This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record.
1. Trial at a Glance
SN FNAC evaluated sentinel lymph node biopsy following neoadjuvant chemotherapy in patients with biopsy-proven node-positive breast cancer. The registered primary endpoint was the false negative rate of sentinel node biopsy, assessed over a 4-7 month time frame.
| Feature | SN FNAC |
|---|---|
| Acronym | SN FNAC |
| ClinicalTrials.gov identifier | NCT00909441 |
| Official title | Sentinel Node Biopsy Following NeoAdjuvant Chemotherapy in Biopsy Proven Node Positive Breast Cancer |
| Condition | Breast Cancer; Invasive Breast Cancer |
| Phase | NA |
| Design model | Single group |
| Masking | None |
| Allocation | NA |
| Primary purpose | Treatment |
| Enrollment | 153 |
| Number of arms | 1 |
| Intervention | Sentinel Lymph Node Biopsy (procedure) |
| Lead sponsor | Centre hospitalier de l'Université de Montréal (CHUM) |
| Sponsor type | OTHER |
| Status | Completed |
2. Clinical Question
The clinical question concerns whether sentinel lymph node biopsy can be used to assess nodal status after neoadjuvant chemotherapy in patients whose breast cancer was biopsy-proven to involve lymph nodes before treatment.
Population
Patients with biopsy-proven node-positive breast cancer, including the registry's condition categories of breast cancer and invasive breast cancer.
Intervention
Sentinel Lymph Node Biopsy, recorded in the registry as a procedure.
Clinical setting
Sentinel node biopsy was evaluated following neoadjuvant chemotherapy.
Primary question
What is the false negative rate of sentinel node biopsy following neoadjuvant chemotherapy in biopsy-proven node-positive breast cancer?
3. Trial Design
The single-group structure is important statistically. There is no randomized comparator arm in the registry record, so the principal inferential question is not a treatment-versus-control comparison. Instead, the primary endpoint is a diagnostic or classification-performance quantity: the false negative rate of sentinel node biopsy in the specified clinical setting.
4. Endpoints
| Endpoint | Registry definition | Time frame |
|---|---|---|
| Primary endpoint | The false negative rate of sentinel node biopsy following neoadjuvant chemotherapy in biopsy proven node positive breast cancer. | 4-7 months |
The registry identifies one primary endpoint. Its wording defines the target estimand at a high level: the proportion or rate of relevant false-negative classifications produced by sentinel node biopsy in this population and clinical setting.
What a false negative means
For a diagnostic classification procedure, a false negative occurs when the test or procedure indicates a negative finding even though the reference condition is actually positive. The false negative rate therefore focuses specifically on missed positive cases rather than on all incorrect classifications.
This expression is a general statistical definition. The registry's endpoint wording identifies the false negative rate as the primary endpoint but does not post a numerical result or a more detailed calculation formula.
5. Statistical Methodology
The registry identifies the false negative rate as the primary endpoint but does not post a statistical-analysis result for that endpoint. Consequently, the central statistical task for understanding this study is to distinguish the endpoint definition from the inferential methods that would ordinarily be applied to it.
Estimating a false negative rate
A false negative rate is naturally expressed as a proportion among cases that are positive according to the reference classification. If there are FN false-negative cases among N+ reference-positive cases, the estimated false negative rate is:
The numerator counts missed positive cases, while the denominator is the number of cases that truly have the positive reference condition.
Confidence intervals for a proportion
Because a false negative rate is a proportion, statistical uncertainty would ordinarily be quantified with a confidence interval for a binomial proportion. Exact binomial intervals are one possible approach, particularly when the number of reference-positive cases is not large; alternative interval methods can also be used depending on the prespecified statistical analysis.
The confidence interval is important because the point estimate alone does not communicate how much statistical uncertainty is associated with the observed number of false negatives. The precision of the estimate depends on the number of relevant reference-positive cases, not simply on total enrollment.
No randomized treatment comparison
The registry records a single-group design with one arm. Therefore, standard randomized comparisons such as a treatment-versus-control hazard ratio, between-arm mean difference, or between-arm risk ratio are not the central statistical framework for this primary endpoint.
Reference standard and classification
Interpretation of a false negative rate requires a reference definition against which the sentinel node result is classified. The registry's endpoint wording identifies the false negative rate but does not provide the detailed reference-standard procedure or a posted statistical-analysis specification.
6. Statistical Methods Explained
What does the false negative rate measure?
The false negative rate answers a narrowly defined question: among cases that are actually positive according to the reference standard, what fraction are classified as negative by the procedure? A lower false negative rate means fewer positive cases are missed, but the numerical estimate must be interpreted together with its uncertainty and the reference standard used.
Why is the denominator important?
The denominator is not necessarily the full enrollment. For a false negative rate, the relevant denominator is the number of cases that are positive under the reference classification. This is a central distinction from measures such as overall accuracy, where all evaluated cases enter the denominator.
Why is a confidence interval useful?
Suppose the observed false negative rate is represented by a proportion p. The point estimate summarizes the observed data, while the confidence interval communicates sampling uncertainty around that estimate. Two studies can have the same point estimate but very different precision if they have different numbers of reference-positive cases.
Why would a binomial model be relevant?
Once the relevant cases are classified as false negative or not false negative, the numerator can be viewed as a count of events among a fixed number of reference-positive cases. That structure naturally leads to binomial-proportion methods for estimating the rate and its uncertainty.
Why is this not a hazard ratio?
The registered primary endpoint is a false negative rate assessed over a 4-7 month time frame. A hazard ratio is designed for comparing time-to-event rates between groups or covariate-defined groups. Nothing in the registry record identifies a time-to-event endpoint or a randomized comparison for the primary analysis.
What would make a false negative rate clinically interpretable?
The estimate becomes meaningful when the reference standard, eligible population, timing of assessment, and classification rules are clearly defined. The false negative rate should be interpreted within the clinical setting in which the procedure was evaluated rather than treated as a universal property of sentinel lymph node biopsy.
7. Planned Analysis
The registry identifies the false negative rate of sentinel node biopsy following neoadjuvant chemotherapy in biopsy-proven node-positive breast cancer as the primary endpoint, with a 4-7 month time frame. A typical analysis would count false-negative sentinel node biopsy classifications among the cases meeting the reference-positive definition and express that count as a proportion of all reference-positive cases.
| Analytic component | Statistical interpretation |
|---|---|
| Primary estimand | False negative rate of sentinel node biopsy in the specified clinical population. |
| Numerator | Cases classified as false negative under the endpoint's reference framework. |
| Denominator | Cases that are positive according to the reference classification. |
| Typical uncertainty measure | Confidence interval for a binomial proportion. |
| Study structure | Single group; no randomized comparator is recorded. |
| Registered time frame | 4-7 months. |
The ClinicalTrials.gov record does not post a formal statistical analysis for the primary endpoint. It therefore reports the endpoint definition and study structure without a posted numerical false-negative-rate estimate, confidence interval, or p-value.
The primary analysis would be descriptive and inferential for a classification-performance proportion. The central result would be the estimated false negative rate together with an uncertainty interval. Because the design is single-group, the statistical interpretation centers on estimating the performance characteristic rather than estimating a causal difference between randomized treatment groups.
8. Understanding the Analysis Population
Total enrollment was 153. However, the statistical denominator for the false negative rate would be determined by the cases that satisfy the reference-positive definition, not automatically by all 153 enrolled participants.
Total enrollment
The registry records 153 enrolled participants.
Endpoint denominator
The denominator for a false negative rate is the set of cases that are positive under the relevant reference classification.
Why this matters
Using total enrollment as the denominator would answer a different question from the registered false negative-rate endpoint.
Precision
The width of a confidence interval depends strongly on the number of reference-positive cases contributing to the endpoint.
This distinction is particularly important for diagnostic and surgical-performance endpoints. A study can enroll a substantial number of participants while still having a smaller denominator for the specific rate being estimated.
9. Statistical Interpretation of a False Negative Rate
A false negative rate quantifies the frequency with which a positive reference condition is missed by the procedure. If the estimated rate were expressed as a percentage, that percentage would describe the proportion of reference-positive cases classified as negative.
The false negative rate is not the probability that any individual negative sentinel-node result is wrong. That latter quantity is related to negative predictive value and depends on the prevalence of the positive condition in the population being evaluated.
A point estimate without an uncertainty interval can obscure the precision of the evidence. A narrow interval indicates greater statistical precision, whereas a wide interval indicates greater uncertainty about the underlying false negative rate.
If a hypothesis test were used for the false negative rate, its p-value would describe evidence against a specified null hypothesis. It would not itself describe the magnitude of the false negative rate or how clinically important that rate is.
10. What Can and Cannot Be Inferred From the Study Design
The single-group design is well suited to estimating a predefined performance characteristic, but it changes what can be concluded statistically compared with a randomized controlled trial.
| Question | What the design supports |
|---|---|
| How often were positive cases missed? | Estimation of a false negative rate, provided the relevant reference-positive cases are defined and assessed. |
| Was one treatment superior to another? | No randomized treatment comparison is recorded in the registry. |
| What is the uncertainty around the false negative rate? | A binomial-proportion confidence interval would ordinarily quantify sampling uncertainty. |
| Is the procedure's performance universal across all breast cancer populations? | The study's population and clinical setting define the context for interpretation; generalization requires consideration of whether other populations are comparable. |
11. Time Frame and Interpretation
The registered primary endpoint has a 4-7 month time frame. This is analytically important because the endpoint is tied to a specified period following the clinical sequence involving neoadjuvant chemotherapy and sentinel lymph node biopsy.
Study start
The registry records the study start in February 2009.
Primary endpoint time frame
The registered false negative rate is assessed over a 4-7 month time frame.
Primary completion
The registry records the primary completion date as February 2012.
A time frame attached to a diagnostic-performance endpoint should not automatically be interpreted as a survival follow-up period. Here, the registry specifically attaches the 4-7 month window to the false negative-rate endpoint.
12. Limitations
- No randomized comparator: the registry records a single-group design with one arm, so the primary endpoint is not a randomized treatment comparison.
- Reference-standard dependence: interpretation of a false negative requires a defined reference-positive classification. The registry's concise endpoint wording does not provide the detailed classification procedure.
- Denominator matters: the false negative rate is conditional on reference-positive cases rather than automatically on all 153 enrolled participants.
- Precision depends on relevant cases: total enrollment alone does not determine the precision of the false negative-rate estimate.
- Generalizability: performance estimates are tied to the population and clinical context in which the procedure was evaluated.
- No posted statistical result: the ClinicalTrials.gov record does not post a formal statistical analysis or numerical result for the registered primary endpoint.
- Endpoint scope: the registered endpoint concerns false negatives and therefore does not, by itself, characterize all dimensions of diagnostic performance such as false positives, specificity, or predictive values.
13. Why This Trial Matters Statistically
SN FNAC is a useful teaching example because it illustrates a type of clinical-trial endpoint that differs substantially from the time-to-event endpoints commonly encountered in oncology trials. The principal statistical object is a classification-performance rate rather than a hazard ratio comparing randomized groups.
| Concept | How it appears in SN FNAC |
|---|---|
| Single-group design | The registry records one study arm. |
| Diagnostic performance | The primary endpoint is the false negative rate. |
| Binomial proportion | A false negative rate can naturally be expressed as a proportion of reference-positive cases. |
| Confidence interval | Uncertainty around the estimated proportion would ordinarily be summarized with a binomial-proportion interval. |
| Reference standard | The meaning of false negative depends on how the positive reference condition is defined. |
| Denominator selection | The relevant denominator is the number of reference-positive cases, not necessarily total enrollment. |
| Generalizability | The estimated rate is interpreted within the population and clinical setting represented by the study. |
This structure also demonstrates why statistical interpretation should begin with the estimand. Once the estimand is clearly defined, the appropriate numerator, denominator, uncertainty calculation, and interpretation become much easier to distinguish.
14. Sources
- ClinicalTrials.gov: SN FNAC — NCT00909441.
- PubMed: PubMed record.
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Clinical trial endpoints become easier to interpret when the estimand, analysis population, uncertainty measure, and study design are considered together.
15. Record Summary
SN FNAC was a completed single-group study enrolling 153 participants with breast cancer, including invasive breast cancer, and evaluating sentinel lymph node biopsy following neoadjuvant chemotherapy in biopsy-proven node-positive disease. The registered primary endpoint was the false negative rate of sentinel node biopsy, with a 4-7 month time frame.
Statistically, the key feature of the study is the nature of its endpoint. A false negative rate is a classification-performance proportion whose interpretation depends on the reference-positive population and the definition of a missed positive case. A suitable analysis would therefore focus on the numerator and denominator defining the rate and on a confidence interval describing its statistical precision. Because the registry records a single-group design, the analysis is fundamentally different from a randomized treatment comparison: the central quantity is the estimated performance of the procedure in the specified clinical setting rather than a between-arm treatment effect.