Positron Emission Tomography and Magnetic Resonance Imaging for Prostate Cancer: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Positron Emission Tomography and Magnetic Resonance Imaging for Prostate Cancer (NCT00924313), a na phase 1, phase 2 study. The primary outcome is Compare the Biodistribution of 11C-acetate Positron Emission Tomography (PET)/Computed Tomography (CT) Imaging in Tumor and Non Tumorous Regions of the Prostate.

2. Clinical Question

3. Trial Design

This completed study is registered as a Phase 1 and Phase 2, single-group study with no masking. The allocation entry is NA, and the record identifies no randomized treatment-group comparison. Its stated enrollment is 40. The study start date is 2008-09-10, and the primary completion date is 2011-04-19. The sponsor is the National Cancer Institute.

The population described in the eligibility summary consists of adults undergoing surgery for localized prostate cancer at the NIH Clinical Center. Participants were to undergo 11C-acetate PET imaging and endorectal-coil MRI. The PET procedure is described as an intravenous tracer injection followed by imaging of the lower pelvis and abdomen. MRI is described as using a rectal coil and gadolinium contrast. The primary endpoint, however, is specifically a comparison of 11C-acetate SUV in prostate regions with and without malignancy.

After prostatectomy, pathology was used to classify each prostate sextant as malignant or non-malignant. The planned analysis first averaged SUV measurements within each participant for tumor and non-tumor regions, then compared those two participant-level averages using a paired t-test. The registry record notes that one patient was not imaged because tracer synthesis failed. It does not specify how that circumstance was handled in the endpoint analysis.

The record lists nine secondary outcomes, including adverse events, measures of PET uptake, MRI-based lesion analyses, and associations with other clinical measures. It also lists four analyses. The detail available does not establish the full statistical plan, the order in which secondary questions were addressed, or the analysis populations used. The study is completed, but numerical primary outcome results 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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: One patient was not imaged because of failed tracer synthesis.

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 Compare the Biodistribution of 11C-acetate Positron Emission Tomography (PET)/Computed Tomography (CT) Imaging in Tumor and Non Tumorous Regions of the Prostate, measured over 2 years.

The primary endpoint concerns the distribution of 11C-acetate uptake across prostate regions. Uptake is represented by the standardized uptake value (SUV), a measure used in PET imaging. For each participant, the planned analysis averaged SUV measurements in sextants classified by pathology as malignant and in sextants classified as non-malignant. It then compared those two averages within the participant.

The registry record gives the unit as ng/mL and describes the endpoint as a mean with standard deviation. It gives a timeframe of 2 years. The analysis description specifies a paired t-test, consistent with treating each participant’s tumor-region and non-tumor-region averages as a related pair rather than as observations from unrelated groups.

General statistical context: a paired comparison focuses on within-participant differences. This can account for the fact that measurements from the same participant may share characteristics, rather than treating them as independent observations. The test addresses whether the average paired difference is distinguishable from zero under its assumptions; it does not by itself establish diagnostic accuracy, clinical utility, or performance in another population.

The endpoint is intended to evaluate whether PET uptake differs between pathology-defined regions. The registry record does not report the observed mean values, the paired difference, a standard deviation for that difference, a confidence interval, or a p-value. Without those results, neither the magnitude nor the precision of the primary comparison can be described.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary analysis is described as a comparison of two measurements from the same participant: average SUV in tumor regions and average SUV in non-tumor regions. Pathology after prostatectomy determines which sextants belong in each category. The study description says the averages across regions are compared using a paired t-test. The registry record does not include the numerical results of that test.

Why use a paired comparison?

General statistical context: paired methods are used when observations are naturally linked, such as two measurements from the same person. Rather than comparing two unrelated collections of values, the analysis calculates a contrast for each person and summarizes those contrasts. This approach accounts for the shared features of the paired measurements. For example, participant-specific characteristics that affect both regional averages may influence their levels while having less influence on their within-person difference.

A paired t-test evaluates whether the average of the within-participant differences is compatible with a null average difference, under the method’s assumptions. The relevant data are the participant-level pairs, not every sextant treated as though it were independent. That distinction matters because multiple prostate regions from one participant can be related. The registry’s analysis description says regional SUV measurements were first averaged by tumor status within each person, then compared. It does not report how many paired observations entered the final analysis or how the failed tracer synthesis affected inclusion.

What does the t-test assume?

General statistical context: the paired t-test relies on the distribution of the participant-level differences being suitable for the t-based inference, particularly with respect to extreme values and the shape of that distribution. The assumption concerns differences, not necessarily the separate distributions of tumor and non-tumor measurements. Diagnostic checks, transformations, robust alternatives, and handling of influential observations are not reported in the registry record. It is therefore not possible to assess whether the analysis examined these issues.

The record describes the endpoint as a mean with standard deviation. A mean summarizes the average on the measurement scale; a standard deviation describes variation among observations around that mean. The standard deviation of the paired differences is especially relevant to the paired test, but the registry record does not say whether it was reported or give its value. It also does not report a confidence interval for the paired contrast.

How do confidence intervals help?

General statistical context: a confidence interval expresses uncertainty around an estimated quantity in a way that reflects the data and the chosen statistical method. Its width is influenced by the variability of the observations and the amount of information available. A narrow interval indicates greater precision under the model than a wide interval, but neither width nor statistical significance alone determines whether a difference is diagnostically meaningful. The primary outcome information in the registry record includes no estimate or interval, so its precision cannot be assessed.

What is the distinction between a primary and a secondary analysis?

The primary outcome is the stated main comparison of tumor and non-tumor regional SUV. The secondary outcomes address additional questions, including adverse events, biodistribution, physiological effects, extraprostatic uptake, SUV by Gleason score, lesion-based imaging analyses, and correlation with PSA. General statistical context: each additional analysis can answer a different scientific question, and the results may depend on distinct definitions, populations, or methods. A result for one secondary measure would not automatically answer the primary question.

The registry record lists nine secondary outcomes and four analyses but does not report a complete statistical analysis plan, the method for each analysis, or the results needed to evaluate them. It also does not report whether the secondary analyses were prespecified in detail, whether they were exploratory, or whether multiplicity adjustments were planned. Those details matter when interpreting a collection of statistical tests, because testing many hypotheses can increase the chance of at least one apparently unusual result even when no corresponding effect exists. This is general statistical context, not a claim about what occurred in this study.

What can sample-size calculations say?

General statistical context: a sample-size calculation uses assumptions about a target effect, variability, significance level, allocation, and analysis method to estimate the amount of information a future study may need. Planning illustrations based on an observed effect are conditional on that effect being a suitable basis for planning. They do not represent observed power, do not establish the probability that the study’s conclusion is correct, and do not replace an uncertainty interval for the actual estimate. The record’s stated planning approach describes a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the target effect expressed as a fraction of the observed effect. That illustration does not match the reported single-group paired primary comparison in a straightforward way, and the registry record does not explain its application or give the corresponding numerical planning results.

There is an additional limitation in interpreting any recalculated summary: recalculations from posted summary statistics are unadjusted and may not reproduce an analysis using participant-level data or a prespecified model. No recalculated primary result is reported in the registry record. If a discrepancy between a sponsor analysis and a simple recalculation were identified, the sponsor’s own analysis would take precedence; the record available for this analysis does not present a primary numerical result to compare.

10. Multiplicity, Missing Data and Analysis Populations

The registry record identifies one primary outcome and nine secondary outcomes. The primary outcome compares participant-level average SUV in pathology-defined tumor and non-tumor regions. Secondary topics include adverse events, uptake distribution, lesion detection and imaging comparisons, physiological effects, SUV by Gleason score, and association with PSA. The record also lists four analyses, but does not describe their full scope or provide a complete analysis plan.

General statistical context: when several hypotheses are tested, the chance of at least one result appearing statistically unusual can increase. Researchers may address this through prespecified hierarchies, multiplicity adjustments, or by treating some analyses as exploratory. The registry record does not report whether any such approach was planned or used. This absence means the multiplicity handling cannot be assessed; it does not establish that no adjustment was made.

For missing data, the record states that one patient was not imaged because tracer synthesis failed. It does not report whether this participant was included in any analysis, whether there were other missing measurements, or what method was used to address missingness. It also does not report the numbers analyzed for the primary or secondary outcomes. The enrollment entry alone does not establish the analysis population.

The record does not describe whether all eligible participants, all imaged participants, or another defined population formed the analysis set. It does not state how incomplete imaging, absent regional measurements, or pathology classifications were handled. Consequently, the amount and potential influence of missing endpoint information cannot be determined from the registry record. These limitations restrict evaluation of both the primary comparison and the secondary findings.

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 safety entries report zero serious adverse events among 40 participants at risk, zero deaths among 40 at risk, and 14 other adverse events among 40 at risk. No serious adverse event terms are listed. These are registry counts, not estimates of comparative risk: the study is described as a single-group study and has no randomized control group in the record.

The serious-event count and the count of other adverse events are separate categories in the safety record. The 14 other adverse events should not be read as 14 serious events. The record does not identify the types, timing, severity, or relatedness of those other events in the information, so their clinical meaning cannot be characterized further. The adverse-event outcome is titled as a count of participants with adverse events, but the registry record does not provide additional event-level detail in the listed safety summary.

General statistical context: an observed count of zero serious events does not establish that the underlying risk is zero. The precision of a safety estimate depends on the amount and duration of follow-up and on how events were defined and collected. The registry record gives a primary outcome timeframe of 2 years, but does not provide a separate safety follow-up description in the available information. These safety counts do not address the unreported primary imaging comparison.

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

This study asks a focused imaging question: whether 11C-acetate PET/CT uptake differs between prostate regions classified as malignant and non-malignant by pathology after prostatectomy. The planned analysis compares within-participant regional averages. The registry record also describes MRI procedures and several secondary imaging questions, but the main endpoint is the PET-derived SUV comparison.

The record establishes the design features and planned endpoint, but does not provide the numerical primary results. It therefore does not show the size or direction of the difference, the variability of the measurements, or the precision of the estimate. There is no reported primary confidence interval or test result on which to base an assessment of statistical evidence. Study completion and a clearly stated research question are not substitutes for those findings.

Even if a numerical difference were reported, general statistical context would distinguish an imaging association from a claim about diagnostic performance or patient benefit. A difference in average uptake between pathology-defined groups would not on its own establish how accurately a scan classifies individual regions, how results generalize to other settings, or whether imaging changes clinical decisions. Those questions require their own outcomes and methods. The registry lists additional diagnostic and lesion-based outcomes, but their numerical results and detailed analysis methods are not reported in the record.

The study’s single-group structure also limits comparative interpretation. There is no randomized comparison of alternative imaging strategies or a separate control arm described for the primary endpoint. Pathology serves as the reference for classifying regions, not as a randomized intervention. The observations are therefore intended to characterize imaging measurements in this surgical population, rather than estimate a treatment effect.

The most defensible conclusion is about what the registration documents: a completed single-group imaging study with a planned paired comparison of PET uptake in pathology-defined regions. The primary numerical result is not reported in the registry record, so the strength, precision, and direction of that comparison cannot be determined from the record.

13. Why This Trial Matters Statistically

This trial illustrates a statistical issue common to imaging studies: the unit of measurement and unit of analysis are not always the same. The study collects SUV measurements in prostate sextants, but the primary description says those values are averaged within each participant by tumor status before the comparison. Treating related regions from the same person as independent observations could misrepresent uncertainty; the paired participant-level approach reflects the within-person structure described in the registry.

Pathology provides the classification used to distinguish tumor from non-tumor regions. This creates a direct link between imaging measurements and tissue-based classification in participants undergoing prostatectomy. The question is therefore more specific than whether a scan produces visible uptake: it asks whether average uptake differs across regions defined by pathology. The registry’s separate secondary outcomes address other imaging and diagnostic questions, which should be kept conceptually distinct from this primary comparison.

The record also shows why registration details and numerical results serve different purposes. It describes the target population, procedures, endpoint, and intended test, but does not report the primary estimate or its uncertainty. A well-defined analysis question helps readers understand what evidence would be relevant; without numerical results, it cannot establish what the observed data showed.

Finally, the record provides a concrete reminder that imaging feasibility can affect analysis availability: one patient was not imaged because tracer synthesis failed. The record does not explain the handling of this missing imaging information. Reporting the analysis population and missing-data approach alongside estimates would be important for judging how the endpoint results relate to the enrolled group. These considerations matter statistically even when the study is exploratory and single-group.

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 central limitation for interpretation is that numerical results for the primary endpoint are not reported in the registry record. Without the tumor-region and non-tumor-region averages, the paired difference, its variability, a confidence interval, or a test result, the magnitude and precision of the primary comparison cannot be assessed. The record’s stated endpoint and analysis method are not evidence of the result itself.

The record notes that one patient was not imaged because tracer synthesis failed. It does not state how that case was handled, whether any other primary measurements were missing, or how many participant-level pairs entered the analysis. The population used for analysis and the treatment of incomplete regional or pathology data are not reported. This limits assessment of possible selection related to available imaging data.

The study is single-group, with no masking and no randomized allocation described. Its primary endpoint compares regional imaging measurements within participants rather than comparing imaging strategies between groups. The design therefore does not provide a randomized estimate of differences between alternative approaches. The registry also lists MRI-related outcomes, but does not give enough detail to establish a complete comparative analysis of PET and MRI for the primary question.

Further limitations include the absence of a reported full statistical analysis plan, details of assumptions and diagnostic checks for the paired t-test, and a description of how the multiple secondary outcomes were handled. Although nine secondary outcomes and four analyses are listed, their numerical results and analysis populations are not given in the information available. The registry record also does not report a sample-size justification for the trial’s own design. Planning illustrations based on an observed effect should not be mistaken for such a justification or for observed power.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Positron Emission Tomography and Magnetic Resonance Imaging for Prostate Cancer — NCT00924313.
• Registry record last updated 2017-07-11; status last verified 2017-06.
• Results first posted 2012-08-17.
• 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

NCT00924313 is a completed Phase 1 and Phase 2, single-group study sponsored by the National Cancer Institute. Its stated enrollment is 40, and it concerns 11C-acetate PET/CT and MRI in men undergoing prostatectomy for localized prostate cancer. The study started on 2008-09-10, with primary completion on 2011-04-19.

The primary outcome is the comparison of average 11C-acetate SUV in pathology-defined tumor and non-tumor prostate regions. The registry describes a paired t-test of participant-level averages and gives a timeframe of 2 years. It notes that one patient was not imaged because tracer synthesis failed.

The registry record does not report numerical results for the primary endpoint, including an estimate, confidence interval, or test result. Safety entries list zero serious adverse events, 14 other adverse events, and zero deaths. The record lists nine secondary outcomes and four analyses, but does not provide a complete account of their results or analysis populations.