Internal Radiation Therapy in Treating Patients With Prostate Cancer: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Internal Radiation Therapy in Treating Patients With Prostate Cancer (NCT00573833), a na na study. The primary outcome is Number of Patients With an Acceptable Level of Severe Toxicity as Defined at < Grade 3 CTC Toxicity.

2. Clinical Question

3. Trial Design

This is a completed pilot study of HDR brachytherapy as definitive management for intermediate-risk prostate cancer. The record lists a single-group model and one treatment group, HDR Brachytherapy. Its description specifies 9.5 Gy for 4 fractions given over 2 days. There is no randomized control group: allocation is listed as NA, and masking is listed as NONE. The trial therefore provides a description of treatment and outcomes in the study group, not a direct estimate of how this treatment compares with another intervention.

The listed enrollment is 23. The study is marked COMPLETED, with a start date of 2007-11 and primary completion date of 2014-09. Phase is listed as NA. Memorial Sloan Kettering Cancer Center is the sponsor. These registry entries describe the study record but do not by themselves establish how many participants were included in each outcome analysis or whether every enrolled participant completed follow-up.

The registry lists questionnaire administration and quality-of-life assessment alongside brachytherapy. It does not provide enough detail to reconstruct their administration schedule, analytic role, or relationship to the primary endpoint. The primary outcome timeframe is assessment at scheduled 3 month intervals for one year. The description says that feasibility involves an acceptable level of acute and late severe toxicity and adequate dosimetric coverage. The record does not specify how adequate coverage was assessed or how the toxicity observations were combined into an overall feasibility judgment.

A pilot study can describe whether a treatment approach was evaluated and what outcomes were intended for monitoring. In a single-group design, however, treatment outcomes can also reflect the characteristics of the enrolled population, follow-up, and other influences. Without a concurrent comparator, the record cannot isolate a treatment effect through a randomized between-group contrast. The primary endpoint count and its analysis are not reported in the registry record, so the trial design information does not support a conclusion about the observed 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

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 Number of Patients With an Acceptable Level of Severe Toxicity as Defined at < Grade 3 CTC Toxicity, measured over At scheduled 3 month intervals for one year.

The primary endpoint is a count of patients with an acceptable level of severe toxicity. Its title specifies an acceptable level defined at less than Grade 3 CTC toxicity. The description says feasibility will be judged by acceptable severe toxicity, including both acute and late effects, and adequate dosimetric coverage. It defines severe toxicity as greater than or equal to Grade 3 NCI CTC toxicity. In practical terms, the threshold distinguishes toxicity below the stated severe grade from toxicity at or above it. The endpoint is recorded in participants, rather than as a continuous measurement.

Toxicity monitoring is relevant to a pilot study because treatment feasibility is not only about delivering the intended radiation; the study description also emphasizes adverse effects. The stated timeframe, scheduled 3 month intervals for one year, indicates repeated assessment over follow-up rather than a single assessment at treatment. The record does not state how observations across those scheduled visits were summarized into the primary count, or how acute and late effects were handled if a participant had multiple observations.

The endpoint description also mentions adequate dosimetric coverage as part of feasibility, but the primary endpoint title is a toxicity count. The registry does not explain whether dosimetric coverage was a separate outcome, a supporting criterion, or part of a combined feasibility rule. Most importantly, the number meeting the primary endpoint and any uncertainty estimate are not reported in the registry record. The endpoint definition can therefore be described, but the observed primary outcome cannot be interpreted from this record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

A single-group design follows a treatment group without assigning participants to a concurrent comparison group. The record identifies this study as single-group and lists allocation as NA. Consequently, its design does not create a randomized contrast between HDR brachytherapy and another intervention. If outcomes are reported, they can describe what was observed in the treated group, but attributing differences from an external expectation to treatment alone requires caution. General statistical principle: random allocation can help balance measured and unmeasured characteristics across groups, while a single-group study does not provide that protection through a concurrent randomized comparison.

What does the primary count represent?

The primary endpoint is a count of participants meeting the stated acceptable toxicity criterion. Counts are useful when the clinical question is how many participants experienced an outcome, but a count alone depends on how many participants were actually assessed. Interpretation typically needs both the count and its relevant denominator, together with a clear definition of the outcome and follow-up. The registry record specifies the endpoint unit as participants, but does not report the primary count, denominator, or an analysis population for that endpoint. Therefore, no primary event proportion or other derived estimate can be stated.

The outcome description refers to severe toxicity and states that severe toxicity is greater than or equal to Grade 3 NCI CTC toxicity. The title describes an acceptable level as less than Grade 3 CTC toxicity. These expressions frame a threshold, but the record does not fully explain how participants with observations at multiple visits were classified for the count. General statistical principle: prespecifying how repeated measurements and multiple events are reduced to a participant-level endpoint helps avoid ambiguity in analysis. That operational rule is not reported in the registry record.

How should uncertainty be understood?

A confidence interval is a range of values compatible with the observed data under a specified statistical model. It conveys precision: a narrow interval indicates greater precision than a wide interval, while neither interval alone resolves possible bias or limitations in design. No confidence interval for the primary endpoint is reported in the registry record. Without the endpoint estimate and its uncertainty, readers cannot assess how precisely the feasibility outcome was estimated.

General statistical principle: an outcome count from a small study can be imprecise, especially when the event is uncommon. The study's listed enrollment is 23, but that figure should not be substituted for the primary endpoint denominator, which is not reported. The safety entries have their own at-risk denominator of 21; it is not appropriate to reuse that denominator for a different endpoint without a registry statement that it applies.

What do the planning assumptions mean?

The record describes sample-size planning illustrations based on a stated fraction of an observed effect. It specifies a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. Those assumptions describe a hypothetical planning framework rather than the actual single-group study design. The record's planning note says the illustrations are not the trial's own design. The resulting sample sizes are planning illustrations, not observed power. No sample-size justification for this pilot or trial-specific statistical plan is reported in the registry record.

General statistical principle: planning calculations depend on the effect size a future study aims to detect, the chosen significance threshold, the desired power, and design assumptions. Changing the assumed effect changes the required sample size. A planning illustration is not evidence that the current study had a particular probability of detecting an effect, and it cannot replace an analysis of observed outcomes. The record does not provide the numerical planning results in the registry record describing this trial, so no planning count can be interpreted.

Why can over-dispersion matter?

General statistical principle: over-dispersion occurs when variability in count data exceeds what a chosen model assumes. If a model underestimates variability, standard errors may be too small and confidence intervals may be too narrow. This concern is relevant to some count outcomes, but the primary endpoint is described as a participant count, and no model or dispersion estimate is reported. There is no basis in the registry record to state that over-dispersion was evaluated or to claim that it affected this analysis.

The record lists 0 analyses. That registry entry does not identify an analytical method for the primary endpoint. It also does not report an adjustment strategy, confidence interval method, or hypothesis test. Statistical methods should therefore be described as unreported rather than inferred from the endpoint wording or from generic planning assumptions. The appropriate reading is limited to the registered design and outcome definitions, with no reconstructed or recalculated primary estimate.

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("HDR Brachytherapy")
n      <- c(21)
events <- c(20)
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  HDR Brachytherapy  21  20  95.2  76.2  99.9  77.3  99.2  77.2  98.9

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 4 outcome measures and 0 analyses. It does not report a statistical plan explaining how the outcomes were prioritized or whether any formal adjustment for multiple comparisons was intended. The primary outcome is identified by title, but the record does not describe a hierarchy of secondary outcomes, a family-wise error strategy, or how multiple tests would be interpreted. These details are not reported in the registry record.

Multiplicity arises when several outcomes or hypotheses are evaluated: the more opportunities there are to declare a result notable, the more important it becomes to know how the analyses were planned and interpreted. This is a general statistical concern, not evidence that a particular error occurred in this study. Because no analysis results are listed, no multiplicity-adjusted or unadjusted inference can be assessed.

Missing-data procedures and analysis populations are also not reported in the registry record. The listed enrollment is 23, while the safety group entries report 21 at risk. The record does not explain the difference or state how missing observations, withdrawals, or incomplete follow-up were handled. The primary endpoint timeframe is scheduled assessments at 3 month intervals for one year, but the registry does not state how missed visits or partial follow-up affected endpoint classification.

It would be inappropriate to infer an intention-to-treat population, a per-protocol population, or any imputation method from the design description alone. The denominator for the primary endpoint, reasons for any exclusions, and methods for handling missing toxicity assessments are not reported in the registry record. These omissions limit evaluation of both the completeness and the statistical interpretation of the outcomes.

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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: esophagitis (4.8%), hemorrhage, esophagus (4.8%).

For HDR Brachytherapy, the record lists 21 participants at risk for serious adverse events, with 2 affected. It separately lists 21 at risk for other adverse events, with 11 affected. These are safety counts and denominators as recorded; they are not the primary endpoint result. No totals should be inferred by combining the categories, since the record does not state whether affected participants overlap across event types.

The top serious adverse event terms listed are Esophagitis and Hemorrhage, Esophagus, each at 4.8%. The registry does not provide additional detail in the registry record about event timing, severity grade, duration, management, or how the terms relate to individual participants. The terms are reproduced as listed and should not be interpreted as evidence of causation or as a comparison with another treatment.

The safety denominator of 21 differs from the listed enrollment of 23. The registry does not explain this difference; it should not be assigned a cause. Also, the safety denominators do not establish the number included in the primary toxicity endpoint analysis. That primary result and its denominator are not reported in the registry record.

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

The registry record establishes that this was a completed, single-group pilot study of HDR brachytherapy for intermediate-risk prostate cancer. It specifies the treatment schedule and describes a feasibility question centered on acceptable severe toxicity and adequate dosimetric coverage. It also records selected adverse-event counts. These are useful details for understanding the study's intent and the scope of its posted safety information.

The primary endpoint result is not reported in the registry record. As a result, the central feasibility outcome cannot be judged from the posted information: there is no count of participants meeting the stated acceptable toxicity criterion, no endpoint-specific denominator, and no estimate of uncertainty. The record also does not explain how dosimetric coverage contributed to the feasibility assessment. The absence of these details is not evidence that the outcome was favorable or unfavorable; it means the result cannot be determined from this record.

The trial does not include a separate control group. Even if the outcome estimate were available, a single-group design would describe observed outcomes in the study group rather than provide a randomized comparison against another treatment. The registry record therefore does not establish comparative benefit or harm. The listed serious and other adverse-event counts provide safety information as recorded, but do not answer the primary endpoint question or support a causal comparison.

The pilot designation indicates the study's stated status as a pilot in its official title. It should not be taken as proof of a particular degree of success, precision, or readiness for broader use. Likewise, COMPLETED describes the registry status, not whether prespecified criteria were met. The defensible interpretation is narrow: the record documents an evaluation of HDR brachytherapy, a planned toxicity-based feasibility endpoint, and selected safety counts, while leaving the primary result and important analysis details unreported.

14. Why This Trial Matters Statistically

This study illustrates how a clearly stated clinical aim and an interpretable result are separate parts of a trial record. The official title describes a pilot evaluation of HDR brachytherapy as definitive management for intermediate-risk prostate cancer. The primary endpoint focuses on toxicity, and the description also names dosimetric coverage as part of feasibility. Those elements help identify what investigators intended to examine. But without the reported endpoint count and denominator, readers cannot assess whether the feasibility criterion was met or how precisely it was estimated.

The single-group design is also statistically important. It can describe observations in the treated group, but it does not provide the protection or interpretive structure of a randomized comparison. The record lists allocation as NA and masking as NONE, and no comparator group is described. A reader should therefore distinguish descriptive safety information from evidence of relative effects. The safety counts do not establish how outcomes would differ under another treatment or under no treatment.

Finally, the record shows why denominators and analysis details matter. Enrollment is listed as 23, while the adverse-event risk groups use 21. The reason is not reported. The primary endpoint denominator, missing-data handling, analysis populations, and analytic methods are also not reported in the registry record. Statistical interpretation depends not just on outcome labels, but on knowing who contributed data, how outcomes were defined across follow-up, and how uncertainty was quantified. In this case, those missing details constrain interpretation regardless of the study's completed status.

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 most consequential limitation of the registry information is that it does not report the primary endpoint result. The number meeting the acceptable toxicity criterion, its denominator, and any estimate of precision are not reported in the registry record. The description also includes adequate dosimetric coverage as part of feasibility without explaining how that criterion was measured or integrated with the toxicity endpoint.

The single-group design has no concurrent control, so the registry record cannot support a randomized treatment comparison. Allocation is listed as NA and masking as NONE. The record does not report eligibility criteria beyond the official title's focus on intermediate-risk prostate cancer, nor does it provide detailed baseline characteristics that would help describe the population.

The enrollment is listed as 23, while safety outcomes use 21 participants at risk. The registry does not explain this difference. It also does not describe whether the same participants contributed to both safety categories, how follow-up completeness was assessed, or how missing assessments were handled. The scheduled assessment timeframe is given, but rules for classifying repeated toxicity observations are not.

Although the record lists 4 outcome measures, it reports 0 analyses. The statistical analysis plan, analysis populations, multiplicity approach, interim analysis plan, and sample-size justification are not reported in the registry record. The adverse-event terms and counts offer limited safety detail without event-level context such as timing or duration. These limitations mean that the registered design and safety entries can be described, but the primary feasibility result and its uncertainty cannot be evaluated.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Internal Radiation Therapy in Treating Patients With Prostate Cancer — NCT00573833.
• Registry record last updated 2017-10-20; status last verified 2017-09.
• Results first posted 2017-10-20.
• 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.

19. Record Summary

NCT00573833 is a completed, single-group pilot study titled “Internal Radiation Therapy in Treating Patients With Prostate Cancer.” Its official title describes HDR brachytherapy as definitive management for intermediate-risk prostate cancer. Memorial Sloan Kettering Cancer Center is the sponsor. The listed enrollment is 23, the start date is 2007-11, and the primary completion date is 2014-09. Phase is listed as NA; allocation is NA and masking is NONE.

The HDR Brachytherapy group received 9.5 Gy for 4 fractions over 2 days. The primary endpoint concerns an acceptable level of severe toxicity, with scheduled assessments at 3 month intervals for one year. The record lists 4 outcome measures and 0 analyses. Serious adverse events are listed for 21 at risk, with 2 affected; other adverse events are listed for 21 at risk, with 11 affected. The primary endpoint result, its denominator, and the statistical analysis details are not reported in the registry record.