Aromasin® Interventional Study Of Early Invasive Breast Cancer Patients In China: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Aromasin® Interventional Study Of Early Invasive Breast Cancer Patients In China (NCT01176916), a registered phase 4 study. The primary outcome is Time-to-Event.

2. Clinical Question

The registry describes the study as a prospective pragmatic clinical trial. Its stated purpose was systematic collection and assessment of efficacy and safety data for adjuvant Aromasin use in a Chinese population, where the brief summary says systematic collection and analysis had been lacking. That purpose makes the study relevant as a source of observational experience in the stated treatment setting, but the absence of a described randomized comparison limits what it can say about relative treatment effects.

3. Trial Design

The registry identifies this as an interventional phase 4 study sponsored by Pfizer, with the title describing early invasive breast cancer patients in China. The listed intervention is Aromasin (exemestane). The record is marked completed. The recorded study start is 2011-02-09 and the primary completion date is 2018-11-30. Enrollment is listed as 564.

The design is described as prospective and pragmatic. The brief summary places the treatment in the adjuvant setting after participants had received tamoxifen. In that description, participants switch to Aromasin after 2-3 years of tamoxifen, with the two treatment periods intended to add up to 5 consecutive years of adjuvant hormonal therapy. These statements describe the clinical context in the registry summary; a detailed protocol, dosing schedule, or participant flow is not reported in the registry record.

The registry does not describe a randomized control comparison: allocation is not stated, and the record cautions that the arms are not a like-for-like control comparison. The arm description is blank. Accordingly, the design should be read as a prospective study of participants receiving the listed intervention, not as a randomized trial comparing equivalent groups. The enrollment figure does not identify how many participants contributed to each endpoint analysis.

The full analysis set (FAS) is defined as all participants who received at least 1 dose of Aromasin during the observation period; all efficacy analyses were performed using that set. The number included in the FAS is not reported in the registry record. The primary endpoint timeframe is described as 2-3 years, with the prior tamoxifen time and Aromasin time adding up to 5 years. The record does not provide further detail about the observation schedule or the handling of participants who did not complete follow-up.

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 564 participants were assigned into the study and 558 participants received the study treatment. (6 participants were withdrawn from the study prior to the first dose of Aromasin.)

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: The full analysis set (FAS) was defined as all participants who received at least 1 dose of Aromasin during the observation period. All efficacy analyses were performed using the FAS.

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: Baseline analysis population included all participants who were treated.

6. Primary Endpoint

The registry lists the primary outcome as Time-to-Event, measured over 2-3 years (time for previously taking tamoxifen [prior to this study] and time for taking Aromasin [in this study] add up to 5 years).

The primary endpoint is time-to-event, reported as a median in months with a 95% confidence interval. The composite event is defined as the earliest occurrence of local or distant recurrence of the primary breast cancer, a second primary or contralateral breast cancer, or death due to any cause. Local recurrence includes recurrence in the ipsilateral breast, chest wall, or axillary lymph nodes.

A time-to-event endpoint uses both whether an event occurred and how long it took to occur. Combining recurrence, a new breast cancer, and death into one endpoint can capture several clinically important outcomes in a single measure. The median describes the time by which half of the analyzed event-time distribution has experienced the defined event, subject to the analysis method and follow-up available. A confidence interval communicates uncertainty around the estimated median.

The registry gives the timeframe as 2-3 years for the time on tamoxifen before the study and the time on Aromasin during the study to add up to 5 years. This is a description of the treatment-time context, not a reported endpoint value. The median time-to-event estimate and its 95% confidence interval are not reported in the registry record. Without those results, the direction, magnitude, and precision of the primary endpoint cannot be assessed from the posted record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a median time-to-event measure?

Time-to-event analysis studies the time until a defined event occurs. In this trial, the event is a composite: the earliest of local or distant recurrence of the primary breast cancer, a second primary or contralateral breast cancer, or death due to any cause. The endpoint is specified as a median time in months. In general, the median is a central point in the distribution of event times; it is not an average and does not describe the experience of every participant.

Such analyses can use information from participants who have not experienced the event by the end of observation, provided the analysis method accounts for their incomplete event-time information. This is commonly called censoring. That general feature is important because excluding everyone without an observed event can distort an estimate. The registry record does not report the censoring rules, the estimation method, or how follow-up ended for participants.

What does the confidence interval add?

A confidence interval communicates uncertainty in an estimate. In general, a narrower interval indicates more precision than a wider one, while an interval that is wide indicates substantial uncertainty about the estimate's location. The registry specifies a 95% confidence interval for the median time-to-event, but its numerical limits are not reported in the registry record. Therefore, neither the estimate nor its precision can be evaluated from the recorded primary result.

A confidence interval is not a guarantee that the true value lies inside the particular interval, and it does not correct for problems of study design, missing follow-up, or outcome measurement. Its interpretation depends on the statistical method and assumptions used. Those details are not reported in the registry record, so the exact construction of the interval cannot be assessed.

How should a hazard ratio be understood?

In general, a hazard ratio compares event rates over time between groups or across levels of a variable, conditional on the model used. A hazard ratio is not the same as a ratio of the total number of events, nor does it directly state a difference in median time. Its interpretation depends on the chosen comparison, model specification, and assumptions. The listed secondary outcomes include hazard ratios relating HER2 status and multiple disease variables to time-to-event. The numerical hazard ratios and their uncertainty are not reported in the registry record. The record notes that only sponsor-reported hazard ratios are used, but no such values are present in the stated results.

For a hazard ratio to have a clear comparative interpretation, readers need to know the groups being compared and how the model handled relevant covariates and follow-up. The record does not provide those model details or an analysis output. It would therefore be inappropriate to infer the direction or size of any association from the outcome titles alone.

What do the planning illustrations mean?

The registry's planning assumptions describe calculations based on an observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The effect to detect is described as a stated fraction of the observed effect. For time-to-event calculations, the stated quantity is the total number of events; for other calculations, it is participants per arm. These are planning illustrations, not observed trial results and not observed power.

Planning calculations ask what study size might be needed under chosen assumptions. They do not show that a completed study had a particular probability of finding an effect, and they cannot substitute for the outcome estimate and its uncertainty. The record also cautions that this study is not a randomized comparison and that allocation was not stated. Equal allocation between two arms is therefore a calculation assumption, not evidence that the trial itself used that allocation. Numerical planning values and the observed effect used for the calculations are not reported in the registry record.

Why can over-dispersion matter in count data?

In general, a count-data model can be too optimistic if it assumes less variability than the data contain. Over-dispersion means that observed variation is greater than a model's assumed variation; if not addressed, uncertainty estimates can be too small. This general issue can arise in analyses of event counts, but the registry record does not identify a count-data model or report whether over-dispersion was assessed. It should not be assumed that a particular method was used.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists several secondary outcomes: percentages and incidence rates for each event, hazard ratios relating HER2 status and multiple disease variables to time-to-event, discontinuations due to adverse events, and treatment-emergent adverse events. When a study examines multiple endpoints or multiple associations, the chance of at least one apparently notable result can increase. Statistical approaches to multiplicity can address that issue, but the record does not report a multiplicity adjustment, a hierarchy of endpoints, or a prespecified strategy for interpreting multiple tests. No such plan should be inferred.

The registry record lists 0 analyses. Numerical results for the primary endpoint and the listed secondary outcomes are not reported in the record. Consequently, readers cannot check which analyses were conducted, whether any were prespecified, or how uncertainty was handled across outcomes.

The FAS is defined as all participants who received at least 1 dose of Aromasin during the observation period, and the registry states that all efficacy analyses used this set. Its size is not reported. Enrollment is 564, while the safety listing gives 558 at risk for serious and other adverse events. These figures refer to different recorded quantities; the record does not explain the participant flow between enrollment, the efficacy population, and safety reporting.

Missing outcome data, loss to follow-up, withdrawals, and imputation methods are not reported in the registry record. The handling of incomplete event-time observations is also not described. Without those details, it is not possible to assess whether missingness could have affected the endpoint estimate or whether any sensitivity analyses were performed. The same applies to missing covariate data for the listed hazard-ratio outcomes.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: cerebral infarction (0.7%), gastric polyps (0.4%), cholecystitis chronic (0.4%), cholelithiasis (0.4%), intervertebral disc protrusion (0.4%).

The registry reports 38 participants with serious adverse events among 558 at risk, and 82 participants with other adverse events among 558 at risk. It also records 4 deaths. These are counts in the posted safety record; they are not a comparison of randomized treatment groups. The record does not provide further information about the timing, duration, severity grading, or causal attribution of each event.

The listed serious adverse event terms and reported percentages are cerebral infarction, 0.7%; gastric polyps, 0.4%; chronic cholecystitis, 0.4%; cholelithiasis, 0.4%; intervertebral disc protrusion, 0.4%; and fibroadenoma of breast, 0.4%. These term-level figures should be read as registry-reported entries, not as a complete account of every safety outcome or as evidence that the intervention caused those events.

Adverse-event counts describe what was recorded during the study; interpretation depends on how events were collected, follow-up duration, exposure, and the definitions used. Those details are not reported in the registry record. The safety figures also do not provide a like-for-like comparison with an untreated or alternative-treatment group, because the registry cautions that the arms are not a comparable control comparison.

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

The record describes a prospective pragmatic study of adjuvant Aromasin (exemestane) in the stated Chinese early invasive breast cancer setting. It provides a definition of the primary composite time-to-event endpoint, specifies the FAS used for efficacy analyses, and records safety counts. This information helps clarify what the study set out to assess and how its endpoint is framed.

The primary endpoint result itself is not reported in the registry record. There is no median time-to-event estimate or 95% confidence interval to interpret. The record therefore does not establish the observed time-to-event experience, the precision of an estimate, or which component of the composite contributed to events. It also does not report numerical secondary efficacy analyses or sponsor-reported hazard ratios.

The study is not described as a randomized comparison: allocation is not stated, and the record warns that the arms are not a like-for-like control comparison. This means the record cannot, on its own, provide a randomized estimate of the relative effect of Aromasin versus another treatment. Differences between groups, if any were measured, could reflect differences in participant characteristics, care, or follow-up rather than treatment alone.

The safety counts are descriptive. They report adverse events observed in the study but do not establish that Aromasin caused those events, and the record does not offer a comparable control group for estimating excess risk. Nor do the counts alone establish the overall safety profile in settings beyond the participants and follow-up recorded.

In general, a study's result should be interpreted together with its design, endpoint definition, analysis population, follow-up, missing-data handling, and uncertainty. Several of those details are not reported in the registry record. The appropriate conclusion is therefore limited: the record documents the study's intent, endpoint definition, and selected safety counts, but the posted information does not support a numerical conclusion about primary efficacy or a causal treatment claim.

13. Why This Trial Matters Statistically

This study is statistically relevant because it addresses a setting the registry brief summary describes as lacking systematic collection and analysis of efficacy and safety data for adjuvant Aromasin use in a Chinese population. Prospective data collection in a pragmatic treatment context can contribute information about how outcomes and adverse events are recorded in the population and care setting under study.

The endpoint definition also illustrates an important feature of clinical-trial analysis: a time-to-event outcome can combine different event types. In this study, recurrence, a second primary or contralateral breast cancer, and death all contribute to the same composite endpoint. A median for the composite would summarize time to the first qualifying event, but it would not by itself reveal the contribution of each component. Component-level results are useful for understanding what the composite represents; those numerical results are not reported in the registry record.

The record also illustrates why the design must be considered before interpreting an effect estimate. It does not describe random allocation and cautions that the arms are not a like-for-like control comparison. Even a precisely estimated association would not by itself resolve confounding or establish a treatment effect in the way a well-conducted randomized comparison may do.

Finally, the record separates the definition of an analysis population from its reported size. The FAS definition is stated, but its size is not. Enrollment and safety counts are available, yet they do not replace an endpoint-specific account of participants analyzed, events observed, follow-up, and missingness. The lack of a reported primary estimate and confidence interval is a substantial constraint: the study's statistical purpose is clear, but its primary efficacy result cannot be evaluated from this record.

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 most important limitation for interpretation is that the registry record does not report the median time-to-event result or its 95% confidence interval. Without these, the primary outcome cannot be assessed for magnitude or precision. The listed secondary outcomes likewise lack numerical analysis results in the information, and the record lists 0 analyses.

The study does not provide a randomized control comparison. Allocation is not stated, and the record explicitly warns that the arms are not a like-for-like control comparison. This limits causal interpretation and prevents a straightforward treatment-versus-control comparison. The arm description is blank, and further details of the treatment regimen are not reported in the registry record.

Although the FAS is defined as participants who received at least 1 dose of Aromasin during the observation period, the number in that analysis population is not reported. The record does not provide participant flow, endpoint-specific denominators, the number of observed primary events, follow-up distributions, or reasons for discontinuation. Missing-data and censoring procedures are not reported, so their influence on the primary analysis cannot be evaluated.

The event definition combines recurrence, a second primary or contralateral cancer, and death. The record does not provide component-specific primary endpoint results, making it impossible to determine which event types contributed to the composite. It also does not report the model or estimation details for the primary endpoint or secondary hazard ratios, any multiplicity strategy, or sensitivity analyses.

Finally, the safety record gives counts and selected serious-event terms but does not report details such as event timing, exposure duration, or causal assessment. With no comparable control group described, the counts are descriptive and cannot establish comparative safety.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Aromasin® Interventional Study Of Early Invasive Breast Cancer Patients In China — NCT01176916.
• Registry record last updated 2021-10-27; status last verified 2021-10.
• Results first posted 2020-10-12.
• 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

The registry identifies a completed prospective pragmatic phase 4 interventional study sponsored by Pfizer, titled as a study of Aromasin in early invasive breast cancer patients in China. Enrollment is listed as 564. The recorded start date is 2011-02-09, and the primary completion date is 2018-11-30. The listed intervention is Aromasin (exemestane).

The primary endpoint is median time-to-event in months with a 95% confidence interval. It includes local or distant recurrence, a second primary or contralateral breast cancer, or death due to any cause. Efficacy analyses used the FAS, defined as participants who received at least 1 dose during the observation period. The median result, confidence interval, and FAS size are not reported in the registry record.

The record does not describe a randomized comparison and cautions that the arms are not a like-for-like control comparison. Safety reporting lists 38 participants with serious adverse events, 82 with other adverse events, and 4 deaths among the recorded safety figures. These counts do not constitute comparative treatment-effect estimates.