SPECT/CT in Measuring Lung Function in Patients With Cancer Undergoing Radiation Therapy: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for SPECT/CT in Measuring Lung Function in Patients With Cancer Undergoing Radiation Therapy (NCT01982123), a na na study. The primary outcome is Spatial Stability of Lung Perfusion and Ventilation Over Time, as Assessed Using 99mTc-MAA SPECT/CT.

2. Clinical Question

This is a question about the consistency of functional imaging measurements over time, not a randomized test of radiation therapy or a comparison of treatment strategies. The registry description says scans before, during, and after radiation were compared. Its stated primary timeframe is baseline to up to 3 months post-treatment, while the intervention description also refers to imaging at 3-6 months post-treatment. The record does not explain the relationship between those time descriptions.

The motivation in the registry summary is that diagnostic procedures measuring lung function may help identify healthy lung tissue and inform treatment planning. That is the rationale for studying the imaging approach; it is not itself a reported finding. The listed endpoint assesses spatial stability in regions outside the radiation field. The record does not state a threshold for acceptable stability or describe a clinical decision rule based on the measurement.

The registry lists a secondary outcome concerning radiation dose associated with a 50% decrease in lung perfusion, assessed using 99mTc-MAA and 99mTc-DTPA SPECT/CT. Numerical results for that outcome are not reported in the registry record. The posted record therefore identifies the questions the pilot was designed to examine, but it does not provide outcome estimates that would answer them.

3. Trial Design

This is a completed, single-group pilot clinical trial sponsored by the University of Washington. It lists an enrollment of 12 and a study population with lung carcinoma or malignant neoplasm. The record gives a study start date of 2014-01-17 and a primary completion date of 2017-09-13. The phase and allocation are recorded as NA, and masking is listed as none.

The intervention is diagnostic imaging rather than assignment to a therapeutic regimen. The listed interventions include SPECT/CT, single photon emission computed tomography, technetium Tc-99m albumin aggregated, and technetium Tc-99m DTPA. The arm description specifies investigational 99mTc-MAA and 99mTc-DTPA SPECT/CT during radiation therapy or up to 1 week post-treatment, as well as at 3-6 months post-treatment.

Because the trial is single-group, there is no separate control arm for a like-for-like comparison. The endpoint description instead refers to repeated scans at different stages of radiation therapy, with voxel-based comparisons between scans. Such comparisons can describe within-study measurement stability, but they do not have the same interpretation as a randomized comparison between treatment groups.

The registry record labels the study completed. It lists 2 outcome measures and 0 analyses. The primary outcome is spatial stability of lung perfusion and ventilation over time, and the listed secondary outcome concerns radiation dose associated with a decrease in lung perfusion. The record does not report numerical results for these outcomes. It also does not report a protocol, the sample-size justification, interim analyses, or a detailed statistical analysis plan. These omissions limit how fully the design and analysis decisions can be evaluated from the registry entry alone.

Planning illustrations based on an observed effect are not part of the trial’s design description. Their stated assumptions use equal allocation between two arms, a normal approximation, and a two-sided significance level of 0.05. Those hypothetical planning assumptions do not turn this single-group imaging pilot into a two-arm study, and they should not be interpreted as observed power or as the trial’s original sample-size rationale.

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

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 Spatial Stability of Lung Perfusion and Ventilation Over Time, as Assessed Using 99mTc-MAA SPECT/CT, measured over Baseline to up to 3 months post-treatment.

The primary endpoint is described as spatial stability of lung perfusion and ventilation over time, assessed using 99mTc-MAA SPECT/CT. The registry says scans obtained before, during, and after radiation were compared using voxel-based comparisons, focusing on regions outside the radiation field. A voxel-based approach compares measurements at corresponding locations in image data, so the endpoint concerns spatial agreement across scans rather than only a single whole-lung summary.

The reported measure is a coefficient of determination, R²; the registry lists the unit as a correlation coefficient. Its description states that R²=1 means perfect reproducibility in perfusion and ventilation between scans. In general, a reproducibility measure can help characterize whether repeated imaging yields a consistent spatial pattern. That is relevant to the stated aim of examining functional imaging for radiation treatment planning, because consistency across scans is a prerequisite for interpreting changes as meaningful rather than simply measurement variation.

The endpoint does not, by itself, establish that imaging improves treatment planning or patient outcomes. It also does not directly measure the benefit or harm of radiation therapy. The registry gives a primary timeframe of baseline to up to 3 months post-treatment, while the intervention description includes imaging at 3-6 months post-treatment; the record does not clarify that difference. Most importantly, no numerical endpoint estimate, uncertainty interval, or analysis result is reported in the registry record. The endpoint’s intended interpretation can therefore be described, but its observed stability cannot be assessed from the posted record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the primary measure represent?

The endpoint description uses voxel-based comparisons between scans and reports a coefficient of determination, R². In general, R² describes how closely values in one set of measurements correspond to variation in another under a specified model. The registry gives a particular interpretation for this endpoint: R²=1 means perfect reproducibility in perfusion and ventilation between scans. That definition is useful for understanding the intended scale, but it does not provide the study’s observed value.

The registry labels the unit as a correlation coefficient while describing the result as R². These are related statistical ideas, but the record does not provide enough analysis detail to determine the precise calculation beyond its statement that R² was generated from voxel-based comparisons. It does not specify the exact model, preprocessing choices, or how scans and regions were selected for the calculation. Those details are not reported in the registry record.

Why compare scans over time?

Repeated scans can be used to examine whether a measurement pattern remains consistent or changes over time. In general, a stability analysis asks about reproducibility across measurements, whereas an analysis of change asks whether measurements differ systematically between times. The primary outcome is framed as spatial stability. Its comparison is limited by the stated focus on regions outside the radiation field, and the registry does not report a numerical result showing the degree of stability.

The endpoint description includes scans before, during, and after radiation therapy. The listed timeframe says baseline to up to 3 months post-treatment, while the intervention description mentions a scan at 3-6 months post-treatment. The record does not reconcile these descriptions. Nor does it state whether all participants had each scan at each scheduled time.

What does a confidence interval add?

In general, a confidence interval expresses the uncertainty around an estimate under the assumptions of the analysis. A narrow interval indicates greater precision than a wide interval, although it does not remove possible bias or design limitations. For an imaging reproducibility estimate, an interval would help show whether the observed value is compatible with a broad range of stability levels. No confidence interval for the primary endpoint is reported in the registry record, so precision cannot be evaluated.

Why can over-dispersion matter?

In general, over-dispersion occurs when observed variability is greater than a statistical model assumes. If a model assumes too little variability, standard errors may be too small and uncertainty may be understated. This concept is relevant to many analyses of clustered or repeated observations, where measurements from the same participant or nearby image locations may not behave like independent observations. The registry describes voxel-based comparisons but does not report a model, an over-dispersion assessment, or an adjustment for dependence between observations. It is therefore not possible to say whether or how these issues were handled.

What do the planning assumptions mean?

The record’s sample-size assumptions describe planning illustrations computed from an observed effect, rather than the trial’s own design. They specify 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 settings, the stated convention is to give total events; for other settings, it is to give participants per arm.

These are general planning assumptions, not a description of how this pilot was conducted. The actual study is listed as single-group, with enrollment of 12. An equal-allocation, two-arm planning scenario is therefore hypothetical and should not be mistaken for an observed comparison or a randomized design. Sample-size illustrations are not observed power. The registry record does not report the trial’s original sample-size justification, and no planning estimates can substitute for missing endpoint results.

What information is absent?

The registry lists 2 outcome measures and 0 analyses, but it does not supply a statistical analysis plan or numerical outcome estimates. The exact analysis population, treatment of missing scans, handling of repeated measurements, and approach to multiplicity are not reported in the registry record. In general, these choices matter because they define which observations contribute, how dependence is handled, and how multiple questions are interpreted. Without them, the endpoint’s intended meaning can be described, but the analysis cannot be independently reconstructed from the registry entry.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 2 outcome measures: a primary imaging-stability outcome and a secondary outcome concerning radiation dose associated with a 50% decrease in lung perfusion. It does not report an adjustment for multiplicity, a hierarchy of testing, or a detailed plan for interpreting multiple outcomes. When multiple outcomes or analyses are considered, general statistical practice distinguishes the primary question from additional or exploratory questions; the registry identifies a primary outcome but does not describe how the secondary outcome was handled inferentially.

The record lists 0 analyses and does not report p-values, confidence intervals, or numerical outcome estimates. It therefore does not reveal whether formal hypothesis tests were performed, what model was used, or whether any multiplicity procedure was applied. No interim analyses are reported in the registry record. That absence should not be interpreted as confirmation that interim analyses did or did not occur; the record simply does not provide that information.

Missing-data handling is also not reported. The enrollment count is 12, but the record does not state how many participants completed each scan, whether any scans were unusable, or how incomplete follow-up was handled. In general, missing imaging can affect both the precision and representativeness of a repeated-scan comparison, especially if the availability of scans is related to participant characteristics or study progress.

The analysis population is not reported in the registry record. It is not stated whether endpoint calculations included all enrolled participants or only those with paired, evaluable images. The descriptions also do not specify how repeated measurements within a participant or spatial dependence between voxels were handled. These omissions limit assessment of uncertainty and the reproducibility of any analysis. They do not establish that a particular method was or was not used; the relevant details are simply not reported.

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 group, with 12 participants at risk for serious events and 0 serious events recorded. It also lists 12 at risk for other events and 0 other events recorded, with 0 deaths. The adverse-event entry is associated with diagnostic 99mTc-MAA and 99mTc-DTPA SPECT/CT.

These counts describe what the registry record reports for this group. They do not give event rates by time period, event severity beyond the serious-versus-other classification, or a comparison with a control group. Because this was a single-group study, the safety counts cannot provide a randomized comparison against an alternative diagnostic approach or against no imaging.

A count of 0 recorded events does not establish that the true risk is zero. In general, a small study can provide limited information about uncommon events, and a registry count alone does not show how events were collected or adjudicated. The record does not report additional details about event definitions, follow-up duration for safety, or missing safety information. The figures should therefore be read narrowly as the listed counts, rather than as proof of absence of harm.

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

The study addresses a measurement question: whether lung perfusion and ventilation patterns assessed with SPECT/CT remain spatially stable across scans around radiation therapy. The registry describes a voxel-based R² comparison in regions outside the radiation field. This provides a clear outline of the intended primary endpoint, but the registry record does not report its numerical result. The degree of observed stability and its precision therefore cannot be determined from the posted information.

The rationale is that functional imaging may help identify healthy lung tissue and inform treatment planning. That rationale is not a trial finding. The registry entry does not report whether imaging changed a plan, improved a clinical outcome, or led to a different treatment decision. Nor does the single-group design provide a randomized comparison of treatment strategies. The results available in the record cannot establish a causal effect of SPECT/CT on care or outcomes.

The secondary outcome concerns radiation dose associated with a 50% decrease in lung perfusion, but its numerical result is not reported. No analysis details or inferential estimates are given for either outcome. Consequently, the record does not show the size of any dose-perfusion association or the uncertainty around it.

The safety record lists 0 serious events, 0 other events, and 0 deaths among 12 participants in the diagnostic group. This is descriptive reporting for the enrolled group, not a comparison and not a precise estimate of the risk of uncommon events.

Overall, the registry describes a completed pilot, its imaging approach, and its intended questions, but not the results needed to answer those questions. The absence of reported estimates should not be mistaken for evidence of no change, perfect reproducibility, or no safety concerns. It means the posted record does not provide enough outcome information to make those judgments.

13. Why This Trial Matters Statistically

This trial is statistically interesting because its main question concerns measurement reproducibility rather than a conventional comparison of treatment groups. Repeated functional imaging can generate many spatial observations, while the scientific question is about whether patterns correspond across scans. The registry specifies voxel-based comparisons and an R² measure, making the spatial nature of the endpoint explicit.

That structure raises important general analysis considerations. Repeated observations from the same participant and observations from neighboring image locations may be dependent. Treating every location as independent could misrepresent uncertainty if the analysis does not account for such dependence. The registry record does not describe the statistical model or how dependence was handled, so the robustness of any estimated precision cannot be assessed.

The study is also a single-group pilot with enrollment of 12. A pilot can be useful for examining feasibility and developing measurement approaches, but the registry does not report feasibility outcomes or numerical reproducibility results. The absence of reported estimates means readers cannot assess how variable the measurements were or how precisely stability was characterized.

Finally, the record’s planning assumptions describe hypothetical equal-allocation, two-arm calculations based on an observed effect, whereas the actual study is single-group. This contrast is a useful reminder that planning illustrations are not the same as a trial’s design or observed power. The registry does not report the original sample-size justification. Clear distinction between endpoint definition, analysis, and hypothetical planning is essential when interpreting a small imaging study.

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 important limitation for interpretation is the lack of numerical primary and secondary outcome results in the registry record. The primary endpoint is described, but no R² estimate or uncertainty measure is reported. The secondary dose-perfusion outcome is named without a result. Without those estimates, neither magnitude nor precision can be judged.

The study has a single-group design and does not include a separate control arm. Its imaging comparisons are described across time points within the study, not as a randomized comparison. This design can address a repeated-measurement question, but it cannot by itself establish that the imaging approach improves treatment planning or patient outcomes.

Enrollment is listed as 12, but the registry does not report the number of participants with complete scans or the number included in each endpoint analysis. The analysis population and missing-data methods are not reported. The record also does not give the statistical model, details of image processing, handling of repeated or spatially dependent measurements, or multiplicity strategy.

The primary timeframe is stated as baseline to up to 3 months post-treatment, whereas the intervention description also mentions imaging at 3-6 months post-treatment. The registry does not explain how these time descriptions relate. The exact timing of scans and completeness of follow-up therefore cannot be fully assessed.

Finally, the registry does not report the original sample-size justification or an analysis plan. The stated planning assumptions are hypothetical two-arm illustrations and are not the design of this single-group pilot. These limitations concern what can be established from the registry entry; they do not prove that additional analyses or documentation do not exist elsewhere.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: SPECT/CT in Measuring Lung Function in Patients With Cancer Undergoing Radiation Therapy — NCT01982123.
• Registry record last updated 2018-12-13; status last verified 2018-11.
• Results first posted 2018-12-13.
• 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 completed University of Washington pilot enrolled 12 participants with lung carcinoma or malignant neoplasm undergoing radiation therapy. The study evaluated SPECT/CT using 99mTc-MAA and 99mTc-DTPA, with imaging described before, during, and after radiation therapy.

The primary outcome concerns spatial stability of lung perfusion and ventilation over time, using voxel-based comparisons and R² in regions outside the radiation field. A secondary outcome concerns radiation dose associated with a 50% decrease in lung perfusion. The registry lists 2 outcome measures and 0 analyses, but does not report numerical results for either outcome.

The design is single-group, with no separate control arm. The record lists 0 serious events, 0 other events, and 0 deaths in the diagnostic group. It does not report the analysis population, missing-data methods, or a detailed statistical analysis plan. The primary endpoint’s result and precision therefore cannot be evaluated from the registry record.