Increasing Patients' Engagement in Breast Cancer Surgery Decision-Making: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Increasing Patients' Engagement in Breast Cancer Surgery Decision-Making (NCT03766009), a randomized na study. The primary outcome is Patient Power: Self-efficacy in Patient Physician Interactions.

2. Clinical Question

The trial also examines patient knowledge, concordance between surgery received and treatment preference, and barriers to patient engagement. These are relevant to the broader research question, but the registry record does not provide numerical results for them either. The central statistical question is therefore clear from the outcome definition, while the reported information is insufficient to determine how the decision-aid and usual-care conditions compare on the primary measure.

3. Trial Design

The registry describes a randomized, crossover study and identifies its structure as a stepped-wedge design. It also identifies the design as cluster-randomized. In a cluster-randomized study, groups rather than individual participants are assigned to conditions. This matters analytically: people treated within the same group may have more similar outcomes than people in different groups. An analysis that treats every participant as statistically independent can therefore give misleading estimates of uncertainty.

The study compares usual care with a web-based breast cancer surgery decision aid. Before institutional crossover, participants receive usual care. The intervention description states that after a 10 week implementation period, at the time of institutional crossover, participants receive the web-based aid before the surgical consultation. The record does not give the institutional sequence, the number or identity of clusters, or details of how crossover timing was assigned.

Enrollment is listed as 627, and the study status is completed. The recorded start date is 2019-06-05, and the primary completion date is 2023-01-26. The trial includes patients with breast cancer stages 0, I, II, and III. Its stated purpose includes assessing engagement and examining barriers, including possible differences in barriers for socioeconomically disadvantaged patients.

The primary outcome is patient self-efficacy in interactions with physicians, measured within 3 weeks after the surgical consultation. The registry describes a population with PEPPI-5 data available, with specified exclusions in the usual-care and decision-aid conditions. It does not report the number of clusters, the allocation procedure, the exact crossover schedule, or the statistical model used to account for cluster assignment and time. Those details are important for evaluating the design and cannot be inferred from the brief descriptions.

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: This stepped wedge cluster randomized trial across 10 sites transitioned sites from UC to DA at pre-determined and randomly assigned timepoints, with waves spanning 10-13 weeks each. Sites started in UC and ended with DA. One wave is used for implementation of the DA at the time of crossover, yielding 6 waves for enrollment/data collection. The extended enrollment was to enrich the sample for the mixed methods components of the analysis. Surgeon enrollment was not linked to specific wave.

Usual Care

Reasons for not completing this period:

Implementation

Intervention

Extended Enrollment Beyond Wave 7

Analysis population for the primary outcome, as defined in the registry: All stepped wedge design participants who had PEPPI-5 data available excluding 5 UC (1 ineligible, 4 enrolled off-schedule) and 3 DA (2 refused follow-up at baseline, 1 enrolled off-schedule).

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: All stepped-wedge design participants excluding 1 ineligible in UC and 2 refused follow-up at baseline in DA; all extended enrollment beyond wave 7-DA and all surgeons.

6. Primary Endpoint

The registry lists the primary outcome as Patient Power: Self-efficacy in Patient Physician Interactions, measured over 3 weeks.

The primary endpoint is patient power, defined in the registry as patients’ self-perceived capacity to influence the decision-making encounter. It is measured using the Patient’s Self-Efficacy in Patient-Physician Interactions (PEPPI)-5 scale. The total score ranges from 5-25, with higher scores indicating increased self-efficacy. Participants complete the questionnaire within 3 weeks after the surgical consultation.

This measure is used to capture a patient-reported aspect of engagement: how capable the patient feels of influencing an interaction with a physician. That is distinct from directly measuring which surgery was selected, whether the patient’s preference matched the surgery received, or how much factual knowledge the patient retained. Those topics appear among the trial’s other outcomes, but they are not interchangeable with the self-efficacy endpoint.

The registry specifies the primary measure as a median with full range. A median describes the middle of an ordered set of scores, while the full range describes the lowest and highest observed values. In general, this summary can convey the central score and the spread across the observed extremes without assuming that scores follow a symmetric distribution. It does not, by itself, show how precisely a difference between conditions has been estimated.

The record gives the measurement definition and timing, but not the observed medians, ranges, between-condition estimate, confidence interval, or test result. Thus, the endpoint is interpretable as a patient-reported measure, but its trial results cannot be evaluated from the registry information available.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Why does the design affect the analysis?

The registry identifies the trial as cluster-randomized and stepped-wedge. In general, cluster randomization assigns groups to conditions rather than assigning each participant independently. Participants in the same cluster may share clinicians, institutional practices, or other influences, making their outcomes statistically related. If an analysis ignores that dependence, it can overstate the amount of independent information and make uncertainty appear smaller than it is.

A stepped-wedge design introduces an intervention across clusters over time, with conditions changing at institutional crossover. In general, that structure means the analysis may need to account for both clustering and calendar or study time. Otherwise, changes over time could be confused with changes associated with intervention exposure. The registry record does not describe the specific statistical model, the cluster structure, the sequence of crossover, or how time was handled. It is not possible to determine from the record whether or how those features were incorporated in the sponsor’s analysis.

The record specifically cautions that a simple individual-level re-analysis would be misleading and indicates that only the sponsor’s own analysis is shown. Since the registry lists zero analyses and no numerical primary outcome result, the sponsor’s estimate and its method are not available in the recorded information. A recalculation from individual-level summary statistics would not substitute for a design-appropriate cluster analysis.

What does the endpoint summary represent?

The primary measure is reported conceptually as a median and full range. In general, the median is the central observation after scores are ordered. The full range communicates the endpoints of the observed score distribution. These summaries can be useful when a measure is ordinal or when a distribution may be skewed, because they do not rely on the same symmetry assumptions as a mean and standard deviation. However, a median and range for each condition do not alone quantify the precision of a comparison. A confidence interval or other uncertainty measure for the treatment contrast would be needed to assess how compatible the observed data are with a range of possible effects.

The PEPPI-5 score ranges from 5-25, and higher scores indicate increased self-efficacy. That direction makes it possible to understand what a higher score means on the instrument. It does not establish what size of score difference would be important to patients, nor does the registry state a threshold for interpreting a difference. Such a threshold is not reported in the registry record.

What can a confidence interval tell a reader?

In general, a confidence interval expresses uncertainty around an estimated effect under the assumptions of the analysis. A narrow interval indicates greater statistical precision than a wide interval; an interval that includes values on both sides of no difference can indicate that the data are compatible with effects in multiple directions. Interpretation also depends on the interval’s scale, the study design, and whether the analysis properly accounts for clustering and time. No confidence interval for the primary outcome is reported in the registry record, so this kind of precision assessment cannot be made for this trial from the available entry.

Why is statistical significance not enough?

In general, a test result addresses how surprising the observed data would be under a particular null hypothesis and model. It does not measure the size or practical importance of an effect. A p-value also depends on the analysis assumptions, including how correlated observations and the study structure are handled. The registry record does not report a p-value or a statistical model for the primary outcome. It would therefore be inappropriate to characterize the result as statistically significant or not significant.

Even if a p-value were available, it would need to be considered alongside the estimated effect, its precision, and the outcome’s meaning. Here, the score is a measure of self-perceived capacity to influence a clinical conversation. It is not itself a direct measure of surgery choice or treatment preference. The registry lists those related outcomes separately.

What is over-dispersion, and is it reported?

In general, over-dispersion occurs when variability in data is greater than a statistical model expects. It can make standard errors too small if the model does not allow for the extra variation. It is particularly relevant to some count outcomes, whereas the primary endpoint in this record is a bounded questionnaire score summarized by median and full range. The registry does not report an over-dispersion assessment or a model for the primary endpoint. There is no basis to claim that over-dispersion was present or tested.

How should planning calculations be read?

In general, sample-size planning calculations illustrate how a study might perform under specified assumptions about an effect, allocation, significance level, and analysis. They are not observed results and do not establish the power achieved by a completed study. The record describes planning assumptions based on a fraction of an observed effect, with two-sided significance level 0.05, equal allocation between arms, and a normal approximation. Those assumptions do not reveal a trial-specific sample-size justification or explain how the cluster-randomized stepped-wedge design was handled in planning. The record does not report a formal sample-size justification. No planning illustration should be read as observed power or as evidence about the outcome effect.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists four outcome measures and identifies patient self-efficacy as the primary outcome. It also lists patient knowledge and the percentage of concordance between surgery received and patient treatment preference as secondary outcomes. Considering multiple outcomes can raise a multiplicity question: when many statistical tests are performed, the chance of at least one apparently notable finding can increase. In general, a prespecified outcome hierarchy or an adjustment strategy can help readers understand how multiple comparisons were handled.

The registry record does not report a multiplicity strategy, a hierarchy among secondary outcomes, or results for the outcome measures. It also lists zero analyses, so there are no analysis records from which to assess the tests performed or any adjustment. Whether an analysis plan specified additional outcomes, subgroup comparisons, or multiplicity control is not reported in the registry record.

The primary outcome population is described as stepped-wedge design participants with PEPPI-5 data available, excluding 5 usual-care participants (1 ineligible, 4 enrolled off-schedule) and 3 decision-aid participants (2 refused follow-up at baseline, 1 enrolled off-schedule). This description identifies some exclusions, but does not report the total number with available data, the amount or pattern of missing outcome data, or the method used to address missingness. It also does not say whether the missingness was related to participant characteristics or outcomes.

In general, an analysis restricted to participants with observed scores can be biased if the likelihood of having a score is related to the outcome or condition. Alternative methods depend on the design and assumptions about why data are missing. The registry does not report whether such methods were used. The exact analysis population, handling of missing data, and any sensitivity analyses are therefore not reported in the registry record.

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

The record establishes what the trial set out to assess: patient self-efficacy in physician interactions after a surgical consultation, in a study comparing usual care with a web-based breast cancer surgery decision aid. It also provides the scale’s direction, the measurement window, and a description of the cluster-based stepped-wedge design. These details help define the question, but they are not outcome evidence.

The registry does not report the primary endpoint’s numerical results, an estimate comparing conditions, a confidence interval, or a test result. As a result, it is not possible to determine from this record whether self-efficacy was higher or lower in either condition, or how precisely a difference was estimated. The completed study status does not fill that gap. Nor can the absence of a result be interpreted as evidence of no difference.

The measure concerns how capable patients feel of influencing a decision-making encounter. It does not directly establish whether they received their preferred surgery, how much they knew about treatment options, or whether other barriers to engagement changed. The record names knowledge and preference concordance as secondary outcomes, but does not report their numerical results.

In general, a patient-reported scale can capture an experience that may not be visible in clinical records, while remaining subject to the limits of self-report and the instrument used. The registry provides no information on a threshold for a meaningful score change, and no results with which to judge the size or importance of any observed contrast. It therefore supports neither a claim that the decision aid works nor a claim that it does not work.

The adverse-event entry reports no serious or other adverse events in either condition, and records deaths in both conditions. Those counts alone do not show whether an event was caused by the intervention or whether the conditions differed in risk. Overall, the available record describes the research question and selected design features, but leaves the primary outcome’s effect and uncertainty unresolved.

12. Why This Trial Matters Statistically

This trial raises a statistical issue that is easy to miss when reading clinical research: the unit of randomization may not be the individual patient. The registry identifies a cluster-randomized stepped-wedge design. In general, outcomes within a cluster can be correlated, and the intervention’s introduction over time can make calendar effects relevant. A suitable analysis needs to reflect these design features. Treating all patient observations as independent can produce misleading uncertainty.

The record itself flags this concern and says a simple individual-level re-analysis would be misleading. That is an important distinction between a descriptive summary and an analysis that respects the randomization structure. It also limits what can be learned from the registry entry: no numerical sponsor analysis or model details are reported, so the key design-adjusted estimate cannot be evaluated.

The endpoint also illustrates why statistical outcomes need clear interpretation. PEPPI-5 captures self-perceived capacity to influence a clinical conversation, a meaningful facet of engagement, but not the entire decision-making process. The trial separately names knowledge and concordance between surgery received and patient treatment preference. Those outcomes address related but different questions and should not be treated as substitutes for the primary endpoint.

Finally, the study’s focus on barriers, including possible barriers among socioeconomically disadvantaged patients, makes the target question broader than a single score comparison. Assessing whether barriers differ across patient groups would require relevant subgroup definitions and analyses; those methods and results are not reported in the registry record. The statistical importance of the study lies in the interaction between its complex allocation structure, patient-reported outcome, and broader engagement aims, while the recorded results remain insufficient to quantify any outcome effect.

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 main limitation for statistical interpretation is the absence of numerical outcome results. The registry describes the primary endpoint but does not report the median, full range, comparison estimate, confidence interval, or test result. Without these, the direction, magnitude, and precision of any difference cannot be assessed.

The record identifies a cluster-randomized stepped-wedge design, but does not report the number of clusters, allocation sequence, crossover schedule, or analysis model. These details are needed to evaluate how clustering and time were addressed. The record cautions against individual-level re-analysis, and no design-adjusted sponsor estimate is included in the recorded analyses.

The primary outcome population description identifies exclusions among participants without eligible PEPPI-5 data, but does not give the overall amount or pattern of missing data, or explain how missing outcomes were handled. The registry also does not report the criteria used to define socioeconomic disadvantage, or methods for assessing whether barriers differed by socioeconomic circumstances.

The outcome is self-reported and represents perceived capacity to influence a decision-making encounter. It does not, on its own, establish changes in knowledge, surgery preference concordance, or other aspects of engagement. The registry does not report a threshold for a meaningful score difference. These limits do not invalidate the measure, but constrain what a score contrast could establish even if results were available.

The record lists no analyses, so it does not describe the statistical plan, multiplicity handling, model assumptions, or sensitivity analyses. The results and analysis details needed to resolve these issues are not reported in the registry record.

14. Related Tutorials

15. Related Statistical Calculators

16. Sources

• ClinicalTrials.gov: Increasing Patients' Engagement in Breast Cancer Surgery Decision-Making — NCT03766009.
• Registry record last updated 2026-10-15; status last verified 2026-09.
• Results first posted 2024-08-27.
• 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.

17. Record Summary

The registry record describes NCT03766009, a completed randomized, cluster-based stepped-wedge study of a web-based breast cancer surgery decision aid compared with usual care. Enrollment is listed as 627. The study concerns patients with newly diagnosed stage 0-III breast cancer and aims to examine patient engagement and barriers to engagement.

The primary outcome is PEPPI-5 self-efficacy, assessed within 3 weeks after surgical consultation and summarized as a median with full range. Higher scores indicate increased self-efficacy. The intervention is introduced at institutional crossover following a 10 week implementation period.

The registry lists four outcome measures and zero analyses. It does not report numerical primary outcome results, a sponsor estimate, confidence intervals, or statistical test results. It also does not describe the analysis model or missing-data methods. Because the design is cluster-randomized and stepped-wedge, a simple individual-level re-analysis would be misleading; the sponsor’s own analysis takes precedence. The available record therefore establishes the trial question and selected design features, but does not permit a statistical conclusion about the primary outcome.