification and planned statistical analysis 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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: All Participants Enrolled.

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 Participants Enrolled: All participants who complied with selection criteria at enrollment.

6. Primary Endpoint

The registry lists the primary outcome as Percentage of Participants With Death or Disease Progression, measured over Up to 5 years (from Baseline until disease progression or death, whichever occurred first).

The primary endpoint is the percentage of participants who experienced death or documented disease progression at any time during the study. The stated timeframe is up to 5 years from baseline, ending at disease progression or death, whichever occurred first. The population is all participants enrolled.

The registry describes disease progression using standardized criteria. A progression event could be identified by at least a 50% increase in the longest diameter of at least two enlarged lymph nodes, an increase in spleen and/or liver size by at least 2 centimeters from baseline as assessed by measurement below the costal margin, or at least a 50% increase in the number of circulating lymphocytes. Death is included as an event alongside documented progression.

This type of endpoint is used to capture clinically important worsening or death in a single outcome measure. It is a binary event outcome: each participant either meets the definition during the specified follow-up or does not. A percentage can describe how common the event was in the study population, but its interpretation depends on having a reported numerator, denominator, and clear handling of participants without complete follow-up.

The registry record provides the endpoint definition and timeframe but does not report the observed percentage, event count, confidence interval, or a statistical test for this primary outcome. The endpoint’s definition alone cannot show how frequently the event occurred.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Understanding the statistical meaning of this study starts with its design. The registry identifies a phase II, single-group study with one treatment arm and no masking. There is no randomized allocation and no separate control arm. The design therefore supports descriptive summaries of what was observed among enrolled participants. It does not produce a randomized estimate of the difference between the regimen and another treatment.

What a single-arm percentage can tell readers

The primary outcome is a percentage of participants with death or documented disease progression during the stated follow-up. In general, a percentage for a binary outcome summarizes the share of a defined population that experienced the event. Its interpretation relies on knowing which participants were included and how event status was determined. The registry names all enrolled participants as the primary population, but does not report the event count or observed percentage. As a result, the endpoint’s definition can be explained, but its frequency cannot be interpreted from this record.

A single-arm event percentage is not the same as a comparative treatment effect. To estimate a treatment contrast, results from a comparator group are generally needed, ideally one made comparable through random assignment. Here, no such group is listed. Even if the primary percentage were reported, it would describe the enrolled group’s experience and would not on its own show what would have occurred under another treatment or without the regimen.

Why uncertainty matters

General statistical interpretation considers both the estimated outcome and its uncertainty. A confidence interval is a range of values compatible with the data under a specified statistical procedure. A narrower interval generally indicates greater precision, while a wider interval indicates more uncertainty. The registry information for this analysis does not report a primary endpoint estimate or confidence interval, so neither the event frequency nor its precision can be assessed.

A p-value is another general statistical tool. It summarizes how compatible observed data are with a specified null hypothesis under the assumptions of a statistical test. It does not measure the size or clinical importance of an effect. No primary endpoint p-value or analysis is reported in the registry record, and there is no listed comparator for a treatment-effect test. No conclusion about statistical significance can be drawn from the endpoint description.

Time-to-event outcomes and the posted endpoint

The endpoint includes events occurring during follow-up, with a stated period of up to 5 years from baseline. The registry describes a percentage of participants with an event, rather than reporting a time-to-event estimate. In general, time-to-event methods can account for differences in follow-up time and participants whose event status is not observed throughout the full period. Whether those methods were used, and how censoring or incomplete follow-up was handled, is not reported in the registry record.

The registry defines progression using specified changes in lymph nodes, spleen and/or liver size, or circulating lymphocytes. A clear definition helps distinguish endpoint events from other clinical observations. Still, the record does not provide the actual adjudication process, the number of participants meeting each component, or whether death and progression were analyzed separately as well as together.

Reading the safety figures

The safety information distinguishes participants at risk from participants affected, and lists selected serious adverse-event terms as percentages. These are descriptive quantities. A participant count affected by an event is not the same as a count of event episodes; an individual may experience more than one event. The registry information does not explain whether the term percentages count participants, episodes, or another unit, so those details should not be inferred beyond their presentation as serious adverse-event percentages.

General statistical methods for event counts may need to account for over-dispersion, which occurs when variability is greater than a simple model assumes. That concern is most relevant when analyzing counts of repeated events, rather than just whether each participant had an event. The record does not state that repeated-event methods or an over-dispersion adjustment were used.

What is not documented

The registry record does not report the planned statistical analysis, sample-size justification, interim analyses, missing-data procedures, or a primary endpoint analysis. It lists 5 outcome measures and an analysis count of 0. That lack of a reported analysis does not establish which methods may have been planned or performed outside the registry; it means those details cannot be assessed from this record. No recalculated results or planning estimates are reported for interpretation.

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("Rituximab + Fludarabine + Cyclophosphamide")
n      <- c(34)
events <- c(8)
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  Rituximab + Fludarabine + Cyclophosphamide  34  8  23.5  10.7  41.2  12.4  40.0  12.5  40.1

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 5 outcome measures, but the information available for this analysis does not identify their full statistical relationship or say whether one endpoint was formally prioritized for hypothesis testing beyond naming the primary outcome. It does not report a multiplicity adjustment, a hierarchy of tests, or a plan for controlling the chance of false-positive findings when assessing multiple outcomes. These procedures are not reported in the registry record.

Multiplicity is a general statistical concern when several hypotheses are tested. As the number of tests grows, the chance of obtaining at least one apparently unusual result by chance can increase if no adjustment or testing strategy is used. That general concern does not establish that the study conducted a particular number of tests or that any result is false; the registry does not report such analyses.

The primary population is described as all participants enrolled. The record does not explain how participants with incomplete follow-up, missing endpoint assessments, or uncertain progression status were handled. It also does not report the number of participants with complete primary endpoint data. Missing-data procedures, including any imputation or sensitivity analyses, are not reported in the registry record.

The registry lists an analysis count of 0 and does not report a primary endpoint estimate, confidence interval, or p-value. Consequently, there is no reported statistical result with which to assess multiplicity or missing-data handling. The protocol’s analysis populations and any departures from planned analyses are also not reported in 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: febrile neutropenia (20.6%), neutropenia (14.7%), fever (8.8%), anemia (2.9%), abdominal pain (2.9%).

The safety record lists 34 participants at risk for serious adverse events and 15 affected. For other adverse events, it lists 34 at risk and 18 affected. These figures describe participants in the single treatment arm; they are not a comparison with a control group.

The listed serious adverse-event terms and percentages are febrile neutropenia, 20.6%; neutropenia, 14.7%; fever, 8.8%; anemia, 2.9%; abdominal pain, 2.9%; and death, 2.9%. The registry lists these as selected serious adverse-event terms. It does not provide a full event listing or explain, in the information, whether the percentages count participants or event episodes. The percentages should therefore be read as posted rather than treated as a complete accounting of all safety events.

Adverse-event figures are descriptive and do not by themselves show that an event was caused by treatment. The record does not provide event timing, duration, attribution, or a comparative safety estimate. The death entry among the serious terms should not be assumed to describe the primary endpoint’s death-or-progression outcome, whose observed result is not reported in the registry record.

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

The record establishes that a phase II, single-arm study evaluated rituximab with fludarabine and cyclophosphamide as first-line treatment for participants with B-cell CLL. It identifies a primary endpoint based on death or documented disease progression, gives the criteria used to define progression, and states that follow-up could extend up to 5 years from baseline. It also provides selected safety figures for the treatment group.

Those details do not answer the primary efficacy question. The observed percentage of participants with death or disease progression is not reported in the registry record. No event count, confidence interval, or statistical test for the primary endpoint is provided. Consequently, the record does not show how frequently the endpoint occurred or how precisely it was estimated.

The study also lacks a comparator group. That means the registry record cannot establish a treatment effect relative to another option. Any outcome observed in a single group would describe the participants’ experience under the study conditions, not the difference attributable to treatment. The absence of a randomized comparison limits causal interpretation.

The safety figures describe affected participants and selected serious-event terms, but they do not establish causation or allow comparison with another group. They should be read as recorded safety observations, with the limitations in event detail and attribution noted.

In general, a study’s results should be interpreted in light of its design, endpoint definition, completeness of follow-up, and uncertainty estimates. Here, the registry record is useful for identifying the question and the framework for measuring outcomes, but the reported information is insufficient to quantify the primary endpoint or assess its precision. It supports neither a claim of benefit nor a claim of lack of benefit.

14. Why This Trial Matters Statistically

This trial is statistically informative as an example of the distinction between an outcome definition and an outcome result. The registry provides a detailed primary endpoint definition, including clinical criteria for progression and a follow-up timeframe. Yet it does not report the observed primary endpoint percentage. A clearly specified outcome is necessary for analysis, but cannot substitute for the result itself.

The single-arm design also makes the comparison question especially important. Descriptive data from one treatment group can characterize what was observed, but cannot provide a randomized contrast. Readers should distinguish a treatment-group event percentage, if reported, from an estimate of the treatment’s effect relative to a control. The registry lists no separate comparator arm.

The record’s safety figures illustrate another statistical distinction: counts and percentages summarize events, but interpretation depends on what is counted, who is included, and whether events are attributed to treatment. Selected serious adverse-event percentages are posted, while details on event timing and attribution are not reported in the registry record.

Finally, the registry’s lack of reported endpoint analysis, uncertainty estimates, and missing-data procedures limits statistical interpretation. These omissions do not prove that analyses were not performed elsewhere; they indicate that those methods and results cannot be evaluated from the registry record. For clinical researchers, the key lesson is to separate the trial’s design and measurement plan from the evidence needed to estimate an outcome and its uncertainty.

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 is the single-group design. There is no randomized comparator arm, so the record cannot support a direct comparative estimate or distinguish treatment effects from other influences on outcomes. This constraint applies even if a descriptive outcome value is available; in this record, the primary endpoint result is not reported.

The registry states that 34 participants were enrolled and that the primary endpoint population is all participants enrolled, but the information available does not report how many contributed evaluable endpoint data. The number of primary endpoint events, completeness of follow-up, and handling of participants with missing assessments are not reported in the registry record. The timeframe is up to 5 years, but participant-level follow-up duration is not given.

The record lists 5 outcome measures but does not report their results or the statistical analysis plan. It does not provide a sample-size justification, interim-analysis plan, multiplicity approach, confidence intervals, or primary endpoint p-value. These details are not reported in the registry record, so the adequacy of the planned analysis and the precision of the findings cannot be assessed.

Safety reporting is also limited to selected figures. The record gives counts of participants at risk and affected, along with selected serious adverse-event terms and percentages, but does not provide event timing, duration, treatment attribution, or a complete event-level account in the information available for this analysis. These limitations restrict what can be inferred from the posted safety information.

The treatment description is incomplete in the registry text available for this analysis, ending partway through the regimen schedule. The complete treatment schedule is not reported in the registry record. These limitations do not negate the design and endpoint information that is stated, but they narrow the conclusions that can responsibly be drawn.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: A Study of Rituximab (MabThera) in Participants With Chronic Lymphocytic Leukemia (CLL) — NCT02533401.
• Registry record last updated 2016-05-02; status last verified 2016-03.
• Results first posted 2016-05-02.
• 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

The registry describes a completed phase II, multicenter, single-arm study of rituximab plus fludarabine and cyclophosphamide as first-line treatment for participants with B-cell CLL. Enrollment was 34. The study began in 2006-02, and primary completion is recorded as 2014-12.

The primary endpoint was the percentage of enrolled participants with death or documented disease progression during follow-up of up to 5 years from baseline. The record defines progression using specified changes in lymph nodes, spleen and/or liver size, or circulating lymphocytes. The observed primary endpoint result and its statistical analysis are not reported in the registry record.

The safety record lists 15 of 34 participants affected by serious adverse events and 18 of 34 affected by other adverse events. Selected serious adverse-event terms are reported with percentages. Because the study has no comparator group, these safety observations are descriptive and do not provide a comparative estimate.