Optimizing Decision Making About Breast Reconstruction After Mastectomy: A Patient-Centered Approach: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Optimizing Decision Making About Breast Reconstruction After Mastectomy: A Patient-Centered Approach (NCT03346161), a randomized phase 1 study. The primary outcome is Percent Correct on the Knowledge Measure (Objective Knowledge Score).

2. Clinical Question

The question is about knowledge measured after the consultation process, not whether participants ultimately chose a particular reconstruction option or whether their decisions matched a specific preference. The primary measure is the percent of answers correct on an objective knowledge measure. The registry describes the comparison as one of mean scores between the two randomized groups.

The broader decision-support objective was to develop and pilot test a tool addressing personalized risk information, patient preferences, and clinical needs. Other listed outcomes cover quality of life, shared decision making, patient activation, receipt and type of reconstruction, timing, and time spent with the tool or in consultation. Those outcomes address aspects of the decision process beyond factual knowledge, but the posted primary result is specifically the knowledge score.

3. Trial Design

This was a randomized, parallel-group study with no masking reported. The registry lists the study as phase 1 and completed, with enrollment of 120 participants. The primary comparison includes 60 participants in each group. The sponsor was Washington University School of Medicine. The recorded study start was 2018-01-09, and primary completion was 2018-10-24.

Participants were patients considering breast reconstruction after a completed or planned mastectomy and scheduled for a plastic or reconstruction consultation. The registry’s arm descriptions say investigators identified eligible patients who did not yet have an appointment with a plastic or reconstructive surgeon, and that a study team member contacted patients. The descriptions are incomplete in the registry record, so further recruitment or delivery details are not reported in the registry record.

One group used BREASTChoice, identified as the decision tool. The other received enhanced usual care with the American Society of Plastic Surgeons booklet “Breast Reconstruction.” The main outcome timeframe ran through completion of the breast consultation appointment, with total participant time described as approximately 30 minutes. This is a short-term assessment around the consultation, rather than a reported evaluation of longer-term decision outcomes.

The registry identifies randomization and the parallel model but does not report the method used to generate or conceal the allocation sequence. The masking entry is none. The original statistical plan, any intended interim analyses, and the original sample-size justification are not reported in the registry record. The planning illustration based on the observed effect is separate from evidence about how the study was originally designed.

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

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.

6. Primary Endpoint

The registry lists the primary outcome as Percent Correct on the Knowledge Measure (Objective Knowledge Score), measured over Through completion of breast consultation appointment (total participant time approximately 30 minutes).

The primary endpoint is percent correct on an objective knowledge measure, expressed as a mean with a standard deviation. It assesses participants’ answers about their choice after the breast consultation appointment. The registry states that the investigators intended to compare scores between participants using the clinical decision tool and participants receiving usual care.

As a general statistical point, an objective knowledge score can quantify how much factual information participants correctly answer at a particular assessment. A group mean gives the average score, while the standard deviation describes the spread of individual scores around that average. This makes the outcome suitable for a comparison of average knowledge across randomized groups. It does not, by itself, establish how well a decision reflected an individual’s preferences, whether a particular reconstruction choice was appropriate, or whether the tool changed later clinical outcomes.

The posted result is measured through completion of the consultation, with total participant time described as approximately 30 minutes. The registry record does not report further detail about the knowledge instrument’s scoring rules, validation, or thresholds for a meaningful score difference. Those details would help readers judge what a given score difference means for individuals, beyond the observed difference in group averages.

7. Results Posted in the Registry

• Arm 1: BREASTChoice (Decision Tool): mean 84.60 versus 59.70 on control; difference 24.90 (95% CI 19.10 to 30.70), standardized effect d = 1.54; z-test p = <0.001.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Gold Standard Shared Decision Making as Measured by the Top collaboRATE Score

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Arm 1: BREASTChoice (Decision Tool): 58.9% (33/56) versus 62.7% (37/59) on control; risk difference -3.8 percentage points (95% CI -21.6 to 14.1), risk ratio 0.94 (0.70–1.26); unadjusted two-proportion z-test p = 0.678.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Arm 1: BREASTChoice (Decision Tool) and the control. The interval gives the range of effects that remain compatible with the data.

The registry lists secondary outcomes spanning quality of life, shared decision making, patient activation, reconstruction receipt and type, timing, and time spent on the tool or consultation. However, numerical data and analyses are not available for every listed outcome in the posted record. The count of posted secondary outcomes is 9, while the record identifies 12 outcome measures overall. The secondary analysis listings are empty, so a complete inferential account of the secondary outcomes is not reported in the registry record.

The available numerical secondary comparison concerns the top collaboRATE score for shared decision making. Its risk-difference confidence interval includes no difference, and its unadjusted p-value is 0.678. This does not provide a clear corroborating signal for a difference on that measure, but it also does not establish equivalence between groups. The confidence interval permits effects in either direction, so the result is uncertain.

The primary knowledge result and the available secondary shared-decision-making result address different constructs. A higher objective knowledge score does not necessarily imply a difference in patients’ reports of shared decision making, just as a shared-decision-making measure does not directly measure factual knowledge. The secondary outcomes therefore provide context rather than a direct replication of the primary endpoint.

Unadjusted secondary results carry less weight when many outcomes are assessed because repeated testing increases the chance of finding an apparently notable result by chance. The registry does not report a multiplicity adjustment or a prespecified hierarchy for secondary outcomes. In addition, incomplete numerical reporting limits assessment of whether the pattern across all secondary outcomes is consistent, mixed, or uncertain. Interpretation should therefore remain centered on the primary knowledge comparison while treating available secondary findings as exploratory context.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Quality of Life as Measured by the BREAST-Q Questionnaire
• Gold Standard Shared Decision Making as Measured by the Top collaboRATE Score
• Patient Activation (PAM) as Measured by the Number of Participants Who Agreed With Each Statement
• Receipt of Reconstruction
• Type of Reconstruction
• Timing of Reconstruction
• Time Spent on Tool
• Consult Time

9. Statistical Interpretation

10. Statistical Methods Explained

What does a mean difference describe?

The primary endpoint is continuous: each participant has an objective knowledge score, and the registry reports the mean score for each group. A mean difference expresses the separation between those group averages in the original score units. In this comparison, the reported mean difference is 24.9 percentage points. It describes an average contrast; it does not imply that every participant’s score changed by that amount or that all individual scores favored one group.

The standard deviation describes the distribution of scores within a group. It is not the uncertainty interval for the group mean and is not a measure of the difference between groups. The posted standard deviations are 14.2 and 18.0. Variation in scores means that participants within each group did not all have the same knowledge score, even though each group is represented by one mean.

How should the confidence interval be understood?

A confidence interval gives a range of estimates compatible with the observed data and the method’s assumptions. For the primary mean difference, the interval runs from 19.1 to 30.7 percentage points. A narrower interval represents greater precision than a wider interval, all else equal. The interval gives information about uncertainty in the group contrast; it does not describe the range containing most individual participants’ scores.

As a general statistical explanation, a confidence interval is not a guarantee that the true value lies within its limits, nor does it account for every possible source of bias. Its interpretation depends on the design, analysis, and assumptions used. The registry record does not report the specific test or model used to construct the primary interval, so the exact analysis procedure cannot be assessed from the record alone.

What does the p-value add?

The primary comparison reports p < 0.001. In general, a p-value measures how surprising data at least as incompatible with a specified no-difference model would be if that model and the test assumptions were correct. It is not the probability that the no-difference model is true, nor a measure of the size or practical importance of the result. The mean difference and confidence interval communicate the estimated magnitude and its precision; the p-value addresses compatibility with a no-difference model.

Why can over-dispersion matter?

For continuous outcomes, the standard deviation indicates how spread out scores are. More variability can make a group mean less precisely estimated, unless the sample size also increases. For binary outcomes, a related concern is over-dispersion: observed variation may exceed what a simple binomial model expects. As a general point, such extra variation can make standard errors too small and confidence intervals too narrow if the analysis does not account for it. The registry record does not report a model-based assessment of over-dispersion for the secondary binary outcome.

What can be concluded about the analysis approach?

The registry gives group sizes, means, standard deviations, a mean difference, its confidence interval, and a p-value for the primary endpoint. It does not report a detailed statistical analysis plan, the exact test, covariate adjustment, handling of repeated measures, or sensitivity analyses. No interim analysis is reported in the registry record. These omissions limit the ability to reproduce or evaluate the full analysis procedure, even though the posted summary statistics allow the central group comparison to be described.

The primary group sizes are 60 participants in each arm. The decision-tool group’s mean was 84.6, and the enhanced usual-care group’s mean was 59.7. The reported pooled standard deviation is 16.21, and the standardized difference is 1.536. These are posted comparison statistics; they are not a substitute for a full account of the analysis method. A standardized difference expresses the mean contrast relative to a measure of score spread, while the mean difference remains in the score’s original units.

Randomization is relevant because, in general, it aims to balance both known and unknown participant characteristics across groups. But the record does not describe sequence generation, allocation concealment, or whether every randomized participant was included in the primary analysis. These design and analysis details matter when assessing whether the observed group contrast can be interpreted without important selection or missing-data concerns.

11. Confidence Intervals and Precision

The primary mean difference is 24.9 percentage points, and the reported 95% confidence interval extends from 19.1 to 30.7 percentage points. The interval is entirely on the positive side of no difference and is bounded within a range of 11.6 percentage points from its lower limit to its upper limit. This last span is a direct description of the posted interval’s endpoints, not a separate estimate of the treatment effect.

Precision concerns how tightly the data estimate the group difference. The interval gives a range of plausible values under the analysis assumptions, whereas the group standard deviations describe participant-to-participant score variability. Both groups had 60 participants for the primary endpoint. The decision-tool group had a standard deviation of 14.2, and the enhanced usual-care group had a standard deviation of 18.0.

The reported interval does not capture uncertainty from every possible limitation. In particular, it cannot resolve questions about the knowledge measure’s properties, the unreported analysis plan, or how missing data and analysis populations were handled. The registry record also does not report a prespecified threshold for a difference considered meaningful to patients or clinicians. Thus, the interval supports a precise description of the observed mean contrast, but it does not by itself settle the significance of that contrast for decision quality or later outcomes.

The reported p-value, p < 0.001, conveys compatibility with a no-difference model under the test assumptions, not precision or practical importance. The confidence interval is the more direct summary of uncertainty around the size of the primary contrast. Neither measure establishes that the same estimate would apply in other patient groups or settings.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The sample-size table and curve are planning illustrations based on the observed effect, not the trial’s original design justification. For this continuous primary outcome, the figures are participants per arm, not total participants and not total events. The listed planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, a normal approximation, and an effect to detect set to the stated fraction of the observed effect. The trial’s own original sample-size assumptions are not reported in the registry record.

The table gives participants per arm for 80% power and participants per arm for 90% power. In plain terms, those columns show the planned number in each group for a design intended to have the corresponding chance of detecting the specified effect under the stated assumptions, if that effect is present. They are prospective planning quantities, not descriptions of the probability that the completed study’s result is correct.

For planning for 100% of the observed effect, the illustration lists 7 participants per arm for 80% power and 9 participants per arm for 90% power. For planning for 75% of the observed effect, it lists 12 and 16 participants per arm, respectively. For planning for 50% of the observed effect, it lists 27 and 36 participants per arm, respectively. Smaller effects need more participants because a subtler group difference is harder to distinguish from variation in scores under the same assumptions.

These figures are not observed power. They are not a retrospective verdict on whether the completed study was adequately designed, and they do not replace the original protocol’s justification, which is not reported in the registry record. The curve should be read as a visual companion to the same planning assumptions and effect fractions, rather than as evidence about the trial’s actual enrollment decisions.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 24.900; pooled standard deviation σ = 16.212.
2. n = 2 × (1.96 + 0.842)² × 16.212² / 24.900² = 6.7, rounded up to 7 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- 24.9                      # observed difference in means
sigma <- 16.2117241526002                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(3346161)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 7 (80% power), 9 (90% power)
 75% of observed effect: n per arm = 12 (80% power), 16 (90% power)
 50% of observed effect: n per arm = 27 (80% power), 36 (90% power)
power.t.test: 7.7 
Simulated power at n = 7 per arm: 0.751 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Multiplicity, Missing Data and Analysis Populations

The registry lists multiple secondary outcomes, including measures of quality of life, shared decision making, patient activation, reconstruction receipt, type and timing, and time use. It does not report a multiplicity strategy, such as adjustment of significance thresholds or a prespecified order for interpreting these outcomes. When many outcomes are tested, the chance of at least one apparently unusual result can increase. This general concern means unadjusted secondary p-values should not be read as if they came from a single isolated test.

The primary endpoint is clearly identified, but the statistical analysis plan is not reported in the registry record. Details such as planned covariate adjustment, the exact test, subgroup analyses, or sensitivity analyses are also not reported. No interim analyses are reported in the registry record. It is therefore not possible to determine from the record whether the posted analyses followed a more detailed prespecified plan.

The primary endpoint includes 60 participants in each group. The available secondary shared-decision-making comparison includes 56 in the decision-tool group and 59 in enhanced usual care. The record does not explain the difference in denominators or report whether any data were missing, why they were missing, or how missing observations were handled. A smaller denominator can reflect several possible processes, but the reason cannot be inferred from the posted information.

The registry record does not identify the analysis population, such as whether analyses included all randomized participants or only participants with a completed assessment. It also does not report an imputation method or a sensitivity analysis for missing data. These details matter because conclusions can depend on which participants are included and on assumptions about unobserved outcomes. The available summaries support describing the reported results, but do not resolve these analysis-population and missing-data questions.

15. 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 0% reporting threshold.

For each group, 60 participants were listed as at risk for serious adverse events, and 0 were listed as affected. The same group sizes and zero affected counts were reported for other adverse events. The registry also lists 1 death in each group. No serious adverse event terms are listed among the top serious terms.

These figures describe the counts recorded for the groups; they do not establish whether an event was caused by the decision tool, the booklet, or another factor. The record does not provide further detail about the deaths, their timing, or their relationship to study participation. Zero participants recorded as affected for the listed adverse-event categories should not be interpreted as proof that no events occurred outside the record’s definitions or observation procedures.

The safety summaries should be read separately from the knowledge endpoint. They do not measure how well participants understood reconstruction options or whether their decisions reflected their preferences. The registry record does not report additional safety analysis or adjudication details.

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

The posted primary result shows that the BREASTChoice group had a higher mean objective knowledge score through completion of the breast consultation than the enhanced usual-care group. The reported mean difference was 24.9 percentage points, with a 95% confidence interval from 19.1 to 30.7 and p < 0.001. This is evidence about the measured knowledge outcome at the stated assessment time.

That result does not establish that participants chose a particular type or timing of reconstruction, that their choices were more consistent with their values, or that they experienced better quality of life. Those questions involve different outcomes. The registry lists such outcomes, but the available posted results do not provide a full set of numerical analyses for them.

The comparison also does not establish how the tool would perform in settings or populations beyond those enrolled. The record identifies patients considering reconstruction after a completed or planned mastectomy and scheduled for consultation, but does not report enough detail to characterize all participant features or the recruitment setting. The study is listed as phase 1, with enrollment of 120 and a short-term primary assessment. Longer-term outcomes are not reported in the primary endpoint timeframe.

Randomization makes a between-group comparison informative, but the record does not report the allocation procedures, analysis population, missing-data handling, or detailed statistical plan. These gaps limit independent assessment of possible sources of bias and analytic choices. The numerical result can be described as the posted group comparison, while broader claims about decision quality or later outcomes remain outside what this endpoint demonstrates.

The confidence interval indicates that the estimated difference is not highly uncertain under the analysis assumptions, but statistical precision does not answer whether the difference is important to patients. The registry record does not report a threshold for a meaningful change in knowledge. Interpretation should therefore distinguish the observed score contrast from claims about practical consequences or clinical benefit.

17. Why This Trial Matters Statistically

This trial raises a statistical question that is central to decision-support research: whether an intervention changes what patients know at the point when they are making a complex choice. The endpoint is a direct score of correct answers, so the primary comparison concerns knowledge rather than an indirect proxy such as tool use alone. The observed group means and their confidence interval allow the size and uncertainty of that contrast to be described.

The study also illustrates why one endpoint cannot represent every dimension of decision quality. Knowledge, shared decision making, patient activation, and eventual reconstruction choices are related but distinct outcomes. A difference on the primary knowledge measure does not automatically establish differences on the other dimensions. Separating those constructs helps prevent an overbroad interpretation of a single positive comparison.

Statistically, the record highlights the value of transparent reporting beyond a p-value. Group sizes, means, standard deviations, a mean difference, and a confidence interval together give readers a clearer view of the primary result. At the same time, missing details about the original sample-size justification, analysis plan, missing data, and multiplicity show how registry reporting affects confidence in interpretation.

The observed-effect planning illustration can help readers understand how assumed effect size relates to planned enrollment, but it is not evidence about the trial’s original design choices or its observed power. Keeping planning assumptions separate from the completed result is important when evaluating a pilot study. The strongest statistical conclusion remains tied to the measured short-term knowledge score, with other questions requiring complete outcome reporting and analysis details.

18. 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 original sample-size justification, so the observed-effect planning illustration cannot establish whether enrollment was selected to detect a prespecified effect. The detailed statistical analysis plan, exact primary test, allocation procedures, and interim-analysis plans are also not reported. These omissions constrain assessment of the design and analysis beyond the posted summaries.

The primary endpoint is measured through completion of the consultation, with total participant time described as approximately 30 minutes. The registry does not report a longer-term primary assessment. The knowledge measure’s scoring rules, validation, and a threshold for a meaningful difference are also not reported, limiting interpretation of the score contrast in terms of practical importance.

The record does not explain why the available secondary shared-decision-making denominators differ from the primary group sizes, nor does it describe missing-data handling or analysis populations. Results for all listed secondary outcomes are not numerically reported, and no multiplicity plan is described. These limitations make it difficult to judge the full pattern of outcomes or the robustness of secondary inferences.

The study is listed as phase 1 and includes 120 participants, with 60 in each primary comparison group. The registry does not provide enough detail about participant characteristics or recruitment context to assess how widely the result may generalize. It also reports no masking. These points do not negate the posted primary comparison, but they define what can be concluded from the record and identify information needed for a fuller appraisal.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Optimizing Decision Making About Breast Reconstruction After Mastectomy: A Patient-Centered Approach — NCT03346161.
• Registry record last updated 2019-09-06; status last verified 2019-07.
• Results first posted 2019-09-06.
• 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.

22. Record Summary

NCT03346161 is a completed randomized, parallel-group study listed as phase 1, with enrollment of 120. It compared BREASTChoice, a clinical decision tool, with enhanced usual care using the American Society of Plastic Surgeons booklet “Breast Reconstruction.” The primary endpoint was percent correct on an objective knowledge measure through completion of the breast consultation appointment.

The primary comparison included 60 participants per group. Mean scores were 84.6 for BREASTChoice and 59.7 for enhanced usual care; the reported mean difference was 24.9 percentage points, with a 95% confidence interval from 19.1 to 30.7 and p < 0.001. The result concerns short-term knowledge scores and does not establish effects on other decision or clinical outcomes.

The record lists multiple secondary outcomes and adverse-event summaries, but full secondary analyses and important statistical-plan details are not reported in the registry record.