Evaluating Stereotactic Body Radiation Therapy for Oligometastatic Disease of the Bone: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Evaluating Stereotactic Body Radiation Therapy for Oligometastatic Disease of the Bone (NCT02880319), a non-randomized phase 2 study. The primary outcome is The 6-month Local Control Rate of SBRT.

2. Clinical Question

The clinical question is about local control at treated bone or spine sites, rather than a direct comparison with another treatment. The primary endpoint description defines local control as being free of local failure at the specified follow-up time. It does not state an expected rate or a threshold that would count as successful treatment.

The record also lists outcomes concerning local progression-free survival, progression-free survival, overall survival, and patient-reported quality of life. These outcomes address different aspects of disease course and participant experience; they should not be treated as interchangeable with local control. The record does not report results for them.

3. Trial Design

This is a Phase II study sponsored by Dana-Farber Cancer Institute. It is registered as non-randomized, with no masking and a single-group model. The record lists enrollment of 150. The status is active, not recruiting. The study start is listed as 2016-11-29, and primary completion as 2022-05.

The record describes two treatment cohorts: Oligometastatic Disease and Re-irradiation to Metastatic Disease. The first description specifies SBRT to up to 3 sites of disease in bone or spine. The second specifies SBRT to site or sites of disease in bone or spine. Both descriptions name a dedicated stereotactic linear accelerator with onboard conebeam CT imaging and orthogonal 2D/3D matching with a robotic couch top. The descriptions do not provide complete dose details; these are not reported in the registry record.

Because allocation is non-randomized and the model is listed as single-group, the cohorts should not be interpreted as randomized treatment arms. Their different clinical contexts also mean that a simple contrast between their outcomes would not establish a treatment effect. The record does not report a concurrent untreated group or another randomized control group.

The primary outcome is the 6-month local control rate, expressed as the proportion free of local failure. The listed secondary outcomes include 1-year local progression-free survival, 2-year progression-free survival, 2-year overall survival, and acute and chronic patient-reported quality of life. Although the record lists six outcome measures, it contains no analysis entries. The protocol's detailed statistical plan, eligibility criteria, recruitment targets by cohort, and 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 The 6-month Local Control Rate of SBRT, measured over 6 months.

The primary endpoint is the 6-month local control rate of SBRT. The registry defines it as the proportion of patients free of local failure at 6 months after treatment. Local failure means biopsy-proven recurrence or radiologic scans demonstrating progression at a treated site. The endpoint therefore focuses on disease status at the sites that received radiation, not on all disease in the body.

A proportion is a natural way to describe a binary outcome: each participant's status at the specified time is classified according to whether local failure has occurred. General statistical interpretation: the estimate describes the observed frequency in the group assessed, while uncertainty around that estimate depends on the number of evaluable participants and the amount of missing follow-up. A confidence interval, if reported, would show a range of values compatible with the data and the method used to calculate it; it would not establish certainty about the true rate.

Local control is clinically and statistically distinct from progression-free survival and overall survival. A participant can have local control at a treated site while experiencing progression elsewhere, so this endpoint should not be read as a measure of whole-body disease control or survival. The record does not report a primary endpoint result, its confidence interval, or the number assessed at 6 months. Those details are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is binary at the participant level: the endpoint definition classifies participants according to whether they are free of local failure at 6 months. General statistical explanation: a binary outcome can be summarized as a proportion, with the number meeting the definition forming the numerator and the number assessed forming the denominator. The denominator matters because participants without the required follow-up may not have an observed status at the target time. The registry does not report the endpoint numerator, denominator, or missing-outcome handling.

What a confidence interval would convey

General statistical explanation: a confidence interval describes uncertainty around an estimated quantity under a specified statistical method and its assumptions. For a proportion, uncertainty is influenced by the number of observations and by the estimated proportion. A narrow interval indicates greater statistical precision than a wide interval, but neither width nor the interval alone resolves possible bias from selection, measurement, or missing follow-up. No confidence interval for the primary endpoint is reported in the registry record.

What the design can estimate

A non-randomized, single-group study can describe outcomes in the treated population that is observed. It does not by itself provide the exchangeability created by random allocation, which helps make groups comparable on average. Here, the registry identifies two distinct cohorts, but explicitly describes a non-randomized design. Their outcomes should not be treated as though they arose from a randomized head-to-head comparison. Differences could arise from cohort composition, clinical history, follow-up, or other factors; the registry does not report adjustment methods that would address such differences.

The absence of masking is also part of the stated design. General statistical explanation: knowledge of treatment can potentially influence outcome assessment or participant reporting, depending on how outcomes are measured. The primary endpoint includes radiologic progression and biopsy-proven recurrence, but the registry does not report details about blinded assessment, independent review, or procedures for resolving disagreement. It would be inappropriate to assume that any particular assessment safeguard was used.

Outcome families and analysis choices

The listed outcomes do not all have the same statistical form. The primary local-control measure is a proportion at a fixed time. The record also lists progression-free and overall survival outcomes, which generally concern time until an event, as well as patient-reported quality of life. General statistical explanation: time-to-event methods can account for differing follow-up durations and censoring, but their interpretation depends on event definitions, follow-up, and model assumptions. The registry record does not report the analysis methods for these outcomes, the event definitions beyond the primary endpoint, or any outcome-specific estimates.

The record lists six outcome measures and no analysis entries. It does not state whether the primary outcome was analyzed with a particular proportion estimator, whether covariates were included, or how multiple outcomes were handled. Statistical analysis plans, if any, are not reported in the registry record. The absence of listed analyses does not establish what may have been planned outside the registry; it means that the registry record does not document those details.

Planning illustrations

The stated assumptions for the sample-size illustrations describe a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The illustrations are based on fractions of an observed effect; the time-to-event illustrations refer to a total number of events, while other illustrations refer to participants per arm for 80% power or other stated power levels. These are planning illustrations, not observed power and not the trial's own design justification. The registry does not report a sample-size justification for this single-group, non-randomized study. The illustrations should not be interpreted as the study's actual allocation plan or as evidence that the study had a particular probability of detecting an effect.

General statistical explanation: power is a planning quantity based on assumptions about an effect, variability, significance level, and design. It is not a measure of whether an observed result is true. A sample-size calculation also does not substitute for the outcome estimate and its uncertainty. Since no primary efficacy analysis is reported in the registry record, the planning assumptions cannot be used to infer a treatment effect or the precision of the observed local-control outcome.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Oligometastatic Disease", "Re-irradiation to Metastatic Disease")
n      <- c(98, 44)
events <- c(94, 40)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Oligometastatic Disease  98  94  95.9  89.9  98.9  90.0  98.4  90.0  98.3
ARM  Re-irradiation to Metastatic Disease  44  40  90.9  78.3  97.5  78.8  96.4  78.8  96.3

11. Multiplicity, Missing Data and Analysis Populations

The record lists several outcomes beyond the primary 6-month local control rate: 1-year local progression-free survival, 2-year progression-free survival, 2-year overall survival, and acute and chronic patient-reported quality of life. Considering multiple outcomes can raise a multiplicity issue when results are tested or interpreted together. General statistical explanation: without a prespecified strategy, examining multiple outcomes can increase the chance of at least one apparently notable finding by chance. The registry does not report a multiplicity adjustment, a testing hierarchy, or a distinction between confirmatory and exploratory outcomes. Those details are not reported in the registry record.

The registry lists no analysis entries. It does not identify analysis populations, such as whether analyses would include all enrolled participants, treated participants, or only those with an evaluable assessment. The number analyzed for each outcome is not reported in the registry record.

Missing-data procedures are also not described. For a fixed-time local-control outcome, incomplete follow-up can affect which participants have an observed status at the endpoint. For patient-reported quality-of-life outcomes, missing assessments may occur at different times or for different reasons. General statistical explanation: missingness can affect both the size of the analysis population and the interpretation of an estimate, particularly if the probability of missing data is related to health status or outcome. No imputation method, censoring rule, sensitivity analysis, or missing-data assumption is reported in the registry record. These omissions limit assessment of how results would be analyzed and how robust they might be to incomplete data.

12. 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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: hospitalization due to pain at an unrelated metastatic site (2.3%), atrial fibrillation (1.0%), prolonged hospitalization/severe esophagitis (1.0%).

The registry lists adverse-event figures separately for the Oligometastatic Disease and Re-irradiation to Metastatic Disease cohorts. For serious adverse events, it records 98 participants at risk and 2 affected in the Oligometastatic Disease cohort, and 44 at risk and 1 affected in the Re-irradiation to Metastatic Disease cohort. For other adverse events, it records 98 at risk and 27 affected in the first cohort, and 44 at risk and 41 affected in the second. Deaths are listed as 28 and 29, respectively.

These cohort figures are descriptive, not a randomized safety comparison. The cohorts differ in clinical context, and the registry record does not report event timing, participant-level overlap among event categories, attribution to treatment, or the methods used to collect and classify events. The death counts should not be interpreted as treatment-related deaths; attribution is not reported in the registry record.

The listed leading serious-event terms are hospitalization due to pain at an unrelated metastatic site (2.3%), atrial fibrillation (1.0%), and prolonged hospitalization/severe esophagitis (1.0%). The registry does not give further context for these terms in the record. The figures describe reported events and should not be interpreted as proof of cause or as comparative risk estimates.

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

The record establishes the study's purpose and planned outcome framework: a Phase II evaluation of SBRT for bone or spine metastatic disease, with 6-month local control as the primary endpoint. It also records two clinical cohorts and a set of secondary outcomes. These details clarify what the investigators intended to study, but they do not establish what the participants experienced on the primary endpoint.

No primary efficacy result is reported in the registry record. There is no posted 6-month local-control estimate, confidence interval, or analysis denominator. As a result, the registry record cannot show the magnitude or precision of local control observed in this study. The enrollment figure of 150 is not a substitute for those outcome data.

Even if cohort outcomes were available, the non-randomized design would make causal interpretation limited. Without randomized allocation and a suitable control group, outcomes could not be attributed to SBRT alone by comparing the cohorts or by observing a treated group in isolation. The two cohorts represent different treatment circumstances, and the record does not report methods that would make them comparable.

The listed survival, progression, quality-of-life, and adverse-event outcomes address distinct questions. They would require their own estimates, follow-up descriptions, and analysis details. Their presence in the registry does not imply that results are available or that they support a particular conclusion. The record likewise does not document how missing outcomes, multiple endpoints, or participant analysis populations were handled.

Accordingly, the statistical interpretation should remain bounded: the registry describes a clinical study and its endpoint definitions, while numerical efficacy analyses are not reported in the registry record. The posted safety counts can be read as descriptive reports within each cohort, not as evidence of comparative or causal effects.

14. Why This Trial Matters Statistically

This study illustrates why a clearly defined endpoint is essential. The primary outcome specifies a follow-up time and a local-failure definition that includes biopsy-proven recurrence or radiologic progression at treated sites. That definition distinguishes local control from broader progression and survival outcomes. Without a reported estimate and denominator, however, the endpoint's practical statistical meaning cannot be quantified for this cohort.

The design also demonstrates the importance of matching claims to the comparison structure. A non-randomized, single-group study may characterize outcomes, but it does not create a randomized control contrast. The two cohorts concern different clinical situations, so their separate adverse-event or outcome figures should not be read as a direct treatment comparison. Design features constrain causal interpretation regardless of how clearly an outcome is defined.

Finally, registry completeness matters for evaluating evidence. The record names secondary outcomes and describes some safety counts, but has no analysis entries and does not document analysis populations, missing-data methods, multiplicity handling, or the primary endpoint result. Those gaps prevent readers from assessing precision, robustness, and the relationship between planned and reported analyses. Statistical interpretation depends not only on a study's question, but also on transparent reporting of who was analyzed, how outcomes were handled, and what uncertainty remains.

15. 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.

Several limitations are specific to the information in this registry record. First, the primary local-control result is not reported, and the number of participants assessed at 6 months is not reported in the registry record. The listed enrollment of 150 therefore cannot be used to determine the endpoint's analysis denominator or precision.

Second, the study is non-randomized and has a single-group model. The two named cohorts address oligometastatic disease and re-irradiation to metastatic disease, so they should not be treated as equivalent groups or as randomized treatment alternatives. The record does not identify a control group for estimating what would have occurred without SBRT or under another treatment.

Third, treatment descriptions are incomplete. They identify SBRT and a stereotactic linear accelerator, but the dose is not reported in the registry record. The registry record also does not provide detailed eligibility criteria, endpoint assessment procedures, or the timing and rules for follow-up beyond the listed outcome timeframes.

Fourth, no analysis entries are listed. Statistical methods, analysis populations, missing-data handling, multiplicity procedures, and a sample-size justification are not reported in the registry record. Adverse-event figures are available as descriptive counts, but attribution, timing, and event-level detail are not reported. These limitations restrict evaluation of efficacy, safety, precision, and potential bias from the registry record alone.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Evaluating Stereotactic Body Radiation Therapy for Oligometastatic Disease of the Bone — NCT02880319.
• Registry record last updated 2025-09-09; status last verified 2025-09.
• Results first posted 2023-08-29.
• 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.

19. Record Summary

The registry record describes NCT02880319, a Phase II study sponsored by Dana-Farber Cancer Institute. It is non-randomized, unmasked, and listed as a single-group model, with enrollment of 150. The study started on 2016-11-29, has primary completion listed as 2022-05, and is active, not recruiting.

The study evaluates SBRT for oligometastatic disease of bone or spine and for re-irradiation to metastatic disease. The primary outcome is the 6-month local control rate, defined by freedom from local failure at treated sites. Secondary outcomes include local progression-free survival, progression-free survival, overall survival, and patient-reported quality of life. No primary efficacy analysis is reported in the registry record. The record lists adverse-event counts by cohort but does not report event attribution or detailed analysis methods.