Study of Ibrutinib in Combination With Rituximab in Previously Untreated Subjects With Follicular Lymphoma: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Study of Ibrutinib in Combination With Rituximab in Previously Untreated Subjects With Follicular Lymphoma (NCT01980654), a non-randomized phase 2 study. The primary outcome is Overall Response Rate (ORR): Proportion of Subjects Achieving the Best Overall Responses of Complete Response (CR) or Partial Response (PR).

2. Clinical Question

The registry frames the study as an assessment of efficacy and safety of the combination in previously untreated follicular lymphoma. Its primary question is descriptive: whether investigator assessments recorded complete or partial responses during the specified treatment context. Without a reported endpoint result, the size and precision of any response estimate cannot be evaluated from the registry record.

3. Trial Design

This was a multicenter, open-label, Phase 2 study with parallel arms and non-randomized allocation. The registry reports enrollment of 80. The study status is completed. Its open-label design means masking was absent; the record does not report a blinded outcome assessment. The registry identifies Pharmacyclics LLC. as sponsor.

The main study arm received ibrutinib continuously, with rituximab once weekly for four doses during the first four weeks of study treatment. The arm description says ibrutinib continued until disease progression or unacceptable toxicity. In the exploratory arm, subjects received ibrutinib alone for the first eight weeks, then ibrutinib with rituximab once weekly for four doses. The remaining stopping-rule text for this arm is incomplete in the registry record, so its full description is not reported there.

The imaging schedules differed. In the main arm, assessments were planned every 12 weeks for the first 8 assessments, then every 24 weeks. In the exploratory arm, assessments began at week 9, continued every 12 weeks for 8 assessments, then every 24 weeks. These differing schedules matter when interpreting when responses could be observed and recorded.

Because allocation was not randomized, the arms are not a like-for-like control comparison. Their schedules also differ, including the timing of rituximab initiation and imaging. The record does not report the reason for arm assignment, whether the arms were intended for a formal comparison, or adjustment methods to address differences between them. The design therefore supports reading each arm as part of a non-randomized study rather than treating one as a randomized control for the other.

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 Overall Response Rate (ORR): Proportion of Subjects Achieving the Best Overall Responses of Complete Response (CR) or Partial Response (PR), measured over Subjects in Arm 1 will have imaging assessments every 12 weeks for the first 8 assessments, then every 24 weeks. Subjects in Arm 2 will have imaging assessments starting at week 9, then every 12 weeks for 8 assessments, then every 24 weeks..

The primary endpoint is the number of subjects whose best overall response was complete response or partial response before initiation of the next line of antineoplastic therapy. The registry describes this as an overall response rate, while the registered measurement parameter is a count of participants. A response count and a response proportion are related but are not interchangeable without a defined denominator. The denominator and numerical primary result are not reported in the registry record.

Responses were assessed by the investigator using the Cheson et al, 2007 criteria. The record defines complete response as disappearance of all evidence of disease. Partial response is defined as at least 50% decrease in the sum of the product of the diameters of up to 6 largest dominant masses. Target lesions were measured by CT, unless MRI was used for lesions in anatomical locations not amenable to CT.

Response endpoints are used in clinical trials to describe tumor response observed under a specified assessment approach. A best overall response combines the response category judged over assessments rather than describing a single scan in isolation. The scheduled assessment timing differs between the two arms, so the opportunity and timing for documenting response are not identical. The registry record does not report the response counts, proportions, uncertainty intervals, or an analysis comparing arms.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical interpretation begins with the outcome definition and the population to which it applies. Here the primary outcome is described as overall response rate, defined by complete or partial response, while the registered measurement is a participant count. A count answers how many subjects met the response definition. A rate or proportion additionally requires a denominator and a clearly specified analysis population. The registry record does not report the primary count, its denominator, or the numerical proportion.

What does a confidence interval tell a reader?

General statistical explanation: a confidence interval expresses uncertainty around an estimate under a stated statistical method. A narrower interval indicates greater precision under that method; a wider interval indicates less precision. It does not describe the range of individual outcomes, and it does not remove bias from non-randomized allocation or incomplete outcome data. No confidence interval for the primary endpoint is reported in the registry record, so its precision cannot be assessed from this record.

Why does non-randomized allocation matter?

General statistical explanation: randomization is used to reduce systematic differences between groups at baseline, on average. Without randomization, group membership can be associated with prognosis, clinical decisions, timing, or other factors. Statistical adjustment can sometimes address measured differences, but it cannot guarantee removal of unmeasured confounding. The registry record identifies the allocation as non-randomized and does not report an adjusted comparison plan. The arm results therefore should not be interpreted as if assignment were random.

The arm schedules reinforce this caution. Rituximab began during the first four weeks in the main arm, whereas the exploratory arm first received ibrutinib alone for eight weeks and then added rituximab. The imaging schedules also start at different times. A comparison would consequently combine differences in assignment, treatment sequence, and assessment timing. The record does not report a method designed to separate these influences.

How should response timing be understood?

General statistical explanation: a best overall response is based on the response categories observed across assessments, rather than one measurement at a single moment. Scheduled imaging determines when an outcome can be observed. If assessment schedules differ, the time available to detect and document responses may also differ. That does not prove that observed responses are biased, but it is a design feature that should be considered. The registry record does not report a sensitivity analysis or other method addressing the differing schedules.

What can safety counts show?

General statistical explanation: a count of participants with at least one event is different from a count of all event episodes. Counts also need a defined observation period and population for meaningful comparison. The adverse-event record gives numbers at risk and numbers affected by serious adverse events for each arm, and it lists selected serious-event terms with percentages. It does not report event exposure time, a statistical comparison, or a detailed definition of the percentage denominator for each listed term. These summaries describe recorded safety experience but do not establish a comparative treatment effect.

How should sample-size illustrations be read?

General statistical explanation: a sample-size calculation is a planning exercise that estimates the number of participants or events needed to detect a specified effect under stated assumptions. It is not a measure of the probability that a completed study found a real effect. In particular, an illustration calculated from an observed effect is not observed power and should not be mistaken for the study's original design justification.

The registry description of the planning illustration specifies a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation. It describes effects to detect as stated fractions of the observed effect. For time-to-event outcomes, the illustration uses total events; for other outcomes, it uses participants per arm. These assumptions describe the illustration rather than a documented original design plan. The registry record does not report the trial's sample-size justification or the statistical plan used for the completed study.

General statistical explanation: a significance test evaluates data under a specified null hypothesis and model. A p-value, when reported, is not the probability that the null hypothesis is true, nor does it measure clinical importance. No primary endpoint analysis or p-value is reported in the registry record. The record lists 0 analyses, so inferential results cannot be assessed from its analysis entries.

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("Main Study Arm 1", "Exploratory Study Arm 2")
n      <- c(60, 20)
events <- c(51, 15)
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  Main Study Arm 1  60  51  85.0  73.4  92.9  73.9  91.9  73.8  91.8
ARM  Exploratory Study Arm 2  20  15  75.0  50.9  91.3  53.1  88.8  52.8  88.7

11. Multiplicity, Missing Data and Analysis Populations

The registry lists the primary overall response endpoint and secondary outcomes of duration of response, progression-free survival, overall survival, and number of participants with treatment-emergent adverse events. It reports 5 outcome measures, but the statistical analysis entries count is 0. The record does not explain how the listed outcomes were prioritized in analysis beyond identifying the primary endpoint.

When a study evaluates multiple outcomes or makes multiple comparisons, the chance of at least one false-positive finding can increase. General statistical approaches include prespecifying a primary test, adjusting for multiple testing, or describing secondary analyses as exploratory. Whether any multiplicity strategy was used is not reported in the registry record. The number and order of formal hypotheses, any adjustment, and any interim analyses are also not reported in the registry record.

The record does not report how missing or unevaluable response assessments were handled, whether subjects who began another line of therapy before assessment were treated in a particular way, or which analysis population was used for the primary endpoint. It does define the response count in relation to the next line of antineoplastic therapy, but that definition does not specify how missing observations were treated. These details matter because exclusions and missing-data assumptions can affect a response estimate.

The registry record also does not report a statistical analysis plan, outcome-specific denominators, or methods for censoring time-to-event outcomes. Consequently, the listed secondary outcome names should not be read as evidence that their results or analysis methods are available in the record.

12. 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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: pyrexia (15.0%), diarrhoea (10.0%), pneumonia (10.0%), rectal haemorrhage (5.0%), non-cardiac chest pain (5.0%).

The registry reports serious adverse events separately for the two study arms. In the main study arm, 14 of 60 subjects at risk were affected; in the exploratory study arm, 6 of 20 were affected. The record also reports 4 deaths in the main arm and 0 in the exploratory arm. These are descriptive counts. The registry record does not report whether deaths were considered related to treatment or provide a comparative statistical analysis.

Listed among the top serious adverse-event terms are Pyrexia at 15.0%, Diarrhoea at 10.0%, Pneumonia at 10.0%, Rectal haemorrhage at 5.0%, Non-cardiac chest pain at 5.0%, and Urinary tract infection at 5.0%. The record does not specify the arm for each listed term in this summary, nor does it report the denominator definition for these term percentages. They should not be treated as directly comparable arm-specific rates.

Serious adverse-event summaries and counts of subjects affected do not establish that treatment caused an event. They also do not indicate how long subjects were observed or how many episodes each affected subject experienced. Those details are not reported in the registry record.

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

This registry record documents a completed, multicenter, open-label, non-randomized Phase 2 study of ibrutinib with rituximab in previously untreated subjects with follicular lymphoma. It describes two treatment schedules and identifies investigator-assessed complete or partial response as the primary outcome. It also records serious adverse-event counts and selected serious-event terms.

The record does not report a numerical primary response result. It therefore cannot show the observed response count or proportion, or how precisely either was estimated. The absence of a reported result in the registry record is not evidence that no response occurred; it means the numerical result is not available in this record.

The two arms do not provide a randomized comparison. Their different treatment sequences and imaging schedules, together with non-randomized allocation, limit interpretation of any arm-to-arm difference. The registry record does not report methods that would account for those differences. A descriptive result in one arm would characterize the recorded outcomes for that group, not establish what would have happened under an alternative treatment schedule.

Safety figures describe recorded events among subjects at risk in each arm. They do not by themselves show that an event was caused by treatment, establish a comparative risk, or describe the event burden over time. The registry record does not report event attribution methods or exposure-adjusted safety analyses.

More generally, the design and the available registry results answer different questions. The design identifies what was intended to be assessed; the missing primary numerical result prevents assessment of the observed response estimate. The study's findings should not be generalized beyond the population and setting described without additional evidence, and the registry record does not report a randomized control comparison.

14. Why This Trial Matters Statistically

This study illustrates why a clear distinction between a treatment description and a treatment comparison is essential. Although the record has two arms, allocation was non-randomized. Calling the arms parallel does not make them randomized controls. Their differing schedules further mean that an arm comparison would not isolate a single treatment difference.

It also highlights how endpoint labels and measurements need to be read carefully. The primary outcome is titled overall response rate, but the registered measurement is a count of participants. To interpret a proportion, readers need the numerator, denominator, analysis population, and handling of unevaluable assessments. The registry record does not report the numerical primary result or these details.

Outcome timing is another important design feature. Response depends on assessments, and imaging schedules differ between the arms. A statistical comparison that ignores timing could be difficult to interpret, particularly when one schedule begins later. The registry record does not describe an analysis that addresses this issue.

Finally, the safety summaries show why counts and percentages need context. Counts affected, numbers at risk, event terms, denominators, and observation time each convey different information. A useful statistical reading keeps those distinctions visible rather than turning descriptive figures into causal claims. Taken together, these features make the registry record valuable for understanding the study's design and reporting limits, while leaving its primary efficacy estimate unavailable.

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.

Several limitations specific to this study affect how its outcomes can be interpreted. First, allocation was non-randomized, and the registry explicitly cautions that the arms are not a like-for-like control comparison. The record does not report how subjects were assigned, what factors informed assignment, or whether analyses adjusted for baseline differences.

Second, the treatment sequences differ. The main arm began rituximab during the first four weeks, whereas the exploratory arm received ibrutinib alone for the first eight weeks before adding rituximab. Imaging schedules also differed, with assessments in the exploratory arm starting at week 9. Those distinctions complicate direct interpretation of response timing or arm differences.

Third, the primary endpoint result is not reported in the registry record. The record also does not report the primary endpoint denominator, missing-data handling, analysis population, confidence interval, or inferential analysis. These omissions prevent assessment of the response estimate and its precision.

Fourth, the description of the exploratory arm's later ibrutinib stopping rule is incomplete in the registry record. The record lists secondary outcomes but does not report analysis results for them. The statistical analysis plan, multiplicity approach, and interim-analysis details are not reported in the registry record.

Finally, the safety summaries do not provide event attribution methods, exposure-adjusted rates, or a statistical comparison. The listed serious-event terms do not specify arm-specific denominators in the registry summary. These limitations restrict both causal interpretation and comparisons across arms.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Study of Ibrutinib in Combination With Rituximab in Previously Untreated Subjects With Follicular Lymphoma — NCT01980654.
• Registry record last updated 2019-04-16; status last verified 2019-03.
• Results first posted 2019-04-16.
• 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, multicenter, open-label, Phase 2 study of ibrutinib with rituximab in previously untreated subjects with follicular lymphoma. Allocation was non-randomized, and the two arms followed different treatment and imaging schedules. Enrollment was 80.

The primary endpoint was investigator-assessed best overall response of complete response or partial response before the next line of antineoplastic therapy. Its numerical result is not reported in the registry record. The record lists duration of response, progression-free survival, overall survival, and treatment-emergent adverse events as secondary outcomes, but reports 0 analysis entries.

Serious adverse-event counts are reported for both arms, along with selected event terms. Because allocation was non-randomized, the arms are not a randomized control comparison. Missing endpoint results and unreported analysis details limit interpretation of efficacy, precision, and between-arm differences.