Treatment Patterns & Clinical Outcomes of Palbociclib Combinations in HR+HER2-MBC: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Treatment Patterns & Clinical Outcomes of Palbociclib Combinations in HR+HER2-MBC (NCT04937660), a registered phase not stated study. The primary outcome is Percentage of Participants Who Were Progression Free at 6 Months Post Palbociclib Initiation.

2. Clinical Question

The study’s broader objective was to describe treatment patterns, clinical outcomes, and quality of life among participants initiating palbociclib combinations. The registry record also lists secondary outcomes concerning objective response, time from initial breast cancer diagnosis to recurrence, and participant characteristics such as stage, node status, menopausal status, prescribed combination, metastatic sites, and metastatic status.

This is a descriptive clinical question about outcomes observed during routine care. It is not a question about whether palbociclib combinations outperform another treatment, because the registry record does not identify a randomized comparator for the primary endpoint. The endpoint estimate itself, including its confidence interval, is not reported in the registry record, so the primary question cannot be answered from the recorded results alone.

3. Trial Design

NCT04937660 is a completed, non-interventional, multicenter prospective observational study sponsored by Pfizer. Its official title describes a study of palbociclib combinations in HR+/HER2- metastatic breast cancer patients and treatment patterns and clinical outcomes in Africa and the Middle East. The registry lists metastatic breast cancer as the condition.

The study began on 2021-07-15 and has a primary completion date of 2025-04-29. The recorded enrollment is 185. These are registry design and status details; the enrollment figure does not establish how many participants contributed data to the primary endpoint or to any particular analysis. The endpoint-specific analysis population size is not reported in the registry record.

Participants initiated palbociclib combination treatment in routine clinical practice. Because the study was non-interventional, treatment was observed rather than allocated by the study. The registry does not state an allocation method. There is no basis for interpreting any treatment group as a randomized control or assuming that groups had comparable baseline characteristics.

The primary outcome was the percentage of participants who were progression free at 6 months from palbociclib initiation. The registry defines progression free as alive with no reported disease progression. Progression was identified as an increase in visible disease and/or the presence of new lesions, evaluated by the clinician according to local guidelines and collected in the electronic case report form.

The record lists 30 outcome measures and 0 analyses. It does not report a statistical analysis plan, sample-size justification for the observational study, or interim-analysis plan. The registry record lists a full analysis set consisting of participants who fulfilled the eligibility criteria, but does not report endpoint-specific exclusions or the number analyzed.

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.

Before assignment: A total of 185 participants were enrolled in the study. Of these, 183 participants initiated palbociclib treatment and constituted the full analysis set (Full analysis set included all participants who fulfilled the eligibility criteria).

Overall Study

Analysis population for the primary outcome, as defined in the registry: Full analysis set included all participants who fulfilled the eligibility criteria.

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: Full analysis set included all participants who fulfilled the eligibility criteria.

6. Primary Endpoint

The registry lists the primary outcome as Percentage of Participants Who Were Progression Free at 6 Months Post Palbociclib Initiation, measured over At 6 months from the date of palbociclib initiation in routine clinical practice.

The primary endpoint is the percentage of participants who were progression free at 6 months after palbociclib initiation in routine clinical practice. A participant met the registry definition if they were alive and no disease progression had been reported. Progression included an increase in visible disease and/or new lesions, assessed by the clinician according to local guidelines and entered into the electronic case report form.

This endpoint combines survival status and disease status at a specified follow-up time. It therefore describes the share of the defined population meeting both parts of the progression-free definition at that time point. The registry states that the Kaplan-Meier method was used. In general, time-to-event methods can use information about follow-up duration and account for participants whose event status is not observed through the full follow-up period, subject to the method’s assumptions and the way censoring is handled.

The registry describes the result as a percentage and specifies a 95% confidence interval as its dispersion measure. A confidence interval communicates uncertainty around an estimate; it is not a range containing a stated proportion of individual participant outcomes. The estimate and its confidence interval are not reported in the registry record, and the number contributing to the endpoint is not reported.

The endpoint is useful for describing disease status at a clinically specified follow-up point in routine practice. It does not, by itself, establish a treatment effect. Without a randomized comparator and an endpoint result, it cannot show whether outcomes differed because of treatment rather than participant characteristics, clinical decisions, follow-up, or other factors.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary endpoint is a time-specific proportion: participants counted as progression free had to be alive and have no reported progression at 6 months from palbociclib initiation. The registry describes the endpoint in percentage terms but also states that Kaplan-Meier methods were used. These descriptions relate to a proportion at a specified time and a method for estimating event-free status over follow-up. The registry does not provide enough detail to reconstruct the exact analysis or its implementation.

What does Kaplan-Meier estimation do?

In general, Kaplan-Meier estimation uses the observed timing of events during follow-up to estimate the probability of remaining free of the event over time. Participants whose event status is not observed through the end of follow-up may contribute information up to their last known observation, rather than being treated as if they had experienced an event. This approach depends on defining the event and censoring rules and on appropriate assumptions about why follow-up ends. The registry identifies the Kaplan-Meier method but does not report its censoring rules, the handling of withdrawals or loss to follow-up, or details of the estimation procedure.

Here, progression is defined through a clinical assessment: an increase in visible disease and/or new lesions, evaluated according to local guidelines and recorded in the electronic case report form. This makes the event definition clinically grounded, while leaving some operational details unknown. The registry record does not state how often disease assessments were scheduled, how differences among local guidelines were addressed, or whether progression assessments were centrally reviewed.

How should the confidence interval be read?

In general, a confidence interval describes the precision of an estimate under the analysis method. A narrower interval indicates less statistical uncertainty about the estimated quantity than a wider interval, while neither interval describes the range of outcomes for individual participants. The registry specifies a 95% confidence interval for the primary endpoint, but it does not report the interval’s limits or the estimate. Its precision therefore cannot be evaluated from the registry record.

The width of an interval is influenced by the amount and distribution of information available, including the number of participants with evaluable follow-up and the number and timing of events. The registry reports enrollment of 185, but the number contributing to the primary endpoint and the event information used in the analysis are not reported. Enrollment alone cannot establish the precision of the estimate.

What does the analysis population represent?

The registry defines the full analysis set as all participants who fulfilled the eligibility criteria. This is a population definition, not a report of how many participants were analyzed. The record does not state whether all eligible participants had sufficient follow-up for the 6-month endpoint, how missing outcome data were handled, or whether exclusions occurred after eligibility was established. Those details matter because the population represented by an estimate depends on who contributes information and how incomplete observations are treated.

The record lists 30 outcome measures and 0 analyses. It does not describe a statistical plan for handling multiple outcomes, selecting models, or controlling the chance of false-positive findings across analyses. It also does not report interim analyses. These absences do not establish that such procedures were or were not used; they mean that the registry record does not report them.

How do the planning illustrations differ from observed analysis?

In general, sample-size planning asks how much information a future study might need under stated assumptions. The planning framework associated with this study describes a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect specified as a fraction of the observed effect. For time-to-event calculations, it describes the total number of events using the Schoenfeld approach; other calculations are expressed as participants per arm.

These assumptions are not a description of the observational study’s allocation. The registry does not state that participants were randomized or assigned equally to two arms, and it cautions that arms are not a like-for-like control comparison. The planning values are illustrations, not observed power, and do not establish the study’s original sample-size justification. The registry record does not report such a justification. No planning output values are reported in the registry information.

More generally, a p-value, if reported, would address compatibility of data with a specified statistical null model; it would not measure clinical importance or prove causation. The registry reports 0 analyses, and no primary p-value is reported in the registry record. Accordingly, interpretation should remain focused on the endpoint definition, the unavailable estimate and interval, and the observational design rather than on unreported tests.

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("Palbociclib Combination Therapy")
n      <- c(183)
events <- c(146)
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  Palbociclib Combination Therapy  183  146  79.8  73.2  85.3  73.4  85.0  73.4  85.0

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 30 outcome measures, including the primary progression-free endpoint and secondary outcomes such as objective response rate, time from initial breast cancer diagnosis to recurrence, and participant characteristics. It reports 0 analyses. The registry record does not describe a multiplicity strategy, such as a hierarchy for testing outcomes or an adjustment to account for examining multiple outcomes. Without such information, the status of any secondary finding as confirmatory or exploratory cannot be determined from this record.

Missing-data procedures are not reported in the registry record. In particular, it does not state how participants without an assessment at 6 months were handled, how loss to follow-up was addressed, or whether missingness was summarized by reason. These details can affect the interpretation of an endpoint estimate, especially when follow-up duration varies. Although the registry says Kaplan-Meier methods were used, it does not specify censoring rules or report the number of participants at risk over time.

The analysis population is defined as the full analysis set, including all participants who fulfilled the eligibility criteria. The registry does not give the number in that set, confirm how many contributed to the primary analysis, or describe post-eligibility exclusions. Enrollment is recorded as 185, but that figure should not be read as the endpoint denominator.

The statistical analysis plan, interim analyses, and sample-size justification are not reported in the registry record. The presence of planning illustrations does not supply those missing details or show that the observational study used the illustrations’ assumed allocation. The record’s statement that arms are not a like-for-like control comparison further limits how group-based findings should be interpreted.

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

The primary endpoint was intended to describe the percentage of participants alive and without reported progression at 6 months after starting palbociclib combination therapy in routine practice. Because the estimate and 95% confidence interval are not reported in the registry record, the endpoint’s observed level and statistical precision cannot be described. The recorded enrollment does not fill that gap or establish how many participants contributed endpoint data.

Even if an endpoint estimate were available, this non-interventional study would describe outcomes among observed participants rather than establish that treatment caused those outcomes. Participants were not described as randomly assigned, and the registry does not specify a concurrent comparator for the primary question. Clinical choices and participant characteristics may differ across treatment groups, so group contrasts would not automatically represent treatment effects.

The registry’s progression definition depends on clinician evaluation under local guidelines and data collection in an electronic case report form. Interpretation therefore depends on how consistently assessments were conducted and recorded. The record does not report enough information to judge assessment schedules, missing follow-up, or any central review procedures.

The listed secondary outcomes broaden the study’s descriptive scope, but their numerical findings are not reported in the registry record. The record also lists 0 analyses, so it does not provide statistical results for evaluating those outcomes. Planning illustrations based on an observed effect do not demonstrate the probability that the study detected a real effect; they are planning calculations, not observed power.

The adverse-event entry lists 7 deaths, but attribution to treatment is not reported in the registry information. The listed event-count fields and absence of serious-event terms also require context that the record does not provide. These entries should be read as registry reporting, not as a causal safety assessment.

Overall, the registry describes the study question and methods at a broad level, but the absent endpoint estimate, interval, analysis details, and missing-data information prevent a quantitative assessment of the primary result. No conclusion about comparative benefit or harm follows from the design details alone.

13. Why This Trial Matters Statistically

This study addresses a practical statistical question: how to describe disease status over follow-up when treatment is initiated in routine care rather than assigned by a trial. Prospective observational data can document treatment patterns and clinical outcomes in the setting where care is delivered. The registry’s focus on Africa and the Middle East is part of that stated context, although the record does not specify the number or identity of participating countries or sites.

The primary endpoint brings together a clinically defined progression event and survival status at a fixed follow-up time. Applying a time-to-event method can be relevant when participants have different follow-up durations, but interpretation depends on event ascertainment, censoring, and completeness of follow-up. The registry names Kaplan-Meier estimation and gives the broad progression definition, while leaving several implementation details unreported.

Statistically, the most important distinction is between describing observed outcomes and estimating a causal treatment effect. A prospective design does not by itself balance prognostic factors or make treatment groups comparable. The registry does not report random allocation and cautions that arms are not like-for-like controls. This limits the claims that could be supported by any unadjusted group contrast.

The record also illustrates why a clearly stated endpoint is not enough to assess results. An estimate, its uncertainty, the analysis population, and the approach to incomplete follow-up are needed to understand what the data show and how precisely. Those primary result details are not reported in the registry record. The listed enrollment is not a substitute for the number analyzed, and planning illustrations are not evidence of observed power.

Finally, a broad set of outcome measures makes transparent analysis planning important. The registry lists 30 outcome measures but 0 analyses, and does not report multiplicity or missing-data methods. That limits reproducibility and the ability to distinguish prespecified findings from exploratory descriptions. These are central considerations for interpreting observational clinical research, not merely technical details.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The registry record leaves the primary endpoint result unavailable: neither the percentage progression free at 6 months nor its 95% confidence interval is reported. It also does not report the number analyzed for this endpoint, the number with evaluable follow-up, or the number of progression events. The enrollment figure of 185 cannot be assumed to be the endpoint denominator.

The study is non-interventional, and no randomized comparator is identified. The registry cautions that arms are not a like-for-like control comparison. As a result, treatment-group differences, if described elsewhere, would be vulnerable to differences in participant characteristics and clinical treatment choices. Adjustment methods and baseline comparability are not reported in the registry record.

Outcome ascertainment was based on clinician evaluation according to local guidelines and was collected in an electronic case report form. The record does not describe assessment schedules, consistency of local criteria, independent review, or procedures for resolving uncertain progression status. It also does not report censoring rules or how missed visits, withdrawal, or other incomplete follow-up were handled.

The registry lists 30 outcome measures and 0 analyses, but does not report multiplicity procedures, detailed statistical methods, interim analyses, or a trial-specific sample-size justification. The primary analysis population is defined by eligibility, but its size and any post-eligibility exclusions are not stated. These omissions make it difficult to assess selection, precision, and the reproducibility of the analysis.

The adverse-event information lists 7 deaths without reported attribution details. The registry record does not provide enough context to interpret the listed adverse-event counts as a complete or causal safety assessment. The number and identity of study sites and countries are also not reported in the registry record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Treatment Patterns & Clinical Outcomes of Palbociclib Combinations in HR+HER2-MBC — NCT04937660.
• Registry record last updated 2026-06-10; status last verified 2026-06.
• Results first posted 2026-06-10.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

18. Record Summary

NCT04937660 is a completed, non-interventional, multicenter prospective observational study sponsored by Pfizer. It concerns palbociclib combinations for HR+/HER2- metastatic breast cancer in routine clinical practice in Africa and the Middle East. The registry lists enrollment of 185, a start date of 2021-07-15, and a primary completion date of 2025-04-29.

The primary endpoint was the percentage of participants alive and without reported disease progression at 6 months after palbociclib initiation. Progression was evaluated by clinicians according to local guidelines, and the registry states that Kaplan-Meier methods were used. A 95% confidence interval was specified, but the estimate and interval are not reported in the registry record.

The full analysis set was defined as participants who fulfilled eligibility criteria. The record lists 30 outcome measures and 0 analyses. It does not report the endpoint-specific analysis population, missing-data procedures, or detailed statistical plan. The adverse-event entry lists 7 deaths, without reported attribution details.