An Investigational Scan (18F-Fluciclovine PET-CT) for the Measurement of Therapeutic Response in Patients With Metastatic Prostate Cancer: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for An Investigational Scan (18F-Fluciclovine PET-CT) for the Measurement of Therapeutic Response in Patients With Metastatic Prostate Cancer (NCT04134208), a na phase 4 study. The primary outcome is Metabolic Response by Fluciclovine F18 (18F-fluciclovine) Positron Emission Tomography (PET) With Standardized Uptake Values (SUV)".

2. Clinical Question

3. Trial Design

This was a phase IV, single-group study sponsored by M.D. Anderson Cancer Center. The registry lists allocation as not applicable and masking as none. Enrollment was 2, and the study status is terminated. The registry lists a start date of 2019-09-19 and a primary completion date of 2022-06-28.

The diagnostic procedure used fluciclovine F18 with PET-CT. The arm description specifies intravenous fluciclovine F18 followed by a PET-CT scan lasting 30 minutes within 4 weeks before starting SST. A second dose and scan were described within 22-28 weeks after starting SST. The record does not expand SST or provide further treatment details in this description.

The within-participant timing is important to the design: the primary outcome concerns change from pretreatment to post-treatment imaging, rather than a difference between randomized groups. The record describes assessment with SUV and also mentions conventional imaging size changes and PSA response as points of correlation. It lists secondary outcomes involving SUVMax, SUVMean, metabolic tumor volume, sites of progressive disease, and a target-to-blood-pool ratio.

The registry does not report a separate control group, masking, or a randomized allocation. It also does not report the protocol rationale for the enrollment, a planned sample-size justification, or a detailed statistical analysis plan. The study’s terminated status is recorded, but the reason for termination is 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.

Before assignment: No enrolled participants were excluded from the study

Overall Study

Analysis population for the primary outcome, as defined in the registry: No ROC analysis was performed due to the small number of patients. An analysis of the quantitative data was recently performed.

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 Metabolic Response by Fluciclovine F18 (18F-fluciclovine) Positron Emission Tomography (PET) With Standardized Uptake Values (SUV)", measured over Up to 2 years.

The primary endpoint is described as metabolic response measured by fluciclovine F18 PET with standardized uptake values. Its unit is percentage of change, and the stated timeframe is up to 2 years. The specified calculation for SUVmax compares the corrected pretreatment value with the corrected post-treatment value, expresses the change relative to the pretreatment value, and multiplies by 100. Similar calculations are described for mean SUV, metabolic tumor volume, and total volume activity.

In general, an SUV is a quantitative measure used to characterize tracer uptake in an imaging region. A change between scans can therefore provide a numerical way to describe how uptake differs over time. That is the rationale for using a metabolic imaging endpoint alongside conventional imaging measures and PSA response: these measures describe different aspects of the observed disease course and may not necessarily move in the same way.

The registry says the study would assess metabolic response qualitatively and semi-quantitatively and relate findings to size changes and PSA response. However, the actual SUV values, percentage changes, correlation estimates, and response classifications are not reported in the registry record. The endpoint’s definition alone does not establish what direction or magnitude of change occurred.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a pre-treatment and post-treatment imaging approach in one group. Each participant was scheduled to receive fluciclovine F18 and undergo PET-CT before starting SST, followed by a second scan after starting SST. The primary endpoint focuses on percentage change in corrected SUVmax. Related SUV, metabolic tumor volume, and total volume activity calculations are also described. No numerical outcome estimates or uncertainty measures are reported in the registry record.

What does a within-participant change measure?

In general, a within-participant comparison uses observations from the same person at different times. It can describe how a measured value changed between the two assessments. This differs from a parallel-group comparison, which contrasts outcomes between participants assigned to different groups. Here, the registry lists a single group and no randomized comparator, so the stated primary measure is change across scans rather than a treatment contrast between groups.

The endpoint description gives a percentage-change calculation based on pretreatment and post-treatment corrected SUVmax. This form expresses the observed difference in relation to the pretreatment value. Related calculations are described for mean SUV, metabolic tumor volume, and total volume activity. Because the actual values are not reported, it is not possible to check the calculations, determine the direction of change, or assess whether results differed among participants.

What do SUV and metabolic volume measures describe?

General explanation: SUV is a quantitative imaging measure of tracer uptake. SUVmax uses the highest measured uptake in the region of interest, while SUVMean refers to an average over a defined region. Metabolic tumor volume describes the volume classified using metabolic imaging criteria. These measures summarize different features of an image and should not be treated as interchangeable. The registry record names these outcome types but does not report the operational details used to define regions, thresholds, or image review procedures.

The registry also lists a target-to-blood-pool ratio and sites of progressive disease as secondary outcomes. These can address questions different from the primary percentage change: a ratio compares uptake with a reference region, while a record of progression sites describes where progression was observed. No numerical results for these secondary measures are reported in the registry record.

Why is the absence of a control group important?

General explanation: when measurements are repeated over time in one group, observed changes can reflect multiple influences, including the course of disease, treatment, measurement variability, and other time-related factors. Without a concurrent comparison group, these influences cannot be separated by a randomized contrast. The registry describes an intended correlation with conventional imaging size changes and PSA response, but a correlation would describe how measurements vary together; it would not on its own establish that one measure causes another or that one predicts outcomes beyond the observed participants.

The registry states that no ROC analysis was performed because of the small number of patients. In general, ROC analysis examines how well a test distinguishes between outcome categories across possible thresholds. Without such an analysis, the record does not provide an ROC-based assessment of discrimination or a threshold-based diagnostic performance summary.

What can be learned from uncertainty estimates?

General explanation: a confidence interval is a range of values compatible with the data under a statistical model and its assumptions. It conveys uncertainty around an estimate; a narrower interval generally indicates greater precision, while a wider interval indicates less precision. The registry record does not report a confidence interval for the primary endpoint, nor does it provide the participant-level values needed to assess variability directly. Consequently, the precision of any observed change cannot be evaluated from the posted information.

General explanation: over-dispersion occurs when observed variability is greater than a statistical model assumes. If present, it can make standard errors and confidence intervals based on an under-dispersed model too small. The registry does not report a model for the primary outcome or information that would allow over-dispersion to be assessed, so this is a general methodological consideration rather than a reported feature of this study.

What does the registry say about analysis?

The primary outcome description states that quantitative data were recently analyzed for the 2 participants. At the same time, the registry record has no analysis entries. The record does not report the statistical methods used for the quantitative analysis, any prespecified decision rules, handling of repeated measurements, missing-data procedures, or estimates with uncertainty. These details cannot be inferred from the endpoint formula alone.

The registry includes assumptions for planning illustrations based on an observed effect, but no illustration values are described in the registry record for this interpretation. In general, a sample-size illustration is a planning calculation under stated assumptions, not an observed result and not observed power. It should not be used to imply that the study was designed to detect a particular effect unless the trial’s own design documentation establishes that. A trial-specific sample-size justification is not reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The record names a primary outcome and several secondary outcomes, including SUVMax, SUVMean, metabolic tumor volume, sites of progressive disease, and a target-to-blood-pool ratio. The primary description also refers to similar percentage-change calculations for mean SUV, metabolic tumor volume, and total volume activity. Evaluating several measures can raise a multiplicity issue: in general, the more statistical questions examined, the greater the chance that an apparently notable result may arise by chance if each is interpreted separately.

The registry record does not report whether any adjustment for multiple comparisons was planned or used, how the primary outcome was distinguished analytically from the additional measures, or whether analyses were exploratory. It reports that no ROC analysis was performed because of the small number of patients. The quantitative data are described as analyzed, but the method and results are not reported in the registry record.

Missing-data methods and analysis populations are also not reported in the registry record. The record does not state whether both participants had complete paired imaging or how unavailable scans, unusable measurements, or other missing observations would have been handled. It does not define an intention-to-treat, per-protocol, or other analysis population. These omissions matter because a within-participant change calculation requires usable measurements at both time points; the record does not provide enough detail to establish how that requirement was addressed.

In general, multiplicity procedures, missing-data rules, and analysis-population definitions help readers understand which questions were tested, which observations contributed to each result, and how much flexibility was available in the analysis. Those details are not reported in the registry record, so the quantitative analysis cannot be fully reproduced or evaluated for these features.

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.

The registry lists one diagnostic arm, with 2 participants at risk for serious adverse events and 0 affected. It also lists 2 at risk for other adverse events and 0 affected, and reports 0 deaths. No serious adverse event terms are listed.

These are event counts in the registry record. They should not be read as precise estimates of risk: with only 2 participants at risk, the observations provide limited information about how often an event might occur in a wider population. A count of 0 records no events in the listed participants; it does not establish that the risk is absent. The record also does not provide further details about the timing, duration, severity grading, or attribution of adverse events.

The safety figures relate to the diagnostic arm as recorded and should not be interpreted as a comparative safety assessment between treatments. There is no separate control group in this single-group study. The registry’s event counts are descriptive, and the available information does not support broader safety conclusions.

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

The record documents a phase IV investigation of fluciclovine F18 PET-CT as a way to measure metabolic response in metastatic prostate cancer. Its primary endpoint uses percentage change in SUVmax between pretreatment and post-treatment imaging, with related measures also described. The study was single-group, had enrollment of 2, and is listed as terminated.

The registry narrative states that quantitative data were analyzed for the 2 participants, but numerical results are not reported in the registry record. As a result, readers cannot determine the observed direction or size of SUV change, compare participant-level responses, assess precision, or evaluate correlations with conventional imaging and PSA response. The registry also says that ROC analysis was not performed due to the small number of patients.

These registry entries do not establish whether the imaging approach identified, failed to identify, or accurately classified response. Nor do they establish whether observed changes were caused by therapy. A single-group pre/post design can describe changes over time but lacks a concurrent randomized comparison that could help distinguish treatment-related change from other explanations.

General interpretation: a measurement can be biologically or clinically interesting without having demonstrated diagnostic performance or predictive value. Such claims require appropriate analyses and reported results. The registry record does not include the numerical findings or analysis details needed to assess those properties. Its safety counts likewise describe only the recorded events in the participants at risk and do not establish the absence of risk.

The appropriate conclusion is therefore limited: the study record specifies an imaging-based response question and a paired-scan design, but does not report enough outcome information to determine what the measurements showed or how precisely they were estimated.

13. Why This Trial Matters Statistically

This study raises a statistical question that is important in imaging research: whether a quantitative imaging measure changes in a way that corresponds to other indicators of disease response. The registry’s primary endpoint focuses on percentage change in SUVmax, while its description also identifies mean SUV, metabolic tumor volume, total volume activity, conventional imaging size changes, and PSA response. Comparing such measures can help characterize what each captures, but interpretation depends on clearly reported methods and results.

The design also illustrates the distinction between a measurement study and a randomized treatment comparison. The record describes repeated imaging in a single group, not random assignment to alternative treatments or imaging strategies. The resulting data can describe observed within-participant changes, but do not by themselves establish causal effects or comparative treatment benefit.

Small studies may be useful for examining whether measurements can be collected and for generating questions, but they generally offer limited information about variability and precision. Here, the registry reports enrollment of 2 and says no ROC analysis was performed due to the small number of patients. Numerical findings are not reported, so even the magnitude and consistency of the measured changes cannot be assessed.

Statistically, the record highlights why transparent reporting matters: participant-level data or estimates, uncertainty intervals, analysis methods, missing-data handling, and prespecified distinctions among outcomes help readers judge both reproducibility and scope. Those details are not reported in the registry record. The study is therefore relevant as an example of a clearly stated imaging endpoint whose quantitative interpretation remains limited by the outcome information available in the record.

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.

Several limitations are specific to the information recorded for this study. The study was single-group, with allocation listed as not applicable and masking listed as none. There was no randomized comparator, so the design does not support a like-for-like comparison between groups. The within-participant scans can describe changes over time, but cannot isolate a treatment effect from other influences on those changes.

Enrollment was 2, limiting the amount of information available about participant-to-participant variability and the precision of any summary. The registry explicitly states that no ROC analysis was performed due to the small number of patients. It does not report numerical results for the primary endpoint or secondary outcomes, so the size and direction of observed changes and any relationship with conventional imaging or PSA response cannot be assessed.

The registry describes an analysis of quantitative data but does not report the statistical methods, estimates, uncertainty intervals, analysis population, or missing-data handling. It does not explain whether multiplicity was addressed across the listed outcomes. Details of image measurement procedures, including how regions or thresholds were defined, are not reported in the registry record.

The study is marked terminated, but the reason is not reported in the registry record. The record also does not report a trial-specific sample-size justification or a detailed statistical analysis plan. These limits concern what can be concluded from the registry information; they do not establish why the study ended or what its investigators found beyond the narrative statement that a quantitative analysis was performed.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: An Investigational Scan (18F-Fluciclovine PET-CT) for the Measurement of Therapeutic Response in Patients With Metastatic Prostate Cancer — NCT04134208.
• Registry record last updated 2025-01-16; status last verified 2025-01.
• Results first posted 2025-01-16.
• 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 phase IV, single-group study of fluciclovine F18 PET-CT for assessing metabolic response in metastatic prostate cancer. Enrollment was 2, allocation was not applicable, masking was none, and the status is terminated. Scans were described before and after starting SST.

The primary endpoint was percentage change in SUVmax, with related quantitative measures and correlation with conventional imaging size changes and PSA response also described. The record states that quantitative data were analyzed for the 2 participants and that no ROC analysis was performed due to the small number of patients. Numerical outcome results and detailed analysis methods are not reported in the registry record. The record lists 0 serious adverse events, 0 other adverse events, and 0 deaths among 2 participants at risk in the diagnostic arm.