Stereotactic Body Radiation Therapy (SBRT) for Tumors Near the Spinal Cord: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Stereotactic Body Radiation Therapy (SBRT) for Tumors Near the Spinal Cord (NCT00631670), a non-randomized na study. The primary outcome is Toxicity.

2. Clinical Question

Statistically, the study asks about toxicity under different SBRT schedules in a population selected for treatment according to clinical and patient considerations. It does not establish a randomized comparison of those schedules. The registry also lists Local Control, Neurologic Function, Pain Relief, and Overall One Year Survival as secondary outcomes. Their outcome results are not reported in the registry record. The posted adverse-event entries provide some safety counts, but they do not supply a complete comparison of toxicity between treatment schedules.

3. Trial Design

This was a completed, parallel, non-randomized study of SBRT for tumors near the spinal cord. The registry lists the allocation as NON RANDOMIZED and masking as NONE. It records enrollment of 21 and identifies spinal tumors as the condition. The phase is listed as NA. The sponsor was the University of Florida. The study start is recorded as 2005-10 and primary completion as 2008-10.

The two treatment schedules were a single SBRT treatment of 15 Gy and a course of 25 treatments, described as 70 Gy at 2.8 Gy per treatment. The brief summary says the protocol used life expectancy, patient preference, and tumor size to determine which schedule was delivered. Because assignment was not randomized and treatment choice reflected these factors, participants in the groups may have differed before treatment. The registry record does not report enough information to assess the magnitude or direction of those differences.

A parallel design assigns participants to treatment groups that proceed alongside one another, rather than having each participant receive both schedules. In a randomized trial, random assignment is used to make treatment groups comparable on average. That protection does not apply to this study. Any contrast between its schedules could reflect differences in who received each schedule, the schedules themselves, or both. This is why the registry record’s non-randomized designation matters to interpretation.

The record lists five outcome measures and four secondary outcome topics: Local Control, Neurologic Function, Pain Relief, and Overall One Year Survival. It describes toxicity as the primary outcome, with acute and late assessment, and a timeframe of 2 yrs. The record does not report a statistical analysis plan, treatment-group results for the primary outcome, or details of how the outcome measures were analyzed. A rationale for the enrollment target and the trial’s original sample-size justification are not reported in the registry record.

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 Toxicity, measured over 2 yrs.

The primary outcome is Toxicity, measured as the number of participants. The registry describes grading with the RTOG-EORTC system and also an informal classification of complications as mild, moderate, or severe according to their perceived effect on overall quality of life. Toxicity was divided into acute events, meaning during treatment, and late events, meaning several months after treatment ended. The stated timeframe is 2 yrs.

Toxicity is relevant to evaluating a radiation treatment because complications are an important part of describing the experience of treatment, alongside outcomes such as local control, neurologic function, pain relief, and survival. Recording both timing and severity can help distinguish events arising during treatment from those occurring later, and can describe the range of reported complications. The registry does not explain how the formal grading and informal severity classification were combined or prioritized in the primary outcome analysis. That detail is not reported in the registry record.

The posted adverse-event figures are not the same as a complete report of the primary endpoint. They give serious-event and other-event counts for the Single Treatment Group, but list no participants at risk in the 25 Treatments Group. Arm-specific results for the described primary toxicity endpoint, including its severity categories and acute-versus-late breakdown, are not reported in the registry record. The available counts therefore support only a limited description of recorded adverse events, not a full treatment-schedule comparison.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does non-randomized allocation imply?

In general, random allocation helps separate treatment assignment from participant characteristics that may influence outcomes. This trial did not use random allocation. Its brief summary says life expectancy, patient preference, and tumor size informed whether a participant received 1 or 25 treatments. Those factors may also be related to toxicity or other outcomes. Consequently, a difference between the groups, if one were reported, could reflect differences in participant characteristics as well as differences in treatment schedule. Statistical adjustment can sometimes account for measured characteristics, but it cannot guarantee removal of bias from unmeasured or poorly measured factors. The registry record does not report an adjusted comparison.

The parallel structure means participants were assigned to a schedule rather than each participant serving as their own comparison across schedules. The registry lists masking as NONE. Without masking, outcome assessment may be more susceptible to knowledge of the treatment schedule, particularly when judgments include an informal assessment of effects on quality of life. This is a general methodological concern; the registry record does not report whether or how assessors’ knowledge affected classification.

How should event counts be interpreted?

The primary outcome is described as a participant count, and the posted adverse-event entries use counts of participants at risk and affected. For the Single Treatment Group, the registry lists 21 at risk for serious events and 0 affected, and 21 at risk for other events and 14 affected. For the 25 Treatments Group, the entries list 0 at risk and 0 affected in both categories. A zero count among participants at risk is different from a zero count paired with no participants at risk: the former records no events in the listed group; the latter does not provide an observed denominator from which to describe an event frequency.

In general, binary outcomes are often summarized by the number of participants with an event and the number assessed or at risk. The denominator matters because it defines the observed group from which the count comes. Event counts alone do not convey uncertainty, differences in follow-up, or severity. A confidence interval can express uncertainty around an estimate, but it does not remedy an incomplete denominator, an unclear endpoint definition, or non-randomized selection. The registry record does not report confidence intervals or a statistical comparison of the adverse-event counts.

What do the endpoint definitions contribute?

The registry describes toxicity grading using the RTOG-EORTC system and an additional informal severity assessment. It distinguishes acute toxicity during treatment from late toxicity several months after treatment ended, with a stated timeframe of 2 yrs. In general, explicit definitions and consistent assessment schedules help readers determine what events count and when they were sought. The record does not report the operational details needed to understand how the two grading approaches were reconciled, how missing assessments were handled, or how event timing was summarized.

What can the sample-size illustrations establish?

The statistical planning illustrations are based on the observed effect and assume a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation. They are illustrations of the sample size that would be associated with specified effect assumptions, not evidence of the study’s original design rationale. The registry record does not report the original sample-size justification or enough outcome-analysis detail to establish that these assumptions governed the trial. Such planning figures are not observed power. In general, power is a design-stage probability under specified assumptions; a calculation using an observed effect after the study does not establish the probability that the completed study detected a true effect.

What analyses are available?

The registry lists five outcome measures but no analyses. The posted information therefore does not establish which statistical tests, models, or adjustment procedures were used for the primary endpoint or secondary outcomes. In general, a statistical analysis plan would clarify the target contrast, outcome definitions, handling of repeated or incomplete observations, and the approach to uncertainty. Those details are not reported in the registry record. Without them, readers should rely on the explicitly posted counts and avoid interpreting them as results of an undocumented comparative analysis.

Over-dispersion is a general issue for count outcomes when variability exceeds what a chosen statistical model expects. It may affect uncertainty estimates if such a model is used. The posted primary outcome is described as participant counts, and the registry does not report a model for these results, so there is no basis to conclude that an over-dispersion adjustment was relevant or performed. More broadly, no statistical method can turn the 25 Treatments Group’s zero at-risk entries into an informative observed comparison. The basic limitation is the absence of recorded participants at risk in that group.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists five outcome measures, including toxicity as the primary outcome and Local Control, Neurologic Function, Pain Relief, and Overall One Year Survival as secondary outcomes. It does not report a statistical analysis plan or analyses. The approach to multiplicity—how the possibility of chance findings across multiple outcomes or analyses was addressed—is not reported in the registry record. Without that information, the secondary outcomes cannot be interpreted as a set of confirmatory statistical tests, and no adjustment procedure should be assumed.

The registry record does not report how missing observations were defined or handled, whether follow-up differed by schedule, or how participants with incomplete outcome assessments were treated in analyses. It also does not describe analysis populations, such as whether results were based on everyone enrolled or on a subset with available outcome data. These details matter because incomplete follow-up can change both the denominator and the interpretation of an event count.

For the adverse-event entries, the Single Treatment Group has participants recorded at risk, while the 25 Treatments Group has none recorded at risk. The latter entries should not be interpreted as a complete observation of zero events. The reason for those entries is not reported in the registry record. The primary toxicity outcome results by treatment schedule, missing-data handling, and the analyses supporting the listed outcome measures are likewise not reported in the registry record. These gaps limit both within-group descriptions and any comparison across schedules.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

Most frequent non-serious adverse event terms

The registry lists 0 serious adverse events among 21 participants at risk in the Single Treatment Group. It separately lists 14 participants affected by other adverse events among 21 at risk. These are descriptive counts in distinct registry categories; they do not give details about event severity, timing, or individual event types. The serious adverse-event terms are not listed.

For the 25 Treatments Group, the registry lists 0 participants at risk and 0 affected in both the serious and other adverse-event categories. This is not evidence that no adverse events occurred in that group. With no participants recorded at risk, the entries do not supply an observed group denominator for interpreting events.

In general, a safety count should be read alongside its at-risk population, the event definition, and the observation period. The posted figures do not provide a complete toxicity comparison between schedules or a full account of the primary endpoint. The reason the second group has no participants recorded at risk is not reported in the registry record.

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

The posted information establishes that the registry describes a completed, non-randomized SBRT study with enrollment of 21 and a primary endpoint of toxicity over 2 yrs. It records adverse-event counts for the Single Treatment Group: 0 serious events among 21 participants at risk, and 14 participants with other events among 21 at risk. It does not provide a usable adverse-event denominator for the 25 Treatments Group, which is listed with 0 participants at risk.

These observations do not establish whether either schedule is more effective or safer. The primary endpoint’s arm-specific results are not reported in the registry record, and the posted adverse-event figures do not describe the full severity and timing assessment. The registry also lists secondary outcomes, but their results are not reported. A comparison would be especially difficult to interpret because treatment assignment was non-randomized and was informed by life expectancy, patient preference, and tumor size.

In general, statistical precision concerns how much uncertainty surrounds an estimate; it is not the same as validity. Even a precise estimate can be biased if groups differ in important ways, while an incomplete denominator can prevent a meaningful estimate from being formed at all. The record does not report inferential analyses or confidence intervals for toxicity. Therefore, the posted counts should be read as limited descriptive safety information, not as a precise estimate of comparative risk.

The study also cannot be used to infer that the schedules are equivalent or that an event-free observation proves the absence of risk. A lack of reported results is not a null finding. The registry record does not provide the primary outcome comparison, the relevant data for the 25 Treatments Group, or the analysis details needed to draw stronger conclusions. These distinctions describe the reach of the posted evidence without making a treatment recommendation.

13. Why This Trial Matters Statistically

This trial is statistically instructive because it shows how allocation and reporting shape what can be learned from clinical outcomes. Although the registry describes two SBRT schedules, allocation was non-randomized and depended on life expectancy, patient preference, and tumor size. The groups therefore do not function as a like-for-like control comparison. This design feature affects interpretation even before considering the small enrollment or the outcome data that are absent.

The safety entries also illustrate why numerators and denominators must be read together. For the Single Treatment Group, the registry records participants at risk and reports event counts. For the 25 Treatments Group, no participants are recorded at risk. The zero event entries in that group cannot be read as a zero event rate or as evidence of no toxicity. A numerical field can appear complete while still lacking the information required for a useful comparison.

The registry’s primary endpoint description includes formal grading, an informal severity assessment, and a distinction between acute and late toxicity. Yet arm-specific primary endpoint results and details of the analysis are not reported in the registry record. This highlights the difference between defining an outcome and publishing results that allow readers to evaluate it. Outcome labels alone do not reveal how assessments were combined, how follow-up was handled, or how uncertainty was quantified.

Finally, planning illustrations based on an observed effect should not be confused with the rationale for the original enrollment target or with observed power. In general, design assumptions and post-study calculations answer different questions. The registry does not report the original sample-size justification. Keeping these distinctions clear helps prevent a limited set of descriptive counts from being interpreted as a definitive comparative result.

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 immediate limitation is incomplete safety information for the 25 Treatments Group: the registry lists 0 participants at risk and 0 affected in the serious and other adverse-event categories. The reason is not reported in the registry record. This prevents a meaningful adverse-event comparison with the Single Treatment Group.

The study was non-randomized, and schedule selection was informed by life expectancy, patient preference, and tumor size. These factors may be related to outcomes, so the groups may differ in ways that complicate comparisons. The registry record does not report baseline characteristics or adjusted analyses that would help assess or account for such differences.

The primary toxicity endpoint is described, but its arm-specific results are not reported in the registry record. The available adverse-event entries do not provide severity distributions, acute-versus-late counts, or an explanation of how the formal and informal grading approaches were combined. Follow-up completeness, missing-data handling, and analysis populations are also not reported.

The record lists five outcome measures but no analyses. It does not report a statistical analysis plan, multiplicity procedures, confidence intervals, or inferential comparisons. Results for the listed secondary outcomes are not reported in the registry record. Consequently, the posted information supports only a narrow descriptive reading of the Single Treatment Group’s adverse-event counts and does not support a complete assessment of toxicity or comparative outcomes across schedules.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Stereotactic Body Radiation Therapy (SBRT) for Tumors Near the Spinal Cord — NCT00631670.
• Registry record last updated 2012-02-03; status last verified 2010-06.
• Results first posted 2012-01-25.
• 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, parallel, non-randomized study evaluated SBRT schedules for tumors near the spinal cord. Enrollment was 21. The registry lists the sponsor as the University of Florida, the phase as NA, the study start as 2005-10, and primary completion as 2008-10.

The schedules were one treatment of 15 Gy and 25 treatments described as 70 Gy at 2.8 Gy per treatment. The primary outcome was toxicity over 2 yrs, with formal and informal severity descriptions and acute and late categories. The registry lists Local Control, Neurologic Function, Pain Relief, and Overall One Year Survival as secondary outcomes.

For the Single Treatment Group, the registry records 0 serious adverse events among 21 at risk and 14 participants with other adverse events among 21 at risk. The 25 Treatments Group has 0 participants recorded at risk. Primary endpoint results by schedule, secondary outcome results, and statistical analyses are not reported in the registry record. Non-randomized allocation and incomplete group-level safety information limit comparative interpretation.