Blossom Smart Expander Technology in Breast Reconstruction in Participants With Breast Cancer Undergoing Mastectomy: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Blossom Smart Expander Technology in Breast Reconstruction in Participants With Breast Cancer Undergoing Mastectomy (NCT03657069), a na na study. The primary outcome is Time to Full Expansion Defined as Number of Days Until Desired Breast Tissue Expansion Volume is Achieved.

2. Clinical Question

The study concerns the use of a device intended to deliver small, continuous saline injections from an external pouch, with pressure and volume measurements. The brief summary describes a possible aim of reaching reconstructive goals over a shorter period and avoiding frequent injections through the skin. Those aims frame the rationale for studying the device; they are not outcome findings.

Because the study has a single group, its primary question is descriptive: what expansion time was observed among participants treated with the Blossom technology? It cannot, on its own, estimate how expansion time compares with a separate group receiving conventional tissue expansion. Such a comparison would require results from an appropriate control group and a design that supports a between-group interpretation.

3. Trial Design

The registry record lists this as a completed, single-group study sponsored by Stanford University. Its enrollment is 11. The allocation field is NA, and masking is listed as none. The phase field is NA, although the brief summary describes the study as phase 1. The record does not explain the phase-field discrepancy.

Participants underwent two-stage implant-based breast reconstruction after mastectomy using the Blossom Smart Expander Technology. The arm description identifies a Blossom syringe assist device connected to a Mentor SPECTRUM adjustable saline breast implant. There is no randomized allocation or concurrent control arm recorded. The study therefore describes experience with the device in the enrolled group rather than a randomized comparison with another expansion approach.

The primary outcome is time to full expansion, defined by the number of days from expander placement until the desired expansion volume is achieved. Assessment was planned weekly for up to 12 weeks. The description also notes that data collection continued until breast expansion was complete, surgical scars had stabilized, and percutaneous drains had been removed. These details describe the outcome collection context, but the registry record does not state how the final analysis handled participants who did not reach the endpoint within the assessment period.

The record lists the BREAST-Q Reconstruction Module Version 2.0 patient satisfaction score, major and minor complications associated with tissue expansion, device malfunction, and pain score among secondary outcomes. It reports 6 outcome measures, but does not provide results for these secondary measures in the information available for this analysis. It also reports no analyses. The registry record does not describe a protocol for interim analyses, a sample-size justification, or an adjusted statistical analysis plan.

The record gives the study start as 2018-08-01 and primary completion as 2020-08-19, and marks the study completed. Completion status indicates that the study has ended according to the registry; it does not by itself establish that every planned outcome was reported.

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 Time to Full Expansion Defined as Number of Days Until Desired Breast Tissue Expansion Volume is Achieved, measured over Assessed weekly for up to 12 weeks.

The primary endpoint is time to full expansion, measured in days from expander placement until the desired breast tissue expansion volume is achieved. The registry record specifies that the result is to be described by the median and inter-quartile range. It was assessed weekly for up to 12 weeks, with data collection described as continuing until completion of expansion along with stabilization of surgical scars and removal of percutaneous drains.

Time to an event is useful when the interval required to reach a clinically defined milestone is relevant. Here, the event is not a complication or a general health outcome: it is reaching the desired expansion volume. The elapsed time can characterize how long the expansion process took in the treated group. A median gives the midpoint of the observed distribution, while the inter-quartile range describes the spread of the middle portion of that distribution. These are descriptive summaries; they do not by themselves establish a causal effect of the device.

Weekly assessment means the endpoint is observed through repeated checks rather than continuously. In general, when an event occurs between assessment visits, its exact timing may be less precise than its recorded assessment time. The registry description does not state the convention used to assign an event date in that situation.

The record does not report the observed median, inter-quartile range, number reaching full expansion, or number not reaching it during follow-up. Consequently, the endpoint definition and intended summary can be described, but the actual expansion-time result cannot be interpreted from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary endpoint is a duration: the number of days from expander placement to the desired expansion volume. The registry calls the summary a median and specifies an inter-quartile range. These choices are often suitable for time measurements because durations can be unevenly distributed, with some participants reaching the endpoint sooner or later than others. A median is the central value in an ordered distribution. The inter-quartile range describes the span of the middle half of observations and gives information about variability without relying on the mean.

A median and inter-quartile range are descriptive summaries. They do not, by themselves, quantify how precisely the median has been estimated. A confidence interval is a general statistical tool for expressing uncertainty around an estimate. No confidence interval for the primary endpoint is reported in the registry record. Without the observed median, inter-quartile range, and an uncertainty measure, readers cannot judge the magnitude or precision of the expansion-time result.

Although the endpoint is a duration, the record describes weekly assessment, not continuous monitoring. In general, event-time methods are useful when the time until a defined event is of interest and when some participants may not have the event observed during follow-up. Such methods can account for incomplete event observation under stated assumptions. The registry record does not report whether any participants failed to reach full expansion during follow-up or how such observations were handled. It does not report a survival curve, a hazard ratio, or another event-time estimate for this endpoint.

The registry’s sample-size assumptions describe planning illustrations based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. For time-to-event planning, the record says the total number of events is used in the Schoenfeld approach; other planning illustrations use participants per arm. These are planning conventions, not evidence that the trial had a particular probability of detecting an effect. Such illustrations are not observed power. The record does not report the numerical planning illustrations or a sample-size justification from the trial’s own design. Since the registered study is single-group, a two-arm planning illustration should not be mistaken for the design actually used.

In general, a hazard ratio compares event rates over time between groups under a time-to-event model. The registry’s methods note says that only sponsor-reported hazard ratios are used, but no hazard ratio is reported in the record information available for this analysis. A hazard ratio is not interchangeable with a difference in medians: the former describes a relative event rate under model assumptions, while the latter describes a difference in the time distribution. No comparative hazard ratio should be inferred for a single-group study.

Over-dispersion is a general concern when outcome variability is greater than a model assumes. If it is ignored, standard errors can be too small and confidence intervals too narrow. This consideration is relevant to count outcomes or other models whose variance assumptions may not fit the data. The registry record does not specify a model for the listed secondary outcomes, report an over-dispersion assessment, or describe any adjustment to standard errors. It would therefore be inappropriate to attribute a particular model or correction to this trial.

For a single-group study, the most direct statistical summaries would describe the observed outcomes in the treated group. Such summaries can help characterize feasibility and the range of experience, but they do not isolate the effect of the device from other influences. A control group, a prespecified comparison, and suitable analysis would be needed to support a treatment contrast. The registry record lists no randomized comparison and no analysis results.

Statistical significance and clinical importance are also different concepts. In general, a small p-value addresses compatibility with a specified null model under assumptions; it does not establish that an effect is important to participants. Conversely, a result that is not statistically significant does not demonstrate absence of an effect. The registry record reports no p-value for the primary endpoint, no effect estimate, and no confidence interval, so these questions cannot be evaluated for the primary result.

The record reports 0 analyses. That does not reveal whether analyses were performed outside the registry, but it means no analysis results are available in the record for interpretation. The registry also does not state whether the primary endpoint was analyzed according to a prespecified plan, how missing observations were treated, or which participants were included in each outcome analysis. Those details matter because analysis decisions can affect the interpretation of a result, especially when follow-up is incomplete.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 6 outcome measures, including the primary time-to-full-expansion endpoint and secondary measures concerning BREAST-Q satisfaction, major and minor complications, device malfunction, and pain. When a study evaluates multiple outcomes, general statistical practice considers whether any adjustment or hierarchy was planned to manage the chance of misleading findings across repeated tests. The registry record does not report a multiplicity strategy, outcome hierarchy beyond identifying the primary endpoint, or analysis results for the listed secondary outcomes.

The record reports 0 analyses. It does not provide p-values, confidence intervals, or effect estimates for the primary or secondary outcomes in the information available for this analysis. Therefore, the statistical significance of any outcome and the consistency of results across outcomes cannot be assessed. No multiplicity correction should be assumed.

Missing data handling is also not reported in the registry record. The endpoint was assessed weekly for up to 12 weeks, but the record does not state whether all participants completed follow-up, whether all reached full expansion, or what method was used for participants with an unobserved endpoint. It does not describe imputation, censoring, or a sensitivity analysis. These are distinct approaches, and none should be attributed to the study without a report.

The analysis population is not reported in the registry record. The record gives enrollment of 11 but does not say how many participants contributed to the primary endpoint analysis or to each secondary outcome. Enrollment should not be assumed to equal the analysis population. The record also does not describe exclusions, deviations from the intended treatment, or the handling of incomplete assessments. These gaps prevent assessment of whether reported analyses, if any, included all enrolled participants or a selected subset.

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 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: infection (9.1%).

The registry reports one study group, titled Supportive Care (Blossom Smart Expander Technology). For serious adverse events, 11 participants were at risk and 1 was affected. The listed top serious adverse event term is Infection, at 9.1%. The registry also reports 0 deaths. These figures are the serious adverse event information recorded for this group.

The at-risk value describes the group considered in the registry’s reporting; the affected value is the number reported with a serious adverse event. The infection percentage is reproduced as listed and should not be treated as a separate count. The record does not provide event timing, severity details beyond the serious classification, relatedness assessments, or a narrative explaining the infection entry. The serious-event figures do not provide a complete account of all minor complications, pain, or device malfunction, which are listed as separate outcomes.

These safety data are descriptive for a single group. With no concurrent control group, they do not show whether the observed events were more or less common than under another reconstruction approach. The registry’s safety figures should not be interpreted as proof of safety or as a comparative risk estimate.

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

The registry record establishes that a completed single-group pilot study evaluated Blossom Smart Expander Technology in breast reconstruction after mastectomy. It describes the device configuration and defines the primary endpoint as days from expander placement to the desired expansion volume. It also records a weekly assessment schedule for up to 12 weeks and lists patient satisfaction, complications, device malfunction, and pain among the outcomes.

The record does not report the observed primary endpoint result. The median time to full expansion and inter-quartile range are not available, nor is a confidence interval or other measure of precision. The listed secondary outcomes also lack results in the information available for this analysis. As a result, the registry record cannot establish how long expansion took in the enrolled group or how much that timing varied.

The design does not include a recorded control group. Therefore, even if the group’s outcome estimates were available, they would describe outcomes among participants treated with the device rather than a causal difference attributable to the device. The aims mentioned in the brief summary, including reducing time or avoiding frequent injections, remain rationale rather than demonstrated findings in this record.

The serious adverse event report identifies one affected participant among 11 at risk, lists Infection at 9.1% among the top serious terms, and records 0 deaths. These observations are useful as a limited description of the group, but do not establish comparative safety. The registry does not provide enough detail to interpret event circumstances or connect those figures to all listed complication outcomes.

Thus, the available record supports a description of the trial’s question and structure, along with limited safety reporting. It does not support a conclusion about the magnitude, precision, or comparative effect of the device on expansion time, satisfaction, complications, or pain.

13. Why This Trial Matters Statistically

This study is statistically notable because it focuses on a time-based endpoint in a device pilot. Time to a defined milestone can be informative when the process of reaching that milestone is itself important. The registry clearly defines the milestone as achievement of the desired breast expansion volume and specifies a median with an inter-quartile range, which would describe both a central time and the spread of observed times.

The study also illustrates why endpoint definitions and outcome reporting need to be considered together. A clear definition tells readers what is intended to be measured, but it does not reveal the result. The registry record does not report the median, inter-quartile range, or uncertainty for the primary endpoint. As a result, the principal statistical question remains unanswered in the available record.

The single-group design is appropriate to describe a treated cohort, but it does not create a like-for-like comparison with conventional tissue expansion. This distinction is important because the study rationale discusses possible advantages relative to frequent injections and clinic visits. Without a concurrent comparator and reported comparative analysis, those possibilities cannot be interpreted as established effects.

Finally, the record shows how pilot studies can generate questions for later evaluation while leaving important statistical details unresolved. The listed secondary outcomes cover satisfaction, complications, device malfunction, and pain, but their results and the analysis populations are not reported. The record gives a defined primary outcome and some serious adverse event information, yet does not report the analyses needed to judge the precision or comparative meaning of the findings. That is a reporting limitation, not evidence that a particular outcome was favorable or unfavorable.

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 main trial-specific limitation is the absence of reported primary outcome results. The endpoint is defined and its planned summary is specified, but the registry record does not give the observed median time to full expansion or inter-quartile range. It also does not report an uncertainty interval. This prevents assessment of the magnitude and precision of the primary finding.

The single-group design lacks a concurrent control arm. The registry record therefore does not support a direct comparison with conventional tissue expansion or another approach. The brief summary’s statements about possible shorter timing and avoiding frequent injections describe the motivation for the device, not an observed comparative effect.

Enrollment is reported as 11, but the record does not report the analysis population for the primary or secondary outcomes. It does not state whether all enrolled participants completed follow-up or reached full expansion. Although assessment was weekly for up to 12 weeks, the handling of outcomes not observed by the end of follow-up is not reported. Missing-data procedures, outcome-specific denominators, and sensitivity analyses are also not reported in the registry record.

The registry lists secondary outcomes but does not report their results in the information available for this analysis. It also reports 0 analyses and does not describe a multiplicity plan, an analysis model, or a protocol for interim analyses. The absence of these details makes it difficult to evaluate how outcomes were prioritized and analyzed.

The serious adverse event reporting is limited to the group-level figures and the top serious event term. The record does not give event narratives, timing, or relatedness assessments. These omissions restrict the safety interpretation, especially in a single-group study where no comparator is available.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Blossom Smart Expander Technology in Breast Reconstruction in Participants With Breast Cancer Undergoing Mastectomy — NCT03657069.
• Registry record last updated 2024-01-22; status last verified 2023-04.
• Results first posted 2024-01-22.
• 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

NCT03657069 is a completed, single-group pilot study sponsored by Stanford University. It evaluated Blossom Smart Expander Technology for breast reconstruction after mastectomy. The registry reports enrollment of 11, no masking, and allocation listed as NA.

The primary endpoint is time in days from expander placement to the desired breast expansion volume, summarized by the median and inter-quartile range. Assessment was weekly for up to 12 weeks. The primary result and secondary outcome results are not reported in the registry record available for this analysis. The record lists 6 outcome measures and 0 analyses.

For serious adverse events, the group had 11 participants at risk and 1 affected; Infection is listed at 9.1%, and deaths are reported as 0. The single-group design does not provide a concurrent comparison, and the available record does not establish a comparative effect on expansion time or safety.