MammoSite as Sole Radiation Therapy Technique for Ductal Carcinoma In-Situ: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for MammoSite as Sole Radiation Therapy Technique for Ductal Carcinoma In-Situ (NCT00586326), a na phase 2 study. The primary outcome is Local Control Rate for Follow-up Period of 5 Years..

2. Clinical Question

This is a descriptive question about local control after one treatment approach in a single-group study, not a randomized estimate of comparative benefit. The registry also lists overall survival, cause-specific survival, disease-free survival, and cosmetic evaluations over time as secondary outcomes. Their results are not reported in the registry record. Without posted outcome estimates and an analysis, the record does not establish the frequency or timing of local failures or the precision of a local-control estimate.

3. Trial Design

The registry identifies NCT00586326 as a phase 2, single-group study of MammoSite Radiation Therapy System as the sole radiation therapy technique for DCIS. The listed intervention is a device, and the study arm is “Women with DCIS.” Enrollment is recorded as 133. The study status is completed; the recorded start is 2003-08 and primary completion is 2006-01.

Allocation is listed as NA, and masking is listed as none. Those entries fit the single-group design: the registry does not describe assignment between treatment arms, blinding, or a control group. In consequence, results from this study would describe the treated group rather than estimate a contrast between treatment strategies. Differences that might arise in a comparison with another group cannot be separated from differences in patient characteristics, care, or follow-up using this design alone.

The primary outcome is titled “Local Control Rate for Follow-up Period of 5 Years.” Its specified timeframe includes assessment at implant, during radiation therapy, and at the patient’s 3 month, 6 month, 1 year, 2 year, 3 year, 4 year, and 5 year follow-up visits. The registry lists overall survival, cause-specific survival, disease-free survival, and cosmetic evaluations over time as secondary outcomes.

Although the study is marked completed, the registry record does not report a primary endpoint result or analysis. It lists no analyses. The detailed protocol, eligibility criteria, treatment-delivery procedures, follow-up completeness, and statistical analysis plan are not reported in the registry record. Completion status alone does not establish that all planned measurements were obtained or analyzed.

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.

Before assignment: Consented patients who were willing to enroll were evaluated prior to surgery. The lumpectomy was performed per the usual standard of care. The MammoSite applicator could be placed at the time of lumpectomy surgery or post-surgery in a separate procedure if adequate evacuated cavity was available as assessed by ultrasound.

Enrollment to Device Placement-Enrolled

Reasons for not completing this period:

Device Placed toTreatment-ITT

Reasons for not completing this period:

Treated Through 5-yr Follow Up-Treated

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 Local Control Rate for Follow-up Period of 5 Years., measured over Data collected at the time of implant, radiation therapy, and at the patient's 3 month, 6 month, 1 year, 2 year, 3 year, 4 year and 5 year follow-up visits..

The primary endpoint is the local control rate during a follow-up period of 5 years, expressed as a percentage of subjects. It is intended to describe whether recurrence occurs within the treated breast area defined by the prescription isodose volume. The registry defines failure as a histologically confirmed recurrence, invasive or non-invasive, within that volume. That definition specifies which events count toward the endpoint rather than treating every subsequent cancer-related event as local failure.

In particular, ipsilateral axillary, infraclavicular, internal mammary, or supraclavicular recurrence, and distant metastases, were not considered treatment failures unless accompanied by ipsilateral breast failure. This distinction makes the endpoint focused on control in the specified breast volume, rather than a general measure of disease elsewhere or survival.

Local control is used as an outcome because recurrence in the treated area is directly relevant to the stated purpose of evaluating a sole radiation therapy technique. A rate can summarize the proportion of participants meeting the endpoint definition over the specified follow-up. Interpreting such a rate requires the event definition, follow-up duration, analysis population, and handling of missing observations to be clear.

The registry record does not report a numerical local-control result, confidence interval, event count, or analysis population for this endpoint. It also notes that histological evaluation was required by protocol for recurrences, but the case report forms did not provide space to capture that data. Thus, the endpoint definition is available, but the posted record does not show the observed result or its precision.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The statistical information available in the registry record is limited. It identifies a phase 2, single-group study, an endpoint expressed as a percentage of subjects, and a follow-up schedule. It does not report a primary outcome analysis, an analysis population for that endpoint, or a statistical analysis plan. General statistical explanations can clarify what an analysis would mean, but cannot supply the missing result.

What does a percentage endpoint represent?

In general, a percentage summarizes the number of participants meeting an event definition relative to a specified denominator. For this study, the endpoint is local control, and the registry defines failure as histologically confirmed recurrence within the prescription isodose volume. To interpret a percentage, readers need to know which participants contributed to its denominator, how recurrence was assessed, and how participants with incomplete follow-up were handled. Those analysis details are not reported in the registry record.

The title calls the endpoint a local-control rate, while the description defines a failure event. Those are complementary ways to frame the outcome, but a reported rate would still need to state its actual calculation and analysis population. The registry does not give an event count, estimate, or calculation method beyond identifying the unit as percentage of subjects.

Why does the follow-up schedule matter?

The registry specifies assessments at implant, during radiation therapy, and at the patient’s 3 month, 6 month, 1 year, 2 year, 3 year, 4 year, and 5 year follow-up visits. Repeated visits can provide information about when events are detected and whether participants remain under observation. A simple proportion and a time-to-event analysis answer different questions: a proportion describes an event frequency in a defined group, whereas a time-to-event method also uses event timing and can account for differing observation periods under its assumptions. The registry record does not state which method was used for local control or provide event times.

In general, a confidence interval accompanies an estimate to describe its statistical uncertainty. A narrower interval indicates greater precision under the model and data assumptions; a wider interval indicates less precision. Neither an interval nor the underlying primary outcome estimate is reported in the registry record. As a result, precision cannot be assessed from the posted primary outcome information.

What can a single-group design estimate?

A single-group design can describe outcomes observed among the participants in that group. It does not include a concurrent control group for estimating a between-group difference. In general, without random allocation to comparison groups, an observed outcome cannot separate the effect of treatment from other influences on the result. This study is recorded as single group, with allocation NA and masking none, so there is no randomized comparison in the registry record.

This is not a criticism of a descriptive estimate; it is a distinction about the question the design can answer. A group’s observed local-control rate, if posted, would be a summary of that group under its follow-up and endpoint definitions. It would not, by itself, establish how outcomes would differ under another treatment.

How should planning illustrations be read?

Planning illustrations are not observed trial outcomes and are not observed power. The stated illustration assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is a stated fraction of the observed effect. These are assumptions for hypothetical planning, not a description of the study’s single-group design. The record does not report that these assumptions formed the original design or sample-size justification. The illustrations therefore should not be interpreted as evidence that this study had a particular power, nor as a reconstruction of its protocol.

In general, a planning calculation asks how much information a future comparison might require under specified assumptions. If the assumed effect changes, the resulting planning requirement changes too. Such calculations depend on the selected endpoint, event frequency, allocation, significance level, and analysis model. The registry does not report the original sample-size justification, and the posted record provides no local-control estimate from which to assess an observed effect.

What does over-dispersion mean in general?

For outcomes that are counts, over-dispersion means that variability is greater than a chosen statistical model expects. If it is ignored, standard errors can be too small and confidence intervals too narrow. That concept is not a basis for interpreting this record’s primary endpoint: the endpoint is identified as a percentage of subjects, and the registry does not report a count model or an analysis method. No claim about over-dispersion in this study is warranted.

Similarly, different kinds of outcomes call for different methods. A binary event outcome may be analyzed as a proportion, while time-to-event outcomes use timing information and may account for censoring. The registry lists survival outcomes but does not report their analyses. The method used for any listed outcome is not reported in the registry record.

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("Treated")
n      <- c(100)
events <- c(99)
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  Treated  100  99  99.0  94.6  100.0  94.6  99.8  94.6  99.8

11. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary local-control endpoint and secondary outcomes of overall survival, cause-specific survival, disease-free survival, and cosmetic evaluations over time. It does not report results for these outcomes or describe a plan for controlling the risk of false-positive findings when several outcomes are examined. The multiplicity strategy is not reported in the registry record.

In general, multiplicity arises when several statistical tests or outcome measures are considered. If each is interpreted without regard to the others, the chance of finding at least one apparently notable result by chance can increase. Common approaches include prioritizing one primary outcome, adjusting inference across a specified family of tests, or treating secondary analyses as exploratory. The registry record does not say which approach, if any, was planned or used. No significance tests or analysis results are listed.

The record also does not report how missing primary outcome observations were handled, whether follow-up was complete, or which participants were included in the local-control analysis. The safety group is labeled “Intent to Treat,” but that label does not establish the analysis population for the primary endpoint. Enrollment is recorded as 133, whereas the safety group lists 118 at risk; the reason for this distinction is not reported in the registry record. No further inference about participant flow or missingness is possible from those entries alone.

In general, missing data can affect an estimate when the availability of follow-up is related to outcome or differs across participants. Methods such as censoring rules, imputation, or sensitivity analyses may address particular missing-data questions, but the method must be specified and its assumptions considered. The registry does not describe any such method for this study. The required histological evaluations and the lack of a place to capture those data on case report forms are an additional documentation concern; the record does not say how that issue affected the endpoint analysis.

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 1% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: cerebral vascular accident (1.7%), lung cancer with metastases to the brain (0.8%), abnormal uterine bleeding (0.8%), cellulitis (0.8%), infection (0.8%).

The safety entry is labeled “Intent to Treat” and lists 118 at risk for serious events and 118 at risk for other events. It reports 6 participants affected in the serious-event category and 97 affected in the other-event category. These are registry counts, not comparative estimates. The record provides no control group against which to compare them and does not report a statistical analysis of these counts.

The listed serious-event terms and percentages are Cerebral Vascular Accident, 1.7%; Lung cancer with metastases to the brain, 0.8%; Abnormal uterine bleeding, 0.8%; Cellulitis, 0.8%; and Infection, 0.8%. They describe the terms shown in the record. They should not be read as a complete account of all possible harms, nor as proof that the intervention caused each event. The registry does not report event timing, attribution, duration, or how repeat events were counted.

The denominator is important: percentages and counts describe the safety group as recorded, not necessarily every enrolled participant. The registry does not explain why the safety entry’s at-risk count differs from the enrollment figure or how missing safety observations were handled. The listed safety information is therefore descriptive. It cannot establish comparative risk, causation, or the absence of unlisted events.

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

The registry record establishes that a completed phase 2, single-group study evaluated MammoSite Radiation Therapy System as the sole radiation therapy technique for women with DCIS. It defines a primary local-control endpoint, specifies follow-up visits through 5 years, and identifies secondary outcomes. These details describe the study’s question and intended outcome framework.

The central limitation is that no numerical primary outcome result or analysis is reported. The registry therefore does not show the observed local-control rate, the number of local failures, or the precision of any estimate. It also does not report results for the listed secondary outcomes. The existence of an endpoint definition is not a substitute for a posted outcome result.

Even if an outcome estimate were available, a single-group design would describe what was observed among participants in that group; it would not provide a randomized comparison with another strategy. The study has no listed comparator arm, and allocation is recorded as NA. The posted information cannot establish a comparative treatment effect.

The record’s endpoint definition and documentation note also matter. Failure was defined by histologically confirmed recurrence within a specified volume, but the registry says the case report forms did not provide space to capture the required histological evaluation data. The effect of this limitation on outcome ascertainment or analysis is not reported in the registry record.

The safety entry reports counts and selected serious-event terms, but it does not supply a control group, event attribution, or a statistical comparison. Those entries should be read as descriptive safety information rather than evidence of causation or comparative risk. Overall, the record communicates the study design and endpoint definitions, but leaves the primary result, its uncertainty, and important analysis details unavailable.

14. Why This Trial Matters Statistically

This study illustrates why registry design details and posted results need to be read together. A clearly named endpoint and a specified event definition help readers understand what investigators intended to measure. Here, local control is tied to recurrence within the prescription isodose volume, with specified exclusions for certain regional or distant events. That level of definition is important because different event rules can produce different endpoint interpretations.

The record also shows the limits of interpreting a single-group study. Such a design can describe the outcomes recorded in one group, but without a comparator it cannot isolate a difference attributable to the intervention. The entries for allocation and masking, together with the single-group model, make the absence of a randomized comparison explicit.

Most importantly, the primary outcome result and analysis are not reported in the registry record. Statistical interpretation requires more than knowing the endpoint’s name: readers need an estimate, the analysis population, the event count or underlying data, and a measure of uncertainty. Without those elements, the result’s magnitude and precision cannot be evaluated. A completed status does not remove this reporting gap.

The registry’s note about histological documentation is also statistically relevant. Endpoint classification depends on applying the stated definition consistently. The record says the protocol called for histological evaluation, while the case report forms lacked space to capture it. It does not report how that issue was resolved or whether it affected the analysis.

Finally, the safety counts and planning assumptions answer different questions. Safety counts are descriptive entries for the recorded group; planning illustrations are hypothetical calculations under stated assumptions. Neither supplies the missing local-control result or creates a valid comparison. Keeping these distinctions clear prevents design information, safety summaries, and planning exercises from being mistaken for evidence of an observed treatment contrast.

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 recorded for this study. First, although the status is completed and the primary endpoint is defined, the registry does not report a numerical local-control rate, event count, confidence interval, or analysis. The primary outcome therefore cannot be assessed quantitatively from the registry record.

Second, the study is recorded as single group, with no comparator, allocation listed as NA, and masking listed as none. This design does not support a randomized comparison. Any group outcome, if available, would be descriptive rather than a direct estimate of the difference from another treatment strategy.

Third, the endpoint requires histologically confirmed recurrence, but the registry notes that case report forms did not provide space to capture the histological evaluation data required by protocol. The record does not explain how this data-capture issue was handled, how events were classified, or whether it affected the endpoint analysis.

Fourth, the primary endpoint analysis population, follow-up completeness, and approach to missing observations are not reported in the registry record. Enrollment is listed as 133, while the safety entry lists 118 at risk. The record does not explain this difference, and it should not be used to infer the primary endpoint denominator or participant flow.

Finally, results for the listed secondary outcomes and details of multiplicity handling, the statistical analysis plan, and original sample-size justification are not reported in the registry record. Planning illustrations based on an observed effect are not a substitute for the trial’s original design documentation or an observed primary result.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: MammoSite as Sole Radiation Therapy Technique for Ductal Carcinoma In-Situ — NCT00586326.
• Registry record last updated 2012-11-06; status last verified 2012-11.
• Results first posted 2012-10-22.
• 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

NCT00586326 is a completed phase 2, single-group study of MammoSite Radiation Therapy System as sole radiation therapy for women with DCIS. Enrollment is recorded as 133. The study started in 2003-08, with primary completion in 2006-01. Allocation is listed as NA and masking as none.

The primary endpoint is local control during a follow-up period of 5 years, with failure defined as histologically confirmed invasive or non-invasive recurrence within the prescription isodose volume. The registry lists overall survival, cause-specific survival, disease-free survival, and cosmetic evaluations over time as secondary outcomes.

The primary outcome result, secondary outcome results, and analyses are not reported in the registry record. The safety entry lists 6 affected participants for serious events and 97 for other events, with 118 at risk in each category. The registry also notes a limitation in capturing histological evaluation data on case report forms.