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 Study of HR+/HER2- Metastatic Breast Cancer Patients Treated With Palbociclib Together With an Aromatase Inhibitor From 2017 to 2023 in Denmark. (NCT06307457), a registered phase not stated study. The primary outcome is Progression-Free Survival (PFS).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT06307457 |
| Phase | Phase not stated |
| Condition | Breast Cancer |
| Allocation | Not Stated |
| Design model | Not Stated |
| Masking | Not Stated |
| Enrollment | 604 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Pfizer |
| Results posted | Yes |
2. Clinical Question
Population
Patients in Denmark with HR+/HER2- locally advanced or metastatic breast cancer who started treatment between January 2017 and December 2021. The analysis population is described as eligible participants whose data were retrieved and observed in the study. Enrollment is listed as 604.
Intervention
The treatment of interest is palbociclib in combination with an aromatase inhibitor (AI). The registry describes the study as non-interventional and reports treatment received in clinical practice rather than a randomized assignment.
Comparator
No comparison treatment group is described. The registry record does not report a like-for-like control comparison, and allocation is not stated. The intended analyses instead examine outcomes across age and comorbidity groups.
Primary question
The primary endpoint is progression-free survival (PFS), measured from the index date to disease progression, death, or censoring, whichever occurred first. The study’s stated focus is describing treatment outcomes by age and comorbidities. The registry record does not report numerical PFS estimates or a treatment-effect comparison.
The clinical question is therefore descriptive: how was PFS characterized among eligible patients receiving the combination, and how did outcomes vary across the age and comorbidity groupings considered by the study? The registry lists secondary outcomes for overall survival (OS) and PFS by age, Charlson Comorbidity Index (CCI) score, number of comorbidities, and type of comorbidity. These planned outcome categories indicate the study’s focus, but do not establish what the analyses found.
3. Trial Design
The registry describes a Danish non-interventional study of patients with HR+/HER2- locally advanced or metastatic breast cancer treated with palbociclib in combination with an aromatase inhibitor. The study title identifies first-line treatment, while the brief summary describes eligible patients as having started treatment between January 2017 and December 2021. The listed enrollment is 604.
This is a retrospective analysis of treatment and outcome data, not a randomized comparison. The record lists no comparison treatment group, and allocation is not stated. It therefore does not describe a design in which patients were assigned to palbociclib plus an AI versus another treatment. Differences between age or comorbidity groups, if reported, would be observational group comparisons rather than randomized treatment effects.
The registry lists the study start date as 2024-03-06 and the primary completion date as 2024-04-19, with status COMPLETED. The PFS timeframe describes data collected from 1 January 2017 to 1 February 2024, with maximum follow-up up to 7.09 years, and says the data were observed retrospectively for approximately 1.3 months of this study. These dates describe different aspects of the record: the treatment period, the outcome-data period, and the registered study dates.
The primary analysis population is described as all eligible participants whose data were retrieved and observed in the study. The registry does not report the eligibility criteria in full, the number of participants contributing to each analysis, a sample-size justification, or a detailed analysis plan. The stated intervention and outcome categories define the study’s scope, but do not by themselves establish the completeness or comparability of the underlying records.
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: Data collected retrospectively from 1 January 2017 to 1 February 2024 from Danish Breast Cancer Group (DBCG) registry and was evaluated for approximately 1.3 months (duration from start of the study to end of the study) in this retrospective study.
Overall Study
| Stage | All Participants |
|---|---|
| STARTED | 604 |
| COMPLETED | 604 |
| NOT COMPLETED | 0 |
Analysis population for the primary outcome, as defined in the registry: Analysis population included all eligible participants whose data were retrieved and observed in the study.
5. Baseline Characteristics
The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.
| Characteristic | Unit | All Participants |
|---|---|---|
| Participants analysed | 604 | |
| Age, Continuous | Years | 66.8 (SD 10.9) |
| Sex: Female, Male: Female | Participants | 604 |
| Sex: Female, Male: Male | Participants | 0 |
| Race and Ethnicity Not Collected | Participants | — |
6. Primary Endpoint
The registry lists the primary outcome as Progression-Free Survival (PFS), measured over From index date to disease progression or death or censoring date, whichever occurred first (data collected from 1 January 2017 to 1 February 2024 [maximum up to 7.09 years] and observed retrospectively for approximately 1.3 months of this study).
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | 95% Confidence Interval |
| Unit | Months |
| Endpoint classification | Time-to-Event Analysis |
The primary endpoint is progression-free survival (PFS), reported as a median in months with a 95% confidence interval. PFS measures the time from the index date until disease progression or death, whichever occurs first; participants may also be censored at a censoring date. The index date is defined as the date of relapse or stage IV disease.
Progression was based on scans and blood testing results. The registry defines progression as at least a 20% increase in the sum of the diameters of target lesions, using the smallest sum on study as the reference, including the baseline sum if it is the smallest. The increase must also be at least 5 millimeters. These criteria specify how progression was defined for the endpoint.
In general, PFS is used in time-to-event analyses because it incorporates both how long participants remain without a recorded progression and the occurrence of death before progression. A median describes the time by which the estimated survival curve has reached its midpoint; it is not an average follow-up time. The confidence interval conveys uncertainty around the estimated median. The registry record does not report the numerical median PFS or its confidence interval, so the endpoint’s observed value and precision cannot be described from this record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry identifies PFS as the primary endpoint and says it was analyzed using the Kaplan-Meier method. However, a numerical PFS estimate, its 95% confidence interval, and any subgroup estimates are not reported in the registry record. The posted information therefore does not establish the observed median PFS or how precisely it was estimated. It also does not support a conclusion about the direction or size of differences between age or comorbidity groups.
The study’s stated objective is to describe outcomes for patients treated with palbociclib and an AI, with attention to age and comorbidities. Because the record describes a non-interventional retrospective study and no comparison treatment group, it does not provide a randomized estimate of the effect of this treatment relative to another treatment. In general, observed differences between patient groups can reflect differences in health status, treatment histories, clinical decisions, or other factors, as well as the group characteristic being examined. The registry record does not report methods that would allow the contribution of such factors to be assessed.
The registry lists secondary outcomes involving PFS and OS by age, CCI score, number of comorbidities, and type of comorbidity. Listing these outcomes indicates what was considered for analysis; it does not report the estimates or demonstrate that every listed analysis was completed. The record lists 16 outcome measures and 18 analyses, but does not provide numerical results for the outcomes in the registry record.
The adverse-event summary lists 322 deaths for all participants. It also lists zero for the serious and other adverse-event counts at risk and affected, with no serious-event terms listed. These fields should be read as registry entries, not as evidence that serious or other adverse events did not occur. The record does not provide further explanation of those entries or a detailed adverse-event analysis.
Planning assumptions for sample-size illustrations are described as two-sided significance level 0.05, equal allocation between two arms, and a normal approximation, with effects framed as fractions of the observed effect. For time-to-event illustrations, the stated quantity is the total number of events; other illustrations use participants per arm. These are planning assumptions, not observed power and not a description of the study’s non-interventional allocation. Numerical sample-size illustrations and the observed effect used for them are not reported in the registry record.
9. Statistical Methods Explained
What does a Kaplan-Meier analysis estimate?
The registry says PFS was analyzed with the Kaplan-Meier method. In general, this method estimates the probability of remaining free of the event over time while allowing participants to have different lengths of observation. The event for this endpoint is disease progression or death, whichever occurs first. A participant without a recorded event by the end of their observation contributes information up to the censoring date. Censoring does not mean that an event occurred on that date; it means the event time is not observed within the available follow-up.
The method relies on the recorded event and censoring times being suitable for the analysis. In general, interpretation can be affected if follow-up ends for reasons related to a participant’s unobserved event risk. The registry record defines the endpoint and mentions a censoring date, but does not report the detailed censoring rules or how losses to follow-up were handled.
What does the median and its confidence interval mean?
The primary endpoint is specified as median PFS in months with a 95% confidence interval. In general, the median is the time at which the estimated Kaplan-Meier curve reaches 50% event-free survival, if the curve reaches that point during follow-up. It is a summary of the estimated time-to-event distribution, not the mean time and not a statement that every participant experienced an event by that time.
A confidence interval expresses uncertainty around an estimate under the analysis assumptions. A narrower interval generally indicates greater precision, while a wider interval indicates more uncertainty. The interval is not a guarantee that the true value lies within it. Because neither the median nor its confidence interval is reported in the registry record, its precision cannot be assessed from the posted information.
How is progression defined?
The record defines progression using scans and blood testing results, with a specified increase in the sum of target-lesion diameters: at least 20% relative to the smallest sum on study and an absolute increase of at least 5 millimeters. The reference can include the baseline sum when that is the smallest sum on study. These rules make the event definition more explicit than a general clinical description of worsening disease. The record does not report further details about how assessments were scheduled, reviewed, or adjudicated.
The PFS clock starts at the index date, defined as relapse or stage IV disease, and ends at progression, death, or censoring, whichever occurs first. Thus, the time origin is not described as the date of study registration. The registry’s timeframe gives data collection from 1 January 2017 to 1 February 2024 and maximum follow-up up to 7.09 years. It also says participants were observed retrospectively for approximately 1.3 months of this study. The record does not explain further how follow-up varied between participants.
What can subgroup analyses establish?
The stated focus is outcomes by age and comorbidities. The secondary outcome list specifies PFS and OS by age, CCI score, number of comorbidities, and type of comorbidity. In general, subgroup estimates can describe outcomes within categories, but comparisons across categories are observational when group membership is not randomized. They may be influenced by differences in other characteristics. A difference between subgroup estimates alone does not establish that age or comorbidity caused the difference.
The record does not provide the age cutoffs, CCI categories, comorbidity definitions, subgroup sizes, or numerical subgroup results. It also does not report whether any adjusted analyses were used. Consequently, the degree to which the listed group comparisons account for other factors is not reported in the registry record.
How should planning calculations be read?
The registry describes sample-size assumptions for planning illustrations: two-sided significance level 0.05, equal allocation between two arms, a normal approximation, and effects expressed as fractions of the observed effect. For time-to-event illustrations, the stated quantity is the total number of events; for other illustrations, it is participants per arm. In general, such calculations ask what sample size might be needed under stated assumptions. They are not observed power, and they do not show that the study was designed or conducted with those assumptions.
Those assumptions do not describe the reported non-interventional study as a randomized, equal-allocation comparison. The registry record does not report a sample-size justification for the retrospective analysis or numerical planning-illustration results. The statistical assumptions therefore should not be treated as evidence about the study’s actual allocation, precision, or ability to detect differences.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 16 outcome measures and 18 analyses. The secondary outcomes include PFS and OS by age, CCI score, number of comorbidities, and type of comorbidity. The primary endpoint is PFS. Considering several outcomes and subgroup analyses raises a general multiplicity issue: when many estimates or comparisons are examined, some may appear notable by chance. The registry record does not report whether multiplicity was addressed, for example through adjustment or a prespecified hierarchy.
Missing-data handling is not reported in the registry record. The endpoint definition includes censoring, but details on censoring rules, incomplete records, loss to follow-up, or how missing covariates were handled are not reported. These details matter because the amount and pattern of missing information can affect which participants contribute to each estimate and how representative the analysis population is.
The analysis population is described as all eligible participants whose data were retrieved and observed in the study. The record does not report the number contributing to each endpoint or subgroup analysis, exclusions from the eligible population, or reasons for unavailable data. Enrollment is listed as 604, but that figure alone does not establish how many participants contributed information to a particular analysis.
The registry names Kaplan-Meier analysis for PFS, but does not report the full statistical plan, adjustment strategy, or any interim analyses. These details are not reported in the registry record and should not be inferred from the endpoint list or the number of analyses.
11. What the Result Does, and Does Not, Mean
This study addresses a practical descriptive question: what PFS and OS outcomes were examined among patients in Denmark receiving palbociclib with an aromatase inhibitor, and how were outcomes considered across age and comorbidity groups? The registry specifies a retrospective, non-interventional setting and identifies the endpoint definitions and analysis topics. Those details help define what the study set out to describe.
The record does not report numerical PFS estimates, confidence intervals, or subgroup results. It therefore does not show the observed duration of PFS or the precision of any estimate. The listed secondary outcomes likewise do not reveal the observed OS or subgroup findings. No conclusion about a difference between groups can be drawn from outcome titles alone.
In general, data from non-interventional studies describe outcomes among people who received treatment in practice, but treatment and group membership are not randomly assigned. Comparisons between groups can therefore reflect differences beyond age or comorbidity. Without reported results and details of adjustment, the registry record cannot establish the magnitude or causes of any observed group differences.
The record also does not describe a comparison treatment group. Accordingly, it does not provide a randomized comparison of palbociclib plus an AI against another treatment. The enrollment figure, study status, and endpoint definitions do not by themselves establish treatment effectiveness, safety, or the generalizability of any particular outcome. The adverse-event entries should also be interpreted cautiously: the listed death count and zero serious or other adverse-event fields do not, without further reporting, establish the full safety experience.
12. Why This Trial Matters Statistically
Statistically, this study focuses on an important challenge in routine-care data: describing time-to-event outcomes while accounting for different lengths of follow-up. PFS is defined from a clinical index date to progression or death, with censoring when the event time is not observed. The use of Kaplan-Meier analysis is consistent with summarizing such time-to-event data, and the planned median with a confidence interval would communicate both the estimated outcome and its uncertainty if numerical results were reported.
The focus on age and comorbidities also highlights why patient characteristics matter when interpreting observational outcomes. In general, these characteristics can be associated with other differences among patients, so subgroup patterns are descriptive unless the analysis supports stronger inference. The record’s specified groupings provide a framework for examining heterogeneity, but the absent subgroup estimates and analysis details limit interpretation.
The study is also statistically instructive because its planning assumptions refer to equal allocation between two arms, while the registry describes a non-interventional analysis and does not report a comparison treatment group. This distinction reinforces that planning calculations are conditional illustrations, not proof of the design or precision of the retrospective study.
Finally, the registry identifies multiple outcomes and analyses without reporting whether multiplicity, missingness, or subgroup-specific data availability were addressed. These omissions matter when readers assess how stable and interpretable a set of observational estimates might be. The record’s endpoint definitions are useful, but numerical results and fuller methods are needed to evaluate the findings themselves.
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 registry record does not report the numerical primary PFS result, its 95% confidence interval, or numerical results for the listed secondary outcomes. This prevents assessment of the estimated outcomes, their precision, or differences across age and comorbidity groups. Although enrollment is listed as 604, the number contributing to each endpoint or subgroup analysis is not reported.
The study is described as non-interventional and retrospective, with no comparison treatment group reported and allocation not stated. Consequently, the record does not describe a randomized treatment comparison. Any age- or comorbidity-related differences would need to be interpreted in light of potential differences among groups; adjustment methods are not reported in the registry record.
Further details needed to assess the analyses are also not reported: the subgroup cutoffs and definitions, missing-data procedures, censoring rules beyond the endpoint description, multiplicity approach, and full statistical plan. The registry lists several outcomes and analyses but does not establish from the information reported whether all were completed or how each was handled.
The adverse-event summary contains limited entries, including 322 deaths and zero serious and other adverse-event counts at risk and affected. No serious-event terms are listed, and the record does not explain these fields further. They should not be treated as a complete account of adverse events. The registry also gives a retrospective data-collection timeframe and registered study dates, but does not provide additional detail about variation in follow-up or data completeness across participants.
14. Related Tutorials
15. Related Statistical Calculators
16. Sources
- ClinicalTrials.gov: A Study of HR+/HER2- Metastatic Breast Cancer Patients Treated With Palbociclib Together With an Aromatase Inhibitor From 2017 to 2023 in Denmark. — NCT06307457.
- Registry record last updated 2025-06-29; status last verified 2025-06.
- Results first posted 2025-06-29.
- 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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17. Record Summary
The registry describes a completed Danish non-interventional study of palbociclib in combination with an aromatase inhibitor among patients with HR+/HER2- locally advanced or metastatic breast cancer. Enrollment is listed as 604. The treatment period described in the summary is January 2017 to December 2021; the registry lists study dates of 2024-03-06 to 2024-04-19.
The primary endpoint is median PFS in months with a 95% confidence interval, analyzed using Kaplan-Meier methods. PFS is defined from the index date to progression or death, or censoring, whichever occurred first. The stated focus is outcomes by age and comorbidities, with secondary PFS and OS analyses across age and comorbidity groupings.
Numerical outcome estimates, subgroup results, and details of missing-data and multiplicity handling are not reported in the registry record. No comparison treatment group is described.