A Study to Evaluate the Accuracy of a Breast Cancer Locator (BCL) in Patients With Palpable Cancers: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study to Evaluate the Accuracy of a Breast Cancer Locator (BCL) in Patients With Palpable Cancers (NCT02550210), a na na study. The primary outcome is The Distance Measured by Pathology From the Tumor Edge to the Center of the Ink Spots, as Marked by the Black Inked Pins..

2. Clinical Question

3. Trial Design

This is a completed, single-group device study of the Breast Cancer Locator in patients with palpable breast cancers. The registry record lists an enrollment of 23. Allocation is recorded as NA, masking as NONE, and the study model as SINGLE GROUP. The record therefore does not describe random assignment or a masked comparison. Its own description says the study was intended to assess BCL accuracy and the concomitant procedure in palpable cancers, before an evaluative trial in non-palpable breast cancer cases.

The intervention description specifies a 3D-printed, bra-like plastic form shaped to match the breast surface when the patient is supine for MRI and surgery. The locator is constructed pre-operatively, sterilized, and made available to the surgeon during the procedure. The registry description says the approach was intended to ensure that using the BCL would not substantially alter or modify the standard-of-care procedure. That is the stated rationale, not a reported result about whether the procedure was altered.

The study dates recorded are 2015-08 for start and 2018-02 for primary completion; the status is COMPLETED. The primary outcome timeframe is 30 Days. No separate comparator group, randomization procedure, masking process, or protocol-level statistical plan is reported in the registry record. These design features matter when interpreting the evidence: measurements from a single group can describe the observed procedure and its outcomes, but do not provide a randomized between-group estimate of comparative performance.

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 The Distance Measured by Pathology From the Tumor Edge to the Center of the Ink Spots, as Marked by the Black Inked Pins., measured over 30 Days.

The primary endpoint is a continuous distance measure, reported in cm, with the parameter specified as a mean and dispersion specified as a standard deviation. It concerns the distance measured by pathology from the tumor edge to the center of black-inked pins. The registry description says five measurements will be made per patient and that a mean difference in distance will be derived between palpated and co-registered supine MRI-optical scan image predicted tumor edges. It defines the BCL as accurate if all five measurements are greater than zero cm from the tumor edge.

The endpoint is intended to assess how the predicted tumor-edge locations relate to pathology measurements after the procedure. A distance measure preserves information about how far apart locations are, rather than only recording whether they agree or disagree. The stated all-measurements criterion is stricter than a rule based only on an average, because every specified measurement must satisfy it. The registry record does not report the observed distances, their mean, their standard deviation, or whether the accuracy criterion was met. Thus, the endpoint definition is available, but the endpoint result is not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a mean and standard deviation describe?

General statistical context: A mean summarizes the central value of a set of measurements. A standard deviation describes how spread out individual measurements are around that mean. For a distance endpoint, these statistics can convey both the average measured separation and the variability among measurements. They do not, by themselves, show every individual value or establish whether a specified accuracy rule was met.

In this study description, the primary endpoint is a mean distance in cm, with standard deviation specified as the dispersion measure. The registry record also describes five measurements per patient and a mean difference derived between predicted tumor edges from palpation and a co-registered supine MRI-optical scan image. It does not report the endpoint mean or standard deviation, so readers cannot assess the observed central value or spread. Nor does the record explain how the five measurements are combined across participants for a study-level estimate.

Why do repeated measurements matter?

General statistical context: Repeated measurements from the same person are often related to one another. They may share characteristics of that person, the procedure, or the measurement setting. Treating related measurements as if each came from an unrelated person can make uncertainty appear smaller than it is. Statistical approaches can account for this dependence, for example by first summarizing within each person or by using a model that recognizes clustering. The appropriate method depends on the design and estimand.

The registry description specifies five measurements per patient, but the analysis method for those repeated observations is not reported in the registry record. It does not say whether the five values are first summarized within a patient, analyzed individually with a dependence-aware method, or handled in another way. The stated accuracy rule applies to all five measurements, which is distinct from testing or estimating a mean. An average alone could conceal a value that did not meet the all-five rule; the registry does not report participant-level values needed to evaluate that rule.

How should the accuracy criterion be read?

General statistical context: A decision rule and a statistical estimate answer different questions. A decision rule classifies results according to a prespecified threshold. An estimate describes a quantity, such as a mean distance, and an uncertainty interval indicates the range of values compatible with the data under a stated method. A threshold rule may be clinically or procedurally meaningful, but its interpretation depends on the measurement definition and the study’s analysis procedures.

The registered rule says the BCL will be considered accurate if all five measurements are greater than zero cm from the tumor edge. The rule does not itself report how often that condition occurred. The record gives no estimate, uncertainty interval, or analysis of the rule. It also does not explain whether the distances are signed, how boundary cases are handled, or how any missing measurements would affect classification; those details are not reported in the registry record.

What can a single-group design establish?

General statistical context: A single-group study can describe outcomes observed in the group receiving or undergoing the intervention. It can estimate a mean or event frequency if outcome data and an analysis are reported. Without a separate comparison group, it does not estimate a randomized difference between intervention and control groups. A measurement comparison within a participant or procedure may still be informative, but it answers a different question from a comparative treatment trial.

The record identifies one BCL group and lists allocation as NA and masking as NONE. It does not report a separate control arm. The primary endpoint compares predicted tumor-edge locations with pathology measurements as described in the registry; that comparison should not be recast as a randomized comparison between treatments. The record does not report a statistical model, inferential test, or uncertainty calculation for this endpoint.

What do the planning assumptions mean?

General statistical context: Sample-size calculations are planning illustrations based on assumptions about an effect, variability, significance level, allocation, and analysis method. They are not observed outcomes and do not establish the precision achieved in a completed study. A planning calculation based on a stated fraction of an observed effect also depends on the effect estimate used as its input; it should not be confused with a trial’s observed power.

The registry record describes planning illustrations using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect defined as a stated fraction of the observed effect. It says time-to-event illustrations give total events using the Schoenfeld approach, while other illustrations give participants per arm. These are described as planning assumptions, not as the trial’s own design. They do not change the recorded single-group model, and they do not establish an actual two-arm comparison in this study. The registry does not report a trial-specific sample-size justification or statistical analysis plan.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Breast Cancer Locator (BCL)")
n   <- c(18)
m   <- c(1.7)
sp  <- c(1.2)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Breast Cancer Locator (BCL)  18  1.700  1.200  1.103  2.297

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists a primary outcome and secondary outcomes of positive margin rate, distances between specimen edges as determined by the BCL and by the supine MRI/optical scan/tracker system, and mean resection specimen volume. It lists four outcome measures overall, but does not report results or analyses for them. No multiplicity procedure—such as an adjustment to account for testing several outcomes—is reported in the registry record. Without reported tests or estimates, the implications of multiple outcome testing cannot be assessed.

Missing-data information is not reported in the registry record. The record does not say whether any outcome measurements were unavailable, how missing measurements would be handled, or whether participants withdrew or were excluded from an analysis. It also does not describe a missing-data sensitivity analysis. These omissions matter because the primary accuracy rule requires all five measurements per patient; interpreting that rule would require knowing how incomplete sets were treated.

The record lists no analyses and does not identify an analysis population, such as all enrolled participants or participants with evaluable measurements. It does not state which participants contributed to each outcome or whether any exclusions were made. As a result, the relationship between the recorded enrollment and any endpoint analysis cannot be evaluated. No imputation method, per-protocol population, intention-to-treat population, or other analysis set is reported in the registry record. These are reporting gaps; they do not establish that missing data or exclusions occurred.

12. 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.

The registry records zero serious adverse events, zero other adverse events, and zero deaths in the BCL group. It records 23 at risk for the serious-event category and 23 at risk for the other-event category. These are the counts entered in the registry record; they should be read as reported event counts, not as a complete description of every aspect of safety monitoring.

The record does not list serious adverse-event terms, event narratives, timing, severity details, or the method used to collect events. It also does not report additional information about follow-up or whether all participants had the same observation period. The primary outcome timeframe is 30 Days, but the record does not establish that this is the adverse-event follow-up period. The absence of recorded events in these fields is not a substitute for detailed safety reporting, and it does not resolve questions about event ascertainment or duration of observation. These figures concern the BCL group only; there is no separate control group in the registered design for a comparative safety estimate.

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

This record is useful for identifying the study’s objective, its single-group structure, the device procedure described, and the intended primary measurement. It shows that the investigators planned to assess the Breast Cancer Locator in patients with palpable cancers, using pathology-related distance measurements and a stated criterion requiring all five measurements per patient to be greater than zero cm from the tumor edge. It also records the study as completed and lists enrollment of 23.

Those design details do not establish the observed accuracy of the locator. The registry record does not report the primary endpoint data, an estimate of mean distance, its standard deviation, or the number of measurement sets meeting the criterion. It likewise does not report results for the listed secondary outcomes. Without outcome estimates, the magnitude and precision of the findings cannot be judged from the posted results.

The registered single-group design also does not provide a randomized treatment comparison. The measurement approach described in the primary endpoint can address the relationship between predicted locations and pathology measurements, but the record does not report a comparative effect against a control intervention. The study’s rationale concerning preservation of the standard-of-care procedure is a stated aim, not evidence of what occurred during procedures.

The safety entries record zero serious adverse events, zero other adverse events, and zero deaths in the BCL group. Those counts should be interpreted within the limits of the event details and follow-up information reported in the registry. Taken together, the record gives an account of what was intended to be measured and how the study was structured, while leaving the central numerical efficacy and accuracy findings unreported. It therefore supports understanding the study question, but not a numerical conclusion about the primary result.

14. Why This Trial Matters Statistically

Statistically, this study illustrates the distinction between defining an endpoint and reporting its result. The registry gives a specific distance-based endpoint, identifies a mean and standard deviation as the summary measures, and states an accuracy criterion involving five measurements per patient. These details allow readers to understand the intended measurement framework. But without the resulting values or an analysis, the stated endpoint cannot be evaluated quantitatively.

The design also clarifies why the estimand matters. A single-group device study can describe measurements in the enrolled group, while a randomized comparison addresses a different question about differences between assigned groups. The registry identifies a single group and does not describe a randomized control comparison. The primary measurement comparison should therefore be understood on its own terms rather than treated as a treatment-effect estimate.

Repeated measurements create an additional statistical issue. Measurements from the same patient may be dependent, so the way those observations are combined affects both the estimate and its uncertainty. The registry specifies five measurements per patient but does not report the analysis strategy for their dependence. The all-measurements criterion also cannot be inferred from a mean alone: assessment requires information about each relevant measurement or an explicit summary of whether the rule was met.

Finally, the record shows how registry completeness affects interpretation. It lists secondary outcomes and safety counts, but gives no outcome analyses and little detail about missingness, analysis populations, or event follow-up. These gaps do not prove that the study lacked methods or data; they mean those details are not reported in the registry record. For clinical researchers and biostatisticians, separating registered aims, available counts, and unreported estimates is essential to avoid drawing conclusions beyond what the record can support.

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 main limitation for interpreting this specific study is that the registry record does not report the primary outcome result. It gives the endpoint definition and timeframe, but not the measured distances, mean, standard deviation, or whether the stated accuracy criterion was met. The listed secondary outcomes also have no reported results. Consequently, the magnitude and precision of the study’s findings cannot be evaluated from the registry record.

The design is single-group, with allocation recorded as NA and masking as NONE. There is no separate control group described, so the record does not support a randomized between-group comparison. The stated aim of avoiding substantial alteration or modification of the standard-of-care procedure is not accompanied by a reported result measuring whether this aim was achieved.

Important analytic details are not reported in the registry record. These include how the five measurements per patient were analyzed, how dependence among repeated measurements was handled, how missing measurements would be treated, and which participants formed each analysis population. No statistical plan, inferential method, or multiplicity approach is reported. The record also does not provide detail about the handling of measurements at or near the stated threshold.

Safety interpretation is limited by the absence of event descriptions and follow-up detail. The recorded zero counts do not show how events were collected or how long participants were observed for adverse events. The primary endpoint timeframe of 30 Days should not be assumed to define safety follow-up, because that relationship is not reported. These limitations concern what the registry record makes available; they do not establish that the underlying study did not collect further information.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: A Study to Evaluate the Accuracy of a Breast Cancer Locator (BCL) in Patients With Palpable Cancers — NCT02550210.
• Registry record last updated 2019-04-30; status last verified 2019-04.
• Results first posted 2019-04-30.
• 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.

19. Record Summary

NCT02550210 is a completed, single-group study of the Breast Cancer Locator in patients with palpable breast cancer. The sponsor is Dartmouth-Hitchcock Medical Center, and the registry lists enrollment of 23. The recorded start is 2015-08 and primary completion is 2018-02. Allocation is listed as NA and masking as NONE.

The primary outcome is a pathology-related distance measure in cm, with a mean and standard deviation specified and a timeframe of 30 Days. The registry describes five measurements per patient and defines accuracy using a requirement that all five be greater than zero cm from the tumor edge. It also lists positive margin rate, specimen-edge distances, and mean resection specimen volume as secondary outcomes.

The registry record does not report primary or secondary outcome results, analysis methods, or missing-data handling. It records zero serious adverse events, zero other adverse events, and zero deaths in the BCL group. The study structure and intended endpoint are described, but the posted results do not quantify the primary accuracy finding.