FFNP-PET/MR Imaging of Progesterone Receptor Expression in Invasive Breast Cancer: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for FFNP-PET/MR Imaging of Progesterone Receptor Expression in Invasive Breast Cancer (NCT03212170), a na phase 2 study. The primary outcome is Correlation Coefficient Between FFNP Uptake and Allred Score.

2. Clinical Question

3. Trial Design

The registry describes NCT03212170 as a phase 2, single-group study of FFNP PET/MR imaging in invasive breast cancer. It lists enrollment of 21 and a completed status. The recorded start date is 2017-12-13, and the primary completion date is 2024-11-14. These dates describe the registry record; they do not provide the timing or duration of any individual participant's follow-up beyond the primary outcome timeframe of up to 1 day.

The study was not a randomized comparison. Allocation is listed as NA, masking as none, and the model as single group. The study arm is FFNP PET/MRI, with FFNP administered for imaging of biopsy-proven primary PR-positive malignancies. The primary comparison is between an imaging measurement and a tissue-based reference measurement, not between two assigned treatment groups.

The primary objective was to compare FFNP uptake with progesterone receptor IHC measured using the Allred score. Listed secondary outcomes include test-retest reproducibility, intra- and inter-observer assessment, correlation of tumor FFNP uptake with Oncotype DX score, and distinguishing PR-negative from PR-positive breast cancer using AUC and an optimal cut point. Numerical results for these outcomes are not reported in the registry record.

The registry record does not report a sample-size justification, a detailed protocol, or a statistical analysis plan beyond the primary endpoint description. In particular, the reason for the enrollment target and the analysis population for each outcome are not reported in the registry record. A single-group imaging study can describe agreement or association with a reference measure, but it does not establish a treatment effect against a concurrent control group.

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

Reasons for not completing this period:

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 Correlation Coefficient Between FFNP Uptake and Allred Score, measured over Up to 1 day.

The primary endpoint is the correlation coefficient between FFNP uptake and the Allred score. FFNP uptake is measured by PET/MR imaging, while the Allred score is a semi-quantitative IHC measure of progesterone receptor expression. The registry states that the Allred score ranges from 0-8 and that higher scores indicate more receptors. The endpoint therefore asks whether variation in the imaging measure tracks variation in the tissue-based receptor score across the assessed malignancies.

The registry specifies Pearson's correlation coefficient and gives the endpoint timeframe as up to 1 day. In general, a correlation coefficient describes the direction and strength of a linear association between two measurements. It does not, by itself, show that one measurement causes changes in the other, nor does it establish that the measures are interchangeable for individual patients. Interpretation also depends on the observed estimate and its uncertainty.

The registry describes hypotheses of H0: p0=0.50 and H1: p1 =0.75. However, the primary correlation estimate, confidence interval, and p-value are not reported in the registry record. The endpoint's numerical result and precision therefore cannot be evaluated from the posted results.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary analysis is described as a correlation assessment. In general, correlation quantifies how two measured variables vary together. Pearson's correlation coefficient specifically summarizes linear association. A positive value indicates that higher values of one measure tend to accompany higher values of the other; a negative value indicates that higher values of one tend to accompany lower values of the other. A value near zero indicates little linear association, but does not rule out every possible non-linear relationship. These are general interpretations, not findings from this study.

What does the primary correlation address?

The two measures named in the registry are FFNP uptake from PET/MR imaging and the Allred IHC score. The endpoint asks whether the imaging measurement tracks the tissue-based score across the study observations. The registry specifies Pearson's correlation coefficient and states H0: p0=0.50 and H1: p1 =0.75. It does not report the observed coefficient, confidence interval, or p-value. The hypotheses identify values used in the stated statistical question; they do not reveal the study's numerical result.

In general, a confidence interval gives a range of estimates compatible with the observed data under the method's assumptions, and communicates precision. A narrow interval indicates greater precision than a wide interval, while neither interval width nor the coefficient alone establishes clinical usefulness. No confidence interval is reported in the registry record for the primary endpoint. The record also does not report diagnostic thresholds or a numerical assessment of how well imaging values predict IHC scores.

Why is a correlation not the same as agreement?

In general, two methods can be highly correlated because they rank observations similarly while still giving different values or disagreeing for individual observations. Correlation therefore addresses co-variation, not whether two methods are interchangeable. Assessing agreement typically requires methods and results that directly examine differences between paired measurements. Although the registry lists reproducibility and observer assessment among secondary outcomes, their numerical results and detailed analysis methods are not reported in the registry record.

Correlation also does not establish causation. Here, the research question is about how FFNP uptake relates to PR expression measured by IHC. A correlation result would describe association in the measured sample; it would not demonstrate that the imaging measurement causes receptor expression or that using one measurement changes an outcome.

How should the secondary analyses be understood?

The record lists test-retest reproducibility and intra- and inter-observer assessment. In general, reproducibility concerns the consistency of measurements when repeated or assessed under differing measurement conditions. The meaning of any reproducibility estimate depends on the specific statistic, measurement protocol, and uncertainty. Those details and numerical results are not reported in the registry record.

The record also lists correlation between tumor FFNP uptake and Oncotype DX score, and evaluation of whether FFNP imaging distinguishes PR-negative from PR-positive breast cancer. AUC is a summary of discrimination across possible thresholds; an optimal cut point selects a threshold according to a chosen criterion. In general, both require careful interpretation in light of the sample and the method used to choose or evaluate a threshold. The registry record does not report the AUC, the cut point, their uncertainty, or the criteria used to select the cut point.

What can the sample-size illustrations establish?

Any sample-size illustrations associated with the posted results are planning exercises, not observed power. Their stated assumptions are a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect to detect defined as a stated fraction of the observed effect. Those are illustration assumptions and are not reported as the study's own design rationale. The trial itself is listed as single group, so an equal-allocation two-arm illustration should not be mistaken for its actual design. The registry record does not report a trial-specific sample-size justification. In general, a post hoc planning illustration cannot show that the completed study had a particular probability of detecting its effect.

The registry does not report enough analysis detail to determine whether adjustments, transformations, prespecified exclusions, or other modeling choices were used. It also does not report the analysis population or the handling of incomplete observations. Such details can affect how a correlation or secondary analysis should be interpreted, and cannot be reconstructed from the endpoint descriptions alone.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists six outcome measures and three analyses. The primary outcome is the correlation coefficient between FFNP uptake and Allred score. Listed secondary outcomes include reproducibility, observer assessments, correlation with Oncotype DX score, and two approaches to distinguishing PR-negative from PR-positive disease. Numerical estimates for the listed outcomes are not reported in the registry record.

When a study examines multiple outcomes or analyses, the chance of at least one apparently notable result can increase if each is assessed separately. In general, statistical plans may address this through prespecified primary and secondary questions or adjustment procedures. The registry record does not report whether any multiplicity adjustment was planned or used, how the primary outcome was prioritized relative to secondary outcomes, or how the three analyses relate to the listed outcomes. It is therefore not possible to assess how multiplicity was handled.

The analysis population for the primary or secondary endpoints is not reported in the registry record. Enrollment is 21, but that number alone does not establish how many participants had usable measurements for each analysis. Missing-data counts, reasons for missingness, and methods for handling missing values are also not reported in the registry record. No imputation method or complete-case approach is specified in the available record.

The adverse-event results give a risk denominator of 20, but the reason it differs from the enrollment count is not reported. That safety denominator should not be assumed to be the analysis denominator for imaging outcomes. Without endpoint-specific participant counts and missing-data information, the completeness and representativeness of each analysis cannot be assessed.

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 non-serious adverse event terms

The registry reports safety counts for the FFNP PET/MRI group. For serious adverse events, 20 participants were listed as at risk and 0 as affected; deaths were 0. For other adverse events, 20 participants were listed as at risk and 2 as affected. No serious adverse-event terms are listed. The registry record does not provide descriptions of the two other adverse events, their timing, severity, or relationship to the imaging procedure or intervention.

These figures are counts, not estimates of comparative risk: the study is single group and has no randomized control arm. The reason the safety denominator is 20 when enrollment is 21 is not reported in the registry record. The counts should therefore be read with the stated denominator and without assuming that all enrolled participants were assessed for every safety outcome. A zero count for serious events in this record does not establish that an event cannot occur, and the posted safety information does not support a comparison with another group.

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

This study is designed to examine whether FFNP uptake measured by PET/MR imaging is associated with progesterone receptor expression measured by IHC using the Allred score. It is a single-group phase 2 study, and the tissue-based IHC score serves as the reference measure for the primary question. The registry record identifies the intended comparison and specifies Pearson's correlation coefficient.

The primary estimate and its uncertainty are not reported in the registry record. As a result, the posted results do not establish whether the measured association was positive or negative, how strong it was, or how precisely it was estimated. The record's stated hypotheses cannot substitute for an observed result. Numerical findings for the listed secondary outcomes are also not reported, so reproducibility, observer assessment, Oncotype DX association, AUC, and the optimal cut point cannot be judged from the registry results.

Even if a correlation estimate were available, in general it would describe association rather than prove agreement or interchangeability between imaging and IHC. It would not show that imaging can replace a tissue measurement in all settings, nor establish an effect on patient outcomes. Those claims require evidence beyond the design and endpoint description recorded.

The record does not report a trial-specific sample-size justification, detailed missing-data handling, the analysis population, or multiplicity procedures. The enrollment count alone cannot indicate the number of participants analyzed for each endpoint. These omissions limit the assessment of precision, possible analysis selection, and how broadly the findings could apply.

The safety counts are limited to the reported single-group denominators and event categories. They are not a controlled comparison and do not provide event descriptions for the other adverse events. Overall, the registry record establishes what the study set out to measure and gives a small set of safety counts, but it does not report the numerical efficacy or diagnostic-performance results needed to judge the primary or secondary statistical questions.

13. Why This Trial Matters Statistically

This trial raises a useful measurement question: whether a PET/MR imaging signal based on FFNP tracks a tissue-based measure of progesterone receptor expression. Statistically, that is different from asking whether a treatment improves an outcome. The primary endpoint is a correlation between an imaging measure and the Allred IHC score, so the main issue is the strength and precision of association between two measurements.

That distinction matters because correlation, agreement, reproducibility, and diagnostic discrimination answer different questions. A correlation may describe whether measurements move together. Reproducibility concerns consistency across repetitions or observers. AUC and a cut point address classification of PR-negative and PR-positive cases. The registry lists outcomes covering these areas, but their numerical results are not reported in the registry record; the different questions therefore cannot be answered from the posted results.

The single-group design also shapes interpretation. IHC serves as the reference measure, but there is no randomized control group. The study can be framed around comparing imaging and tissue measurements, not estimating a treatment effect between assigned groups. The record's sample-size illustrations, which use equal allocation between two arms and other stated assumptions, are planning exercises and not the study's own documented design justification.

For biostatisticians and clinical researchers, the record illustrates why an endpoint definition is not the same as an endpoint result. Knowing the planned correlation method and hypotheses does not reveal the estimated association or its uncertainty. Likewise, listing secondary outcomes does not establish performance without reported estimates and analysis details. The primary result, analysis population, missing-data handling, and multiplicity approach are not reported in the registry record. Those omissions make transparent reporting especially important when interpreting a diagnostic imaging study.

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 principal limitation for interpreting the registry record is that it does not report the primary correlation estimate or its uncertainty. The endpoint description gives the measurement pair, method, and hypotheses, but without an observed result the direction, magnitude, and precision of the association cannot be assessed. Numerical results for the listed secondary outcomes are also not reported.

The study is described as single group, with allocation listed as NA and masking as none. There is no like-for-like randomized control comparison. IHC is the reference measure for the primary endpoint, not a control arm. Accordingly, the design described does not support a between-group treatment-effect interpretation.

The record identifies a specific population of biopsy-proven primary PR-positive malignancies for the imaging arm. It does not report the number of participants included in each endpoint analysis or the extent to which participants with different PR status contributed to the secondary classification outcomes. Generalizability beyond the enrolled sample cannot be evaluated from the available record.

Enrollment is 21, whereas the safety denominators are 20. The reason for this difference is not reported in the registry record. Analysis populations, missing-data counts, reasons for missingness, and methods for handling missing observations are also not reported. The record does not report a trial-specific sample-size justification or detailed multiplicity procedures. These limitations leave uncertainty about precision, completeness of the analyses, and how multiple outcomes were interpreted.

The reported safety counts do not include descriptions of the other adverse events, and no serious adverse-event terms are listed. The available record therefore offers limited detail for interpreting safety beyond the counts and denominators stated.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: FFNP-PET/MR Imaging of Progesterone Receptor Expression in Invasive Breast Cancer — NCT03212170.
• Registry record last updated 2026-01-02; status last verified 2025-12.
• Results first posted 2025-12-10.
• 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

NCT03212170 is a completed phase 2, single-group study of [18F]Fluorofuranylnorprogesterone (FFNP) PET/MR imaging in invasive breast cancer. The registry records enrollment of 21, a start date of 2017-12-13, and a primary completion date of 2024-11-14. The primary endpoint compares FFNP uptake with PR expression measured by IHC using the Allred score, with Pearson's correlation coefficient specified.

The primary numerical result and numerical results for the listed secondary outcomes are not reported in the registry record. The safety results list 20 participants at risk for each category, 0 serious adverse events, 2 affected by other adverse events, and 0 deaths. The reason for the difference between enrollment and the safety denominator is not reported. The record does not report the analysis populations, missing-data methods, multiplicity procedures, or a trial-specific sample-size justification.