Accelerated Partial Breast Radiation Therapy Using High-Dose Rate Brachytherapy in Treating Patients With Early Stage Breast Cancer After Surgery: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Accelerated Partial Breast Radiation Therapy Using High-Dose Rate Brachytherapy in Treating Patients With Early Stage Breast Cancer After Surgery (NCT02526498), a na phase 2 study. The primary outcome is Number of Participants With Adverse Events Greater Than Grade 2 Serious Toxicity Rate, Defined as Toxicity Greater Than Grade 2 Using Common Terminology Criteria for Adverse Events Version 4.0 Criteria.

2. Clinical Question

The trial examined a shortened course of partial-breast radiation after surgery. Its rationale, as described in the registry summary, was to deliver radiation near the space where the tumor was removed over less time than standard radiation therapy. The record describes the study as phase II and lists 200 participants as the enrollment.

The primary question focuses on treatment-attributed toxicity. To count toward that endpoint, toxicity had to be greater than grade 2 under the Common Terminology Criteria for Adverse Events version 4.0 and judged probably or definitely related to study treatment. Physical examination at follow-up visits was specified for assessment. The reported timeframe was 2 years.

Other outcomes listed in the record concern local control assessed by physical examination and mammography, and cosmetic results assessed with the Harvard Cosmesis Scale. The registry record does not report results for those outcomes in the information available for this analysis. Without a comparison group, the study also cannot estimate a treatment difference against another radiation approach or no treatment.

3. Trial Design

The registry describes TRIUMPH-T as a phase II, single-group trial. It lists enrollment of 200 and no allocation to comparative arms. The study status is completed. The listed start date is 2015-07-15 and the primary completion date is 2017-08-18.

Participants received accelerated partial breast irradiation using high-dose rate brachytherapy. The treatment description states that, within 1-5 days after balloon placement, patients underwent treatment over 15-60 minutes for 2-3 days. Questionnaire administration is also listed as an intervention, alongside the radiation interventions.

Because this was a single-group study, the observed outcomes describe participants receiving the study treatment; they do not represent a randomized comparison. There is no control arm against which to distinguish treatment-related outcomes from outcomes that might also occur after surgery, from the underlying condition, or under another treatment strategy. Those distinctions cannot be established from the design reported in the registry.

The primary endpoint is a count of participants with toxicity greater than grade 2 that was judged probably or definitely attributable to study treatment. Assessment was described as occurring through physical examination at each follow-up visit, over a 2-year timeframe. Secondary outcomes listed are local control assessed by physical examination, cosmetic results using the Harvard Cosmesis Scale, and local control assessed by mammography.

The registry record does not report a detailed statistical analysis plan, a sample-size justification for the trial, or interim analyses. It also does not list analysis entries. The posted enrollment and study design therefore describe the planned and recorded structure, but do not establish how all outcomes were analyzed or how missing follow-up was handled.

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 Number of Participants With Adverse Events Greater Than Grade 2 Serious Toxicity Rate, Defined as Toxicity Greater Than Grade 2 Using Common Terminology Criteria for Adverse Events Version 4.0 Criteria, measured over 2 years.

The primary endpoint counts participants with toxicity greater than grade 2 that was considered probably or definitely related to study treatment. The registry identifies the Common Terminology Criteria for Adverse Events version 4.0 as the grading framework and gives 2 years as the assessment timeframe. The endpoint description says toxicity and cosmesis were collected as dichotomous variables and that physical examinations at follow-up visits were used for assessment.

A count is useful for describing how many participants met a prespecified safety definition in the treated group. Requiring both a toxicity grade above the stated threshold and probable or definite attribution makes the endpoint narrower than a count of every reported adverse event. It is therefore important not to treat the primary count as interchangeable with the count of all adverse events.

The record labels the endpoint as a serious toxicity rate, but the posted result is a participant count. It lists zero serious treatment-attributed events among 200 participants at risk. That count describes the recorded outcome under the endpoint definition; it is not a comparison with another treatment and does not by itself quantify uncertainty about the underlying risk.

Local control and cosmetic outcomes are separate secondary questions. The registry record lists their assessment methods but does not report corresponding results in this record summary. The endpoint should therefore be interpreted as a safety measure, not as evidence about local control or cosmetic results.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary result is a count in a single-group study. For a binary endpoint, each participant is classified according to whether the endpoint occurred, and the count records those classified as having the event. Here, the endpoint is specifically toxicity greater than grade 2 with probable or definite attribution to study treatment. A count is straightforward to interpret, but a count alone does not convey how precisely the underlying event frequency has been estimated.

In general, statistical uncertainty around an event frequency can be expressed with a confidence interval. The interval describes values compatible with the observed data under a statistical procedure and its assumptions. It is not a guarantee that the true value lies within the interval. The registry record does not report a confidence interval for the primary endpoint, so no interval-based precision claim can be made from the posted results.

There is also a distinction between an observed count and a comparison. A treatment effect generally requires a contrast between outcomes under different treatments or conditions. In this study, the registry identifies a single group and no comparator. The reported count can describe what was recorded among participants receiving treatment, but it cannot estimate a relative effect against another regimen. General statistical adjustment cannot replace a missing control group, and no adjusted analysis is reported in the registry record.

Event definitions matter. The primary endpoint uses both a severity threshold and an attribution requirement. Other adverse events are reported separately, so those events should not be merged conceptually with the primary endpoint. An event count may also depend on how follow-up, grading, and attribution are recorded. The registry describes physical examination at follow-up visits but does not report the completeness of those assessments or detailed adjudication procedures.

For binary outcomes, a model may estimate an event probability, or an analysis may compare proportions across groups when a suitable comparison exists. General methods differ in their assumptions and in how they handle small counts. A zero observed count can make some standard approximations unreliable; exact or other suitable methods may be considered in general, depending on the design and analysis objective. The registry record does not name a method used for this endpoint, so it would be inappropriate to infer which approach was applied.

What does over-dispersion mean?

In general, over-dispersion means that observed variability is greater than a model expects. It can arise when outcomes vary more across participants or clusters than a simple model allows. When that happens, standard errors from the too-restrictive model may be too small, which can make intervals too narrow and tests too confident. This concept is relevant to some count and grouped-data analyses, but the primary endpoint is described as a dichotomous participant outcome. The registry does not report a model or an over-dispersion assessment.

What do the planning assumptions mean?

The record describes planning illustrations based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The effect to detect is defined as a stated fraction of the observed effect. For time-to-event outcomes, the stated planning convention uses a total event count; for other outcomes, it uses participants per arm. These are planning assumptions, not observed trial results. They do not constitute observed power and do not imply that this single-group trial had two randomized arms.

Sample-size planning asks what study size could be needed under specified assumptions to detect an effect using a chosen procedure. It depends on the assumed effect, variability, significance level, power target, allocation, and outcome model. A planning illustration based on an observed effect is especially dependent on that estimate, which may be uncertain. It should not be read as evidence that the trial had sufficient precision or as a substitute for a confidence interval. The registry record does not report the trial's own sample-size justification or statistical design calculations.

What can be concluded from the posted analysis information?

The registry lists no analysis entries. It does not report a test statistic, p-value, confidence interval, adjusted estimate, or method for handling missing outcomes for the primary endpoint. This does not establish that no analysis occurred outside the registry; it means those methods and results are not reported in the registry record. Accordingly, the strongest interpretation is descriptive: the record lists the observed safety counts and their endpoint definitions, while comparative or model-based conclusions are not available from the reported information.

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("Treatment (APBI Using HDR Brachytherapy)")
n      <- c(200)
events <- c(200)
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  Treatment (APBI Using HDR Brachytherapy)  200  200  100.0  98.2  100.0  98.1  100.0  98.2  100.0

11. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary safety endpoint and secondary outcomes concerning local control and cosmetic results. Multiple outcomes create a general multiplicity issue: when several hypotheses are tested, the chance of at least one apparently unusual result can increase if each test is considered separately. A prespecified testing hierarchy or adjustment can address that issue, but the registry record does not report a multiplicity strategy, a testing hierarchy, or inferential results for the listed secondary outcomes.

The record describes the primary endpoint as a dichotomous measure and gives its assessment timeframe, but it does not report how missing or incomplete assessments were handled. The number of participants with complete primary endpoint follow-up is not reported in the registry record. Nor does the record specify whether participants with unavailable assessments were excluded, treated as having no event, or handled through another method. No such approach should be assumed.

The analysis population is also not described in detail. The registry lists enrollment and the number at risk for the adverse-event group, but does not define an intention-to-treat, per-protocol, or other analysis set. It does not provide participant flow or explain whether all enrolled participants contributed to each outcome. The reported at-risk counts should therefore be read as the denominators recorded for the adverse-event summaries, not as proof of complete outcome ascertainment for every endpoint.

These gaps limit assessment of how robust the results are to missing data, outcome selection, or multiple testing. The absence of those details does not imply that a particular method was or was not used; it means the relevant method is not reported in the registry record.

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 non-serious adverse event terms

The registry lists zero serious treatment-attributed toxicities among 200 participants at risk. The serious endpoint required toxicity greater than grade 2 and probable or definite attribution to treatment. The record also lists zero deaths. These counts are descriptive and refer to the endpoint definitions and group recorded in the registry.

Separately, the record lists 165 participants under other adverse events among 200 at risk. That figure should not be read as a count of serious toxicities: the registry distinguishes other adverse events from the serious treatment-attributed endpoint. The details needed to characterize the other events by type, grade, attribution, or timing are not reported in the registry record.

Counts do not show how precisely the event frequency is known. The registry does not report a confidence interval or statistical test for the serious toxicity count. A zero observed count does not establish that the underlying risk is zero, and it does not support a comparison with another treatment because no comparator group is listed.

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

The result establishes what the registry reports for this endpoint in the treated group: zero participants with toxicity greater than grade 2 considered probably or definitely related to treatment, among 200 at risk. The registry also reports 165 participants under other adverse events and zero deaths. The distinction between the endpoint-specific count and the separate other-event count is important.

The result does not establish that the treatment has no serious toxicity risk. An observed zero is compatible with uncertainty about events that could occur in a broader population, and the record provides no confidence interval to quantify that uncertainty. It also does not show whether the count would be higher or lower under another treatment, because the study is single-group and has no control arm.

The safety count does not answer the listed questions about local control or cosmetic results. Although the registry names those secondary outcomes and their assessment approaches, corresponding results are not reported in the registry record. The record also does not describe detailed analysis populations, missing-data methods, or statistical tests, which limits assessment of precision and completeness.

More broadly, the trial's phase II, single-group design provides a descriptive account of outcomes during the stated follow-up timeframe, rather than a randomized estimate of comparative effectiveness. The registry summary gives the treatment schedule and endpoint definitions, but does not report enough comparative or inferential information to attribute differences against another approach. Interpretation should stay within those limits: the posted counts describe recorded events, not proof of benefit, absence of risk, or superiority.

14. Why This Trial Matters Statistically

This trial is statistically notable because its primary outcome is a treatment-attributed safety count, while the study design is single-group. That pairing allows a direct description of how many participants met the endpoint definition in the treated group. It does not permit a randomized comparison or isolate how much of an outcome is attributable to treatment relative to another approach.

The endpoint definition also illustrates why safety summaries need careful reading. The primary outcome applies a severity threshold and an attribution requirement, whereas other adverse events are reported separately. A broad adverse-event count and a narrowly defined serious-toxicity count answer different questions. Keeping those categories distinct prevents an overall event count from being mistaken for the primary safety result.

The registry's lack of reported confidence intervals and analysis methods is statistically consequential. A count can be clear while its precision remains uncertain. Without interval estimates or a stated method, readers cannot assess the range of event frequencies compatible with the data from the registry result alone. Without a comparator, they also cannot estimate a treatment contrast.

The listed secondary outcomes extend beyond safety to local control and cosmetic results, but their results are not reported in the registry record. This demonstrates the difference between outcomes named in a protocol record and outcomes for which results are available. Statistical interpretation depends not only on what was planned to be measured, but also on whether outcome data and analytic details are reported.

Finally, planning illustrations and observed trial evidence serve different purposes. Planning assumptions describe hypothetical future study requirements under specified conditions; they do not turn a single-group trial into a comparison or provide observed power. The distinction matters when readers assess what the registry result can support.

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 main design limitation is the absence of a comparator group. The trial's single-group structure means the posted outcomes describe the treated group but cannot estimate differences from another radiation approach or establish a comparative treatment effect. The registry lists no random allocation.

The registry record does not report confidence intervals, p-values, or the statistical method used for the primary endpoint. It also does not give a detailed statistical analysis plan, sample-size justification, or interim-analysis information. The result therefore cannot be assessed from the registry record in terms of model choice, inferential precision, or planned stopping and monitoring procedures.

Although the primary endpoint has a defined severity and attribution threshold, the registry does not report detailed event-level information or how attribution was determined beyond requiring probable or definite relation to treatment. It does not report completeness of follow-up or handling of missing assessments. The analysis population is not described beyond the recorded group at risk.

The other adverse-event count is not broken down by grade, type, attribution, or timing in the registry information. Results for the listed local-control and cosmetic outcomes are also not reported in the registry record. Consequently, the posted safety count cannot serve as a substitute for those outcomes or for a fuller account of tolerability.

The treatment description and condition list identify the study context, but detailed participant eligibility criteria and further population characteristics are not reported in the registry record. Generalization beyond the participants represented by this study cannot be assessed fully from the information available.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Accelerated Partial Breast Radiation Therapy Using High-Dose Rate Brachytherapy in Treating Patients With Early Stage Breast Cancer After Surgery — NCT02526498.
• Registry record last updated 2023-05-15; status last verified 2023-04.
• Results first posted 2022-08-16.
• 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 TRIUMPH-T Trial is registered as a completed phase II, single-group study of accelerated partial breast irradiation using high-dose rate brachytherapy after surgery for early-stage breast cancer. The registry lists enrollment of 200, a start date of 2015-07-15, and a primary completion date of 2017-08-18.

The primary endpoint concerns toxicity greater than grade 2 that was probably or definitely attributable to treatment, assessed over 2 years. The record lists zero such events among 200 participants at risk, 165 participants under other adverse events, and zero deaths. Secondary outcomes include local control by examination and mammography and cosmetic results using the Harvard Cosmesis Scale; their results are not reported in the registry record.

No comparator group is listed. Confidence intervals, inferential analyses, detailed missing-data methods, and a statistical analysis plan are not reported in the registry record. The safety figures should therefore be interpreted as descriptive counts rather than comparative estimates.