PET/CT-Assessment of Liver Tumor Ablation: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for PET/CT-Assessment of Liver Tumor Ablation (NCT02018107), a na na study. The primary outcome is Number and Percentage of Tumors With Complete, Circumferential Ablation Margin Visibility During FDG PET/CT-guided Liver Ablations (AP-PET-1 v. Contrast-enhanced MRI).

2. Clinical Question

The clinical question is about imaging assessment of the ablation margin, rather than a randomized comparison of treatments. Ablation is described as heating or freezing a tumor. The study asks whether PET-based imaging can help assess how completely the tumor has been destroyed, in comparison with imaging approaches already used in clinical practice. The registry summary notes that CT may not always show how completely a tumor has been destroyed, and frames ammonia PET as another way to assess this.

The primary endpoint specifically concerns visibility of a complete circumferential margin. That is an imaging finding: it describes whether the margin can be seen around the tumor. It is not itself a measure of survival, symptoms, or confirmed local tumor control. A secondary outcome asks whether an inadequate PET margin predicts local progression in comparison with MRI, but the registry record does not report an analysis of that question.

3. Trial Design

NCT02018107, titled PET/CT-Assessment of Liver Tumor Ablation, is recorded as a completed single-group study. The registry lists enrollment of 33, no random allocation, and no masking. The study start is listed as 2014-01, and primary completion as 2018-02-16. The phase is recorded as not applicable. These design features do not describe a randomized, masked, parallel-group treatment comparison.

The intervention descriptions concern diagnostic imaging during liver tumor ablation. The listed interventions are N-13 ammonia or F-18 fluorodeoxyglucose and PET scanning. The arm description identifies N-13 ammonia perfusion PET as a diagnostic imaging test and states that one to two doses of a radiopharmaceutical may be administered during the ablation procedure. The registry describes the administration as non-therapeutic. It also notes that one participant took part in both interventions, so the imaging group descriptions should not be treated as mutually exclusive participant groups.

The primary endpoint is framed around FDG-avid tumors and compares intra-procedural AP-PET-1 with post-procedural contrast-enhanced MRI. The stated timeframe is 2 Years. The registry population description reports 11 tumors from 8 participants analysed for N-13 ammonia PET perfusion, and 31 tumors from 20 patients analysed for F-18 fluorodeoxyglucose PET perfusion. Those are tumor counts within the described imaging groups, not interchangeable participant counts. The record does not explain the relationship between those group-specific counts and the enrollment figure in sufficient detail to reconcile them.

The record identifies a single-group model and says allocation is not applicable. It also cautions that this is not a randomized comparison and that the arms are not a like-for-like control comparison. Thus, any contrast between imaging methods should be understood in light of the study’s imaging design, not as a randomized estimate of a treatment effect. The registry record does not report a protocol-level statistical plan, a sample-size justification, or details of how the primary endpoint was analyzed.

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: 33 unique participants were enrolled and consented for this study, 6 participants were then excluded from the study. Thus, the count of subjects is 27. Out of 27 participants, 1 subject participated in both interventions.

Overall Study

Analysis population for the primary outcome, as defined in the registry: In this study, the number of tumors were analysed. There 8 participants with 11 tumors that were analysed for N-13 ammonia to image liver PET perfusion and 31 tumors in 20 patients were analysed in F-18 fluorodeoxyglucose to image liver PET perfusion. 1 participant participated in both interventions. Total unique participants 27.

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.

Population: There were 27 unique participants and one participant participated twice (in both interventions).

6. Primary Endpoint

The registry lists the primary outcome as Number and Percentage of Tumors With Complete, Circumferential Ablation Margin Visibility During FDG PET/CT-guided Liver Ablations (AP-PET-1 v. Contrast-enhanced MRI), measured over 2 Years.

The primary endpoint counts tumors with complete, circumferential ablation margin visibility during FDG PET/CT-guided liver ablations. It names two imaging assessments: intra-procedural AP-PET-1 and post-procedural contrast-enhanced MRI. The description says rates of complete margin visibility will be compared and discordance between the methods calculated. The listed timeframe is 2 Years.

Margin visibility is relevant because the study is concerned with assessing the extent of ablation during the procedure and comparing that assessment with later imaging. A circumferential margin finding describes whether the imaging shows a complete margin around the tumor. Comparing two imaging assessments can reveal whether they classify visibility consistently or disagree. The registry record does not define a numerical threshold for a complete margin, explain how images were read, or report how disagreements were categorized.

This endpoint is an imaging measure, not a direct measure of long-term clinical benefit. The registry also lists a secondary question about whether an inadequate PET margin predicts local progression in comparison with MRI, but that question is distinct from counting visible margins. The primary endpoint title gives no observed count or percentage, and no numerical comparison or discordance result is reported in the registry record. Without those results, the direction and precision of any difference between imaging methods cannot be assessed.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The endpoint is expressed as a count and percentage of tumors with complete, circumferential ablation margin visibility. A count states how many tumors met the endpoint definition; a percentage relates that count to the tumors assessed for that endpoint. To interpret a percentage, readers need to know both the numerator and its denominator, and how the endpoint was classified. Although the registry gives group-specific tumor counts in its population description, it does not report primary endpoint counts, percentages, or a complete account of the endpoint analysis population.

What does a comparison of imaging methods estimate?

The primary description sets out a comparison between intra-procedural AP-PET-1 and post-procedural contrast-enhanced MRI for FDG-avid tumors. It also names discordance rates. Agreement and discordance are related but not identical ways to describe two assessments. Agreement concerns how often assessments give matching classifications; discordance concerns how often they differ. A discordance rate alone may not show which method more often classified a margin as complete unless the direction of disagreement is also reported. The registry record does not provide those values or state the precise classification rules.

Because the assessments concern tumors in a study of ablation, the intended comparison may involve information from both imaging methods for the same tumor. General statistical consideration: when measurements are paired, analysis should preserve the pairing rather than treat the measurements as unrelated. The registry description identifies the two imaging techniques, but the statistical method used to compare them is not reported in the registry record. It would therefore be inappropriate to attribute a particular paired test, model, or confidence-interval method to the investigators.

Why does the unit of analysis matter?

The primary outcome is defined for tumors. The population description reports tumors nested within participant groups, and says that one participant took part in both interventions. General statistical consideration: observations from one person can be more alike than observations from different people. If multiple tumors from a participant are included, accounting for within-person dependence can affect standard errors and confidence intervals. The record does not report whether clustering was addressed, whether every eligible tumor was included, or how tumors were assigned to an analysis when a participant had more than one imaging intervention.

The distinction between tumor counts and participant counts matters for interpretation. Tumor-level counts answer a question about tumors assessed; they should not be presented as participant-level rates without a documented method for translating between those units. The record gives 11 tumors from 8 participants for N-13 ammonia PET perfusion and 31 tumors from 20 patients for F-18 fluorodeoxyglucose PET perfusion. These values describe the analysis groups in the registry population text, but the primary outcome results and their denominators are not reported.

What can a confidence interval contribute?

General statistical explanation: an estimate gives a central summary of the data, while a confidence interval conveys its statistical precision under specified assumptions. A narrow interval indicates greater precision than a wide interval, but does not by itself establish clinical importance or remove potential bias. For a comparison of imaging methods, an interval around a difference or discordance measure could help show which values remain compatible with the observed data. The registry record does not report such an estimate or interval for the primary endpoint.

Likewise, a p-value, if reported, would address compatibility of the data with a specified statistical model or null hypothesis. It would not measure the size or clinical importance of a difference. No primary inferential result is reported in the registry record, so there is no reported p-value to interpret. The record lists 0 analyses.

How should planning illustrations be read?

General statistical explanation: a sample-size calculation is a planning exercise based on assumptions about the effect to detect, variability, significance level, allocation, and analysis method. It is not a measure of the strength of evidence observed in a completed study. The registry’s planning illustration is described as based on the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is a stated fraction of the observed effect. The record says that time-to-event tables give the total number of events, while other planning tables give participants per arm for 80% or 90% power. Those are planning quantities, not observed power, and they do not supply a result for the primary imaging endpoint.

The registry does not report the trial’s own sample-size justification or explain whether the planning illustration reflects the original design. It also does not report the statistical analysis plan, how missing images or unclassifiable margins were handled, or whether estimates were adjusted for relevant features of the tumors or participants. These omissions limit assessment of model assumptions, precision, and the robustness of any comparison.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists two outcome measures, including the primary margin-visibility outcome and a secondary question about whether an inadequate PET margin predicts local progression in comparison with MRI. It does not report a multiplicity strategy, such as whether inferential testing across outcomes was adjusted or which outcome would take priority if findings differed. The absence of a reported strategy does not establish that no strategy existed; it means the approach is not reported in the registry record.

The record lists 0 analyses and does not provide numerical findings for the primary or secondary outcomes. It therefore offers no analysis results from which to assess whether multiple comparisons were made, which models were used, or how any estimates were selected for reporting. The statistical analysis plan is not reported in the registry record.

Missing-data handling is also not reported. The registry does not state how investigators handled missing scans, images that could not be interpreted, tumors without an evaluable margin, or incomplete follow-up for the secondary local-progression question. It does not provide missingness counts or explain whether missingness was assessed as potentially related to tumor or participant characteristics. General statistical consideration: missing observations can affect both the denominator and the interpretation of an estimate, particularly if the chance of missingness is related to the outcome.

The primary endpoint is defined for tumors, whereas participants may contribute more than one tumor and one participant took part in both interventions. The record does not specify the analysis population beyond its group-level population description, or explain whether analyses used all available tumors, a subset with both imaging assessments, or another rule. Those details are important for interpreting denominators and comparability. No conclusion about the actual handling of multiplicity, missing data, or analysis populations can be drawn from 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 0% reporting threshold.

The registry lists the N-13 ammonia PET perfusion group with 27 at risk. It reports 0 serious adverse events, 0 other adverse events, and 0 deaths for that group. No serious adverse event terms are listed. These are the safety figures recorded for this group; the registry does not provide corresponding figures for every intervention grouping in the population description.

A zero count means that no events in the listed categories were recorded in the registry entry for the group. It does not establish that the risk of an event is absent. General statistical consideration: when no events are observed, the precision of an estimate of event risk depends on the amount of safety follow-up and on how events were collected and defined. The registry record does not report the adverse-event ascertainment period, detailed definitions, or whether all participants had complete safety follow-up.

The safety figures should also be kept separate from the primary imaging outcome. They describe adverse events, not the visibility or accuracy of the ablation-margin assessments. The registry describes radiopharmaceutical administration as non-therapeutic and identifies PET as a diagnostic test, but the reported zero counts alone do not establish the safety profile of the imaging procedures beyond the recorded group and categories.

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

The record describes a study asking whether PET-based imaging can assess ablation margins and how those assessments compare with contrast-enhanced MRI. Its primary endpoint is the number and percentage of tumors with complete, circumferential margin visibility, alongside a planned assessment of discordance. This is a relevant diagnostic imaging question because the study summary notes that standard CT imaging may not always show how completely a tumor has been destroyed.

However, the registry record does not report the primary endpoint counts, percentages, or discordance rates. It therefore does not show whether complete margin visibility was more frequent with one imaging assessment, whether the methods generally agreed, or how precise any comparison was. No conclusion about the comparative performance of PET and MRI can be drawn from the posted results in this record.

Even if numerical visibility results were available, they would describe an imaging endpoint. Visibility of a complete margin is not equivalent to proof that a tumor was completely destroyed or that local progression will not occur. The secondary outcome asks whether an inadequate PET margin predicts local progression in comparison with MRI, but no result for that question is reported in the registry record. Prediction of progression and visibility of a margin are related questions, but they are not the same endpoint.

The design also matters. The record identifies a single-group study, no random allocation, and no masking. It cautions that the interventions are not a like-for-like control comparison. The findings, if reported, would need to be understood as an imaging assessment in the study context rather than a randomized treatment comparison. The tumor-level population descriptions and participant overlap further mean that group counts cannot be treated as independent participant totals.

The completed status records the study’s administrative status, but does not fill the gap in reported outcomes. The most defensible conclusion is that the registry defines a clinically motivated imaging comparison, while leaving its primary numerical result and the precision of that result unavailable. This distinction separates the question a study was designed to address from what its posted results establish.

13. Why This Trial Matters Statistically

This study raises a statistical issue that is common in diagnostic research: the measured outcome may be an imaging classification rather than a direct patient outcome. The primary endpoint concerns whether a complete circumferential ablation margin is visible. That makes the unit of observation a tumor and places emphasis on the definition, reproducibility, and comparison of imaging assessments. Statistical interpretation must match that measurement target.

A second issue is the relationship between tumors and participants. The registry describes multiple tumors within participant groups and notes that one participant took part in both interventions. General statistical consideration: analyses that ignore dependence among observations from the same person may give overly precise uncertainty estimates. A clear report would identify the analysis unit, describe how repeated observations were handled, and make denominators transparent. Those methods are not reported in the registry record.

The study also illustrates why agreement and clinical prediction should be distinguished. Comparing margin visibility across imaging methods addresses whether the methods produce similar classifications. Asking whether an inadequate margin predicts local progression addresses a later outcome. Each requires its own definition and analysis, and neither result is reported in this record. A visible margin finding alone does not settle the question of later progression.

Finally, an endpoint description is not a result. The registry gives a specific comparison and a stated timeframe, but reports no primary endpoint values or inferential analyses. Without estimates and measures of uncertainty, readers cannot judge the magnitude, direction, or precision of the comparison. The study is statistically noteworthy for the questions it poses about imaging concordance and tumor-level analysis, while the registry record does not provide the outcome information needed to resolve those questions.

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 consequential limitation of the registry record for interpretation is that it does not report numerical primary outcome results. The endpoint is described, but no counts, percentages, discordance rates, confidence intervals, or inferential results are available. The secondary question about local progression is also listed without an analysis result. As a result, the imaging comparison cannot be evaluated from the posted outcomes.

The design is recorded as single-group, with allocation listed as not applicable and masking listed as none. The registry explicitly cautions that this is not a randomized comparison and that the arms are not like-for-like controls. This limits interpretation of any apparent differences between intervention groups as direct comparative effects. The primary outcome’s comparison of imaging methods should not be confused with a randomized comparison of treatments.

The endpoint is tumor-based, and the population description includes multiple tumors within participant groups. One participant took part in both interventions. The registry does not report whether tumor-level dependence was handled statistically, how overlapping participation was treated, or whether all tumors had assessments with both imaging methods. These details affect the interpretation of denominators and uncertainty.

Important analysis details are not reported in the registry record, including endpoint classification rules, missing-image handling, the analysis population, multiplicity procedures, and the statistical model. The record also does not give the adverse-event ascertainment period or detailed safety definitions. These omissions prevent a full assessment of analytic assumptions and outcome completeness. The listed timeframe for the primary outcome is 2 Years, but no results for that timeframe are posted.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: PET/CT-Assessment of Liver Tumor Ablation — NCT02018107.
• Registry record last updated 2020-03-26; status last verified 2020-03.
• Results first posted 2020-03-26.
• 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

NCT02018107 is a completed, single-group study of PET imaging during liver tumor ablation. It lists enrollment of 33 and compares intra-procedural AP-PET-1 with post-procedural contrast-enhanced MRI for the primary endpoint of complete, circumferential ablation margin visibility in FDG-avid tumors. The record describes N-13 ammonia and F-18 fluorodeoxyglucose PET imaging and includes a secondary question about inadequate margins and local progression.

The population description reports tumor counts and participant counts for the two imaging groupings, and notes that one participant took part in both interventions. The registry reports 27 at risk in the listed N-13 ammonia safety group, with 0 serious adverse events, 0 other adverse events, and 0 deaths. No primary numerical result or analysis is reported in the registry record, so the comparative imaging findings and their precision cannot be assessed.