This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the ClinicalTrials.gov record.
1. Trial at a Glance
CLL14 was a randomized, parallel-group, open-label phase 3 treatment trial in chronic lymphocytic leukemia. The registry reports a comparison of obinutuzumab plus venetoclax with obinutuzumab plus chlorambucil, with progression-free survival based on investigator assessment according to IWCLL criteria as the registered primary endpoint.
| Feature | CLL14 |
|---|---|
| Phase | Phase 3 |
| Condition | Lymphocytic Leukemia, Chronic |
| Design | Randomized, parallel |
| Masking | None |
| Primary purpose | Treatment |
| Enrollment | 445 |
| Primary endpoint | Progression Free Survival (PFS) Based on Investigator Assessment According to IWCLL Criteria |
| Primary endpoint type | Time-to-event |
| Results posted | Yes |
| Outcome measures posted | 23 |
| Statistical analyses posted | 10 |
| ClinicalTrials.gov | NCT02242942 |
2. Clinical Question
The principal statistical question was whether obinutuzumab plus venetoclax produced a different time-to-event outcome from obinutuzumab plus chlorambucil, as measured by investigator-assessed progression-free survival under the IWCLL criteria. The registered hypothesis type for the formal analyses was superiority.
Population
Participants with chronic lymphocytic leukemia enrolled in the CLL14 trial.
Intervention
Obinutuzumab plus venetoclax.
Comparator
Obinutuzumab plus chlorambucil.
Primary question
Does obinutuzumab plus venetoclax improve investigator-assessed progression-free survival relative to obinutuzumab plus chlorambucil?
3. Trial Design
Obinutuzumab + Chlorambucil
- Comparator treatment group in the posted statistical analyses.
- Compared directly with obinutuzumab + venetoclax for the reported efficacy endpoints.
- Included in the reported ITT efficacy analyses.
Obinutuzumab + Venetoclax
- Intervention treatment group in the posted statistical analyses.
- Compared directly with obinutuzumab + chlorambucil for the reported efficacy endpoints.
- Included in the reported ITT efficacy analyses.
4. Trial Timing and Registry Status
Trial start
The registry lists December 31, 2014 as the study start date.
Primary completion
The registry lists August 17, 2018 as the primary completion date.
Registry status
The trial is listed as completed, with results posted on ClinicalTrials.gov.
5. Primary Endpoint
| Endpoint | Registry definition / time frame | Analysis |
|---|---|---|
| Progression Free Survival (PFS) Based on Investigator Assessment According to IWCLL Criteria | Baseline until disease progression or death up to approximately 3.75 years | Log-rank test; hazard ratio estimated by Cox regression model |
6. Secondary Endpoints
The posted statistical analyses cover several categories of secondary efficacy outcomes. Time-to-event PFS was analyzed using a log-rank framework, while binary response and minimal-residual-disease outcomes were analyzed using either the Cochran-Mantel-Haenszel test or chi-squared test.
| Secondary endpoint | Time frame | Method | Effect measure |
|---|---|---|---|
| PFS based on Institutional Review Committee assessments according to IWCLL criteria | Baseline until disease progression or death up to approximately 3.75 years | Log-rank test | Hazard ratio |
| Overall response at completion of treatment | 3 months after treatment completion, approximately 15 months) | Cochran-Mantel-Haenszel test | Difference in response rates |
| Complete response rate at completion of treatment | 3 months after treatment completion, approximately 15 months) | Cochran-Mantel-Haenszel test | Difference in response rates |
| MRD negativity in peripheral blood at completion of treatment | 3 months after treatment completion, approximately 15 months) | Cochran-Mantel-Haenszel test | Difference in MRD-negative rates |
| MRD negativity in bone marrow at completion of treatment | 3 months after treatment completion, approximately 15 months) | Cochran-Mantel-Haenszel test | Difference in MRD-negative rates |
| MRD negativity in peripheral blood at completion of combination treatment | Day 1 Cycle 9 or 3 months after last IV infusion, approximately 9 months | Chi-squared test | Difference in MRD-negative rates |
| MRD negativity in bone marrow at completion of combination treatment | Day 1 Cycle 9 or 3 months after last IV infusion, approximately 9 months | Chi-squared test | Difference in MRD-negative rates |
| Overall response at completion of combination treatment | Day 1 Cycle 7 or 28 days after last IV infusion, approximately 6 months | Cochran-Mantel-Haenszel test | Difference in response rates |
| Best response achieved | Baseline up to completion of treatment assessment, up to approximately 15 months) | Cochran-Mantel-Haenszel test | Difference in response rates |
7. Primary Result: Investigator-Assessed Progression-Free Survival
The primary analysis compared obinutuzumab plus chlorambucil with obinutuzumab plus venetoclax in the intention-to-treat population, defined in the registry as all randomized participants. The reported method was the log-rank test, with hazard ratios estimated using a Cox regression model.
Hazard ratio for progression or death
95% CI: 0.23–0.53 · P < 0.0001
Two-sided 95% confidence interval; superiority hypothesis.
| Primary endpoint | Comparison | Estimate | 95% CI | P-value |
|---|---|---|---|---|
| Investigator-assessed PFS according to IWCLL criteria | Obinutuzumab + Chlorambucil vs Obinutuzumab + Venetoclax | HR 0.35 | 0.23–0.53 | <0.0001 |
An HR of 0.35 means that, under the fitted Cox model, the estimated instantaneous rate of progression or death for the obinutuzumab-plus-venetoclax group was approximately 35% of the corresponding rate in the obinutuzumab-plus-chlorambucil group. Equivalently, the estimated hazard was approximately 65% lower in relative terms.
The HR is not a statement that 65% of patients were protected from progression or death, nor does it mean that every patient experienced a 65% reduction in individual risk. It is a relative time-to-event measure derived from the statistical model.
The two-sided 95% CI of 0.23–0.53 describes uncertainty around the estimated hazard ratio. It does not describe the range of treatment effects across individual patients. Because the entire interval is below 1, the reported data are consistent with a lower estimated hazard in the obinutuzumab-plus-venetoclax group under this analysis.
The P-value <0.0001 addresses evidence against the null hypothesis specified for the statistical comparison; it does not measure the magnitude or clinical importance of the treatment effect. The magnitude is described by the HR and its confidence interval.
As with other Cox-model hazard ratios, interpretation should account for the proportional-hazards structure implicit in summarizing the treatment contrast with a single HR. The ClinicalTrials.gov record does not report a separate assessment of that assumption.
8. Secondary Result: IRC-Assessed Progression-Free Survival
The second reported PFS analysis used assessments from an Institutional Review Committee according to IWCLL criteria. Like the primary PFS analysis, it used the ITT population and a log-rank test, with the hazard ratio estimated from a Cox regression model stratified by Binet and Geographic region.
Hazard ratio for progression or death
95% CI: 0.22–0.51 · P < 0.0001
Two-sided 95% confidence interval; superiority hypothesis.
The IRC-assessed HR of 0.33 corresponds to an estimated instantaneous progression-or-death hazard approximately 33% as large in the obinutuzumab-plus-venetoclax group as in the obinutuzumab-plus-chlorambucil group, or approximately a 67% lower estimated hazard under the fitted model.
The 95% CI of 0.22–0.51 gives the statistical uncertainty around that relative estimate. It should not be interpreted as a prediction interval for individual patients. The P-value of <0.0001 provides evidence against the null hypothesis used for the comparison; it is not a measure of the size of the observed treatment effect.
The similarity in direction between investigator-assessed and IRC-assessed PFS is relevant descriptively because the two analyses use different assessment sources. It does not turn the secondary endpoint into an independent replication of the primary hypothesis, and the ClinicalTrials.gov record does not provide an adjusted multiplicity framework for interpreting the entire set of posted secondary analyses.
9. Secondary Results: Overall Response
Overall response was analyzed as a binary outcome using the Cochran-Mantel-Haenszel test. The analysis population was the ITT population. The reported effect measure was the difference in response rates, with two-sided 95% confidence intervals constructed using the Anderson-Hauck method.
Overall response at approximately 15 months)
95% CI: 5.47–21.38 · P = 0.0007
Assessment at treatment completion, 3 months after treatment completion.
The reported difference in response rates of 13.43 percentage points describes the contrast between the two treatment groups using the registry's stated direction of comparison: obinutuzumab plus chlorambucil versus obinutuzumab plus venetoclax. A positive reported difference therefore represents a higher response rate for the latter group under the registry's comparison.
The 95% CI of 5.47–21.38 quantifies uncertainty around that difference. Unlike a hazard ratio, a difference in response rates is an absolute percentage-point contrast and is directly interpretable on the probability scale.
The P-value of 0.0007 assesses the evidence against the null comparison used by the CMH analysis. It does not tell us that the effect is "0.0007 large," nor does it establish that every individual patient has the same response benefit.
10. Secondary Results: Complete Response Rate
Complete response rate was assessed at the completion-of-treatment assessment, 3 months after treatment completion at approximately 15 months. The registry reports a Cochran-Mantel-Haenszel analysis in the ITT population.
Complete response rate difference
95% CI: 17.41–35.36 · P < 0.0001
Two-sided 95% confidence interval using the Anderson-Hauck method.
The estimated difference of 26.39 percentage points indicates a substantially different observed complete-response proportion between the two randomized treatment groups at the specified assessment time. Because the comparison is expressed as an absolute difference, it is not directly interchangeable with the PFS hazard ratio.
The 95% CI of 17.41–35.36 indicates that the estimated difference is subject to sampling uncertainty, while remaining entirely above zero. The P-value of <0.0001 supplies evidence against the null hypothesis of no difference in the reported CMH comparison but does not itself describe the magnitude of the difference.
The endpoint is also time-specific: it concerns the completion-of-treatment assessment approximately 15 months into the specified time frame, rather than a time-to-event measure over the entire follow-up period.
11. Secondary Results: Minimal Residual Disease
Several MRD-negativity endpoints were posted. The ClinicalTrials.gov record distinguishes peripheral blood and bone marrow measurements and also distinguish the approximately 9-month completion-of-combination-treatment assessment from the approximately 15-month completion-of-treatment assessment.
| MRD endpoint | Assessment | Difference | 95% CI | P-value |
|---|---|---|---|---|
| Peripheral blood MRD negativity | Completion of treatment, approximately 15 months) | 40.28 | 31.45–49.10 | <0.0001 |
| Bone marrow MRD negativity | Completion of treatment, approximately 15 months) | 39.81 | 31.27–48.36 | <0.0001 |
| Peripheral blood MRD negativity | Completion of combination treatment, approximately 9 months | 32.87 | 23.76–41.98 | <0.0001 |
| Bone marrow MRD negativity | Completion of combination treatment, approximately 9 months | 38.43 | 30.15–46.71 | <0.0001 |
The approximately 15-month peripheral-blood and bone-marrow analyses used the Cochran-Mantel-Haenszel test. The approximately 9-month analyses used the chi-squared test. The registry states that the 95% confidence intervals for the differences in rates were constructed using the Anderson-Hauck method.
These estimates are differences in MRD-negative rates, not hazard ratios. For example, the reported peripheral-blood estimate of 40.28 at approximately 15 months represents a 40.28-percentage-point difference under the registry's specified comparison.
The confidence intervals provide uncertainty around the percentage-point differences. They do not indicate the range of MRD values among individual participants. The consistently positive intervals reported for these four analyses indicate that the corresponding observed rate differences were separated from zero under their respective statistical comparisons.
The different assessment times also matter. The approximately 9-month endpoints and approximately 15-month endpoints answer related but distinct questions about MRD negativity. They should not be treated as repeated measurements of exactly the same endpoint at the same time.
12. Secondary Result: Overall Response at Approximately 6 Months
The registry also reports overall response at the completion-of-combination-treatment assessment, defined as Day 1 Cycle 7 or 28 days after the last IV infusion, approximately 6 months.
Overall response difference
95% CI: -4.63–8.33 · P = 0.5612
Cochran-Mantel-Haenszel analysis in the ITT population.
The point estimate of 1.85 percentage points is close to zero relative to the uncertainty represented by its 95% CI. The interval spans both negative and positive values, from -4.63 to 8.33.
The P-value of 0.5612 does not provide evidence against the null hypothesis for this particular comparison. Importantly, this should not be converted into a claim that the treatments are equivalent or identical. A nonsignificant superiority test means that the analysis did not demonstrate a statistically detectable difference under its specified framework; it is not a formal non-inferiority or equivalence analysis.
This result also illustrates why the assessment time matters. A response comparison at approximately 6 months can differ from a response comparison at approximately 15 months without the two analyses being contradictory.
13. Secondary Result: Best Response Achieved
The registry defines this outcome as the percentage of participants by best response achieved, including complete response, complete response with incomplete marrow recovery, partial response, stable disease, or progressive disease, from baseline through the completion-of-treatment assessment up to approximately 15 months.
Best-response difference
95% CI: -4.66–6.51 · P = 0.7169
Cochran-Mantel-Haenszel analysis stratified by the IvRS randomization stratification factors.
The reported difference of 0.93 percentage points is close to zero, while the 95% CI of -4.66–6.51 includes zero. The P-value of 0.7169 indicates that this analysis did not demonstrate a statistically detectable difference under the reported CMH framework.
The important statistical distinction is between failure to demonstrate a difference and demonstration of equivalence. The ClinicalTrials.gov record identifies the hypothesis as superiority, not equivalence or non-inferiority. Therefore, the result should not be reinterpreted as proof that the two treatments have identical best-response distributions.
14. Statistical Methodology
Intention-to-treat analysis
The registry defines the ITT population as all randomized participants. The primary PFS analysis and the posted secondary efficacy analyses described here use that population. An ITT analysis preserves treatment assignment as the basis of comparison rather than redefining groups according to treatment received or subsequent treatment experience.
The principal statistical advantage is preservation of the randomized comparison. This is particularly important for causal interpretation because randomization is the mechanism intended to balance prognostic factors between treatment groups.
Log-rank test
The primary PFS analysis and the IRC-assessed PFS analysis used the log-rank test. This is a time-to-event comparison that uses information from the entire observed follow-up rather than comparing only one fixed time point.
For each event time, the analysis considers the participants still at risk immediately before that time and compares the observed number of events with what would be expected under the null hypothesis of equal survival distributions. Repeating that comparison across event times produces the overall test statistic.
Cox regression and hazard ratios
The registry states that hazard ratios were estimated using a Cox regression model. The primary and IRC-assessed PFS analyses used Binet and Geographic region as stratification factors.
An HR below 1 indicates a lower estimated event hazard for the numerator group under the fitted model. It is not an absolute risk difference and is not the same as a ratio of cumulative event probabilities.
Cochran-Mantel-Haenszel testing
The CMH test was used for several binary response and MRD outcomes. This method can compare categorical outcomes while accounting for stratification factors. The registry specifically notes stratification by IvRS randomization stratification factors for the best-response analysis.
Chi-squared testing
The approximately 9-month peripheral-blood and bone-marrow MRD-negativity analyses used the chi-squared test. For a binary outcome, the test evaluates whether the observed distribution of the outcome differs between treatment groups under the specified null hypothesis.
Anderson-Hauck confidence intervals
The registry states that the 95% confidence intervals for differences in rates were constructed using the Anderson-Hauck method. This is important because the interval construction is part of the statistical specification of the reported percentage-point effects; the confidence intervals should not be treated as if they had necessarily been generated by a generic Wald approximation.
15. Statistical Methods Explained
Why was a log-rank test used for PFS?
PFS is a time-to-event endpoint. Some participants can experience progression or death early, while others remain event-free at the end of their observed follow-up and are therefore censored. A log-rank analysis is designed for this structure because it uses event timing and accounts for censoring rather than treating every participant as if everyone had been observed for exactly the same duration.
What does an HR of 0.35 mean?
An HR of 0.35 means that the fitted Cox model estimates the instantaneous progression-or-death hazard in the obinutuzumab-plus-venetoclax group at about 35% of the comparator hazard. The complementary interpretation is an approximately 65% lower estimated hazard. It does not mean a 65% absolute reduction in the probability of progression or death.
Why is the confidence interval important?
The point estimate alone does not describe statistical precision. For the primary PFS analysis, the HR is 0.35, while the 95% CI is 0.23–0.53. The interval communicates uncertainty around the estimated relative effect. It is therefore more informative to report the HR together with its confidence interval than to report the HR alone.
Why does the P-value not measure effect size?
A P-value summarizes the compatibility of the observed data with the null hypothesis under the statistical model. It is affected by both the magnitude of an effect and the amount of information available. A very small P-value therefore does not mean that the effect is necessarily large, clinically important, or precisely estimated to a particular degree.
Why use both investigator and IRC assessments?
The trial reports PFS using two assessment sources. The primary endpoint uses investigator assessment, while a secondary endpoint uses Institutional Review Committee assessment. Comparing results from these approaches can provide useful information about the consistency of the observed time-to-event comparison, but the secondary analysis remains a separate endpoint rather than a second primary endpoint.
What is the difference between a response-rate difference and a hazard ratio?
A response-rate difference compares proportions at a defined assessment. A hazard ratio compares instantaneous event rates over time. A difference such as 26.39 percentage points for complete response is therefore answering a different statistical question from a PFS HR of 0.35. Neither measure substitutes for the other.
Does a nonsignificant superiority test establish equivalence?
No. For the approximately 6-month overall-response analysis, the P-value is 0.5612 and the 95% CI includes zero. This means the superiority analysis did not demonstrate a statistically detectable difference. It does not establish that the treatments are equivalent, because equivalence would require a separately specified equivalence framework and margins.
16. Reading the Primary PFS Result Correctly
Relative effect
HR 0.35 summarizes the estimated relative time-to-event effect under the Cox model.
Precision
The 95% CI of 0.23–0.53 quantifies uncertainty around the estimated hazard ratio.
Statistical evidence
P < 0.0001 indicates strong evidence against the null hypothesis used for the superiority comparison.
What is not reported
The ClinicalTrials.gov record does not provide median PFS, Kaplan-Meier survival probabilities, event counts, or a survival curve for this page.
This distinction is important. A hazard ratio is a compact summary of a time-to-event comparison, but it does not contain every clinically relevant feature of the survival distributions. Median PFS, fixed-time PFS probabilities, numbers of events, and the shape of the Kaplan-Meier curves would answer additional questions. Because those values are not contained in the ClinicalTrials.gov record, they are not added here.
17. Stratification and the Role of Randomization
The registry identifies Binet and Geographic region as stratification factors for the Cox regression analyses of PFS. Stratification allows the model to account for differences in baseline hazard across the specified strata without requiring a single common baseline hazard for all strata.
The best-response analysis also states that its P-value was assessed using a CMH test stratified by the IvRS randomization stratification factors. Thus, the ClinicalTrials.gov record shows stratification being used in both time-to-event and categorical analyses, although the exact full list of IvRS factors is not provided in the registry extract.
Stratification does not create balance after the fact. Rather, it incorporates the trial's prespecified randomization structure into the statistical comparison.
18. Multiplicity and the Set of Reported Analyses
The registry reports 23 outcome measures and 10 statistical analyses, including one posted primary-endpoint analysis and nine posted secondary analyses in the ClinicalTrials.gov record.
| Feature | Registry data reported |
|---|---|
| Registered primary endpoints | 1 |
| Primary endpoint analyses posted | 1 |
| Primary analyses with estimate + CI | 1 |
| Statistical analyses posted | 10 |
| Outcome measures posted | 23 |
| Hypothesis type | Superiority |
The ClinicalTrials.gov record identifies superiority as the hypothesis type for the posted analyses but do not provide an explicit multiplicity-adjustment procedure or alpha-allocation scheme for the entire family of secondary endpoints. Consequently, each secondary P-value should be understood as the reported result of its individual analysis rather than automatically interpreted as an independently confirmatory test of a new hypothesis family.
19. Missing Data, Censoring, and Analysis Assumptions
The primary endpoint is a time-to-event outcome, so censoring is intrinsically part of the analysis. Participants who have not experienced progression or death by the end of their observed follow-up can contribute information up to the point at which their event status is no longer observed.
For binary response and MRD outcomes, the ClinicalTrials.gov record identifies the analysis population and statistical tests but do not provide a missing-data or imputation specification. Accordingly, this page does not assume a particular imputation method.
| Issue | What the ClinicalTrials.gov record supports | What is not specified |
|---|---|---|
| Censoring | PFS is a time-to-event endpoint analyzed with log-rank and Cox methods. | A detailed censoring algorithm is not provided in the registry-reported extract. |
| Missing binary outcomes | Binary endpoints were analyzed in the ITT population using CMH or chi-squared methods. | No imputation method is provided. |
| Proportional hazards | Hazard ratios were estimated using Cox regression. | No formal proportional-hazards diagnostic is provided. |
| Interim analysis | No interim-analysis method is identified in the ClinicalTrials.gov record. | Timing, stopping boundaries, and alpha spending are not reported here. |
20. Safety Results
The ClinicalTrials.gov record reports serious adverse events by arm using affected participants divided by participants at risk. The available safety figures include the two principal randomized treatment groups and the separate safety run-in group.
| Treatment group | Serious adverse events | At risk |
|---|---|---|
| Obinutuzumab + Chlorambucil | 90 | 214 |
| Obinutuzumab + Venetoclax | 104 | 212 |
| Safety Run-in Obinutuzumab + Venetoclax | 10 | 13 |
The ClinicalTrials.gov record does not provide a formal between-group hypothesis test for serious adverse events, confidence intervals, exposure-adjusted incidence rates, or detailed adverse-event categories. Therefore, the safety information is presented descriptively rather than converted into an unsupported comparative statistical conclusion.
The denominators matter. The serious-adverse-event counts are accompanied by the number at risk for each group, and the safety run-in has a much smaller denominator of 13. A raw count alone would therefore be misleading as a comparison.
Safety and efficacy also have different statistical structures. The primary PFS analysis is anchored to randomization and uses time-to-event methods, whereas the ClinicalTrials.gov record is a descriptive count of participants affected by serious adverse events. The two should not be collapsed into a single numerical "benefit-risk" statistic.
21. What the Posted Secondary Results Show Statistically
| Endpoint | Estimate | 95% CI | P-value | Method |
|---|---|---|---|---|
| IRC-assessed PFS | HR 0.33 | 0.22–0.51 | <0.0001 | Log-rank / Cox |
| Overall response, approximately 15 months) | 13.43 | 5.47–21.38 | 0.0007 | CMH |
| Complete response rate, approximately 15 months) | 26.39 | 17.41–35.36 | <0.0001 | CMH |
| Peripheral blood MRD negativity, approximately 15 months) | 40.28 | 31.45–49.10 | <0.0001 | CMH |
| Bone marrow MRD negativity, approximately 15 months) | 39.81 | 31.27–48.36 | <0.0001 | CMH |
| Peripheral blood MRD negativity, approximately 9 months | 32.87 | 23.76–41.98 | <0.0001 | Chi-squared |
| Bone marrow MRD negativity, approximately 9 months | 38.43 | 30.15–46.71 | <0.0001 | Chi-squared |
| Overall response, approximately 6 months | 1.85 | -4.63–8.33 | 0.5612 | CMH |
| Best response, up to approximately 15 months) | 0.93 | -4.66–6.51 | 0.7169 | CMH |
Several statistical patterns are worth noticing. The time-to-event analyses report hazard ratios substantially below 1. The later response and MRD analyses report positive percentage-point differences with confidence intervals that do not cross zero. In contrast, the approximately 6-month overall-response and best-response analyses have confidence intervals that cross zero and larger P-values.
These results should not be treated as contradictory simply because some secondary endpoints are more strongly separated than others. Different endpoints measure different biological and clinical phenomena, use different assessment times, and have different statistical information content.
22. Why the Assessment Time Matters
CLL14's posted secondary endpoints illustrate an important principle in longitudinal clinical-trial analysis: an endpoint defined at one assessment time is not interchangeable with the same type of endpoint assessed at another time.
Approximately 6 months
Overall response at Day 1 Cycle 7 or 28 days after the last IV infusion: difference 1.85, 95% CI -4.63–8.33.
Approximately 9 months
Peripheral-blood and bone-marrow MRD negativity were analyzed at the completion of combination treatment.
Approximately 15 months)
Response, complete response, and MRD-negativity outcomes were assessed at completion of treatment, 3 months after treatment completion.
Up to approximately 3.75 years
The PFS endpoints followed participants from baseline until disease progression or death over the registered time frame.
A time-specific binary endpoint asks, in effect, "what proportion had the specified status at this assessment?" A PFS endpoint instead asks "how long until progression or death?" Those questions require different statistical methods and should be interpreted on their own scales.
23. Limitations
- Registry-derived scope: this analysis is restricted to the ClinicalTrials.gov record. It does not add results from publications or other external sources.
- Incomplete quantitative survival detail: the ClinicalTrials.gov record does not report median PFS, Kaplan-Meier estimates at fixed time points, event counts, or survival-curve coordinates.
- Incomplete baseline detail: the ClinicalTrials.gov record does not provide a baseline characteristics table or subgroup estimates.
- No formal multiplicity procedure reported: the data identify multiple secondary analyses but do not provide an overall alpha-allocation or adjustment strategy for interpreting all posted P-values jointly.
- No interim-analysis specification reported: the ClinicalTrials.gov record do not identify interim looks, stopping boundaries, or alpha spending.
- No missing-data method reported: the registry extract identifies the analysis populations and tests but does not specify an imputation strategy for the binary endpoints.
- Hazard-ratio assumptions: Cox-model HRs are model-based summaries. The ClinicalTrials.gov record does not report a formal assessment of the proportional-hazards assumption.
- Assessment-source differences: investigator-assessed PFS and IRC-assessed PFS are distinct endpoints and should not be treated as identical measurements.
- Safety comparison: serious adverse-event counts are reported descriptively, without a formal comparative analysis or confidence intervals.
- Third-arm interpretation: the trial lists three arms, but the posted statistical efficacy analyses reported here compare only obinutuzumab plus chlorambucil with obinutuzumab plus venetoclax. The separate safety run-in is therefore not included in the efficacy comparisons.
24. Why This Trial Matters Statistically
CLL14 is a useful statistical teaching case because the registry data bring together two major classes of clinical-trial endpoints: time-to-event outcomes and binary categorical outcomes. The trial therefore shows why a single clinical study can require several statistical tools rather than one universal test.
| Concept | How it appears in CLL14 |
|---|---|
| Randomization | The trial is randomized with a parallel-group design. |
| Intention-to-treat analysis | The ITT population is defined as all randomized participants. |
| Time-to-event endpoint | Primary PFS is measured from baseline until disease progression or death. |
| Log-rank test | Used for the primary and IRC-assessed PFS comparisons. |
| Hazard ratio | Used to quantify the relative PFS treatment effect. |
| Cox regression | Used to estimate PFS hazard ratios. |
| Stratified analysis | Binet and Geographic region were used as Cox-model stratification factors. |
| CMH test | Used for multiple response and MRD categorical endpoints. |
| Chi-squared test | Used for approximately 9-month MRD-negativity comparisons. |
| Confidence intervals | Two-sided 95% intervals accompany the posted effect estimates. |
| Multiple endpoints | The registry contains 23 posted outcome measures and 10 statistical analyses. |
| Safety analysis | Serious adverse events are reported by treatment group using affected/at-risk counts. |
The educational value is particularly clear when the PFS HR of 0.35 is placed beside the response-rate difference of 13.43 percentage points. These are not competing ways of expressing exactly the same statistic. The first summarizes a longitudinal event process; the second summarizes a binary outcome at a defined assessment.
25. Related Tutorials
Learn more about the methods used in this trial:
26. Related Calculators
27. Sources
- ClinicalTrials.gov: NCT02242942 — CLL14.
- Linked PubMed record: PMID 40944848.
- Linked PubMed record: PMID 39082668.
- Linked PubMed record: PMID 38620092.
- Linked PubMed record: PMID 37072421.
- Linked PubMed record: PMID 35829925.
Continue through the Clinical Biostats statistical pathway
Use the methods illustrated by CLL14 to explore time-to-event analysis, categorical-data methods, confidence intervals, and clinical-trial analysis.
28. Record Summary
CLL14 provides a compact example of how modern clinical-trial statistics combine randomized treatment comparisons, a time-to-event primary endpoint, stratified survival analysis, hazard ratios, and several categorical secondary endpoints. The primary investigator-assessed PFS analysis reported an HR of 0.35 with a two-sided 95% CI of 0.23–0.53 and P < 0.0001. The registry also reports an IRC-assessed PFS HR of 0.33, together with differences in response and MRD-negativity rates analyzed using CMH or chi-squared methods.
The most important statistical lesson is that these results should be read according to the scale and structure of each endpoint. Hazard ratios describe relative time-to-event effects; percentage-point differences describe contrasts in binary outcomes at defined assessment times; confidence intervals describe statistical precision; and P-values address evidence against specified null hypotheses rather than measuring effect size.