Gallium-68 PSMA-11 Positron Emission Tomography (PET) Imaging in Patients With Biochemical Recurrence: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Gallium-68 PSMA-11 Positron Emission Tomography (PET) Imaging in Patients With Biochemical Recurrence (NCT03353740), a na phase 3 study. The primary outcome is True Positive Rate for Detection of Tumor Location in Lymph Nodes Confirmed by Histopathology/Biopsy, Clinical and Conventional Imaging Follow-up.

2. Clinical Question

The central statistical question concerns detection of disease location, rather than comparison of outcomes between treatments. The primary endpoint is described as a true positive rate, also called sensitivity or detection rate. It relates a positive imaging finding to lymph-node disease confirmation using histopathology or biopsy, clinical follow-up, and conventional imaging follow-up.

The registry record also lists location-specific outcomes involving lymph nodes, visceral lesions, bone metastasis lesions, and the prostate bed. These include positive predictive value and true positive rate measures with different confirmation descriptions. The primary endpoint timeframe is 1 Day. The record states that data on clinical and conventional imaging follow-up were not collected, an important qualification when interpreting the primary endpoint's stated confirmation approach.

The record does not report an observed primary endpoint estimate, its confidence interval, or analysis results. It therefore does not establish from the posted information how often the scan detected confirmed lymph-node disease or how precisely that rate was estimated.

3. Trial Design

The registry classifies this as a Phase 3, completed, single-group study. Enrollment is 346. The listed intervention is Ga-68 labeled PSMA-11 PET, and the arm description says patients undergo PET/CT or PET/MRI approximately 55-70 minutes after receiving the imaging agent. Allocation is listed as NA and masking as none. No separate comparison arm is described, so the design does not provide a like-for-like control group.

The stated aim is to evaluate the imaging agent's ability to detect prostate cancer in patients with biochemical recurrence after prostatectomy and radiation therapy. The registry dates the study start as 2017-09-20 and primary completion as 2020-09-01, and lists the status as completed. These administrative details describe the study record; they do not establish that the primary endpoint analysis or all planned reporting was completed.

The primary outcome is a lymph-node true positive rate assessed over a timeframe of 1 Day. Its description defines detection using Ga68-PSMA-11 and confirmation by histopathology or biopsy, clinical follow-up, and conventional imaging follow-up. However, the endpoint population note states that data on clinical and conventional imaging follow-up were not collected. The record does not explain how that limitation affected the endpoint definition or analysis.

The registry lists 22 outcome measures and no analyses. Its listed secondary outcomes cover location-specific positive predictive values and true positive rates, with confirmation approaches that include histology or pathology and, in some descriptions, clinical and conventional imaging follow-up. The record does not report a detailed statistical analysis plan, analysis populations, a sample-size justification, interim analyses, or a reason for the stated enrollment. Those details are not reported in the registry record.

Because this is a single-group diagnostic imaging study, its estimates, if reported, would characterize detection performance against the specified confirmation criteria in the study population. Without a control group, the design cannot directly estimate a comparative effect against another imaging strategy or treatment.

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:

Analysis population for the primary outcome, as defined in the registry: Data on clinical and conventional imaging follow-up not collected

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 True Positive Rate for Detection of Tumor Location in Lymph Nodes Confirmed by Histopathology/Biopsy, Clinical and Conventional Imaging Follow-up, measured over 1 Day.

The primary endpoint is the true positive rate for detection of tumor location in lymph nodes. The registry defines this as the proportion of participants who have prostate cancer detected in lymph nodes using Ga68-PSMA-11, where the disease location is also confirmed by histopathology or biopsy, clinical follow-up, and conventional imaging follow-up. The timeframe is 1 Day.

In general, a true positive rate, or sensitivity, describes how often a test identifies the condition among those who have that condition according to a reference standard. It is used to characterize detection, rather than to show whether a treatment changes health outcomes. The meaning of the estimate depends on how disease is confirmed, who is included in the denominator, and whether the reference information is available and applied consistently.

There is a specific interpretive qualification in this record: the endpoint population note says data on clinical and conventional imaging follow-up were not collected, although the endpoint definition names those sources. The record does not clarify whether histopathology or biopsy alone was used in practice, whether the endpoint was modified, or how unavailable follow-up information was handled. No observed true positive rate or confidence interval is reported in the registry record, so the endpoint's estimated value and precision cannot be assessed from the posted results.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary endpoint is a proportion-based diagnostic measure: the true positive rate for lymph-node tumor detection. The registry says two-sided 95% confidence intervals will be constructed using the Wilson score method. No estimate or interval is reported, so the method can be explained, but its application cannot be checked against an observed result.

What does a true positive rate describe?

In general, sensitivity is the share of people who have the condition according to a reference standard who are identified as positive by the test being evaluated. Here, the registry's endpoint description focuses on participants with prostate cancer detected in lymph nodes using Ga68-PSMA-11, with disease location confirmed by the stated sources. The exact numerator and denominator used in an analysis would be necessary to understand the estimate fully. Those counts are not reported in the registry record.

A sensitivity estimate is not the same as the chance that a positive scan is correct. That latter question is commonly described by positive predictive value, which is separately listed among the secondary outcomes. In general, predictive values reflect the frequency of disease in the tested population as well as test performance. Therefore, a true positive rate and a positive predictive value answer related but distinct questions and should not be treated as interchangeable.

Why use a confidence interval?

In general, a confidence interval communicates uncertainty around an estimated quantity. The interval reflects that an estimate from a study population may vary across samples, even when the underlying process is unchanged. The registry specifies a two-sided 95% confidence interval for the primary true positive rate. That stated level describes the intended interval procedure; it does not give the interval's width or show how precise the result was. Because the registry record does not report the estimate or interval, the primary endpoint's precision cannot be assessed.

The Wilson score method is a commonly used method for confidence intervals around a proportion. In general, it accounts for the bounded nature of a proportion and tends to behave more sensibly than a simple symmetric interval in situations where a proportion is near a boundary or the data are limited. That is a general explanation of the method, not a claim about the values or performance of this study's unreported analysis. The registry does not state whether other interval methods were used for secondary outcomes.

What does the reference standard contribute?

For diagnostic studies, the reference standard is the process used to classify whether the disease is present and where it is located. Histopathology or biopsy can provide tissue-based confirmation; clinical and conventional imaging follow-up are also named in the primary endpoint definition. Different reference sources can have different strengths and may classify findings differently. In general, an endpoint's interpretation depends on which sources were actually applied, how disagreements were resolved, and whether all participants received the same verification process.

The registry record has an unresolved reporting tension: the endpoint definition includes clinical and conventional imaging follow-up, but the population note says data on clinical and conventional imaging follow-up were not collected. It does not specify whether the analysis relied on biopsy or histopathology alone, used another definition, or excluded cases lacking follow-up information. No resolution should be assumed. This affects the ability to reconstruct the endpoint and to assess potential verification bias, which can occur when confirmation differs according to participant or test result.

How should the design shape statistical interpretation?

In general, a single-group diagnostic study estimates performance in the population studied under the procedures used. It does not estimate a between-group contrast when no control group is included. The registry lists a single-group model, allocation as NA, and masking as none. These features should be considered when interpreting any detection estimate, because the information does not support a direct comparison with a separate imaging strategy within this trial.

Masking can matter in general when knowledge of a test result could influence interpretation of a reference standard, or when knowledge of confirmation could influence test reading. The record states that masking was none, but does not describe who knew which results, how readings were conducted, or whether independent review occurred. Those procedural details are not reported in the registry record, so the potential for interpretation or ascertainment effects cannot be evaluated from the registry entries.

What can planning illustrations say?

Any sample-size figures should be read as planning illustrations computed from an observed effect, not as the trial's own design justification or as observed power. The stated assumptions for those illustrations are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is described as a stated fraction of the observed effect. For time-to-event calculations, the stated quantity is total events using the Schoenfeld method; other calculations are expressed as participants per arm. These are generic planning assumptions and do not change the fact that the registry describes this study as single group.

In general, a planning calculation asks what sample size might be needed under specified assumptions. It is not a measure of the probability that a completed study found a true effect, and it is not observed power. The registry record does not report its own sample-size justification or the assumptions used to select enrollment. The registry entries also do not report an observed primary effect from which to evaluate any illustrative calculations. Such illustrations cannot replace the missing outcome estimate or a documented design rationale.

Finally, the registry lists 22 outcome measures and no analyses. This does not tell readers which analyses were actually conducted outside the registry, nor whether planned outcomes were modified. A statistical method can be evaluated only alongside the analysis population, endpoint construction, observed data, and handling of unavailable information; those details are not reported for the primary result.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 22 outcome measures, including the primary lymph-node true positive rate and secondary outcomes involving positive predictive value and true positive rate for several anatomical locations. Multiple outcomes can create multiplicity concerns in general: when many hypotheses are tested, the chance of at least one apparently notable result can increase unless the analysis plan addresses that issue. The record does not report a multiplicity adjustment, a hierarchy among secondary outcomes, or a plan for interpreting multiple tests. It also lists no analyses, so the handling of multiplicity cannot be assessed from reported results.

The primary endpoint description specifies a two-sided 95% confidence interval using the Wilson score method. It does not state how uncertainty was handled across secondary outcomes, or whether confidence intervals were intended as descriptive or inferential for those measures. No claim about adjustment or family-wise error control can be made from the registry information.

Missing data require particular attention because the primary endpoint definition names clinical and conventional imaging follow-up, while the population note says those data were not collected. The registry does not report the number of participants with evaluable endpoint information, the reasons information was unavailable, or whether incomplete cases were excluded, classified in another way, or addressed through a sensitivity analysis. The record also does not describe analysis populations, such as whether all enrolled participants or only those with a particular form of confirmation were included.

In general, missingness can affect both the estimated proportion and the population to which it applies, especially when the availability of confirmation is related to test findings or disease status. Without a clear denominator and missing-data approach, readers cannot assess that risk. These details 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 reports the serious adverse event figures for the Ga-68 Labeled PSMA-11 PET group: 346 participants at risk, zero affected, and zero deaths. These are the counts recorded for the serious-event summary. They do not establish that no adverse events of any kind occurred, because the figures concern serious adverse events and the record does not provide a broader adverse-event summary in the registry record.

The record does not state the observation period for these figures, give definitions or event-level details, or describe how adverse events were collected. A zero count should therefore be read narrowly as zero reported serious adverse events in this registry summary, not as proof that the imaging procedure has no risks. The figures also do not compare safety with another method: the study is listed as single group and has no control group.

In general, safety counts are most informative when the at-risk population, follow-up duration, event definitions, and completeness of reporting are clear. Here, the at-risk count is stated, but the remaining details are not reported in the registry record.

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

The registry record establishes that a completed Phase 3, single-group study evaluated Ga-68 labeled PSMA-11 PET imaging in patients with prostate cancer and biochemical recurrence. It specifies a primary lymph-node true positive rate and a plan to construct a two-sided 95% confidence interval using the Wilson score method. It also records the intervention procedure and lists location-specific secondary outcomes.

It does not report the primary endpoint estimate, its confidence interval, or analyses. Accordingly, the posted information does not show the observed rate of lymph-node detection, the uncertainty around that rate, or the results for the secondary outcomes. The study's completed status is not itself evidence of a particular result. Without the numerical estimates and analysis details, neither the magnitude nor precision of detection performance can be judged.

The design also limits what any result could establish. A single-group study without a separate control group can describe performance in the studied participants but cannot directly quantify a comparative advantage over another imaging approach. The record's masking entry is none, but it does not describe the reading and confirmation procedures in enough detail to evaluate how knowledge of findings may have affected classification.

The reference-standard information is especially important. The primary endpoint definition names histopathology or biopsy, clinical follow-up, and conventional imaging follow-up; the endpoint population note says clinical and conventional imaging follow-up data were not collected. The record does not explain how that discrepancy was handled. It is therefore not possible to determine from this information which reference sources underlie the planned endpoint or how missing confirmation affected its denominator.

The serious adverse event summary records zero affected and zero deaths among 346 at risk in the listed intervention group. That is a narrow registry safety summary, not a comprehensive statement about all adverse events or a comparison with another intervention. The observation period and broader adverse-event details are not reported in the registry record.

Overall, the record describes the study question and intended statistical measure but does not provide the outcome data needed to answer the question quantitatively. Any broader statement about diagnostic performance, comparative value, or safety would require information not reported in the registry record.

13. Why This Trial Matters Statistically

This trial is statistically relevant because it illustrates how a diagnostic imaging question is translated into an endpoint. The primary measure is a true positive rate for lymph-node disease, paired with a stated confirmation approach and a planned confidence interval method. That makes the denominator, reference standard, and availability of follow-up data central to understanding what the endpoint would mean.

The record also highlights a practical reporting issue: the primary endpoint definition names clinical and conventional imaging follow-up, while the population note says those data were not collected. When endpoint language and data-availability notes do not align, readers need a clear account of the implemented definition and analysis population. Without that account, even a familiar statistical measure can be difficult to interpret or reproduce.

The single-group structure further clarifies the boundary between estimation and comparison. A study can estimate a detection measure within its participants, but a separate comparator is needed for a direct within-trial comparison of strategies. Allocation is listed as NA, masking as none, and the model as single group; these details matter when deciding what types of conclusions the design could support.

Finally, the record lists 22 outcome measures but no analyses or numerical primary results. This underscores why registry status, endpoint specification, and outcome reporting are distinct elements of evidence. A completed record can document what was intended without supplying the estimates necessary to assess statistical precision or observed diagnostic performance.

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 most immediate limitation for interpreting the registry record is that no primary outcome estimate, confidence interval, or analysis result is reported. The study's status is completed, but the record does not provide the numerical findings needed to assess the primary detection measure or its precision.

The endpoint's confirmation description is also difficult to reconcile with its population note. The definition includes histopathology or biopsy, clinical follow-up, and conventional imaging follow-up, while the note says clinical and conventional imaging follow-up data were not collected. The record does not state which confirmation sources were actually used, whether the definition changed, or how participants without confirmation information were handled. It also does not report the endpoint denominator or analysis population.

The single-group design provides no separate control arm for direct comparison. The record lists masking as none, but does not describe test reading, reference assessment, or safeguards against knowledge of one result influencing interpretation of another. These procedural details are not reported in the registry record.

Although the registry lists 22 outcome measures, it does not report a statistical analysis plan, multiplicity approach, interim analyses, or methods for missing data. It lists no analyses. The registry also does not report the rationale for enrollment or a trial-specific sample-size justification. The sample-size assumptions described for planning illustrations are not a substitute for those design details or for observed outcome results.

Safety interpretation is limited to the serious adverse event counts. The record does not give the observation period, detailed event information, or a broader adverse-event summary. These limitations restrict the conclusions that can be drawn from the registry record; they do not establish what the unreported analyses or other study reports may contain.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Gallium-68 PSMA-11 Positron Emission Tomography (PET) Imaging in Patients With Biochemical Recurrence — NCT03353740.
• Registry record last updated 2021-10-21; status last verified 2021-09.
• Results first posted 2021-10-21.
• 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

This is a completed Phase 3, single-group study of Ga-68 labeled PSMA-11 PET imaging in patients with prostate cancer and biochemical recurrence. The record lists enrollment of 346, allocation as NA, masking as none, and PET/CT or PET/MRI approximately 55-70 minutes after the imaging agent. Its primary outcome is the lymph-node true positive rate, with a stated two-sided 95% confidence interval using the Wilson score method.

The registry lists 22 outcome measures and no analyses. It does not report the primary endpoint estimate or confidence interval. The primary endpoint definition names clinical and conventional imaging follow-up, while its population note says those data were not collected; the record does not explain how this was handled. The serious adverse event summary reports zero affected and zero deaths among 346 at risk in the intervention group. A separate comparator, broader safety results, and a detailed analysis plan are not reported in the registry record.