This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for MarginProbe, a Device for Intraoperative Assessment of Margin Status in Breast Conservation Surgery (NCT00749931), a randomized na study. The primary outcome is The Primary Effectiveness Endpoint is a Measure of Intraoperative Success in Addressing Positive Margins as Detected by Permanent Pathology)by Additional Oriented Tissue Re-excision From the Surgical Cavity..
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00749931 |
| Phase | NA |
| Condition | Breast Cancer |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 664 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Dune Medical Devices |
| Results posted | Yes |
2. Clinical Question
Population
Participants with breast cancer undergoing breast-conservation surgery were enrolled. The primary analysis population was narrower: patients with at least one histologically positive margin on the main lumpectomy specimen, described in the registry record as Positive specimen subjects.
Intervention
MarginProbe was used in addition to the standard-of-care lumpectomy procedure. The stated purpose was to assist intraoperative assessment of margin status and the extent of excision.
Comparator
The comparator was standard-of-care lumpectomy without the device. The registry describes this as the Standard of Care arm.
Primary question
Among participants with at least one histologically positive margin on the main specimen, how often were all positive margins addressed during surgery by additional oriented tissue re-excision from the surgical cavity? The registry reports the endpoint as a percentage of participants analyzed, with a timeframe of two weeks after surgery.
3. Trial Design
The registry describes a randomized, parallel-group trial with no masking. The comparison was between standard-of-care lumpectomy and use of MarginProbe in addition to standard-of-care lumpectomy. Because masking was listed as none, the trial was open-label in the sense that masking was not reported. Further details about allocation concealment or other procedures used to implement randomization are not reported in the registry record.
The listed enrollment was 664. The registry lists breast cancer as the condition, Dune Medical Devices as the sponsor, and the study status as completed. The recorded start was 2008-10 and primary completion was 2010-03. The phase is listed as NA. These entries describe the overall registered study; the primary effectiveness analysis population was restricted to participants with at least one histologically positive margin on the main lumpectomy specimen.
The registry’s primary analysis population is therefore not interchangeable with the overall enrolled population. The reported arm counts for the primary endpoint were 147 for standard of care and 163 for device plus standard of care. The record does not explain the relationship between overall enrollment and the primary analysis counts, or give a participant-flow account that would clarify how individuals entered or left each analysis population.
The study’s stated purpose was to assess whether adding device use to routine tumor excision could assist the surgeon in determining the extent of excision. The primary endpoint focused on intraoperative response to positive margins, rather than on a broader measure of long-term cancer outcomes. The registry record does not report additional design details such as eligibility criteria beyond the primary analysis population description, the randomization procedure, or a detailed statistical analysis plan.
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
| Stage | Standard of Care (SOC) | Device + (Standard of Care) SOC | Roll-in |
|---|---|---|---|
| STARTED | 298 | 298 | 68 |
| COMPLETED | 298 | 298 | 68 |
| NOT COMPLETED | 0 | 0 | 0 |
Analysis population for the primary outcome, as defined in the registry: The Analysis Set for evaluating intraoperative assessment consisted of patients with at least one histologically positive margin on main lumpectomy specimen ("PSS" - Positive specimen subjects)
5. Baseline Characteristics
The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.
| Characteristic | Unit | Standard of Care (SOC) | Device + (Standard of Care) SOC | Total |
|---|---|---|---|---|
| Participants analysed | 298 | 298 | 596 | |
| Age, Continuous | years | 60.2 (SD 11.1) | 60.3 (SD 11.4) | 60.3 (SD 11.3) |
| Sex: Female, Male: Female | Participants | 298 | 298 | 596 |
| Sex: Female, Male: Male | Participants | 0 | 0 | 0 |
6. Primary Endpoint
The registry lists the primary outcome as The Primary Effectiveness Endpoint is a Measure of Intraoperative Success in Addressing Positive Margins as Detected by Permanent Pathology)by Additional Oriented Tissue Re-excision From the Surgical Cavity., measured over two weeks after surgery.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | percentage of participants analyzed |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is a measure of intraoperative success in addressing positive margins detected by permanent pathology. It is expressed as the percentage of participants analyzed. The registry defines success as all positive margins detected by histology on the main specimen being addressed intraoperatively through additional oriented tissue re-excision from the surgical cavity. The stated timeframe is two weeks after surgery.
The analysis population consisted of patients with at least one histologically positive margin on the main lumpectomy specimen, termed Positive specimen subjects in the registry record. Restricting the endpoint to this population makes the measure relevant to the specific situation in which the main specimen has a positive margin; it does not describe the experience of every enrolled participant.
For the standard-of-care arm, the posted endpoint value was 22.4 among 147 participants analyzed. For device plus standard of care, it was 71.8 among 163 participants analyzed. These are the registry’s reported percentages, not percentages recalculated from individual participant records. The record does not provide confidence intervals for these arm-level values.
In general, an endpoint focused on an intraoperative action can describe whether a prespecified surgical response occurred, but it does not by itself establish effects on later clinical outcomes. The registry record does not report a separate long-term outcome as part of this primary endpoint. The measure should therefore be interpreted as an assessment of the stated margin-addressing process, within the defined analysis population and timeframe.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The posted primary endpoint values were 22.4 for standard of care and 71.8 for device plus standard of care, among the stated analysis populations. The registry reports a Fisher Exact test with p < 0.001 for the two-arm comparison. These results indicate that the observed endpoint percentages differed between the arms in this analysis. The p-value describes evidence against the statistical null used for the reported test; it does not measure the size or clinical importance of an effect, and it is not the probability that the null hypothesis is true.
The comparison is specific to participants with at least one histologically positive margin on the main lumpectomy specimen. It should not be read as a comparison across all participants enrolled in the trial. The endpoint captures whether all positive margins detected on the main specimen were addressed intraoperatively through additional oriented tissue re-excision. It does not directly report longer-term outcomes or establish what happened after the two-week timeframe.
The registry reports arm-level percentages and analysis counts, but no confidence intervals or detailed effect estimate for the comparison. A confidence interval would communicate the uncertainty around an estimated quantity, and its absence limits how precisely the size of the between-arm difference can be assessed from the registry record. The reported p-value supplies evidence about incompatibility with a null comparison under the test, but it is not a substitute for an interval estimate or a full account of the data.
The trial was randomized, which is relevant to the interpretation of a treatment-group comparison, but the record does not provide details about sequence generation, allocation concealment, or participant flow. Masking was listed as none. The primary endpoint involves an intraoperative assessment and response, and the record does not describe additional procedures to reduce the influence of awareness of assigned group. These details matter when assessing the possible sources of bias, but their absence does not by itself establish that bias occurred.
The results do not show that the endpoint was achieved by every participant in either arm. The values are group-level percentages, and the record does not provide individual outcomes or further detail on missing endpoint observations. Nor should the reported statistical significance be interpreted as proof of benefit on outcomes not measured by this endpoint. It supports a difference in the posted endpoint comparison; broader conclusions would require evidence on the relevant outcomes and a fuller account of the study conduct.
Any sample-size figures associated with the posted analysis are planning illustrations based on the observed effect and stated assumptions, not observed power. The registry record does not report the trial’s own sample-size justification. Such illustrations can help show how assumptions about a target effect relate to planning, but they should not be used to claim that the completed study had a particular probability of detecting an effect.
9. Statistical Methods Explained
The registry reports a Fisher Exact test for the primary comparison. This is a method for testing an association between group assignment and a categorical outcome. It is often used when the data can be arranged as counts in categories and when a test based on large-sample approximations may be less suitable. The record does not provide the underlying participant-level counts or a more detailed specification of the test input, so the posted method and p-value are the available description of the sponsor’s comparison.
What does the p-value say?
In general, a p-value measures how unusual data at least as incompatible with a stated null hypothesis would be if that null hypothesis and the assumptions of the test were true. A small p-value is evidence against that null model. It does not give the probability that the null is true, quantify the probability that the result will replicate, or measure the clinical importance of the observed endpoint values. Here, the registry reports p < 0.001. That is evidence of a difference under the reported test, but it does not on its own describe the precision of the estimated difference.
Why is a confidence interval useful?
In general, a confidence interval gives a range of values compatible with the data and the method used to estimate uncertainty. It helps readers assess precision and the range of effects that remain plausible under the analysis. The registry record does not report a confidence interval for the primary comparison or the arm-level percentages. Without one, the p-value cannot show how narrowly or broadly the magnitude of the group contrast is estimated. No confidence interval should be inferred from the reported p-value alone.
What does the analysis population represent?
The primary analysis was limited to patients with at least one histologically positive margin on the main lumpectomy specimen. This population is described as Positive specimen subjects. The endpoint asks whether all positive margins identified on that specimen were addressed intraoperatively. In general, defining a population around a condition needed for the endpoint can make the question more focused, but it also means that the result applies directly to that defined population rather than automatically to all people enrolled. The registry does not report additional details about the analysis-population rules, such as how missing pathology or other deviations were handled.
What is the role of randomization and masking?
In general, random allocation is intended to create comparable groups with respect to both measured and unmeasured characteristics, on average. It does not guarantee that every aspect of trial conduct is free of bias. The registry identifies the trial as randomized and parallel-group, but details of sequence generation and allocation concealment are not reported in the registry record. Masking is listed as none. When participants and study staff know the assigned group, knowledge of assignment can potentially influence assessments or care processes, depending on how outcomes are defined and measured. The record does not describe whether independent assessment or other safeguards were used.
How should planning illustrations be read?
In general, a sample-size calculation estimates the number of participants needed under specified assumptions about an effect, variability, significance level, allocation, and analysis method. The planning assumptions described for this study use the observed effect, a two-sided significance level of 0.05, equal allocation, and a normal approximation; the target effect is specified as a fraction of the observed effect. These are planning illustrations, not observed power and not evidence of the trial’s original design rationale. The trial’s own sample-size justification is not reported in the registry record. For non-time-to-event outcomes, sample-size outputs are stated as participants per arm for 80% power or 90% power, depending on the planning target; no such output value is necessary to interpret the posted endpoint comparison.
In general, a planning estimate based on an observed effect can be sensitive to the size of that observed effect. It should not be treated as an independent confirmation of the result, because the observed effect comes from the same trial being interpreted. Likewise, a planned sample size does not establish that the actual analysis population matched the plan. The registry does not report the protocol’s assumed effect or its original sample-size calculation, so the planning illustrations cannot be used to reconstruct that rationale.
The record reports two outcome measures and two analyses overall, while no secondary outcome results are posted. The primary result is therefore the main posted efficacy comparison described in this record. The registry does not provide a detailed statistical plan, a list of all planned analyses, or information about interim analyses. Those elements should not be inferred from the test method or the number of posted analyses.
10. Analyses Reported by the Sponsor
| Method | Estimate | 95% CI | P-value |
|---|---|---|---|
| Fisher Exact | not reported | < 0.001 |
The registry reports the sponsor’s primary comparison using a Fisher Exact test, with p < 0.001. It does not provide a confidence interval or a more detailed comparison estimate. The registry record does not flag a discrepancy between the reported result and the recalculated result. Accordingly, the sponsor’s reported analysis is the inferential result to cite, while the arm-level percentages remain the direct description of the posted endpoint values.
A recalculation from summary statistics is unadjusted and cannot reproduce analyses that depend on participant-level data or additional model details. In general, such recalculations are best viewed as checks of the posted summary rather than replacements for a sponsor’s analysis. In this record, no discrepancy is flagged, so there is no conflicting result to resolve. The registry does not report additional adjustments or model specifications beyond the stated Fisher Exact test.
The reported p-value should still be interpreted within the limits of the available record. It does not provide an effect-size interval, establish the importance of the endpoint difference, or extend the conclusion to outcomes not measured by the primary endpoint. The sponsor’s test result and the descriptive endpoint percentages answer related but distinct questions: the percentages describe the observed arm-level results, while the test evaluates evidence against its statistical null model.
11. Multiplicity, Missing Data and Analysis Populations
The registry record reports two outcome measures and two analyses overall, but no secondary outcome results are posted. The primary endpoint is identified, and the reported comparison uses a Fisher Exact test. A detailed statistical analysis plan, including a strategy for controlling multiplicity across endpoints or analyses, is not reported in the registry record. It is therefore not possible to determine from this record whether any adjustment for multiple testing was planned or applied.
In general, testing several outcomes or comparisons can increase the chance of observing at least one small p-value even when none of the underlying effects is real. Multiplicity procedures address that issue by specifying how inference will be controlled across a family of tests. Without a reported plan, the primary p-value should be read as the result for the stated comparison, not as evidence that all possible analyses were accounted for in a prespecified strategy. The record does not state whether interim analyses were conducted.
The registry identifies the primary analysis population as patients with at least one histologically positive margin on the main lumpectomy specimen. It does not report a full definition of the analysis set or the handling of missing endpoint data, withdrawals, protocol deviations, or participants without an assessable pathology result. No imputation method or sensitivity analysis is described. These omissions limit assessment of how the analyzed population was formed and whether incomplete information could have influenced the endpoint estimates.
The overall enrollment was 664, while the primary endpoint is reported for 147 participants in the standard-of-care arm and 163 in the device-plus-standard-of-care arm. The registry does not provide a participant-flow account explaining the difference between the overall enrollment and these analysis counts. These figures should not be combined or treated as interchangeable denominators. The endpoint values apply to the reported analysis populations, and the record does not establish how missing or excluded cases were distributed across groups.
12. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Standard of Care (SOC) | 5 | 298 | 1.7% |
| Device + (Standard of Care) SOC | 6 | 298 | 2.0% |
| Roll-in | 3 | 68 | 4.4% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Standard of Care (SOC) | 0 of 298 |
| Device + (Standard of Care) SOC | 0 of 298 |
| Roll-in | 0 of 68 |
Most frequent serious adverse event terms
| Event term | Organ system | Standard of Care (SOC) | Device + (Standard of Care) SOC | Roll-in |
|---|---|---|---|---|
| Infections and infestations | Infections and infestations | 1 of 298 | 2 of 298 | 2 of 68 |
| Injury, poisoning and procedural complications | Injury, poisoning and procedural complications | 3 of 298 | 2 of 298 | 0 of 68 |
| Vascular disorders | Vascular disorders | 0 of 298 | 1 of 298 | 1 of 68 |
| Neoplasms benign, malignant and unspecified (incl cysts and polyps) | Neoplasms benign, malignant and unspecified (incl cysts and polyps) | 0 of 298 | 1 of 298 | 0 of 68 |
| Reproductive system and breast disorders | Reproductive system and breast disorders | 1 of 298 | 0 of 298 | 0 of 68 |
Serious events with the highest arm-level rate: infections and infestations (2.9%), vascular disorders (1.5%), injury, poisoning and procedural complications (1.0%), neoplasms benign, malignant and unspecified (incl cysts and polyps) (0.3%), reproductive system and breast disorders (0.3%).
The serious adverse-event figures are reported separately from the primary effectiveness endpoint. The registry lists 298 participants at risk in the standard-of-care group, with 5 affected; it lists 298 at risk in the device-plus-standard-of-care group, with 6 affected. For the Roll-in group, it lists 68 at risk, with 3 affected. The record does not report deaths for these groups. These figures should be read as the registry’s reported serious adverse-event counts, not as a causal comparison between randomized groups.
The registry also reports 0 for the separate other-adverse-event count in each listed group. It lists serious-event terms and percentages including Infections and infestations at 2.9%, Vascular disorders at 1.5%, Injury, poisoning and procedural complications at 1.0%, and Neoplasms benign, malignant and unspecified (incl cysts and polyps) and Reproductive system and breast disorders at 0.3% each. The record does not explain in detail how these term-level percentages were calculated or whether events were adjudicated for relation to the device.
In general, event counts need context: definitions, collection methods, follow-up duration, severity criteria, and attribution procedures affect interpretation. The registry record does not provide those details. The Roll-in group is listed separately and should not be treated as one of the two randomized comparison arms based on the information reported. These safety entries describe what the registry records; they do not establish that an event was caused by a particular intervention or support a broader safety conclusion.
13. What the Result Does, and Does Not, Mean
The primary result concerns a narrowly defined procedural endpoint: among participants with at least one histologically positive margin on the main specimen, whether all positive margins were addressed intraoperatively through additional oriented tissue re-excision from the surgical cavity. The registry reports higher observed endpoint percentage in the device-plus-standard-of-care arm than in the standard-of-care arm, together with a Fisher Exact test result of p < 0.001. This supports a difference in the posted endpoint comparison under the reported test.
The result does not, by itself, establish effects on outcomes beyond the endpoint’s definition and timeframe. It does not report long-term cancer outcomes, and it should not be read as a comparison of outcomes among all enrolled participants. Nor does a small p-value say how large or important a difference is. The registry record does not give a confidence interval for the primary comparison, so the precision of the size of the difference cannot be evaluated from an interval estimate in this record.
The trial is described as randomized, which is an important design feature for comparing groups, but masking was listed as none. Details about allocation concealment, participant flow, missing data, and endpoint assessment procedures are not reported in the registry record. Those gaps constrain assessment of the risk of bias and the exact population to which the reported results apply.
The serious adverse-event counts are reported separately and should not be used to infer that the device caused or prevented events. The registry does not provide detailed definitions, follow-up context, or attribution information for those entries. Overall, the posted data describe an observed difference in the specified intraoperative endpoint and provide a statistical test for that comparison. They do not alone settle questions about broader clinical outcomes, long-term effects, or the full safety profile.
14. Why This Trial Matters Statistically
This trial is statistically instructive because its primary endpoint is defined around a specific intraoperative decision and a population in whom a positive margin was found on the main specimen. That definition makes clear that the reported comparison is conditional on a pathology finding, rather than a summary of every participant enrolled. Readers can therefore distinguish the population relevant to the endpoint from the overall trial enrollment.
The registry reports both descriptive arm-level percentages and a formal test. These convey different information. The percentages show the observed endpoint values in each analysis arm; Fisher Exact p < 0.001 addresses how compatible the comparison is with a null model under the test. Neither the test result nor the percentages provide the precision that a confidence interval would convey, and the registry does not report such an interval.
The record also illustrates why endpoint interpretation must remain tied to the stated measure. A measure of whether positive margins were addressed intraoperatively is not equivalent to a measure of later clinical outcomes. A statistically clear difference in the registered process endpoint should not be extended to outcomes that are not reported.
Finally, the primary analysis counts are smaller than the overall enrollment, and the registry does not explain the participant flow that connects them. This makes transparent reporting of analysis populations, missing data, and planned analyses important for judging how broadly a result can be applied. The record identifies the relevant analysis population but leaves several details unreported. Recognizing both the strong statistical evidence for a difference in the posted endpoint and the limits of the available information is central to a balanced reading.
15. 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 principal limitation is that the posted primary endpoint applies to patients with at least one histologically positive margin on the main specimen, rather than to all enrolled participants. The registry gives the arm-level analysis counts but does not provide a participant-flow account explaining how those counts relate to overall enrollment or how participants without an assessable primary endpoint were handled.
The endpoint values are presented as percentages, and no confidence interval is reported for the comparison. The registry also does not provide participant-level outcome counts, a detailed analysis plan, or additional model specifications beyond Fisher Exact. These omissions limit independent assessment of the precision of the estimated contrast and of the exact analysis procedures.
Masking is listed as none. The record does not describe whether outcome assessment was independently conducted or whether other safeguards addressed possible effects of knowing the assigned group. It also does not report allocation concealment details, missing-data methods, imputation, or sensitivity analyses. These are reporting limitations; the available record does not establish that a particular bias occurred.
The registry reports two outcome measures and two analyses overall, but no secondary outcome results are posted. It does not describe a multiplicity strategy, interim analyses, or the trial’s own sample-size justification. Planning illustrations based on the observed effect cannot substitute for that missing design information and are not observed power. Safety reporting includes serious adverse-event counts and selected terms, but detailed definitions, follow-up context, and attribution are not reported in the registry record. The result should consequently be interpreted as evidence about the specified primary endpoint, with these limits in mind.
16. Related Tutorials
17. Related Statistical Calculators
18. Sources
- ClinicalTrials.gov: MarginProbe, a Device for Intraoperative Assessment of Margin Status in Breast Conservation Surgery — NCT00749931.
- Registry record last updated 2014-06-27; status last verified 2014-05.
- Results first posted 2014-06-27.
- 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.
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19. Record Summary
NCT00749931 is a completed, randomized, parallel-group study with no masking, sponsored by Dune Medical Devices. It compared standard-of-care lumpectomy with use of MarginProbe in addition to standard-of-care lumpectomy. Listed enrollment was 664; the recorded start was 2008-10 and primary completion was 2010-03.
The primary endpoint assessed whether all positive margins detected histologically on the main specimen were addressed intraoperatively through additional oriented tissue re-excision from the surgical cavity. The analysis population comprised patients with at least one histologically positive margin on the main lumpectomy specimen. The registry reports endpoint values of 22.4 for standard of care and 71.8 for device plus standard of care, and a Fisher Exact test result of p < 0.001.
The registry does not report a confidence interval for the comparison, a detailed participant-flow account, missing-data methods, or a detailed multiplicity strategy. Serious adverse-event counts are listed separately for the two arms and a Roll-in group. No secondary outcome results are posted.