68Ga PSMA in Preprostatectomy Patients: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for 68Ga PSMA in Preprostatectomy Patients (NCT03388346), a na phase 2, phase 3 study. The primary outcome is Sensitivity of Ga 68-labeled PSMA-11 Positron Emission Tomography/Computed Tomography (PET/CT) for the Detection of Regional Pelvic Nodal Metastases on a Per Patient Basis.

2. Clinical Question

The clinical rationale in the registry is to investigate whether PSMA imaging can make prostate cancer easier to identify on PET imaging, with the aim of relating disease location to treatment planning. The study used gallium-68 radiolabeled PSMA-HBED-CC. Its brief summary describes an injection followed by a PET scan, with imaging findings entered into the medical record and shared with treating oncologists.

The primary outcome focuses on regional pelvic lymph nodes in a per-participant assessment. It is one part of a broader diagnostic evaluation: the registry also lists outcomes for extra-pelvic nodal and visceral metastases. These secondary outcomes include sensitivity, specificity, positive predictive value, and negative predictive value. The record does not report their numerical results either.

This is a diagnostic-imaging question in a preprostatectomy population, not a comparison of two treatments. The study can therefore describe how imaging classifications relate to pathology in the assessed participants, but its design does not establish a randomized treatment effect. The record does not report a numerical estimate of the primary diagnostic performance.

3. Trial Design

The registry describes a completed, single-group study with phase designations of Phase 2 and Phase 3. It records enrollment of 22 participants. The study started on 2018-02-16, and primary completion was recorded as 2021-07-22. The intervention was Ga-68 PSMA-HBED-CC PET imaging.

Participants received an injection of the radiolabeled agent and underwent PET imaging. The registered primary outcome was sensitivity of Ga 68-labeled PSMA-11 PET/CT for detecting regional pelvic nodal metastases on a per-participant basis. Its timeframe was within 2 weeks of prostatectomy. The record states that 21 of the 22 subjects had a prostatectomy.

The design is single-group, and allocation is listed as not applicable. The record indicates no masking. There is no randomized comparator arm, so the study does not make a like-for-like comparison between groups receiving different interventions. For the diagnostic assessment, the reference information was pathology: imaging and pathology findings were used to classify true-positive, true-negative, false-positive, and false-negative results.

The registry lists 16 outcome measures in total. The secondary outcomes address detection of extra-pelvic nodal and visceral metastases and include sensitivity, specificity, positive predictive value, and negative predictive value. However, the registry records zero analyses, and numerical results for the primary and secondary diagnostic outcomes are not reported in the registry record.

The registry does not report a sample-size justification, a planned statistical analysis protocol, or details of how participants were selected for analysis. Its stated sample-size calculations are described as planning illustrations based on an observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. Those calculations are not the trial's own design justification; planning illustrations are not observed power. Details of any interim analyses 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: 21 of the 22 subjects had a prostatectomy

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 Sensitivity of Ga 68-labeled PSMA-11 Positron Emission Tomography/Computed Tomography (PET/CT) for the Detection of Regional Pelvic Nodal Metastases on a Per Patient Basis, measured over within 2 weeks of prostatectomy.

The primary endpoint is the sensitivity of Ga 68-labeled PSMA-11 PET/CT for detecting regional pelvic nodal metastases, assessed per participant. The registry defines the assessment by comparing imaging with pathology within 2 weeks of prostatectomy. An imaging-positive finding with positive pathology is classified as a true positive; imaging-negative findings with negative pathology are classified as true negatives. An imaging-positive finding with negative pathology is a false positive, while pathology-positive disease missed on imaging is a false negative.

In general, sensitivity describes how often a test identifies the condition among people who have it according to the reference standard. It is used to characterize detection, rather than to describe agreement across all participants or to establish the cause of disease. In this study, pathology provides the reference classification for the registered primary question.

Interpreting sensitivity requires knowing which participants had usable imaging and pathology information and how many had regional nodal metastases according to pathology. Those denominators and the numerical endpoint result are not reported in the registry record. The record states that 21 of the 22 subjects had a prostatectomy, but that information alone does not establish the analysis denominator or the number of pathology-positive participants.

The outcome is diagnostic performance in the studied group, not evidence from a treatment comparison. It also does not directly report whether imaging changed management or improved clinical outcomes; such results are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registered primary outcome is a binary diagnostic classification summarized as a proportion of participants. For each participant, imaging is compared with pathology and categorized as true positive, true negative, false positive, or false negative. The primary measure, sensitivity, is based on participants classified as having regional pelvic nodal metastases by pathology. The registry states the classification rules, but the counts required to reproduce the estimate are not reported in the registry record.

What does sensitivity describe?

In general, sensitivity is the proportion of reference-standard positive cases that the test identifies as positive. It is a conditional measure: it focuses on participants with disease according to the reference standard. It does not describe the proportion of all imaging-positive findings that are correct; that is the role of positive predictive value. Nor does it describe the proportion of reference-standard negative cases correctly identified; that is the role of specificity.

For this study, pathology is the reference standard named in the endpoint description. A positive imaging result paired with positive pathology is a true positive; positive pathology with negative imaging is a false negative. These classifications determine the sensitivity estimate. Because the registry does not report their counts, a numerical estimate cannot be interpreted or independently checked from the record.

Why do the other diagnostic measures differ?

Specificity concerns participants without disease according to the reference standard and asks how often imaging is negative in that group. Positive predictive value asks how often a positive imaging result corresponds to positive pathology. Negative predictive value asks how often a negative imaging result corresponds to negative pathology. These are different conditional views of the same diagnostic classifications.

As a general statistical point, predictive values depend on the proportion of participants with disease in the assessed population, as well as on test performance. They may therefore vary across populations even when the test is used in the same way. The record lists secondary measures for extra-pelvic nodal and visceral metastases, but their numerical results and underlying counts are not reported in the registry record.

What does the single-group design imply?

The registry records a single-group model, no masking, and allocation as not applicable. There is no randomized control group. Pathology serves as a reference for evaluating imaging classifications; it is not a comparator arm. Accordingly, the study's registered question concerns diagnostic performance in the evaluated participants rather than a difference between treatment groups.

In general, blinding can affect diagnostic classification if knowledge of one assessment influences interpretation of another. The record indicates no masking, but does not report operational details such as who interpreted the images or pathology and what information each assessor had. Those details are not reported in the registry record, so the potential for interpretation effects cannot be assessed from the available account.

How should uncertainty be considered?

A point estimate alone would not fully characterize the uncertainty in a diagnostic measure. In general, a confidence interval communicates the range of values reasonably compatible with the observed data under a specified method and assumptions. Its width depends on the information in the data, including the number of participants with the relevant reference-standard status. No primary sensitivity estimate or confidence interval is reported in the registry record, so neither the magnitude nor precision of the primary result can be evaluated.

The overall enrollment is 22, and 21 of the 22 subjects had a prostatectomy. These figures do not reveal how many participants had pathology-confirmed nodal metastases, how many had both assessments available, or how many were included in each diagnostic calculation. The analysis population and missing-data handling are not reported in the registry record. In general, diagnostic estimates can be affected if participants with incomplete assessments differ from those with complete assessments.

What do the planning calculations represent?

The registry describes sample-size calculations as planning illustrations based on an observed effect. The stated assumptions include a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The record explicitly characterizes these as illustrations rather than the trial's own design. They are not observed power, and the stated two-arm planning assumptions do not change the single-group nature of the registered study. A sample-size justification for the actual study is not reported in the registry record.

More generally, planning calculations depend on assumptions about the effect to detect, the analysis method, and the design. They do not show that a trial was adequately powered after the fact, and they cannot replace observed estimates with measures of uncertainty. The registry's planning description does not report the protocol rationale or a statistical analysis plan for the diagnostic endpoints.

The record lists zero analyses. It does not report whether any interim analyses were planned or performed, which statistical methods were used for the diagnostic estimates, or how multiple outcomes were handled. These are distinct from the definitions of the registered outcomes and cannot be inferred from those definitions alone.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("68Ga PSMA PET Scan")
n      <- c(21)
events <- c(0)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  68Ga PSMA PET Scan  21  0  0.0  0.0  16.1  -0.0  15.5  0.1  15.4

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 16 outcome measures, including the primary sensitivity outcome and secondary diagnostic measures for extra-pelvic nodal and visceral metastases. The secondary measures include sensitivity, specificity, positive predictive value, and negative predictive value. Considering multiple outcomes can raise a multiplicity issue: in general, examining several hypotheses may increase the chance of at least one apparently notable result if each is assessed without accounting for the others. The registry does not report a multiplicity strategy or identify a hierarchy for interpreting the secondary outcomes.

The record lists zero analyses and does not report numerical results for the primary or secondary diagnostic outcomes. It also does not report a statistical analysis plan, the intended handling of missing observations, or whether any planned analyses were changed. Those details are not reported in the registry record; no particular approach should be assumed.

The study enrolled 22 participants, and 21 of the 22 subjects had a prostatectomy. The record does not state whether those participants all had evaluable imaging and pathology, whether additional participants were excluded from a particular outcome, or which analysis population was used. The number with complete paired assessments and the handling of incomplete or indeterminate findings are not reported in the registry record.

These omissions matter because diagnostic measures use different denominators. Sensitivity and specificity depend on reference-standard status, while predictive values depend on imaging classification. Without outcome-specific counts and analysis populations, the reported enrollment cannot establish the denominator for any measure. The absence of a stated missing-data or multiplicity method should be read as missing reporting, not evidence that no such considerations were made.

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 1% reporting threshold.

Most frequent non-serious adverse event terms

The registry lists safety information for the 68Ga PSMA PET Scan group, with 22 participants at risk in each recorded adverse-event category. It reports zero participants with a serious adverse event, one participant with another adverse event, and zero deaths. These are participant counts in the registry's safety record; they are not diagnostic accuracy results.

The record lists no serious adverse-event terms. It does not report a comparison group, so the counts cannot be used to make a comparative safety estimate. The record also does not provide further detail about the non-serious adverse event, including its nature, timing, severity, or relationship to the intervention. Those details are not reported in the registry record.

In general, observing no serious adverse events in a study does not establish that an event is impossible or that a risk is absent. The small recorded group and the lack of a comparator limit what these counts can establish. The safety figures should be understood as what was recorded among this study group, not as a general estimate for other populations or settings.

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

The registry establishes that a completed, single-group study enrolled 22 participants to evaluate Ga-68 PSMA-HBED-CC PET imaging before prostatectomy. Its primary registered diagnostic question concerned sensitivity for regional pelvic nodal metastases, with imaging and pathology compared within 2 weeks of prostatectomy. The registry specifies the classification rules and notes that 21 of the 22 subjects had a prostatectomy.

What the record does not establish is the numerical diagnostic performance. The primary sensitivity result, the counts underlying it, and confidence intervals are not reported in the registry record. Numerical results for the secondary measures are also not reported. Consequently, the registry information does not allow the magnitude or precision of the imaging estimates to be assessed.

The design also does not establish comparative effectiveness. There was no randomized control group, and the study is recorded as a single-group study with no masking. Pathology is used as a reference for diagnostic classification, rather than as a competing intervention. The record therefore cannot show a causal difference between treatments or establish the effect of imaging on subsequent care.

The study rationale describes identifying disease location as potentially relevant to treatment planning, and the brief summary says imaging findings would be entered into the medical record and shared with treating oncologists. However, whether imaging changed treatment decisions or patient outcomes is not reported in the registry record. The registered diagnostic outcomes alone cannot answer those downstream questions.

The adverse-event counts describe the safety record for the study group: zero participants with a serious adverse event, one with another adverse event, and zero deaths. They do not prove absence of risk, and without a comparator they do not quantify a relative safety difference. Overall, the registry supports a description of the study's objective, design, endpoint definitions, enrollment, and recorded safety counts, but not a conclusion about the primary diagnostic result.

14. Why This Trial Matters Statistically

This trial is statistically notable because its primary question is diagnostic rather than comparative. The outcome is sensitivity against pathology, assessed per participant. That requires a clear reference standard and a defined relationship between imaging and pathology findings. The registry describes those classification rules, making the intended estimand understandable even though its numerical value is not reported.

The record also illustrates why total enrollment is not enough to interpret a diagnostic estimate. Although 22 participants were enrolled and 21 had a prostatectomy, the key denominators would depend on how many had evaluable imaging and pathology and how many were positive according to pathology. Those counts are not reported in the registry record. Different diagnostic measures also use different denominators, so an overall participant count cannot substitute for outcome-specific results.

The single-group structure is important to interpretation. A pathology assessment can serve as a reference for evaluating the imaging classification, but it does not create a randomized control comparison. This distinction helps prevent diagnostic accuracy from being confused with comparative treatment effects or evidence that imaging changes clinical outcomes.

Finally, the registry separates detailed outcome definitions from numerical outcome reporting. It lists primary and secondary diagnostic questions, but records zero analyses and does not report the estimates needed to evaluate performance or precision. That gap is consequential: an endpoint definition shows what investigators intended to assess, while the estimate and its uncertainty are needed to understand what the study observed.

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 most direct limitation of the registry record is that it does not report the numerical primary sensitivity result or the counts underlying it. It also does not report confidence intervals or numerical results for the listed secondary diagnostic measures. The diagnostic performance and its precision therefore cannot be assessed from the registry record.

The enrolled group was small in absolute terms, with 22 participants recorded, and 21 of the 22 subjects had a prostatectomy. The record does not state how many participants had pathology-confirmed regional nodal metastases or had complete paired assessments. The analysis population and handling of missing or indeterminate assessments are not reported in the registry record.

The design was single-group, unmasked, and had no randomized comparator. These features mean that it is not a comparative trial of alternative imaging or treatment strategies. The record also does not report details about image interpretation, pathology review, assessor knowledge, or whether assessments were independent. The effect of those procedures on classification cannot be evaluated from the registry record.

The registry lists 16 outcome measures but does not report a multiplicity plan or a hierarchy for interpreting the secondary outcomes. A statistical analysis plan, interim-analysis details, and a sample-size justification for the actual study are not reported in the registry record. Its planning calculations are described as illustrations and should not be taken as observed power.

Finally, the safety record gives counts but little detail about the one non-serious adverse event. The nature and timing of that event and its relationship to the intervention are not reported in the registry record. These reporting gaps limit interpretation without establishing that the underlying information was never collected.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: 68Ga PSMA in Preprostatectomy Patients — NCT03388346.
• Registry record last updated 2024-02-15; status last verified 2024-01.
• Results first posted 2024-02-15.
• 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

The registry identifies a completed Phase 2 and Phase 3 single-group study of Ga-68 PSMA-HBED-CC PET imaging in patients with intermediate- to high-risk prostate cancer before prostatectomy. Enrollment was 22. The recorded start date was 2018-02-16, and primary completion was 2021-07-22. The primary outcome was sensitivity for regional pelvic nodal metastases per participant, assessed against pathology within 2 weeks of prostatectomy. The record states that 21 of the 22 subjects had a prostatectomy.

The record lists 16 outcome measures and zero analyses. Numerical results for the primary and secondary diagnostic outcomes are not reported in the registry record. Safety entries list zero participants with a serious adverse event, one with another adverse event, and zero deaths. The study had no randomized comparator and was not masked.