This page separates reported trial results from statistical interpretation. Numerical trial results are restricted to the ClinicalTrials.gov record. The registry provides one formal statistical analysis for the primary recurrence-free survival endpoint.
1. Trial at a Glance
CheckMate-76K is a randomized, parallel-group, phase 3 trial evaluating nivolumab compared with placebo in participants with melanoma after complete resection of stage IIB/C melanoma. The registered primary endpoint is recurrence-free survival (RFS), a time-to-event endpoint analyzed using a Cox proportional-hazards model.
| Feature | CheckMate-76K |
|---|---|
| Phase | Phase 3 |
| Condition | Melanoma |
| Population | Prevention of recurrent melanoma after complete resection of stage IIB/C melanoma |
| Design | Randomized, parallel-group, triple-masked |
| Primary purpose | Treatment |
| Enrollment | 790 |
| Interventions | Nivolumab and placebo |
| Primary endpoint | Recurrence Free Survival (RFS) |
| Primary endpoint type | Time-to-event |
| Primary hypothesis | Superiority |
| Primary analysis method | Cox proportional-hazards model |
| ClinicalTrials.gov | NCT04099251 |
| Trial status | Active, not recruiting |
| Lead sponsor | Bristol-Myers Squibb |
2. Clinical Question
The central statistical question is whether nivolumab produces a different recurrence-free survival experience than placebo after complete resection of stage IIB/C melanoma. The registry classifies the primary hypothesis as superiority.
Population
Participants with melanoma after complete resection of stage IIB/C melanoma, as described by the registered brief title.
Intervention
Nivolumab, classified in the registry as a biological intervention.
Comparator
Placebo, classified in the registry as an other intervention.
Primary question
Does nivolumab improve recurrence-free survival compared with placebo after complete resection of stage IIB/C melanoma?
3. Trial Design
The registry describes CheckMate-76K as a randomized, parallel-group, triple-masked phase 3 trial. Its primary purpose is treatment, and the trial contains two intervention arms.
Nivolumab
- Nivolumab
- Biological intervention
- Compared with placebo in the randomized trial
Placebo
- Placebo
- Other intervention
- Comparator for the randomized treatment comparison
The registry reports 790 participants enrolled and two arms, but the ClinicalTrials.gov record does not provide arm-specific randomized sample sizes. They therefore are not inferred here.
Trial timing
Trial start
The registered study start date was 2019-10-28.
Primary completion
The registered primary completion date was 2022-06-28.
Active, not recruiting
The ClinicalTrials.gov record classifies the study as ACTIVE_NOT_RECRUITING.
4. Endpoints
The registry identifies one primary endpoint, and it is a time-to-event endpoint.
| Endpoint | Registry definition / time frame | Analysis |
|---|---|---|
| Recurrence Free Survival (RFS) | Time between the date of randomization and the date of first recurrence (local, regional or distant metastasis), new primary melanoma (including melanoma in situ), or death (whatever the cause), whichever occurs first. For participants who remain alive and whose disease has not recurred or did not die, RFS will be censored on the date of last evaluable disease assessment. For those participants who remained alive and had no recorded post-randomization tumor assessment, RFS will be censored on the day of randomization. | Cox proportional-hazards model |
5. Statistical Methodology
Primary analysis population
The posted statistical analysis specifies all randomized participants as the analysis population. This is important because the primary efficacy comparison remains anchored to treatment assignment rather than being restricted to participants who completed treatment.
Time-to-event framework
RFS is measured over time rather than as a simple binary endpoint. Participants who experience recurrence, a new primary melanoma, or death contribute an event time. Participants who remain alive without a qualifying event contribute follow-up until censoring.
Cox proportional-hazards model
The registry reports the method as Regression, Cox, normalized here as a Cox proportional-hazards model. The effect measure is the hazard ratio.
The hazard ratio for a treatment indicator compares the modeled instantaneous event rates between treatment groups, conditional on the model structure.
Hazard ratio
The hazard ratio is a relative measure of the event rate at a given point in follow-up under the fitted model. It is not a ratio of median RFS times, not a relative risk at a fixed time point, and not a statement that the same percentage of individuals experience the same reduction in recurrence risk.
For this trial, the estimated HR is below 1, so the fitted model estimates a lower instantaneous rate of an RFS event for nivolumab relative to placebo over the analyzed follow-up.
Confidence interval
The reported confidence interval quantifies uncertainty around the estimated hazard ratio under the statistical model and sampling framework. It does not describe the range of effects experienced by individual participants.
Superiority hypothesis
The registry classifies the primary hypothesis as superiority. In a superiority analysis, the treatment comparison asks whether the observed data provide evidence that the treatment groups differ in the prespecified direction of interest rather than asking whether a treatment is merely no worse than a predefined non-inferiority margin.
6. Results: Recurrence-Free Survival
ClinicalTrials.gov reports one formal statistical analysis for the primary endpoint. It compares nivolumab with placebo among all randomized participants using a Cox proportional-hazards model.
Primary endpoint: Recurrence-Free Survival
95% CI: 0.30–0.59 · P < 0.0001
Analysis population: all randomized participants · Hypothesis: superiority
| Primary endpoint | Nivolumab vs placebo | 95% CI | P-value | Method |
|---|---|---|---|---|
| Recurrence Free Survival (RFS) | HR 0.42 | 0.30–0.59 | < 0.0001 | Cox proportional-hazards model |
The estimated hazard ratio of 0.42 means that, under the fitted Cox model, the estimated instantaneous rate of an RFS event in the nivolumab group was approximately 42% of the rate in the placebo group over the analyzed follow-up. Equivalently, 1 − 0.42 = 0.58, so the estimate corresponds to an approximately 58% lower estimated hazard of an RFS event.
This does not mean that 58% of participants were protected from recurrence, that 58% of participants were cured, or that every individual participant had exactly a 58% reduction in risk. A hazard ratio is a model-based relative measure of event rates over time.
The 95% confidence interval of 0.30–0.59 describes the statistical uncertainty around the estimated hazard ratio. The interval is entirely below 1, which is consistent with a treatment effect favoring nivolumab under the prespecified superiority framework.
The P < 0.0001 result addresses evidence against the relevant null hypothesis under the statistical testing framework. It does not measure the size of the treatment effect. Effect size is described by the hazard ratio, while the confidence interval communicates its precision.
Because the analysis uses a Cox proportional-hazards model, interpretation of a single hazard ratio should be considered in light of the model's proportional-hazards assumption. The ClinicalTrials.gov record does not report a formal assessment of that assumption, nor do they provide a Kaplan-Meier curve, median RFS, event counts, or time-specific RFS estimates.
7. How to Read the Primary Result
Relative effect
The HR of 0.42 is the primary reported relative treatment-effect measure. It compares the modeled instantaneous rates of the RFS event between the randomized groups.
Direction
An HR below 1 indicates a lower estimated event hazard for nivolumab relative to placebo under the fitted model.
Precision
The 95% CI of 0.30–0.59 shows the uncertainty around the point estimate. It should not be interpreted as an interval containing individual patient treatment effects.
Statistical evidence
The P-value is reported as < 0.0001. It describes statistical evidence against the null hypothesis; it is not a measure of clinical importance or effect magnitude.
8. Statistical Methods Explained
Why was a Cox proportional-hazards model used?
RFS is a time-to-event endpoint. Some participants experience an event during follow-up, while others may be censored before an event is observed. A Cox model is designed for this setting because it compares event hazards over time while accommodating censored observations.
What does an HR of 0.42 mean?
An HR of 0.42 means that the estimated instantaneous event rate under the fitted model is 0.42 times the comparator rate. Expressed as a relative reduction, 1 − 0.42 = 0.58, corresponding to an approximately 58% lower estimated hazard. This is not equivalent to saying that 58% of patients avoid recurrence.
Why is RFS a time-to-event endpoint rather than a simple recurrence rate?
The registered definition incorporates the time from randomization to the first recurrence, new primary melanoma, or death. The time dimension therefore carries information that would be lost if the analysis simply classified every participant as having or not having an event.
What does the 95% confidence interval tell us?
The interval of 0.30–0.59 expresses uncertainty around the estimated HR under the model and statistical framework. A narrower interval would generally indicate greater precision, while a wider interval would indicate more uncertainty. The interval should not be read as the range of effects among individual patients.
Why doesn't the P-value measure effect size?
The P-value evaluates the compatibility of the observed data with a specified null hypothesis under the statistical testing framework. It depends on both the observed effect and the amount of information in the analysis. The HR communicates the estimated relative effect, while the confidence interval communicates uncertainty around that estimate.
What does the proportional-hazards assumption mean?
The Cox model expresses treatment effects through a hazard ratio that is commonly interpreted as a relative hazard over time. If the proportional-hazards assumption does not adequately describe the underlying event process, a single HR may provide an incomplete summary of how treatment effects vary during follow-up. The ClinicalTrials.gov record does not report a formal proportional-hazards diagnostic.
9. What the Hazard Ratio Does — and Does Not — Mean
The reported RFS hazard ratio is 0.42. In the context of the Cox model, this corresponds to an estimated instantaneous RFS event rate that is 42% of the placebo rate, or approximately a 58% lower estimated hazard for nivolumab.
The HR is not a 58% probability of avoiding recurrence, not a 58% reduction in every patient's individual risk, and not a 58% increase in median RFS. Those interpretations require different quantities and, where applicable, different statistical summaries.
A hazard ratio provides a relative treatment effect but does not directly state the absolute probability of remaining recurrence-free at a specified time. The ClinicalTrials.gov record does not provide time-specific RFS estimates or median RFS, so those quantities are not inferred here.
10. Safety: Serious Adverse Events
The ClinicalTrials.gov record reports serious adverse events by arm as affected participants divided by participants at risk. These figures should be kept separate from the efficacy analysis because safety and efficacy answer different questions and can use different analysis populations or definitions.
| Group | Participants with serious adverse events | Participants at risk |
|---|---|---|
| Nivolumab | 95 | 524 |
| Placebo | 37 | 264 |
| Open-Label Nivolumab | 5 | 30 |
11. Analysis Population and Randomization
The formal RFS analysis specifies all randomized participants as the analysis population. This is an important feature of randomized clinical-trial inference because treatment assignment is determined before the outcome is observed.
| Feature | Registered information |
|---|---|
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Triple |
| Primary analysis population | All randomized participants |
| Groups compared | Nivolumab vs placebo |
| Primary hypothesis | Superiority |
| Primary endpoint type | Time-to-event |
Randomization helps make the treatment groups comparable in expectation with respect to measured and unmeasured baseline factors. Triple masking can additionally reduce opportunities for treatment knowledge to influence aspects of trial conduct or assessment, although the ClinicalTrials.gov record does not specify the identities of the three masked parties.
12. Multiplicity, Interim Analysis, and Other Design Topics
The ClinicalTrials.gov record identifies one registered primary endpoint and one posted formal statistical analysis. They do not provide a multiplicity-adjustment procedure, an interim-analysis schedule, an alpha-spending plan, a non-inferiority margin, a crossover strategy, an imputation method, or a Bayesian analysis.
| Design topic | What can be concluded from the ClinicalTrials.gov record |
|---|---|
| Primary endpoint multiplicity | One primary endpoint is identified: RFS. |
| Formal primary analyses | One statistical analysis is posted for the primary endpoint. |
| Hypothesis type | Superiority. |
| Non-inferiority margin | Not applicable to the reported superiority hypothesis; no margin is reported. |
| Interim analysis | No interim-analysis details are reported. |
| Crossover | No crossover details are reported. |
| Missing-data / imputation method | No specific imputation method is posted on ClinicalTrials.gov for the primary analysis. |
| Bayesian methods | No Bayesian method is reported in the ClinicalTrials.gov record. |
This distinction is important. The absence of a registry-reported design detail should not be converted into an assumption about how the protocol or statistical analysis plan handled it.
13. What Is and Is Not Reported in the Supplied Results
The ClinicalTrials.gov record contains 12 posted outcome measures but only one posted statistical analysis. That formal analysis concerns the primary RFS endpoint.
Reported formally
RFS, analyzed among all randomized participants using a Cox proportional-hazards model, with HR 0.42, 95% CI 0.30–0.59, and P < 0.0001.
Not interpreted as formal comparisons
The ClinicalTrials.gov record does not provide formal statistical analyses for secondary endpoints, so no secondary efficacy comparison is constructed here.
Not inferred
Median RFS, event counts, time-specific RFS rates, subgroup estimates, and Kaplan-Meier estimates are not reported and are therefore not calculated.
Safety information available
Serious adverse-event counts and denominators are posted on ClinicalTrials.gov for nivolumab, placebo, and open-label nivolumab.
14. Limitations and Interpretation Issues
- Single formal analysis: the ClinicalTrials.gov record contains one posted statistical analysis, so the page cannot responsibly construct additional efficacy comparisons that are not reported.
- Limited time-to-event detail: the ClinicalTrials.gov record provides the HR and confidence interval but not median RFS, event counts, censoring counts, or time-specific RFS estimates.
- Proportional-hazards assumption: the Cox model provides a compact HR summary, but the ClinicalTrials.gov record does not report a formal diagnostic of proportional hazards.
- Confidence interval interpretation: the 95% CI quantifies uncertainty around the estimated hazard ratio; it does not describe individual patient outcomes.
- P-value interpretation: P < 0.0001 is evidence against the relevant null hypothesis under the stated testing framework, but it does not measure effect magnitude.
- Safety denominators: serious-adverse-event information is posted on ClinicalTrials.gov for randomized and open-label groups, but the ClinicalTrials.gov record do not establish a single common randomized analysis population for all three groups.
- Unreported design details: the ClinicalTrials.gov record does not specify interim-analysis procedures, multiplicity adjustments, imputation methods, crossover rules, or Bayesian methods.
- Subgroup interpretation: no subgroup estimates are reported, so treatment-effect heterogeneity cannot be assessed from the ClinicalTrials.gov record.
15. Why This Trial Matters Statistically
CheckMate-76K is a useful teaching example because the ClinicalTrials.gov record illustrates the central statistical structure of a randomized time-to-event trial without requiring unsupported assumptions about additional analyses.
| Concept | How it appears in CheckMate-76K |
|---|---|
| Randomization | The allocation is explicitly randomized. |
| Parallel-group design | The registry identifies a parallel design model with two intervention groups. |
| Blinding | The trial is classified as triple-masked. |
| Time-to-event endpoint | RFS is the registered primary endpoint. |
| Kaplan-Meier framework | RFS is a time-to-event endpoint for which Kaplan-Meier estimation is a standard descriptive approach. |
| Cox model | The formal posted analysis uses a Cox proportional-hazards model. |
| Hazard ratio | The primary treatment effect is reported as an HR of 0.42. |
| Confidence interval | The 95% CI is 0.30–0.59. |
| P-value | The primary analysis reports P < 0.0001. |
| Superiority testing | The registered hypothesis type is superiority. |
| ITT-style efficacy principle | The primary analysis population is all randomized participants. |
| Safety analysis | Serious adverse events are reported by group with affected and at-risk counts. |
16. Statistical Concepts in This Trial
Learn more about the methods used in this trial:
17. Related Statistical Calculators
18. Sources
- ClinicalTrials.gov: CheckMate-76K, NCT04099251.
- Linked publication: PubMed record for PMID 40139004.
- Linked publication: PubMed record for PMID 37845511.
Continue with the statistical methods
Explore the underlying survival-analysis concepts, confidence intervals, hypothesis testing, and clinical-trial methods used to interpret randomized time-to-event studies.
19. Record Summary
CheckMate-76K provides a clear example of randomized time-to-event analysis. The trial enrolled 790 participants in a randomized, parallel, triple-masked phase 3 design comparing nivolumab with placebo. Its registered primary endpoint was recurrence-free survival, defined from randomization to the first recurrence, new primary melanoma, or death, with censoring for participants remaining alive without a qualifying event. The posted formal analysis used a Cox proportional-hazards model in all randomized participants and reported an HR of 0.42 with a 95% CI of 0.30–0.59 and P < 0.0001.
Statistically, the most important lesson is that these three quantities answer different questions. The hazard ratio describes the estimated relative event rate under the Cox model, the confidence interval describes uncertainty around that estimate, and the P-value describes statistical evidence against the relevant null hypothesis. None of these quantities alone describes the absolute probability of remaining recurrence-free at a particular time.
The ClinicalTrials.gov record does not provide median RFS, event counts, time-specific RFS estimates, subgroup estimates, or detailed interim and multiplicity procedures. Those quantities are therefore not reconstructed here. Keeping the distinction between reported evidence and statistical interpretation is essential when analyzing a clinical trial from registry data.