Incorporating MR Imaging Into Prostate Radiotherapy Treatment Planning: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Incorporating MR Imaging Into Prostate Radiotherapy Treatment Planning (NCT02470910), a na na study. The primary outcome is Comparison of Rectal Volume Receiving 70 Gy or More With CT Versus MRI-planned Prostate Radiotherapy..

2. Clinical Question

The central question concerns treatment planning rather than a comparison of clinical outcomes between two assigned therapies. The primary endpoint is a dose-volume measure: the amount of rectum that a plan would expose to at least the stated dose threshold. The registry describes calculating this measure from a dose-volume histogram and comparing CT- and MRI-based plans within 1 year of the MRI examination.

The study’s stated purpose is to evaluate whether a standard prostate MRI examination can improve planning by helping limit radiation dose to normal tissues. The endpoint is therefore a planning measure related to radiation exposure, not a direct measure of symptoms, tumor control, or survival. The registry record does not report the observed rectal or bladder measurements, the size or direction of any difference between planning approaches, or an estimate of uncertainty. It also does not report whether the planned comparison favored either approach.

3. Trial Design

This is a completed, single-group pilot study sponsored by Dana-Farber Cancer Institute. The registry lists an enrollment of 15 and describes magnetic resonance imaging as the intervention. The study start is recorded as 2015-07 and primary completion as 2018-07. The phase is listed as NA. The record identifies the design model as single group and masking as none; allocation is listed as NA.

Participants underwent an MRI examination after intraprostatic fiducial markers had been placed and before radiotherapy began. The primary outcome compares the rectal volume receiving 70 Gy or more under CT-based and MRI-based prostate radiotherapy plans. The secondary outcome compares the bladder volume receiving the same threshold dose under those planning approaches. Both outcomes are planning comparisons, not randomized comparisons of patient groups receiving different treatments.

Because this is a single-group study, the CT- and MRI-based plans should not be described as independent randomized arms. The record does not specify the exact sequence of imaging or planning procedures beyond the intervention description, nor does it state whether each participant contributed measurements to both planning approaches. The statistical handling of any within-participant correlation is not reported in the registry record.

The registry identifies two outcome measures and zero analyses. It supplies outcome definitions and a timeframe of within 1 year of the MRI examination for the primary endpoint, but it does not post numerical outcome results, analysis estimates, confidence intervals, or p-values. The sample-size justification, recruitment targets beyond the recorded enrollment, and any interim analyses are not reported in the registry record. Consequently, the study design and outcome questions can be described, but the results cannot be used to quantify the observed comparison.

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 Comparison of Rectal Volume Receiving 70 Gy or More With CT Versus MRI-planned Prostate Radiotherapy., measured over within 1 year of MRI examination.

The primary endpoint is the rectal volume receiving 70 Gy or more, measured in cubic centimeters. The registry says this quantity is calculated from the dose-volume histogram and compared for CT- and MRI-based prostate radiotherapy plans within 1 year of the MRI examination. It specifies the median as the summary measure and the inter-quartile range as the measure of dispersion.

A dose-volume histogram describes how much of a structure receives particular dose levels. A volume defined at a dose threshold focuses attention on the part of the rectum exposed to at least that level in a treatment plan. Comparing the measure across planning approaches can describe whether the plans differ in the planned dose distribution to that structure. This is a planning endpoint, not a direct observation of injury or another clinical outcome.

General statistical context: A median describes the middle of an ordered set of measurements and is less affected by unusually high or low values than a mean. The inter-quartile range describes the spread across the middle portion of the observations. These summaries can be useful when measurements are skewed or when a small study may include influential values. They do not, by themselves, indicate the precision of a comparison or establish whether a difference is statistically distinguishable from chance.

The registry record does not report the observed median or inter-quartile range for either planning approach, nor a direct estimate of the contrast between them. It also does not report the corresponding numerical bladder outcome. Therefore, the endpoint definition is clear, but the magnitude and precision of the observed planning comparison are not available from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry specifies a median and inter-quartile range for the primary endpoint, which is the rectal volume receiving 70 Gy or more. It describes calculating this volume from a dose-volume histogram and comparing CT- and MRI-based plans. The record does not report the numerical summaries, a comparison estimate, or the analysis procedure used to obtain one.

What does a median describe?

General statistical context: The median is the central value when measurements are ordered. It is a useful summary when values are skewed or when a few observations are unusually large or small. It describes the location of the observations but does not show how much individual measurements vary or how precisely a contrast between approaches has been estimated.

The inter-quartile range summarizes the spread of the central portion of a distribution. A narrow range indicates that the middle observations are closer together than a wider range would indicate, but it does not provide a confidence interval for a treatment-planning contrast. The registry lists the inter-quartile range as the endpoint’s dispersion measure. It does not post the observed values for either planning approach, so the distributions and their overlap cannot be examined.

What does the dose-volume measure represent?

General statistical context: A dose-volume histogram relates radiation dose to the volume of a structure receiving that dose. A volume at a chosen threshold condenses that relationship into a clinically interpretable planning measure: the amount of a specified structure receiving at least the threshold dose. Here, the registry names the rectum as the primary structure and 70 Gy or more as the threshold. The secondary outcome applies the same threshold to the bladder.

This endpoint is a feature of a radiotherapy plan. It is not a direct measurement of a participant’s later symptoms, tissue injury, tumor response, or survival. A difference in a planning measure, if observed, would describe the plans on that measure. Connecting it to a clinical outcome would require evidence beyond the endpoint definition, and such evidence is not reported in the registry record.

How should a comparison of plans be understood?

The registry describes comparisons of CT- and MRI-planned radiotherapy, while the study model is single group and allocation is listed as NA. This is not a randomized two-arm clinical comparison. The record does not say whether every participant contributed a plan under each approach or describe the exact unit of analysis. It also does not report whether the comparison used participant-level paired measurements, an independent-samples method, or another procedure.

General statistical context: If two measurements come from the same participant, they are correlated rather than independent. An analysis that accounts for that relationship can use information in the within-participant contrast and generally has different uncertainty from an analysis that treats measurements as unrelated. If observations are independent, different methods may be appropriate. The method depends on how the data were collected and structured. Because the registry does not describe that structure or the analysis, the correct approach cannot be inferred.

What would uncertainty measures add?

General statistical context: A confidence interval for a contrast would communicate the precision of the estimated difference under the chosen analysis. Its width depends on factors including the amount of data and the variability of measurements. A p-value would address a prespecified statistical test, but it would not show the size or practical importance of a difference. Reporting both an estimate and an interval usually gives more information than a significance label alone.

No confidence interval, p-value, or numerical contrast for either outcome is reported in the registry record. The registry lists zero analyses, so there is no posted inferential result to interpret. Without those results, readers cannot assess the range of values compatible with the study data or whether the data distinguish a nonzero contrast from no contrast under any particular test.

What role would over-dispersion play?

General statistical context: Over-dispersion occurs when observed variability is greater than a statistical model assumes. When a model underestimates variability, standard errors may be too small and intervals too narrow. For this study, the registry does not identify a count model, variance model, or analysis that would make over-dispersion relevant to the primary endpoint. The endpoint is described as a volume summarized by a median and inter-quartile range, so no particular model or variance adjustment should be presumed.

How should planning illustrations be read?

General statistical context: Sample-size calculations can illustrate how many participants per arm might be needed under stated assumptions about an effect, variability, significance level, allocation, and statistical method. They are planning scenarios, not observed outcomes and not evidence that a completed study had a particular probability of detecting an effect. The registry’s planning assumptions describe 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 an observed effect. Those are planning assumptions, not a reported analysis of this single-group study.

The registry record does not report the trial’s own sample-size justification or statistical analysis plan. It therefore does not establish that these planning assumptions were used to design or analyze the study. Any planning illustration should be distinguished from the study’s observed enrollment of 15 and from the missing outcome analyses. The registry does not report a primary result from which a planning calculation could be checked against posted outcome estimates.

10. Multiplicity, Missing Data and Analysis Populations

The registry identifies a primary outcome comparing rectal volume receiving 70 Gy or more between CT- and MRI-planned radiotherapy and a secondary outcome comparing bladder volume at the same threshold. It records two outcome measures and zero analyses. No numerical outcome estimates or tests are reported in the registry record.

When a study evaluates more than one outcome or performs multiple statistical tests, the chance of at least one false-positive finding can increase if all tests are interpreted without accounting for multiplicity. General statistical context: A prespecified strategy may identify a primary outcome, define the role of secondary outcomes, or adjust inference across tests. The registry record does not report a multiplicity strategy, adjustment, or hierarchy beyond identifying primary and secondary outcomes. Since no inferential results are posted, it is not possible to determine how multiplicity was handled in practice.

The record does not report the number of participants with evaluable rectal or bladder measurements, reasons for missing measurements, or methods for handling missing data. It also does not identify an analysis population, such as whether analyses included all enrolled participants or only those with complete measurements. The enrollment of 15 should not be treated as evidence that every participant contributed data to each endpoint.

General statistical context: Missingness can affect estimates when the chance that a value is missing is related to the value itself or to other participant characteristics. Different approaches to incomplete observations rely on different assumptions. Without counts, reasons, and a stated analysis method, readers cannot judge whether missing data could have affected the planned comparisons. The registry record does not describe imputation, exclusions, or sensitivity analyses.

The sample-size justification, interim analyses, and complete statistical analysis plan are not reported in the registry record. No claims about their presence, absence in practice, or specific methods can be made from the posted entry.

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 records 15 participants at risk for serious adverse events and zero participants affected. It also records 15 at risk for other adverse events and zero affected, with zero deaths. These are the posted safety counts for the magnetic resonance imaging group.

These counts describe what the registry reports; they should not be interpreted as proof that no adverse event could occur. The record does not report event definitions, the method or frequency of safety monitoring, the duration of follow-up for adverse events, or whether event collection was limited to particular types. The listed counts alone also do not describe the nature or severity of any event beyond the reported zero counts.

General statistical context: A count of zero observed events is not equivalent to a demonstration that the underlying risk is zero. In a study with a limited number of participants, uncommon events may not be observed. Interpreting a zero count requires attention to the number monitored, the completeness and duration of monitoring, and how events were defined and recorded. Those details are not reported in the registry record.

The safety figures should therefore be read narrowly: the registry posted zero serious adverse events, zero other adverse events, and zero deaths among 15 participants at risk in the relevant categories. They do not establish a broader safety conclusion or compare safety between randomized groups, because the study is single group and has no randomized treatment comparison.

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

The registry record establishes that this completed pilot study examined MRI in prostate radiotherapy planning and defined comparisons for rectal and bladder dose-volume measures. The primary question concerns the rectal volume receiving 70 Gy or more under CT- versus MRI-based planning. The study enrolled 15 participants and describes MRI after intraprostatic fiducial marker placement and before radiotherapy.

What the record does not establish is the observed size or direction of either comparison. Numerical endpoint results, analysis estimates, confidence intervals, and p-values are not reported in the registry record. Consequently, the posted information cannot show whether the CT- and MRI-based plans differed, how large any difference was, or how precise an estimate might be. The absence of posted results is not evidence that the approaches produced identical measurements.

The outcomes are measures of planned radiation dose to normal tissues, not direct measures of patient symptoms or other clinical outcomes. Even if a planning contrast were available, it would need to be interpreted as a difference in the specified plan measure. The registry does not report a clinical-outcome analysis that would connect such a difference to later health effects.

The single-group design also matters. The record describes a comparison of planning approaches, not randomized assignment to separate clinical treatment arms. It does not report the details needed to determine how measurements from the two planning approaches were structured or analyzed. The study can therefore be described as a pilot planning evaluation, but the registry record does not support claims about comparative patient outcomes.

General statistical context: A statistically distinguishable difference and a clinically important difference are not the same question. A precise estimate may still be small, while a substantial estimate may be imprecise. Both the magnitude and uncertainty of a result are needed to judge what it indicates. Neither is available for the primary or secondary outcome in the registry record.

The safety counts report zero serious adverse events, zero other adverse events, and zero deaths among 15 participants at risk. Those counts are limited to the record and do not establish that risks are absent. Overall, the registry supports a description of the research question and its measurement approach, but not a conclusion about the results or their clinical implications.

13. Why This Trial Matters Statistically

This study asks a statistical question about how imaging choices relate to radiotherapy plan measurements. It distinguishes a dose-volume endpoint from patient-level clinical outcomes and specifies a threshold-based measure for rectal exposure, with a corresponding bladder measure as a secondary outcome. Clear endpoint definitions help readers understand what a comparison is intended to quantify.

The design also illustrates why the structure of observations matters. A single-group planning study is not the same as a randomized comparison of treatment arms. If the same participants contribute plans under both imaging approaches, measurements may be related within each participant; if the data are structured differently, another analysis may be appropriate. The registry record does not report the data structure or analysis method, so the comparison cannot be evaluated statistically beyond its stated definition.

The record identifies the median and inter-quartile range for the primary endpoint. These summaries describe the center and spread of measurements, but they do not replace an estimate of the contrast and its uncertainty. This distinction is important in small pilot studies: descriptive summaries can characterize observed data, while confidence intervals and an explicit analysis would be needed to assess precision. Here, no numerical outcome results or analyses are reported.

The entry also shows why outcome reporting is essential. A stated research question and defined endpoints do not tell readers what the study observed. Without posted estimates, the direction, magnitude, and precision of the comparisons remain unknown. The planning assumptions recorded for sample-size illustrations should not be confused with evidence of observed effects or with the study’s own design justification.

For biostatistical interpretation, the trial therefore provides a useful example of the difference between a well-described measurement question and an interpretable result. It identifies what was intended to be measured and records an enrollment of 15, but leaves the central quantitative comparison and key analysis details unreported in the registry record.

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 interpreting the study is that no numerical results are reported for either listed outcome. The registry record does not give the rectal or bladder summaries, a contrast between planning approaches, or uncertainty measures. This prevents assessment of direction, magnitude, and precision.

The record lists zero analyses and does not describe the statistical method used for the CT- and MRI-based plan comparisons. It does not say whether each participant contributed data under both planning approaches, how any within-participant dependence was handled, or what unit of analysis was used. These details are important for understanding how a contrast and its uncertainty would be estimated.

The study enrolled 15 participants. The registry record does not report the number with evaluable measurements for each outcome, reasons for any missing data, or the analysis population. It also does not report a sample-size justification, a statistical analysis plan, or interim analyses. Thus, the intended precision and the handling of incomplete observations cannot be assessed from the registry entry.

The design is single group, with allocation listed as NA and masking listed as none. It is not a randomized comparison between two treatment arms. Any comparison is about CT- and MRI-based plans, and the registry does not report clinical outcome results that would establish effects on symptoms or other patient outcomes. This limits the types of conclusions that the design and posted information can support.

The registry describes the primary endpoint as rectal volume receiving 70 Gy or more and specifies a timeframe within 1 year of MRI examination. It does not report the timing of measurements in greater detail, the specific plan-generation procedures, or how potential variation across participants was addressed. The same absence of numerical and analytic detail applies to the secondary bladder outcome.

Finally, the safety record gives zero serious adverse events, zero other adverse events, and zero deaths among 15 participants at risk, but does not describe event definitions or monitoring duration. These counts should not be generalized beyond the recorded study information.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Incorporating MR Imaging Into Prostate Radiotherapy Treatment Planning — NCT02470910.
• Registry record last updated 2019-12-11; status last verified 2019-12.
• Results first posted 2019-11-27.
• 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 registry describes a completed, single-group pilot study of MRI-informed prostate radiotherapy planning, sponsored by Dana-Farber Cancer Institute. It records enrollment of 15, with a study start of 2015-07 and primary completion of 2018-07. The intervention is an MRI examination after intraprostatic fiducial markers are placed and before radiotherapy begins.

The primary outcome compares rectal volume receiving 70 Gy or more under CT- and MRI-based plans, summarized by median and inter-quartile range. A secondary outcome compares bladder volume at the same dose threshold. The registry lists two outcome measures and zero analyses.

Numerical outcome results and analysis estimates are not reported in the registry record. The safety counts are zero serious adverse events, zero other adverse events, and zero deaths among 15 participants at risk in the recorded categories.