Comparison of Yttrium-90 Absorbed Doses Using PET/CT Versus PET/MR Imaging for Hepatic Malignancies: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Comparison of Yttrium-90 Absorbed Doses Using PET/CT Versus PET/MR Imaging for Hepatic Malignancies (NCT04332419), a na na study. The primary outcome is Reproducibility Coefficient (RDC) Between the Two Imaging Modalities in Liver Tumor Tissues.

2. Clinical Question

The central statistical question is whether measurements from the two imaging modalities are sufficiently reproducible when used to assess absorbed dose in liver tumors after Y-90 radioembolization. This is a measurement-comparison question, not a test of whether SIRT is more effective than another treatment. Both imaging modalities are part of the study, and the record describes one study group rather than separate treatment and control groups.

The registry also identifies RDC between the modalities in background liver tissues as a secondary outcome. Comparing tumor and background liver tissue measurements could describe reproducibility in different tissue settings, but the registry record does not report numerical results for either outcome. It therefore does not establish the size or precision of any observed difference between modalities.

The record says the imaging order was randomized based on availability, while its allocation field is listed as NA and it explicitly notes that this is not a randomized comparison. These descriptions concern imaging order, not assignment to competing treatment arms. The modalities are not a like-for-like control comparison of treatment effects.

3. Trial Design

This completed study is registered as a single-group study of PET/CT and PET/MR imaging in people undergoing SIRT with Y-90 for hepatic malignancies. The registry lists an enrollment of 11. It lists the study start as 2020-03-03 and primary completion as 2020-09-21. The phase is recorded as NA, and masking is recorded as none.

The arm description combines PET/CT and PET/MR. Participants received one-time PET/MR imaging in addition to standard PET/CT imaging, with both performed on the same day as the treatment procedure. The primary endpoint timeframe is post-op day 0, with the two measurements one hour apart. The record says participants were randomized to receive either imaging modality first based on imaging availability, although the allocation field is NA. It also cautions that the study is not a randomized comparison and that its arms are not a like-for-like control comparison. Accordingly, the order statement should not be mistaken for random assignment to different treatment groups.

The intervention list includes PET/CT, PET/MR, and SIRT with Y-90. The question concerns agreement or reproducibility between imaging measurements of absorbed dose; it is not a comparison of the clinical effect of SIRT against another therapy. The primary outcome is RDC in liver tumor tissues. The listed secondary outcome is RDC in background liver tissues.

The registry reports no analysis entries. Details such as the analysis population, handling of missing measurements, model used to estimate the RDC, and any prespecified approach for uncertainty are not reported in the registry record. The record also does not provide a sample-size justification. The enrollment figure describes the registered study enrollment; it does not by itself establish how many participants contributed usable paired measurements.

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:

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 Reproducibility Coefficient (RDC) Between the Two Imaging Modalities in Liver Tumor Tissues, measured over Post-op day 0, 1 hour apart.

The primary endpoint is the reproducibility coefficient (RDC) between PET/CT and PET/MR measurements of post-Y-90 radioembolization absorbed doses in liver tumor tissues. The unit is percent difference, the reported parameter is a mean, and the stated dispersion is a 95% confidence interval. The timeframe is post-op day 0, with measurements one hour apart.

The registry defines the RDC as the minimum difference between the two measurements that can be considered a true difference, with 95% confidence. In general, a reproducibility measure helps describe how far apart repeated or paired measurements may be before the difference is considered beyond measurement variability. It addresses the consistency of the measurements, rather than whether either modality is clinically superior or whether treatment changes an outcome.

The mean describes the average endpoint value across the measurements included in the analysis. A confidence interval expresses uncertainty around an estimated quantity; it is not a range containing every individual measurement. For a reproducibility endpoint, the estimate and its interval would be needed to judge both the magnitude of the measurement difference and how precisely it was estimated.

The registry record does not report the RDC estimate or its 95% confidence interval. It therefore supplies the endpoint definition and timing, but not the numerical result needed to characterize reproducibility in this study.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is a continuous measurement, expressed as a mean percent difference. In general, a continuous outcome can take a range of numerical values, unlike a binary outcome that records only whether an event occurred. Here, the endpoint is a reproducibility coefficient between paired imaging modalities. Its purpose is to describe measurement differences, not to estimate a treatment-versus-control effect.

What does reproducibility mean?

In general, reproducibility concerns how close measurements are when methods are used to assess the same quantity under the conditions of a study. A reproducibility coefficient is intended to give a scale for interpreting measurement differences. The registry defines this RDC as the minimum difference between the two measurements that can be considered a true difference, with 95% confidence. That definition does not make the coefficient a direct estimate of clinical benefit, diagnostic accuracy, or the correctness of either modality.

When two imaging measurements are paired within the same study context, the comparison can focus on their differences rather than treating the measurements as coming from unrelated groups. Pairing can account for the fact that both modalities assess the same participants, but interpretation still depends on complete and correctly matched measurements. The registry record does not describe how pairs were formed in the analysis, whether any were incomplete, or how such cases were handled.

What does the confidence interval convey?

In general, a confidence interval expresses uncertainty about an estimated quantity under the statistical method used. A narrower interval indicates greater precision than a wider interval, while neither width nor the estimate alone reveals every participant's measurement. The primary outcome specifies a 95% confidence interval, but the registry does not post its endpoints. Without the estimate and interval, the magnitude and precision of the study's primary result cannot be assessed.

The word “mean” identifies the summary parameter stated for the primary outcome. A mean can describe the average endpoint value, but its interpretation depends on the distribution of the underlying measurements and the method used to estimate uncertainty. The record does not report a distributional assessment, estimation procedure, or model. It is therefore not possible to determine from the registry entry whether the analysis accounted for features such as unusually variable differences or influential observations.

Why can over-dispersion matter?

As a general statistical point, over-dispersion means that observed variability is greater than a model expects. If a method assumes less variability than the data contain, uncertainty can be understated and confidence intervals can be too narrow. This concept is not a reported finding in this study: the registry does not describe an over-dispersion assessment, and the endpoint results are not posted. It is relevant as a general consideration when interpreting continuous measurement differences, not as a claim about these data.

The registry's sample-size assumptions describe a planning illustration based on an 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 described as a stated fraction of the observed effect. This is a planning framework, not evidence about the trial's original design or its achieved ability to detect an effect. The record does not report a sample-size justification for the study, and no numerical planning results are included in the registry record for interpretation. Any such planning values would be illustrations, not observed power.

For a paired imaging study, a two-arm planning framework should not be confused with the study's actual single-group design. The record says the arms are not a like-for-like control comparison. The planning assumptions do not change the design or provide a result for the paired modality comparison. No recalculated estimate is available, and there is no sponsor analysis result in the registry record to compare with a recalculation.

Finally, the registry lists zero analysis entries. It does not give the statistical test, confidence-interval construction, analysis population, missing-data method, or prespecified decision threshold. Those omissions limit assessment of the methods used and of whether the outcome was analyzed as planned. They also prevent independent reconstruction of a numerical result from the registered information.

10. Multiplicity, Missing Data and Analysis Populations

The record lists a primary RDC outcome for liver tumor tissues and a secondary RDC outcome for background liver tissues. These are related measurement questions, but the registry record does not describe a multiplicity adjustment or explain how interpretation of the outcomes was prioritized beyond identifying one as primary and the other as secondary. Whether any adjustment was used is not reported in the registry record.

There are no analysis entries. The statistical method for either outcome, the analysis population, and any rules for excluding or retaining measurements are not reported in the registry record. The record also does not state whether an analysis plan was prespecified or whether any interim analyses were planned or conducted. No assumptions about these matters can be made from the endpoint descriptions.

The enrollment is listed as 11, but the number contributing to each endpoint is not reported in the registry record. It is not clear whether all enrolled participants had usable PET/CT and PET/MR measurements, whether all pairs were obtained at the intended interval, or whether any data were missing. The registry does not describe imputation, complete-case analysis, or another approach to missing data. This matters because a paired comparison relies on information from both modalities for the relevant participant or measurement pair.

The record does not identify an analysis population, such as all enrolled participants or only those with evaluable imaging. It also does not report any sensitivity analysis. Consequently, the posted information is insufficient to assess how incomplete data or analysis choices might affect the RDC estimates. These are unreported methodological details, not evidence that missing data or multiplicity problems occurred.

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 adverse-event record lists one group, PET/CT & PET/MR. It records 11 at risk for serious events and 0 affected; it also records 11 at risk for other events and 0 affected. The death count is 0. No serious-event terms are listed.

These are the recorded counts for this group. They should be read as registry entries, not as proof that no adverse events could occur or that either imaging modality or SIRT is risk-free. The record does not explain how events were defined, what period was used for collection, or whether all event types were actively assessed. It also does not report further safety analyses.

The group combines PET/CT and PET/MR in the arm description, and the study is not a like-for-like control comparison. The counts therefore do not support a comparative safety claim between separate modality groups. They describe the posted adverse-event figures for the registered group only.

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

This study is designed to describe the reproducibility of Y-90 absorbed-dose measurements made with PET/CT and PET/MR in liver tumor tissues. Its primary endpoint is a mean RDC expressed as percent difference, with a 95% confidence interval. A secondary outcome concerns background liver tissues. These endpoints address how measurements compare, not whether one imaging method improves treatment outcomes.

The registry record does not report the primary or secondary numerical results. Without the RDC estimates and confidence intervals, the record cannot show how large the measurement differences were or how precisely they were estimated. It cannot establish that the modalities were equivalent, that they differed, or that either method was more accurate. Such conclusions would require results and, for some claims, additional reference information not reported in the registry record.

The study's single-group design and use of both modalities should not be interpreted as a randomized treatment comparison. The record mentions randomization of imaging order based on availability, but lists allocation as NA and cautions that the study is not a randomized comparison. The question is about paired measurements, not the effect of assigning participants to different treatment arms.

The enrollment listing and adverse-event counts provide descriptive context, but they do not replace an outcome analysis. The registry does not say how many participants had complete paired data, which participants were analyzed, or how missing observations were handled. The safety entries record zero serious events, zero other events, and zero deaths in the listed group; they do not establish the absence of risk.

Accordingly, the registered information supports identifying the study question, outcome definitions, and broad design. It does not support a conclusion about the observed reproducibility of PET/CT and PET/MR or about clinical consequences of choosing either modality.

13. Why This Trial Matters Statistically

Imaging measurements may be used to characterize absorbed dose in tumor tissue, so it is important to distinguish agreement between measurement methods from their clinical consequences. A reproducibility coefficient is one way to express the scale of differences that may be considered beyond measurement variability. A clear estimate and its uncertainty would help readers understand what degree of disagreement the study observed.

This registry entry makes the measurement question explicit and identifies both tumor tissue and background liver tissue as settings of interest. It also specifies the primary outcome's unit, summary parameter, confidence level, and timing. That information helps define what a statistical result would need to address: paired modality measurements, their reproducibility, and uncertainty around the estimate.

The record also illustrates why design labels and the comparison being made matter. Both imaging modalities are part of a single-group study, and the record cautions that the study is not a randomized comparison of like-for-like arms. Imaging-order randomization should not be mistaken for random assignment to competing treatment strategies. The statistical interpretation must follow the measurement-comparison design.

At the same time, the registry record does not report the RDC results or analysis methods. Without those, the statistical importance of the study question cannot be judged from the posted record alone. Its value as a measurement study depends on the result, precision, and handling of paired data—not merely on the presence of two imaging modalities or a defined endpoint.

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 principal limitation for interpreting the registered study is that numerical results for the primary and secondary outcomes are not reported in the registry record. The primary endpoint is defined, but its mean RDC and 95% confidence interval are absent. Consequently, the magnitude and precision of the observed measurement comparison cannot be assessed.

The registry lists an enrollment of 11 but does not report the number of complete PET/CT–PET/MR pairs or the analysis population. It does not describe missing-data handling, exclusions, or how the endpoint was estimated. The absence of analysis entries also means the statistical procedure and any sensitivity analyses are not reported in the registry record.

The design is single-group, and the record explicitly cautions that this is not a randomized comparison with like-for-like control arms. Although imaging order is described as randomized based on availability, allocation is listed as NA. Results, if reported elsewhere, would need interpretation as a comparison of imaging measurements rather than a randomized treatment effect.

The registry does not report a sample-size justification, a clinically meaningful reproducibility threshold, or the details needed to assess whether the study was designed to estimate the endpoint with a particular precision. Its planning assumptions are described as an illustration based on an observed effect, not as the trial's own design. The record also does not explain adverse-event definitions or the safety observation period. These reporting gaps limit both statistical and safety interpretation without establishing that the study was conducted improperly.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Comparison of Yttrium-90 Absorbed Doses Using PET/CT Versus PET/MR Imaging for Hepatic Malignancies — NCT04332419.
• Registry record last updated 2022-06-22; status last verified 2022-06.
• Results first posted 2021-10-05.
• 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

NCT04332419 is a completed, single-group study sponsored by Case Comprehensive Cancer Center. It enrolled 11 people with hepatic malignancies undergoing SIRT with Y-90. The study compared PET/CT with PET/MR imaging performed on the same day as the treatment procedure; the primary endpoint timing is post-op day 0, with measurements one hour apart.

The primary outcome is RDC between modalities in liver tumor tissues, reported as a mean percent difference with a 95% confidence interval. RDC in background liver tissues is listed as a secondary outcome. The registry record does not report numerical results or analysis entries. Serious events, other events, and deaths are each recorded as 0 in the listed group.