Study for Using Radiosurgery on Limited Metastases of Breast Cancer: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Study for Using Radiosurgery on Limited Metastases of Breast Cancer (NCT00167414), a na na study. The primary outcome is Overall Survival.

2. Clinical Question

In statistical terms, the design can describe survival in the treated group as recorded, but it cannot by itself estimate a comparative treatment effect against an untreated or differently treated group. The stated question concerns survival over a specified follow-up period, rather than a direct comparison between randomized treatment strategies. The record’s description of standard therapies does not establish that all participants received the same background care or that any particular therapy was assigned.

3. Trial Design

The registry lists this as a phase II study with phase recorded as NA, no masking, allocation recorded as NA, and a single-group model. It reports an enrollment of 49. The sponsor is the University of Rochester. The record gives a start date of 2000-12, primary completion on 2016-11-01, and status of COMPLETED.

Hypofractionated stereotactic body radiation therapy is the intervention. It appears under both procedure and radiation intervention types, and the arm description refers to its use for limited metastases with breast cancer primary. The study summary describes evaluation of radiosurgery alongside standard chemotherapy, immunotherapy, or hormonal therapy. It also gives a separate purpose: assessing whether blood cytokine levels are related to quality of life during treatment. The registry record does not describe how these additional therapies were selected or delivered, or how cytokines and quality of life were measured.

Because this is a single-group study, the posted design does not supply a contemporaneous control arm for estimating a treatment contrast. Descriptions of standard therapy in the summary are not evidence of a comparison group. A reader should therefore interpret any reported group outcome as descriptive unless an analysis explicitly supports a different interpretation. No such primary endpoint analysis is listed in the registry record.

The record identifies lesion local control and grade 4 or 5 toxicity among its secondary outcomes. It reports five outcome measures overall, but does not provide a complete account of their definitions or results in the registry record for this study description. The registry record also does not report eligibility details, baseline characteristics, treatment schedules, follow-up procedures beyond the primary endpoint timeframe, or the number of participants included in each endpoint analysis.

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 Overall Survival, measured over 2 years.

The primary endpoint is overall survival, expressed as a percentage of participants. Its stated timeframe is 2 years, and the description defines it as the percentage who survived from enrollment until the 2-year follow-up visit. This is a fixed-time survival measure: it asks what proportion of the relevant study population was alive at the specified follow-up point, rather than reporting the timing of every death.

Survival is used in clinical research because it captures an outcome that is directly interpretable and can summarize follow-up status at a defined time. A percentage can communicate the observed frequency in a group, but its meaning depends on the population included, the completeness of follow-up, and the rules used for participants whose status is unknown or whose observation ends early. Those details are not reported in the registry record.

The posted record does not give the observed survival percentage, a numerator, a denominator for this endpoint, or an uncertainty interval. It also does not state whether the analysis used a simple proportion or a time-to-event method that accounts for censoring. The endpoint definition is available, but the result and its precision cannot be assessed from the registry information.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record identifies a single-group model and no randomized allocation. It does not report the statistical methods used for the primary endpoint, secondary endpoints, or safety summaries. The explanations below describe general statistical concepts that help interpret such outcomes; they should not be taken as methods documented for this study.

What does a percentage measure?

A percentage is a proportion expressed on a scale from none of the group to all of the group. For the stated primary endpoint, the proportion would represent participants alive at the 2-year follow-up visit among the participants defined for that analysis. Interpreting it requires a clear denominator and a rule for determining survival status. The registry record reports enrollment of 49, but does not say that all enrolled participants contributed to the primary endpoint or identify the endpoint denominator.

For a simple proportion, statistical uncertainty generally depends on both the observed proportion and the number of observations contributing to it. A confidence interval communicates that uncertainty: it gives a range of values compatible with the data under the chosen statistical method and its assumptions. It is not a guarantee that the true value lies within that range, and it does not account automatically for bias from missing follow-up, measurement, or study design. No primary survival estimate or confidence interval is reported in the registry record.

How does a fixed-time survival percentage differ from a time-to-event analysis?

A fixed-time percentage classifies participants by whether they are known to be alive at the stated follow-up point. A time-to-event analysis uses the timing of events and can retain information from participants whose follow-up ends before the event is observed. Such participants may be censored: their observed time contributes information up to the point follow-up stops, while their later event status remains unknown. The validity of this approach depends on assumptions about why observation ended and how censoring relates to the event. The registry record defines a fixed-time survival percentage but does not state whether the analysis used a direct proportion, a time-to-event estimator, or a method for handling incomplete status.

What does the single-group design permit?

In a single-group study, an outcome can describe the experience of the enrolled group under the care received. It does not provide the concurrent counterfactual outcome that would have occurred under another assigned treatment. As a result, an observed outcome cannot by itself distinguish an intervention effect from differences in disease characteristics, other treatments, follow-up, or selection into the study. Statistical adjustment can sometimes address measured differences in comparative research, but it cannot create a randomized comparator where none is reported. The registry record lists no like-for-like control arm.

Randomization, when used, helps make treatment groups comparable on average with respect to both measured and unmeasured factors. Here, allocation is recorded as NA and the model is single-group. The record therefore does not describe a randomized contrast, and a comparative causal effect should not be inferred from the primary endpoint description alone.

Why report precision as well as an estimate?

A point estimate provides a concise description of the data, while an uncertainty interval indicates how much the estimate may vary because of sampling. These serve different purposes. A precise estimate can still be subject to systematic bias, and a wide interval can reflect limited information even when the analysis is unbiased. Without a posted estimate and interval, the precision of the survival result cannot be evaluated. A significance test, if one had been planned and reported, would answer a different question from the size and precision of an effect; no primary analysis or test is listed.

How should the planning illustrations be understood?

Planning calculations are not trial outcomes. The registry’s stated planning assumptions describe an illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The stated fraction of the observed effect is the effect to detect in that illustration. These assumptions do not describe the actual single-group design, and they do not establish that the study had a particular probability of detecting an effect. Sample-size illustrations are planning quantities, not observed power. The registry record does not report a sample-size justification or show that these illustrative assumptions were part of the trial’s original design.

For binary outcomes, normal approximations can be less reliable when data are sparse or proportions are near the boundaries. In other settings, over-dispersion means that the observed variability exceeds what a basic model assumes; accounting for it can widen uncertainty and alter inference. These are general considerations, not methods reported for this study. The registry entries available do not establish whether either issue arose in an analysis.

Finally, a sound endpoint analysis ordinarily states the analysis population, outcome definition, missing-data rules, estimator, uncertainty measure, and any adjustments. Those details are not reported in the registry record. Without them, readers can understand what the primary endpoint was intended to measure, but cannot reproduce or fully evaluate its statistical analysis.

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("Hypofractionated Stereotactic Body Radiation Thera")
n      <- c(39)
events <- c(29)
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  Hypofractionated Stereotactic Body Radiation Thera  39  29  74.4  57.9  87.0  58.9  85.4  58.8  85.4

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists five outcome measures and identifies overall survival as the primary endpoint. It also names lesion local control and grade 4 or 5 toxicity as secondary outcomes. It does not report a multiplicity strategy, such as a hierarchy of confirmatory tests or an adjustment for assessing several outcomes. When many outcomes or comparisons are examined, the chance of at least one apparently unusual result can increase. This is a general statistical concern; the record does not establish which outcomes were formally tested or whether any adjustment was used.

The registry record lists 0 analyses. This means no analysis details are available in the record described for interpretation. It does not establish whether analyses were conducted outside the registry record. In particular, no statistical analysis plan, hypothesis-testing procedure, or prespecified handling of interim analyses is reported. The record also does not report whether subgroup analyses were planned or conducted.

Missing data are important for a fixed-time survival percentage because participants need a known status at the specified follow-up point, or an analysis method must account for incomplete observation. The record does not report the amount or pattern of missing endpoint data, reasons for loss to follow-up, or an imputation or censoring approach. It does not identify an analysis population, such as all enrolled participants or a subset with evaluable follow-up.

These omissions do not show that missing data or multiplicity necessarily distorted a result. They mean that the available registry information is insufficient to assess those risks. Without endpoint results, population definitions, and analysis methods, readers cannot determine whether conclusions were based on complete follow-up, how uncertainty was estimated, or how multiple outcomes were interpreted.

12. 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 0% reporting threshold.

Most frequent non-serious adverse event terms

The registry adverse-event summary lists the hypofractionated stereotactic body radiation therapy group as having 0 serious events among 39 at risk and 1 other adverse event among 39 at risk. These are the counts reported for the stated categories. They should not be combined with or treated as a result for the primary overall survival endpoint.

The secondary outcomes include the number of participants who experienced a grade 4 or 5 toxicity. The adverse-event summary does not establish whether its serious-event category corresponds exactly to that secondary outcome, and the registry record does not report the definitions or observation window needed to make that connection. It also does not describe how events were collected, classified, or attributed.

The safety denominator of 39 should not be assumed to represent the primary endpoint analysis population. The registry reports enrollment of 49, but does not explain the difference between that enrollment figure and the adverse-event count at risk. The deaths field in the adverse-event summary is not reported in the registry record. These safety figures are therefore limited descriptive counts, not a complete assessment of event frequency over a defined period or a comparison with another treatment group.

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

The registry record supports a description of the study’s purpose and structure: it evaluated hypofractionated stereotactic body radiation therapy for limited metastases with a breast cancer primary, in a single-group design. It identifies overall survival at 2 years as the primary endpoint and describes interest in quality of life and blood cytokines. It also lists lesion local control and grade 4 or 5 toxicity among secondary outcomes.

What the record does not provide is the primary survival percentage, its analysis population, or a measure of uncertainty. It therefore does not show how many participants met the endpoint or how precisely survival was estimated. Completion status alone does not supply those missing results. The posted adverse-event counts offer limited safety information, but event definitions, follow-up duration, and the relationship to the grade 4 or 5 toxicity outcome are not reported.

Even a fully reported outcome from a single-group study would describe an observed experience rather than establish what would have happened to comparable participants under a different treatment. There is no reported randomized comparison or concurrent control group. The registry’s reference to standard therapies does not function as a comparator, and the record does not specify the background treatments received by participants.

Accordingly, the available information cannot support a comparative estimate of treatment benefit or harm, nor can it establish that the intervention caused any observed outcome. It also cannot establish the precision or robustness of the intended primary endpoint analysis. The statistical meaning is bounded by the design and by the absence of endpoint results and analysis details in the registry record.

14. Why This Trial Matters Statistically

This study is statistically informative as an example of how an endpoint’s definition and a study’s design must be read together. Overall survival at 2 years is a clearly stated endpoint concept, but the registry record does not report the observed percentage or the method used to estimate it. A defined endpoint is not the same as a reported result, and a completed study status does not resolve that distinction.

The single-group design is equally important. A descriptive outcome can characterize the enrolled group, but a treatment comparison requires a comparator and an analysis that supports the comparison. Neither a background description of standard therapies nor an intervention label supplies that missing contrast. This distinction helps prevent readers from interpreting a group outcome as evidence of a causal effect.

The study also illustrates why denominators and analysis populations matter. Enrollment is reported as 49, while the adverse-event summary reports 39 at risk. The record does not explain the relationship between these counts, and it does not state the primary endpoint denominator. Those figures should not be treated as interchangeable. Clear reporting of endpoint-specific populations and follow-up would be needed to understand what each estimate represents.

Finally, the registry lists intended outcome areas but no analyses. Without outcome estimates, uncertainty intervals, and methods for missing data and multiplicity, it is not possible to judge the statistical strength of the intended survival assessment. The principal statistical lesson is to separate the question a trial intended to ask from the evidence its posted results actually make available.

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.

The registry record leaves important details about the population and conduct of the study unspecified. It does not report eligibility criteria, baseline disease characteristics, participant characteristics, treatment schedule, or the use and distribution of accompanying chemotherapy, immunotherapy, hormonal therapy, surgery, or radiation therapy. These omissions make it difficult to characterize the group to which any outcome would apply.

The primary endpoint description gives a fixed follow-up timeframe, but the record does not report survival results, endpoint-specific denominators, follow-up completeness, or methods for participants with unknown status. It also does not say whether survival was analyzed as a proportion or with a time-to-event method. The absence of these details prevents assessment of both the estimate and its precision.

The single-group design has no reported concurrent comparator, limiting interpretation to description rather than a controlled treatment contrast. Allocation is recorded as NA, and the record does not report masking. It does not provide a statistical analysis plan, sample-size justification, interim analysis information, or a rationale for the planning assumptions. The planning illustration is not evidence of the trial’s original design or observed power.

Safety reporting is also limited: the registry gives adverse-event counts but not the event definitions, collection methods, follow-up window, or relationship between the summary categories and the stated grade 4 or 5 toxicity outcome. The record does not describe missing-data handling or an analysis population. These are limitations of the available registry information; they do not establish that any particular bias or deficiency occurred in the conduct of the study.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Study for Using Radiosurgery on Limited Metastases of Breast Cancer — NCT00167414.
• Registry record last updated 2018-01-05; status last verified 2017-12.
• Results first posted 2018-01-05.
• 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 a completed, single-group study sponsored by the University of Rochester. It lists an enrollment of 49, a start date of 2000-12, and primary completion on 2016-11-01. Phase is recorded as NA, allocation as NA, and masking as none.

The intervention is hypofractionated stereotactic body radiation therapy for limited metastases with a breast cancer primary. The primary endpoint is the percentage of participants surviving from enrollment until the 2-year follow-up visit. The registry record does not report the endpoint result or a primary analysis. It lists five outcome measures and 0 analyses.

The adverse-event summary reports 0 serious events among 39 at risk and 1 other adverse event among 39 at risk. The record does not provide event definitions or explain the relation between these counts and the secondary outcome concerning grade 4 or 5 toxicity. A concurrent comparator and a comparative treatment effect are not reported.