Efficacy of Gamma Camera Used Intraoperatively for ID of Sentinel Lymph Nodes w/ Lymphoscintigraphy: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Efficacy of Gamma Camera Used Intraoperatively for ID of Sentinel Lymph Nodes w/ Lymphoscintigraphy (NCT01314963), a non-randomized na study. The primary outcome is Relative Node Detection Sensitivity.

2. Clinical Question

3. Trial Design

The registry describes a completed, nonrandomized, single-group device evaluation. Its purpose, as stated in the brief summary, was to assess a prototype intraoperative handheld gamma camera (pIHGC) for imaging or detecting sentinel lymph nodes during surgical excision, in comparison with standard intraoperative gamma probes (GP). The arm descriptions identify the prototype camera and standard-of-care probes. The record also lists lymphoscintigraphy with intraoperative gamma probes and radioactive Tc99M among the interventions.

The registry gives an enrollment of 50. It explicitly states that the unit of study was SLNs rather than individual participants. Therefore, enrollment should not be treated as the number of nodes evaluated, and the registry does not establish how many nodes contributed to either device’s outcome. The number of evaluated nodes, and the relationship between node observations and participants, are not reported in the registry record.

The trial is marked nonrandomized, and the model is listed as single group. These labels do not describe a randomized allocation of participants to independent treatment arms. Although the endpoint concerns detection with each of two devices, whether both devices were applied to the same nodes, whether assessment order was controlled, or how a node was matched across readings is not reported in the registry record. The registry’s caution that the arms are not a like-for-like control comparison is important when interpreting any device contrast.

The study is marked completed. The registry lists a start date of 2008-06 and a primary completion date of 2012-07-26. It identifies Stanford University as sponsor. The phase is recorded as NA, consistent with the device-focused study information in the record. Details about site procedures, operator training, blinding, or a prespecified statistical analysis plan are not reported in the registry record.

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

Analysis population for the primary outcome, as defined in the registry: Sentinel lymph nodes (SLNs) were evaluated for detection by the 2 methods.

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

Population: The required data for baseline results is participant-level data. This study is a comparison of lesion-level data sets, ie, a comparison of intra-participant data. It is not possible to segregate participant baseline data to one group or the other of the intra-participant datasets.

6. Primary Endpoint

The registry lists the primary outcome as Relative Node Detection Sensitivity, measured over 1 day.

The primary endpoint is relative node detection sensitivity, expressed as a percentage of SLNs detected. The registry defines the measure for each instrument as the number of true positives divided by the total evaluated. In practical statistical terms, this describes the observed share of evaluated nodes that a device identified as sentinel lymph nodes under the study’s assessment process. The endpoint timeframe is 1 day.

This measure is used because the study question concerns node identification by imaging or detection devices. Reporting a proportion gives a direct description of detection among the nodes evaluated; reporting a 95% confidence interval is intended to convey uncertainty around that estimate. The interval does not itself establish whether the devices perform similarly or differently. That interpretation requires the actual estimates, interval limits, and a clear account of how observations were paired or otherwise compared.

The registry describes the endpoint’s definition but does not report the true-positive counts, totals evaluated, percentages, or confidence interval limits. These results are not reported in the registry record. Consequently, the endpoint’s numerical values and the precision of either device estimate cannot be reviewed from the registry information.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is a proportion: true-positive SLNs divided by the total SLNs evaluated, reported as a percentage for each device. This type of endpoint is useful when the question is whether a device identifies nodes that are classified as sentinel lymph nodes under the study’s reference or assessment process. The registry defines the numerator and denominator in general terms but does not report their observed values. It also does not describe the operational criteria for a true positive or the reference procedure used to determine that classification.

What does a confidence interval communicate?

A confidence interval expresses uncertainty around an estimated quantity under a specified statistical procedure and its assumptions. For a detection proportion, the interval is intended to show how precisely the proportion has been estimated from the evaluated nodes. A narrower interval generally indicates greater precision, while a wider interval indicates more uncertainty. The interval does not remove possible bias in how nodes were selected, assessed, or classified. It also does not establish that two devices are equivalent merely because their separate intervals overlap.

The registry specifies 95% confidence intervals for the endpoint, but the interval limits and the method used to calculate them are not reported in the registry record. It is therefore not possible to evaluate the reported precision, check the calculation, or determine whether an interval method suited the data structure. The total number of nodes evaluated is also not reported, limiting assessment of the information available for estimating the proportions.

Why does the unit of analysis matter?

The registry says that SLNs, rather than individual participants, were the unit of study. This distinction matters because a participant may contribute more than one node. If multiple observations from a participant are treated as independent when they are related, ordinary methods can understate uncertainty. General approaches to clustered data account for dependence among observations from the same participant. The registry does not report the number of nodes per participant, the number of participants contributing nodes, or whether the analysis accounted for clustering. No conclusion about the adequacy of that handling can be made from the registry record.

The device comparison also depends on whether measurements are paired. If both devices assessed the same nodes, a paired comparison would use the within-node relationship between device readings. If the devices assessed different nodes, the comparison would have a different structure and would depend on the comparability of those sets of nodes. The registry describes both methods as evaluating SLNs but does not report whether the assessments were paired or how any pairing was analyzed. The nonrandomized allocation and single-group model labels do not resolve this question.

What does over-dispersion mean in general?

For count or proportion data, a simple model can assume a particular amount of variability. Over-dispersion means the observed data vary more than that model expects. When present and ignored, uncertainty estimates may be too small, making confidence intervals appear more precise than warranted. Dependence among nodes from the same participant is one possible reason that a simple independent-observation model may not fit, although the registry does not report whether over-dispersion was assessed or present in this study. This is a general statistical consideration, not a finding about the trial.

The registry’s planning assumptions describe an illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation; the effect to detect is described as a stated fraction of the observed effect. For non-time-to-event outcomes, the planning quantities are defined as participants per arm. Such sample-size calculations are planning illustrations, not observed power and not trial results. The observed effect and numerical planning outputs are not reported in the registry record, so those quantities cannot be interpreted or checked from the registry information. The record also does not report that these assumptions were used to design the completed study.

Finally, an analysis of a device contrast requires a prespecified target and suitable uncertainty estimate. Separate sensitivity estimates can describe each device, but a direct comparative claim requires an analysis that reflects the design, node-level outcome, and any within-participant or within-node dependence. The registry lists no analyses and does not report a statistical plan, so the chosen model, comparison method, and handling of uncertainty are not reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary outcome measure and no analyses. It does not report a multiplicity strategy, such as how inference would be controlled if multiple outcomes, subgroups, or comparisons were examined. The absence of listed analyses should not be taken to establish that no other analyses were conducted; it means they are not reported in the registry record.

Missing-data handling is also not reported in the registry record. The outcome definition requires a total number of SLNs evaluated, but the record does not state whether any node assessments were missing, unevaluable, or excluded, nor how such observations would be treated. The true-positive counts and denominators are not reported, so the completeness of outcome data cannot be assessed.

The analysis population is not described beyond the statement that SLNs were evaluated for detection by the two methods and that SLNs, rather than participants, were the unit of study. The record does not specify criteria for including participants or nodes in the primary analysis, or how multiple nodes contributed by a participant were handled. It also does not report whether the device assessments were paired. These omissions prevent assessment of the analysis population and the assumptions underlying a device comparison. Details about a prespecified analysis plan, deviations from that plan, and sensitivity analyses are not reported in the registry record.

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 5% reporting threshold.

The registry’s adverse-event entries list two device groups: the intraoperative handheld gamma camera and the gamma probes. For each listed group, 50 are recorded as at risk for serious adverse events and 0 as affected; the entries also record 50 at risk for other adverse events and 0 affected. Each group lists 0 deaths. No serious adverse event terms are listed.

These figures describe what the registry reports for the listed groups. They should not be read as proof that either device is free of risk. The record does not provide further detail on how adverse events were defined, collected, attributed, or monitored, or how the listed at-risk groups relate to the node-level unit of study. It also does not explain whether the same participants appear in both device groups. The group counts should therefore not be added together or treated as a count of distinct participants.

The registry entries are separate from the primary detection endpoint. They do not establish the performance of either device, and the absence of recorded events does not resolve the missing numerical detection results. Further safety interpretation is limited because event definitions, ascertainment procedures, and additional context are not reported in the registry record.

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

The registry record supports a description of the study question and endpoint, but not a numerical conclusion about device detection. It identifies a prototype handheld gamma camera and standard intraoperative gamma probes as the devices of interest, and defines relative node detection sensitivity as true positives divided by the total evaluated. However, the percentages, counts, and confidence intervals are not reported in the registry record. Consequently, readers cannot determine the observed sensitivity for either device or the precision of those estimates.

Even with numerical estimates, a comparison would need to be interpreted in light of the nonrandomized, single-group design and the node-level unit of study. The record does not explain whether device assessments were paired on the same nodes, how nodes were distributed across assessments, or how observations from a participant were handled. Those design and analysis details are important for judging whether a device contrast is fair and how much uncertainty it carries.

The registry therefore does not establish that the prototype camera is equivalent to, better than, or worse than the gamma probes. It also does not show that the devices produce identical results, because an absent result is not evidence of no difference. The record’s adverse-event entries report zero affected in the listed categories, but these entries alone do not establish overall safety or address detection performance.

The most defensible reading is that the registry documents a completed evaluation with a stated detection endpoint, while leaving the central outcome estimates and important analysis details unreported. Any stronger conclusion would require information not reported in the registry record, including the node-level results, confidence interval limits, and an account of the comparison and analysis methods.

13. Why This Trial Matters Statistically

This study raises a central biostatistical issue in diagnostic and device evaluation: the unit being measured may differ from the unit of enrollment. The registry gives an enrollment of 50 but states that SLNs, rather than participants, were the unit of study. That distinction affects how denominators are understood and whether observations can be treated as independent. It also matters for translating a node-level detection proportion into a clear account of the evidence available.

The record also illustrates why a device comparison cannot be interpreted from endpoint definitions alone. A sensitivity proportion for each device is descriptive, while a comparative claim depends on how devices were assessed, whether observations were paired, and how uncertainty was calculated. The nonrandomized and single-group design labels make it especially important to clarify those features rather than assume a randomized, independent-arm comparison.

Finally, the registry demonstrates the difference between a registered outcome and a reported outcome result. A detailed definition and an intended confidence interval do not provide the estimates themselves. Without the observed proportions, denominators, intervals, and analysis description, readers cannot assess precision or comparative performance. The statistical importance of this record lies in those interpretive requirements, not in an unreported numerical finding.

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 registry record omits the primary outcome estimates, true-positive counts, totals evaluated, and confidence interval limits. These omissions prevent direct assessment of detection sensitivity and statistical precision. The number of evaluated SLNs is not reported, and enrollment cannot be substituted for a node-level denominator because the registry identifies SLNs as the unit of study.

Several features of the comparison are also unclear. The record labels the allocation nonrandomized and the model single group, but does not say whether both devices assessed the same nodes, how nodes were assigned or matched, or whether assessment order was controlled. It does not describe a reference procedure or the criteria for classifying a detection as a true positive. Handling of multiple nodes per participant, missing or unevaluable assessments, and analysis populations is not reported in the registry record.

The condition descriptions differ: the registry lists Multiple Myeloma and Breast Cancer, whereas the brief summary describes melanoma and breast cancer. The reason for this discrepancy is not reported in the registry record. The record also does not provide operator, site, or procedural details that could help readers understand how broadly the findings might apply. Since the outcome results themselves are absent, no numerical conclusion about generalizability or comparative detection can be drawn.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Efficacy of Gamma Camera Used Intraoperatively for ID of Sentinel Lymph Nodes w/ Lymphoscintigraphy — NCT01314963.
• Registry record last updated 2018-04-30; status last verified 2018-03.
• Results first posted 2018-04-30.
• 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.

18. Record Summary

The registry record describes a completed, nonrandomized, single-group evaluation of a prototype intraoperative handheld gamma camera and standard intraoperative gamma probes for sentinel lymph node detection. Enrollment is listed as 50, while SLNs—not individual participants—are identified as the unit of study. The primary endpoint is relative node detection sensitivity, defined as true positives divided by the total evaluated and intended to be reported as a percentage with a 95% confidence interval over a 1 day timeframe.

The record lists Stanford University as sponsor and gives a start date of 2008-06 and a primary completion date of 2012-07-26. It reports 0 serious adverse events, 0 other adverse events, and 0 deaths in each listed device group. The primary detection estimates, confidence interval limits, detailed comparison methods, and handling of missing data are not reported in the registry record. The condition descriptions also differ between the registry listing and brief summary.