Magnetic Resonance Imaging (MRI) Brachytherapy Applicator Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Magnetic Resonance Imaging (MRI) Brachytherapy Applicator Study (NCT01706705), a na na study. The primary outcome is Number of Participants With Improved Image Quality in the Shifted Position.

2. Clinical Question

3. Trial Design

The registry record describes a completed, single-group study of brachytherapy treatment planning for cervical cancer. Its title identifies an MRI brachytherapy applicator study, and the official title describes three-dimensional image-guided intracavitary brachytherapy planning using a novel shielded applicator. The listed sponsor is M.D. Anderson Cancer Center. The phase is recorded as NA.

The enrollment is listed as 57. The study began on 2012-10-22, and its primary completion date is 2018-04-22. The overall status is COMPLETED. These administrative details describe the study record; they do not establish how many enrolled participants contributed usable data to the primary outcome.

The registry lists intracavitary applicator placement, computed tomography (CT), and magnetic resonance imaging (MRI) as interventions. The arm description says that an MRI-compatible applicator was inserted using ultrasound guidance to verify placement of the tandem in the uterus. Tandem and ovoids, tandem and cylinders, or tandem and ring were selected to accommodate the tumor and vaginal anatomy. The description also refers to CT and MRI scans, but further procedural detail is not reported in the registry record.

Allocation is recorded as NA, masking as NONE, and the model as SINGLE GROUP. There is no randomized parallel-group control in the registry description. The primary endpoint instead concerns image quality in shifted versus standard applicator positions. The subjective image assessment is described as blinded to image order; this specific procedure should not be interpreted as masking of the whole study. The registry record does not report a statistical analysis plan, a sample-size justification, or interim analyses.

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 Number of Participants With Improved Image Quality in the Shifted Position, measured over At the time of implant.

The primary endpoint is the number of participants with improved image quality in the shifted position, assessed at the time of implant. It is a participant count, rather than a continuous image-quality score or a clinical outcome. The registry describes subjective and objective assessment of image quality using the novel brachytherapy applicator.

For the subjective assessment, a radiation oncologist compared images taken in the shifted and standard positions without knowing which image came first. Concealing image order can reduce the chance that an assessor’s expectation about sequence influences the comparison. The record does not describe the rating scale, the rule for classifying a participant as improved, or whether any other assessors took part.

The objective assessment was intended to examine reduction in image artifact when the shields were shifted. The bladder, rectum, and sigmoid were contoured, and the average and standard deviation of Hounsfield units within these structures were compared between images. These measurements characterize image values in specified regions; the registry does not report the measurements or a threshold for meaningful improvement.

An image-quality endpoint is relevant to the stated planning question because the study sought to learn whether CT and MRI images could better help plan internal radiation treatment. However, an image-quality count alone does not establish how planning decisions or patient outcomes changed. The registry record does not report the primary endpoint result.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record identifies the primary outcome as a count of participants with improved image quality in the shifted position. It also describes how subjective image review and objective Hounsfield-unit measurements were intended to inform that assessment. The methods below explain how such data are generally interpreted; they should not be read as a claim that any unreported statistical procedure was used in this study.

What does a participant count represent?

A count records how many participants meet a stated outcome definition. To interpret a count as a rate or proportion, the denominator must also be known: the number of participants whose data were eligible for that outcome assessment. Enrollment is not automatically the same as the analysis denominator. Participants may lack usable images or may not have complete assessments, and the registry record does not report whether that occurred. Without a result count and denominator, neither the observed frequency nor its uncertainty can be established.

The outcome definition matters as much as the count. In this study, the registry refers to participants with improved image quality but does not state a rating scale, a decision threshold, or the precise rule used to classify improvement. A count can be reproduced and interpreted consistently only when the classification rule is clear. The record describes image comparisons but does not report those operational details.

How should a within-participant image comparison be understood?

The primary description compares images in shifted and standard positions. When two conditions are assessed within the same participant, the participant serves as their own reference for that comparison. This can account for stable participant characteristics that differ across people. It does not remove possible effects of acquisition order, image quality at baseline, positioning, or assessor judgment. Nor does it create a randomized comparison between treatment groups.

The registry says the radiation oncologist did not know which image was first and which was second when making the subjective comparison. In general, masking image order can reduce the influence of expectations based on sequence. It does not, by itself, establish that the assessor was unaware of every feature that could distinguish images, or that there was agreement between independent assessors. The record does not report those details.

What do the objective image measures add?

The described objective assessment used contours of the bladder, rectum, and sigmoid and compared average and standard deviation of Hounsfield units in those structures. In general, an average describes the central level of measured values in a region, while a standard deviation describes their spread around that average. The study description says these measurements were used to assess reduction in image artifact with shifted shields. The actual measurements, their variability, and any criterion for interpreting them are not reported in the registry record.

Objective measurements can complement subjective review by making the assessment more explicit. They still depend on how regions are contoured, which images are selected, and what comparison is specified. The registry description does not report contouring reliability, repeatability, or a statistical model for these measurements. No particular model or adjustment should therefore be attributed to the study.

What would uncertainty measures mean?

In general, a confidence interval describes a range of effect values compatible with the observed data under the assumptions of the analysis. A narrow interval indicates greater statistical precision than a wide interval, but neither guarantees that the outcome definition or analysis is free of bias. A p-value, when used, summarizes how unusual data would be under a specified null hypothesis and model; it does not measure clinical importance or the probability that a hypothesis is true.

The registry record reports no primary endpoint estimate, confidence interval, or p-value. Thus, there is no posted numerical estimate whose precision or statistical compatibility can be evaluated. A result count without a denominator would not be enough to recover that information, and deriving an estimate from unrelated enrollment or safety figures would be inappropriate.

What can be concluded from the registry’s analysis listing?

The record lists seven outcome measures and zero analyses. This means that outcome descriptions are present but analysis results are not reported in the registry record. It does not reveal whether analyses were conducted elsewhere, how outcomes were selected for analysis, or whether any analysis was prespecified. Those details are not reported in the registry record.

Multiplicity is a general issue when several outcomes or comparisons are assessed. Multiple tests can increase the chance of at least one apparently notable result if each is interpreted separately. Methods to address multiplicity depend on the analysis objectives and prespecified plan. Here, no multiplicity approach is reported, and no effect estimates are available to interpret. It would be unwarranted to infer a particular correction or testing strategy.

How should sample-size illustrations be read?

In general, a sample-size calculation is a planning exercise based on assumptions about an effect, variability, significance level, and desired power. It is not a study result and cannot show that a study had adequate power after the fact. The registry record does not report the trial’s own sample-size justification or analysis plan. Any planning illustration based on an observed effect should not be confused with an observed outcome or with the original design rationale. Since no primary effect estimate is reported, the registry information cannot establish whether the study was planned around a particular image-quality effect.

Overall, the methods description supports understanding of the intended image comparison, but it does not support reconstruction of the analysis. The outcome definition, denominator, observed count, uncertainty, statistical test, and handling of missing observations are not reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists seven outcome measures and zero analyses. It does not report a multiplicity strategy, such as prioritization of outcomes, adjustment of significance thresholds, or another prespecified approach. General concerns about multiplicity arise when several outcomes or comparisons are examined, but the record does not establish which analyses were conducted or how any findings were interpreted. No correction or testing procedure should be assumed.

The primary endpoint description gives the assessment timing as the time of implant and describes subjective and objective image assessments. It does not report the number of participants with evaluable images, the denominator used for the primary outcome, or the number of incomplete assessments. Missing-data definitions, reasons for missingness, and methods for handling missing observations are not reported in the registry record.

The enrollment is 57, but the record does not identify an analysis population or say that all enrolled participants contributed to every outcome. The safety listing reports 37 participants at risk in each adverse-event category. The relationship between these safety denominators and enrollment is not explained, and they cannot be treated as the primary outcome denominator.

The registry record also does not report an intention-to-treat or per-protocol population, a rule for excluding unusable images, or sensitivity analyses. These omissions limit assessment of how representative any outcome estimate would be, even if a count were available. No outcome estimate is posted, so the influence of missing data or multiplicity on a result cannot be evaluated.

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 0 serious adverse events among 37 participants at risk in the experimental brachytherapy treatment-planning group. It also lists 0 other adverse events among 37 participants at risk. A death count of 1 is listed separately. The record does not report a serious adverse-event term or other adverse-event term in the listed top terms.

These figures are safety listings, not results for the primary image-quality endpoint. The separate death listing does not establish that the death was caused by the applicator, imaging, or study procedures. The relationship of the death to the study is not reported in the registry record. Nor does the record provide enough information to determine the timing, circumstances, or completeness of adverse-event follow-up.

The safety denominator is 37, while total enrollment is listed as 57. The registry does not explain this difference, so these safety figures should not be generalized to all enrolled participants. A listing of zero events among those at risk is not proof that no harms occurred outside the recorded category, period, or group. It should be read narrowly as the posted event count and denominator, with the limitations of the registry information in mind.

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

The study addresses a technical question about image quality during intracavitary brachytherapy planning for cervical cancer. The registry describes a novel shielded applicator and a comparison of images acquired in shifted and standard positions. It also describes an assessor who was unaware of image order and objective measurements in the bladder, rectum, and sigmoid. These details explain the intended assessment, not its outcome.

The registry record does not report how many participants had improved image quality, the analyzed denominator, the measured Hounsfield-unit values, or an uncertainty estimate. It therefore does not establish the magnitude or precision of any image-quality difference. The absence of a posted result should not be interpreted as evidence of no difference, equivalence, or benefit.

Even a reported improvement in image quality would address an imaging measure, not necessarily the quality of a treatment plan or a patient outcome. The record does not report whether image findings changed treatment planning decisions, nor does it provide a clinical comparison that could establish an effect on health outcomes. No medical conclusion should be drawn from the stated study aim alone.

The single-group design and lack of randomized allocation also constrain what can be inferred. The image-position comparison is described within the study, but the record does not provide a separate randomized control group. Details about the image assessment rules, missing data, and statistical analysis are not reported. In short, the posted information characterizes the question and the planned measurements, while leaving the primary result and its interpretation unresolved.

13. Why This Trial Matters Statistically

This study is statistically interesting because its main question concerns a technical feature of image acquisition and interpretation rather than a conventional comparison of patient outcomes between randomized groups. The endpoint is a count of participants classified as having improved image quality in the shifted position. That classification depends on how improvement is defined, who assesses it, and which participants have evaluable images.

The registry describes two complementary forms of assessment. A radiation oncologist compared images without knowing their order, while objective assessment compared average and standard deviation of Hounsfield units within contoured critical structures. In general, combining subjective judgment with quantitative measurements can provide different perspectives on an imaging question. It does not eliminate the need for clear definitions, reliable measurement, and a transparent analysis plan.

The record also illustrates the distinction between a study’s stated question and a result that can be interpreted statistically. It reports an enrollment of 57 and lists seven outcomes, but no analyses and no primary outcome result. Without an estimate and its denominator, readers cannot judge the size, uncertainty, or consistency of the image-quality finding. Without a reported analysis plan, they also cannot assess whether outcome selection or multiplicity influenced interpretation.

Finally, a technical endpoint should be kept distinct from clinical impact. Image characteristics can be relevant to treatment planning, but an image-quality measure is not itself proof that planning or patient outcomes changed. This distinction is important when reading studies whose primary outcomes are imaging measurements rather than clinical endpoints.

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 main limitation for interpreting this trial is that the registry record does not report the primary endpoint result. There is no count of participants with improved image quality, no endpoint denominator, and no uncertainty estimate. The objective Hounsfield-unit measurements are described, but their values and analyses are not reported. The registry therefore does not permit an estimate of the observed image-quality effect.

The single-group design and allocation recorded as NA mean that the study is not described as a randomized comparison between groups. Its within-participant image-position comparison may inform the stated imaging question, but it does not provide the same evidence as a randomized group comparison. The masking entry is NONE, although the subjective assessment description says the radiation oncologist did not know the image order. The extent of masking beyond that specific assessment is not reported.

The primary endpoint’s classification rule, rating scale, and threshold for improvement are not reported. The record also omits the number of usable image assessments, handling of missing data, and the analysis population. Although seven outcome measures are listed, no analyses or multiplicity approach are reported. The statistical plan, sample-size justification, and interim analyses are not reported in the registry record.

Enrollment is listed as 57, while the safety group lists 37 participants at risk. The record does not explain how these figures relate. The safety information also does not state whether the listed death was related to study procedures. These gaps limit interpretation of both safety coverage and outcome completeness. Further conclusions would require results and methodological detail not reported in the registry record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Magnetic Resonance Imaging (MRI) Brachytherapy Applicator Study — NCT01706705.
• Registry record last updated 2022-02-23; status last verified 2022-01.
• Results first posted 2022-02-23.
• 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 record describes a completed, single-group study of a novel shielded applicator for intracavitary brachytherapy treatment planning in cervical cancer. Enrollment is listed as 57, and the primary outcome is the number of participants with improved image quality in the shifted position at the time of implant.

The outcome description includes subjective comparison by a radiation oncologist unaware of image order and objective Hounsfield-unit measurements in the bladder, rectum, and sigmoid. The registry lists seven outcome measures and zero analyses. It does not report the primary outcome count, denominator, statistical estimate, or uncertainty.

The safety listing reports 0 serious adverse events and 0 other adverse events among 37 participants at risk in each category, with 1 death listed separately. The relationship of the death to the study is not reported in the registry record. The record identifies the study question and measurement approach, but does not provide results sufficient to assess the primary image-quality finding.