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 results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for A Retrospective Non-interventional Study of Breast Cancer Patients Diagnosed With HR+/HER2- Locally Advanced or Metastatic Breast Cancer Treated With Palbociclib in Denmark (NCT05452798), a registered phase not stated study. The primary outcome is Progression-Free Survival (PFS) for Participants Who Received Palbociclib in Combination With Aromatase Inhibitor (AI).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT05452798 |
| Phase | Phase not stated |
| Condition | Breast Cancer |
| Allocation | Not Stated |
| Design model | Not Stated |
| Masking | Not Stated |
| Enrollment | 1054 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Pfizer |
| Results posted | Yes |
2. Clinical Question
Population
Patients with hormone receptor-positive, HER2-negative locally advanced or metastatic breast cancer. The primary analysis population is described as patients who initiated palbociclib with an aromatase inhibitor between 01 January 2017 and 31 December 2020. The overall study enrollment is 1054.
Intervention
The treatment of interest is palbociclib in combination with an aromatase inhibitor. The study retrospectively describes clinical and demographic characteristics and real-world treatment patterns among people receiving palbociclib combination treatment.
Comparator
No comparator group is specified for the primary question. This is a non-interventional study, and the registry record does not describe a randomized treatment comparison. Other treatment groups or comparisons are not reported in the registry record.
Primary question
Among patients receiving palbociclib with an aromatase inhibitor, what is the median time from the index date to documented disease progression or death? The registry defines the index date as the date of relapse or stage IV disease. The numerical median and inter-quartile range are not reported in the registry record.
3. Trial Design
This is a retrospective, non-interventional study of breast cancer patients in Denmark. Its stated objective is to describe and assess clinical and demographic characteristics and treatment patterns in a real-world setting among patients with HR+/HER2- locally advanced or metastatic breast cancer who received palbociclib combination treatment. The registry lists enrollment of 1054 and study status as completed.
The study start date is 2022-02-01 and the primary completion date is 2022-08-01. For the primary PFS analysis, the population is described as patients who initiated palbociclib with an aromatase inhibitor between 01 January 2017 and 31 December 2020. These dates describe the treatment-initiation window, not the study start and completion dates.
The primary outcome is median PFS, with an inter-quartile range as the stated measure of dispersion. The record says Kaplan-Meier methods were used. Follow-up for this outcome runs from the index date to progression or death, or censoring on 07-Mar-2022, with a maximum of up to 5.2 years. The record also lists secondary outcomes concerning survival, PFS and time on treatment with fulvestrant combinations, subsequent treatment, and metastasis characteristics.
This is not a randomized comparison, and a like-for-like control comparison is not described. Allocation is not stated. The registry lists 14 outcome measures but 0 analyses; numerical outcome estimates are not reported in the registry record. The sample-size justification, interim analyses, and a fuller statistical analysis plan are not reported in the registry record. Any sample-size planning illustrations are not part of the study's reported design and should not be interpreted as observed power.
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
| Stage | Palbociclib |
|---|---|
| STARTED | 1054 |
| COMPLETED | 1054 |
| NOT COMPLETED | 0 |
Analysis population for the primary outcome, as defined in the registry: Analysis was performed on participants with HR+/HER2- locally advanced or metastatic BC who initiated treatment with palbociclib in combination with AI between 01 January 2017 and 31 December 2020.
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: Analysis was performed on all eligible participants with HR+/HER2- locally advanced or metastatic BC who initiated treatment with palbociclib as first or second line treatment between 01 January 2017 and 31 December 2020.
| Characteristic | Unit | Palbociclib |
|---|---|---|
| Participants analysed | 1054 | |
| Age, Continuous: Age | years | 66.8 (SD 11.4) |
| Sex: Female, Male: Sex – Female | Participants | 1054 |
| Sex: Female, Male: Sex – Male | Participants | 0 |
| Race and Ethnicity Not Collected | Participants | — |
6. Primary Endpoint
The registry lists the primary outcome as Progression-Free Survival (PFS) for Participants Who Received Palbociclib in Combination With Aromatase Inhibitor (AI), measured over From index date until the first documentation of disease progression or death or censoring date of 07-Mar-2022 (maximum up to 5.2 years).
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Inter-Quartile Range |
| Unit | Months |
| Endpoint classification | Time-to-Event Analysis |
The primary endpoint is PFS for participants receiving palbociclib with an aromatase inhibitor. It measures the time from the index date to the first documented disease progression or death, whichever occurs first. The index date is defined as the date of relapse or stage IV disease. Stage IV disease means the cancer has spread to distant parts of the body.
Progression was based on scan and blood-testing results. The registry definition requires at least a 20% increase in the sum of diameters of target lesions, relative to the smallest sum recorded on study, including baseline if that is the smallest. It also requires an absolute increase of at least 5 millimeters. The registry says Kaplan-Meier methods were used and that the endpoint is reported as a median in months, with an inter-quartile range.
In general, a time-to-event endpoint incorporates both how long participants are observed and whether the event of interest occurs. Participants without a recorded event by the censoring date can contribute information up to their last relevant observation rather than being treated as if an event occurred then. This approach is useful when follow-up lengths differ. However, the median PFS and its inter-quartile range are not reported in the registry record, so the endpoint's observed value and precision cannot be assessed from the record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The primary outcome is defined clearly enough to identify the event and the time origin: PFS begins at relapse or stage IV disease and ends at documented progression or death, whichever comes first. The progression definition specifies both a relative increase in target-lesion measurements and an absolute increase. The record also identifies the analysis method as Kaplan-Meier and gives a censoring date of 07-Mar-2022, with follow-up up to 5.2 years.
Those design details do not establish the observed PFS result. The median and inter-quartile range are not reported in the registry record, and the record lists 0 analyses. Consequently, there is no reported numerical estimate to interpret, no confidence interval to assess, and no basis for describing the observed duration or precision of PFS. The registry lists 1054 enrolled participants, but does not report how many contributed to the primary analysis. Overall enrollment should not be assumed to equal the analysis population.
The record names secondary outcomes that include overall survival for participants receiving palbociclib with an aromatase inhibitor or fulvestrant, PFS and time on treatment with fulvestrant, subsequent treatment after progression, and metastasis characteristics. Their numerical results are not reported in the registry record. The safety summary lists 525 deaths under the Palbociclib group, but the registry entry does not provide enough analysis context to interpret that count as an estimate of overall survival or to establish its timing or relationship to treatment.
In general, a median time-to-event estimate describes the point by which half of the estimated event-time distribution has been reached, provided that the median is estimable. An inter-quartile range describes the middle half of that distribution. These summaries do not, by themselves, describe every participant's course or quantify uncertainty in the estimated median. A confidence interval would provide information about estimation uncertainty, but one is not reported for the primary outcome in the registry record.
Because the study is retrospective and non-interventional, its primary question is descriptive rather than a randomized treatment-effect comparison. The record does not specify a comparator for PFS. Even if a numerical result were available, it would describe the observed cohort under the stated definitions; it would not alone establish what would have happened to the same patients under another treatment. The registry does not report adjustment methods or other analyses that might address differences between treatment groups.
9. Statistical Methods Explained
The registry identifies the primary outcome as median PFS and states that the Kaplan-Meier method was used. In general, Kaplan-Meier estimation is a way to describe time until an event when some participants have incomplete follow-up at the time of analysis. It uses the event times and the information available up to censoring for participants whose event has not been observed. Censoring is not equivalent to observing that no event will occur; it means that the event was not recorded during the participant's available follow-up for that analysis.
For this study, the event is the first of documented progression or death. The time origin is the index date, defined as relapse or stage IV disease. The record specifies scans and blood-testing results as the basis for progression assessment and gives operational lesion-change criteria. The censoring date is 07-Mar-2022, and the stated maximum follow-up is up to 5.2 years. The actual distribution of follow-up and the number of censored observations are not reported in the registry record.
A Kaplan-Meier curve, when reported, can show how the estimated event-free proportion changes over time. The median is the time at which the estimated curve reaches the median point, if it reaches that point during observed follow-up. The inter-quartile range describes the span between the lower and upper quartiles of the event-time distribution. These are summaries of the observed time-to-event pattern, not comparisons against a control group. The registry states that median and inter-quartile range were the chosen summaries, but the numerical values are not reported in the registry record.
In general, confidence intervals convey statistical uncertainty around an estimate. Their width depends on factors such as the amount of information available and the distribution of event times. The primary result's confidence interval, standard error, and event count are not reported in the registry record. Without those details or the estimate itself, readers cannot judge the statistical precision of the primary result. No inference about precision should be drawn from the total enrollment alone, because the number enrolled is not necessarily the number included in a particular analysis.
The study's retrospective, non-interventional design is important when interpreting its aim. It uses patients treated in a real-world setting to describe characteristics and treatment patterns, rather than assigning participants to treatments through randomization. In general, randomized allocation helps balance measured and unmeasured prognostic factors between groups on average. In an observational study, treatment groups can differ in ways that also relate to outcomes. Here, no comparator is specified for the primary PFS question, so a treatment contrast is not defined in the registry record.
The registry lists 14 outcome measures and 0 analyses. It names additional outcomes, including survival, PFS and time on treatment for fulvestrant combinations, subsequent treatment after progression, and metastasis counts and locations. The entry does not report numerical analyses for these outcomes. It also does not report a detailed statistical analysis plan, the handling of missing data, model adjustments, subgroup analyses, or interim analyses. Those methods cannot be inferred from the use of Kaplan-Meier for the primary endpoint.
Sample-size calculations require a defined statistical objective and assumptions about the effect to detect, variability or event occurrence, allocation, and analysis method. The registry record describes planning illustrations as based on fractions of an observed effect and says that time-to-event illustrations count total events. Such illustrations are hypothetical planning quantities, not observed power and not evidence that the study was designed to detect a particular effect. The record does not report the study's own sample-size justification, and no primary observed effect is reported in the registry record from which to assess the illustrations.
In general, over-dispersion matters for count outcomes when variation exceeds what a simple count model assumes; ignoring it can make uncertainty estimates too small. That issue is not specifically reported as a concern or method in this record. Likewise, the record does not state whether any model beyond Kaplan-Meier was used for other outcomes. Statistical procedures for those endpoints should therefore not be assumed.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 14 outcome measures, including the primary PFS outcome and secondary outcomes concerning survival, PFS and time on treatment with fulvestrant, subsequent treatment, and metastasis characteristics. When a study assesses multiple outcomes, the number of statistical questions can affect how results are interpreted: testing many hypotheses can increase the chance of obtaining a nominally unusual result by chance. In general, multiplicity approaches may define a primary question in advance or adjust inference across several tests. The registry record does not report a multiplicity strategy or a hierarchy among secondary outcomes beyond identifying the primary endpoint.
The entry lists 0 analyses, and numerical outcome results are not reported in the registry record. It therefore does not provide a set of reported tests or estimates from which to assess how multiplicity was handled. An adjustment method should not be assumed.
The primary endpoint allows censoring on 07-Mar-2022 and describes follow-up up to 5.2 years. However, the record does not report the amount or pattern of missing outcome information, reasons for missingness, or a method for handling missing data. In general, censoring in time-to-event analysis uses available follow-up without assigning an event at the censoring time; interpretation depends on the censoring process and the analysis assumptions. Whether those assumptions were assessed is not reported in the registry record.
The primary analysis population is described by disease status and initiation of palbociclib with an aromatase inhibitor within the stated treatment window. The number of participants in that analysis population is not reported in the registry record. The registry does not describe exclusions, analysis-population rules beyond that eligibility description, or how incomplete records were handled. Overall enrollment of 1054 should not be treated as the denominator for every endpoint.
11. What the Result Does, and Does Not, Mean
The registry record describes a real-world, retrospective cohort question: PFS among patients with HR+/HER2- locally advanced or metastatic breast cancer who received palbociclib with an aromatase inhibitor. It defines the time origin, the progression event, the death component, the censoring date, and the use of Kaplan-Meier methods. These details clarify what the intended endpoint represents.
The record does not report the primary median PFS or its inter-quartile range. It also lists 0 analyses. Therefore, it does not establish the observed PFS distribution, the uncertainty around a numerical estimate, or the number of participants whose data contributed to that estimate. The listed enrollment of 1054 is a study-level count and does not establish the size of the primary analysis set.
Because the registry does not describe a comparator for the primary question, the endpoint is not a direct estimate of the difference between palbociclib and another treatment. The non-interventional design also means that treatment was not assigned randomly according to the information in the record. In general, observed outcomes in a treated cohort can reflect patient characteristics, clinical decisions, and follow-up as well as the treatment received. A descriptive result would not by itself identify a causal treatment effect.
The registry also names secondary outcomes, but does not report their numerical results. Its listing of 525 deaths under the Palbociclib group is not accompanied by enough context to interpret it as a survival estimate or a treatment-related safety result. The record does not supply the timing, analysis population, or method for that count. The study can therefore be characterized by its stated objective and methods, but not by an outcome conclusion from the registry entry.
12. Why This Trial Matters Statistically
Real-world studies can describe who received a treatment, how treatment was used, and how outcomes were defined in routine clinical settings. This study's stated objective is to characterize clinical and demographic features and treatment patterns among patients with HR+/HER2- locally advanced or metastatic breast cancer treated with palbociclib combination therapy in Denmark. Its retrospective design and defined treatment-initiation window make the intended setting and population explicit.
Statistically, the primary endpoint illustrates why time-to-event methods are relevant to clinical follow-up. Participants may have different lengths of observation, and some may be censored before progression or death is documented. The registry's definition of PFS specifies both the event and the time origin, while its use of Kaplan-Meier identifies the stated approach to handling event-time data with censoring.
The record also illustrates the distinction between a carefully described endpoint and a reported result. Defining PFS and naming a statistical method do not supply the estimated median, its uncertainty, or the number of observations supporting the analysis. With 0 analyses listed and no numerical primary result reported in the registry record, statistical interpretation must remain focused on the design and reporting gaps rather than on an outcome estimate.
The study is non-interventional and does not specify a comparator for the primary question. That makes it important to distinguish descriptive evidence from a randomized treatment contrast. A real-world cohort can provide context about treatment patterns, but a causal comparison requires a defined contrast and methods suited to the differences between groups. Such a comparison is not reported for the primary endpoint in this record.
13. 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 primary limitation for interpreting outcomes is that the registry record does not report the numerical PFS estimate, its inter-quartile range, or a confidence interval. Although the endpoint definition and Kaplan-Meier method are stated, there are 0 analyses listed. The reported enrollment of 1054 does not identify the number included in the primary analysis.
The retrospective, non-interventional design limits causal interpretation. No comparator is specified for the primary PFS endpoint, and allocation is not stated. The record does not report an adjustment strategy for prognostic differences, confounding, or selection into treatment. It therefore does not support a randomized comparison of palbociclib with another treatment.
The registry describes the primary analysis population as patients who initiated palbociclib with an aromatase inhibitor during the stated period, but the analysis-set size and participant flow are not reported in the registry record. The record also does not describe missing-data handling, the number or pattern of censored observations, or whether the assumptions underlying the time-to-event analysis were assessed.
The censoring date and maximum follow-up are specified, but the distribution of follow-up is not reported. The record lists multiple secondary outcomes without numerical analyses, and does not report a multiplicity strategy. The study's sample-size justification, interim analyses, and detailed statistical analysis plan are not reported in the registry record. These omissions limit assessment of precision, analysis choices, and the extent to which the posted record supports conclusions about outcomes.
14. Related Tutorials
15. Related Statistical Calculators
16. Sources
- ClinicalTrials.gov: A Retrospective Non-interventional Study of Breast Cancer Patients Diagnosed With HR+/HER2- Locally Advanced or Metastatic Breast Cancer Treated With Palbociclib in Denmark — NCT05452798.
- Registry record last updated 2024-03-01; status last verified 2023-07.
- Results first posted 2024-03-01.
- 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.
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Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
17. Record Summary
The registry describes a completed retrospective, non-interventional study of breast cancer patients in Denmark treated with palbociclib combination therapy. Enrollment is 1054; the study start date is 2022-02-01 and primary completion date is 2022-08-01. The stated objective is to describe clinical and demographic characteristics and real-world treatment patterns.
The primary outcome is median PFS for patients receiving palbociclib with an aromatase inhibitor. The analysis population is described as patients initiating that combination between 01 January 2017 and 31 December 2020. PFS is defined from relapse or stage IV disease to progression or death, with Kaplan-Meier analysis and censoring on 07-Mar-2022.
The registry lists 14 outcome measures and 0 analyses. The primary numerical result and secondary outcome estimates are not reported in the registry record. No comparator is specified for the primary question.