Stereotactic Body Radiation Therapy (SBRT) for Lung Tumors: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Stereotactic Body Radiation Therapy (SBRT) for Lung Tumors (NCT00632281), a na na study. The primary outcome is Disease Status.

2. Clinical Question

3. Trial Design

This was a completed, single-group study of SBRT for tumors in the thorax, sponsored by the University of Florida. The registry lists an enrollment of 38 and a study population description of 38 patients with 44 treated lesions. The study began in 2006-01 and reached primary completion in 2008-10. The registry status is completed.

There was no randomized allocation and no masking. The registry lists one radiation intervention, stereotactic body radiation therapy. The study description specifies treatment using intensity-modulated radiation therapy or three-dimensional conformal beams and says patients received 48 Gy or 60 Gy depending on tumor type. The description notes that the majority of patients were treated in 1 week, Monday through Friday, with Wednesday off. It does not provide a treatment assignment algorithm or further detail about how dose or beam technique was selected.

The population description includes primary lung cancer and metastatic disease. Of 32 primary lung cancer patients, 22 had biopsy-proven non-small cell lung cancer, with stage IA and stage IB cases recorded. Six patients had metastatic disease, and six patients had 2 lesions treated. These figures describe the population as recorded; they do not establish that every outcome was analyzed using the same unit. In particular, the primary outcome description refers to percentages of participants while its local-control definition refers to tumors.

Because this is a single-group study, the design can describe outcomes observed after treatment but cannot, on its own, estimate a treatment contrast against a concurrent control group. The registry record does not report a statistical analysis plan, a sample-size justification, or details of an interim analysis. The record lists no analyses for the primary outcome.

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

Analysis population for the primary outcome, as defined in the registry: 44 lesions in 38 patients were treated with IMRT or 3D conformal beams on a prospective trial examining thoracic SBRT. Twenty-two of 32 primary lung cancer patients had biopsy-proven NSCLC (stage IA, 21 patients; stage IB, 11 patients). Six had metastatic disease. Six patients had 2 lesions treated simultaneously.

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 Disease Status, measured over 2 yrs.

The primary outcome is titled “Disease Status,” with a timeframe of 2 yrs. Its description names four measures: local control, cause-specific survival, overall survival, and freedom from failure. Local control is defined as the percentage of tumors that did not recur at the treated site 2 years after treatment. Cause-specific survival concerns the percentage of patients who had not died from the disease under study in the 2 years since treatment. Overall survival concerns the percentage still alive at 2 years after treatment. Freedom from failure concerns the percentage of patients whose treated disease had not progressed or recurred in the 2 years since treatment.

These measures address different aspects of disease status. Local control focuses on recurrence at the treated site, while survival measures distinguish death from the disease under study from death from any cause. Freedom from failure combines progression or recurrence in its definition. Such outcomes can be useful for describing what happened after local treatment, but they are not interchangeable: the event, unit of observation, and denominator may differ.

The registry labels the outcome unit as a percentage of participants, yet the local-control definition refers to tumors. The population description includes 44 lesions in 38 patients, so the distinction between lesion-level and patient-level measurement matters when interpreting a percentage. The registry record does not report numerical values for these primary measures, their denominators, or methods for handling multiple lesions in a patient. It therefore supports explanation of the intended endpoint, but not an estimate of the observed disease-status outcomes.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a percentage describe?

A percentage expresses how many observations in a defined group met an outcome, relative to the denominator used for that outcome. Interpretation depends on knowing both what counts as an event and who or what is included in the denominator. A percentage of participants is not necessarily equivalent to a percentage of tumors, particularly when some patients have more than one treated lesion. The registry describes 44 lesions in 38 patients and names both participant-based and tumor-based outcome concepts. It does not report the outcome-specific denominators or explain how multiple lesions within a patient were handled.

For survival outcomes, the definition also matters. Cause-specific survival concerns death attributed to the disease under study, whereas overall survival concerns whether a patient remains alive regardless of cause. Local control is about recurrence at the treated site, and freedom from failure concerns progression or recurrence of treated disease. These distinct outcomes can have different events and denominators, so they should not be combined into a single interpretation without an explicit analysis definition. The registry groups these measures under “Disease Status” but does not report numerical results for any of them.

Why does a single-group design affect interpretation?

In a single-group study, the observed outcome describes the participants who received the intervention. A treatment effect, in contrast, is a comparison between outcomes under alternative treatment conditions. Without a comparator group, the record cannot directly separate the effects of SBRT from the natural course of disease, patient characteristics, or other care. This is a general principle of comparative inference, not a claim about what happened to any individual in this study.

The registry lists no randomized allocation and no masking. Randomization is a general method for reducing systematic differences between treatment groups, while masking can reduce some kinds of knowledge-related bias in outcome assessment. Neither feature creates a comparison when there is only one study group. The record does not report further safeguards or assessment procedures, so their use cannot be inferred.

What do uncertainty estimates contribute?

A confidence interval is a general statistical tool for showing a range of estimates compatible with the data and analysis assumptions. Its width conveys precision: broader intervals indicate more uncertainty about the estimate, while narrower intervals indicate greater precision. A point estimate without an interval gives less information about uncertainty. The registry record does not report confidence intervals for the primary outcomes, so their precision cannot be judged from the posted record.

A p-value, when reported, addresses how compatible data are with a specified statistical null model under the assumptions of the analysis. It is not a measure of the probability that a treatment works, nor does it communicate the size or clinical importance of an effect. No primary-outcome p-values are reported in the registry record. The absence of such values should not be interpreted as evidence for or against an outcome.

How should event counts and safety percentages be read?

Counts and percentages describe recorded events within a stated group. Their meaning depends on the event definition, observation period, denominator, and whether the count refers to participants or events. When the same participant may experience more than one event, event counts and numbers of affected participants answer different questions. The registry lists participants at risk and affected for serious and other adverse events, along with selected serious-event terms. It does not give the detailed event-level information or definitions needed to establish how entries were grouped.

Over-dispersion is a general issue that can arise when variation in data is greater than a statistical model expects. If present, it can make standard errors and resulting uncertainty estimates misleading unless the analysis accounts for it. The registry record does not report an outcome model or diagnostic assessment, so whether over-dispersion was relevant cannot be determined.

What can planning calculations tell readers?

Sample-size planning is a general exercise for estimating how much information a future study might need to detect a specified effect under stated assumptions. A planning illustration based on an observed effect is not an observed-power result and does not establish that the original study was adequately powered. The registry record does not report the primary outcome estimates needed to assess such an illustration, nor does it give the trial’s own sample-size justification. It would therefore be inappropriate to infer the design rationale or statistical power from the enrollment alone.

The record lists 0 analyses for the primary outcome. This describes what is recorded in the registry; it does not establish that no analysis was conducted elsewhere. The statistical model, handling of missing observations, adjustment for multiple outcomes, and analysis population are not reported in the registry record. These omissions limit reproducibility and make it difficult to determine how an outcome estimate, if reported elsewhere, was obtained.

10. Multiplicity, Missing Data and Analysis Populations

The primary outcome description contains four disease-status measures: local control, cause-specific survival, overall survival, and freedom from failure. Testing or estimating several outcomes raises a general multiplicity question: whether the analysis plan treats them as separate outcomes, defines a hierarchy, or adjusts interpretation for multiple comparisons. The registry record does not report a multiplicity strategy, so it is not possible to determine whether or how multiplicity was addressed. No p-values or numerical primary-outcome results are recorded.

The record lists 0 analyses for the primary outcome. This means the registry does not contain a recorded analysis for that outcome; it does not prove that analyses were not performed elsewhere. The statistical plan and analysis population are not reported in the registry record. In particular, the record does not state which patients or lesions were included in each endpoint analysis, or how outcomes for multiple lesions in one patient were handled.

Missing-data handling is also not reported in the registry record. The entry does not describe whether any observations were missing, how missing outcome status was treated, or whether patients without complete follow-up were included in a particular analysis. These are important details because the interpretation of a percentage or survival measure depends on who contributes information and how unavailable observations are addressed.

The registry provides a 2 yrs timeframe for the primary outcome, but does not report the follow-up distribution or outcome-specific denominators. It therefore does not show how many participants or lesions contributed to each measure or how incomplete follow-up may have affected the reported results. These gaps limit assessment of the completeness and reproducibility of any outcome analysis.

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 1% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: grade 3 fev1 (44.7%), grade 3 dyspnea (23.7%), grade 3 vital capacity (15.8%), grade 4 fev1 (5.3%), grade 3 dermatitis (2.6%).

The registry’s adverse-event entry identifies an “All Patients Receiving SBRT to Thorax” group. It records 38 participants at risk for serious adverse events, with 20 affected, and 38 at risk for other events, with 38 affected. The record also lists serious-event terms with percentages: Grade 3 FEV1, 44.7%; Grade 3 Dyspnea, 23.7%; Grade 3 Vital Capacity, 15.8%; Grade 4 FEV1, 5.3%; and Grade 3 Dermatitis, 2.6%.

These figures should be read as registry-reported safety entries, not as a comparison of treatment-related risk against another group. The study has no comparator arm, and the record does not report the definitions, observation windows, or ascertainment procedures for these entries. The listed percentages are attached to specific event terms; the record does not provide corresponding counts for those terms or clarify whether participants could appear under more than one term. They should not be added together or interpreted as mutually exclusive categories.

The registry distinguishes serious events from other events, but the detailed criteria used for those categories are not reported in the registry record. The entry also does not establish causation: a recorded event among treated participants does not by itself show that SBRT caused it. The safety information is useful as a description of what the registry records, but it does not support a controlled estimate of attributable harm or a complete account of safety.

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

The record describes a completed study of SBRT for thoracic tumors and identifies the disease-status outcomes the investigators intended to assess. It also documents a single-group design, the treatment approach, a population of patients and treated lesions, and selected adverse-event entries. These registry entries provide context for understanding the study’s aims and the type of evidence it could generate.

The record does not report numerical results for local control, cause-specific survival, overall survival, or freedom from failure. It therefore does not show the observed values of the primary outcomes or their precision. Without those estimates and the relevant denominators, readers cannot quantify the disease-status outcomes from the registry record.

Even if outcome percentages were available, a single-group study would describe outcomes among treated participants rather than establish a causal treatment effect against another strategy. The absence of a concurrent comparator prevents a like-for-like assessment of what outcomes might have been under an alternative treatment. No statement about benefit or lack of benefit can be drawn from the design description alone.

The safety entry identifies serious and other adverse events and lists selected serious-event terms. Those data do not provide a controlled comparison or enough methodological detail to attribute events to treatment. The absence of reported outcome analyses, uncertainty estimates, and details on missing data and analysis populations further limits interpretation.

Accordingly, the strongest reading is descriptive: the registry documents the study’s setup, planned outcome concepts, and selected safety information, while leaving the primary outcome results unavailable in the registry record. The record cannot establish the magnitude or precision of disease control or survival outcomes, nor can it isolate treatment effects from other explanations.

13. Why This Trial Matters Statistically

This study illustrates why design and outcome definitions need to be read alongside a trial’s stated purpose. The registry describes SBRT for thoracic tumors and names several clinically distinct disease-status measures, but the record does not report their numerical results. A title or outcome definition alone cannot tell readers what was observed or how precisely it was estimated.

The single-group structure is statistically consequential. It can document outcomes among treated patients, but it does not provide a concurrent control contrast. Descriptive outcomes and comparative treatment effects answer different questions, and the design recorded supports the former more directly than the latter. This distinction remains important even when a study is completed and the registry includes safety entries.

The population description also highlights the importance of the unit of analysis. It refers to both patients and lesions, while the primary outcome description uses participant percentages for the outcome unit and defines local control in terms of tumors. When a patient can contribute more than one lesion, analysis and denominator choices matter. The registry record does not explain how that issue was addressed.

Finally, registry completeness affects statistical interpretation. The absence of primary-outcome estimates, uncertainty measures, and details about analysis populations, missing data, and multiplicity leaves important questions unresolved. These omissions do not show that an analysis was absent outside the registry, but they constrain what can be evaluated from the record. This makes transparent outcome reporting essential for assessing both the findings and their limitations.

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 primary limitation for statistical interpretation is that numerical results for the stated disease-status outcomes are not reported in the registry record. The record therefore does not provide outcome estimates, denominators, confidence intervals, or other measures of uncertainty for local control, cause-specific survival, overall survival, or freedom from failure.

The design is single-group, with no randomized allocation and no comparator group. As a result, the record cannot support a direct comparison with another treatment strategy. The absence of a control group limits causal interpretation of any observed outcome, even if results are available elsewhere.

The population description refers to 38 patients and 44 lesions, while the primary outcome is generally described as a percentage of participants and local control as a percentage of tumors. The registry record does not clarify which unit and denominator were used for each outcome, or how multiple lesions within a patient were handled. It also does not report outcome-specific follow-up or analysis populations.

Details about the statistical plan, missing-data handling, multiplicity, and outcome analysis methods are not reported in the registry record. The record lists 0 analyses for the primary outcome, which indicates that no such analysis is recorded there, not that no analysis occurred elsewhere. Safety entries likewise lack detailed definitions and ascertainment information. These limitations prevent a complete assessment of the reported methods and results from the registry alone.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Stereotactic Body Radiation Therapy (SBRT) for Lung Tumors — NCT00632281.
• Registry record last updated 2012-02-20; status last verified 2010-06.
• Results first posted 2012-02-20.
• 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 record describes NCT00632281, a completed, single-group study of stereotactic body radiation therapy for tumors in the thorax, sponsored by the University of Florida. The listed enrollment is 38. The outcome description refers to 38 patients and 44 treated lesions, including patients with primary lung cancer and metastatic disease. Treatment was described as 48 Gy or 60 Gy depending on tumor type, using intensity-modulated radiation therapy or three-dimensional conformal beams.

The primary outcome, “Disease Status,” has a timeframe of 2 yrs and includes local control, cause-specific survival, overall survival, and freedom from failure. Numerical results for these measures are not reported in the registry record. The record lists safety entries for serious and other events and selected serious-event terms. With no comparator group and no recorded primary-outcome analysis, the registry supports a description of study design and intended outcomes but not an estimate of comparative treatment effects.