Randomized Salvage Radiation Therapy Plus Enzalutamide Post Prostatectomy: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Randomized Salvage Radiation Therapy Plus Enzalutamide Post Prostatectomy (NCT02203695), a randomized phase 2 study. The primary outcome is Percent of Participants With Freedom of PSA (Prostate Specific Antigen) Progression.

2. Clinical Question

The study was framed as a phase II comparison intended to inform further study in a definitive phase III setting. Its primary endpoint was freedom from PSA progression (FFPP), defined by time from randomization to PSA progression. The registry reports 84.0% for SRT plus enzalutamide and 66.0% for SRT plus placebo. An unadjusted recalculation from the posted event counts estimates a risk difference of 0.186, with an interval from 0.006 to 0.366 and p = 0.048. This comparison describes the posted data; it does not by itself establish the size or certainty of an effect in other populations or settings.

3. Trial Design

This completed study was a randomized, triple-masked, parallel phase II trial. The registry records enrollment of 86 participants, with 43 assigned to SRT plus enzalutamide and 43 to SRT plus placebo for the primary result. The record names Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins as sponsor. It lists a start date of 2015-03-28 and primary completion on 2022-12-31.

Both groups received salvage radiation therapy. The experimental group also received enzalutamide, while the control group received placebo. The radiation description specifies 3D-CRT or IMRT and a dose range of 66.6-70.2 Gy, administered in 1.8 Gy fractions over 37-39 treatments. The placebo regimen is described as daily for 6 months, including 2 months before SRT, during SRT, and after SRT. The brief summary describes enzalutamide use for 6 months and says it began 2 months before SRT and continued during SRT; the registry arm description does not fully specify the timing after SRT for that group.

Randomization is the method used to assign participants to study groups. Masking is intended to limit the influence of knowledge about assignment on participant experience, care, or outcome assessment; the registry labels masking as triple but does not identify the masked roles. A parallel design means the assigned groups are compared over the study rather than participants crossing between regimens.

The record reports no sponsor analysis entries for the primary outcome. It also does not report the trial's original sample-size justification, prespecified statistical analysis plan, analysis populations, or details of interim analyses. The planning illustration associated with the observed result is separate from the original trial design and should not be treated as evidence about the assumptions used to plan this study.

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 Percent of Participants With Freedom of PSA (Prostate Specific Antigen) Progression, measured over From time of randomization to date of PSA progression, approximately 2 years..

The primary endpoint is the percent of participants with freedom from PSA progression. The registry defines FFPP as the time from randomization to the date of PSA progression, with participants who have not progressed by the time of analysis censored at their last PSA measurement. The stated timeframe is approximately 2 years from randomization.

PSA progression is the event used to mark loss of freedom from progression. A time-to-event endpoint can account for the timing of that event and can retain information from participants who have not experienced it by the analysis date, rather than requiring every participant to have an observed event. Censoring indicates that the event time is not observed beyond the last measurement; it is not evidence that progression did or did not occur later.

The registry also posts a percentage for each study group, making the result readable as a proportion free of PSA progression at the target time. The posted values are 84.0% for SRT plus enzalutamide and 66.0% for SRT plus placebo. These are the registry's arm-level outcome values; the record does not provide a sponsor-reported time-to-event analysis, a survival curve, or an adjusted estimate for this endpoint. The endpoint therefore gives a clinically relevant measure of disease progression over follow-up, while the interpretation of its uncertainty depends on the precision and analysis details available in the record.

7. Results Posted in the Registry

• SRT Plus Enzalutamide: 83.7% (36/43) versus 65.1% (28/43) on control; risk difference 18.6 percentage points (95% CI 0.6 to 36.6), risk ratio 1.29 (1.00–1.66); unadjusted two-proportion z-test p = 0.048.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Metastatic Free Survival Rate

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • SRT Plus Enzalutamide: 0.0% (0/43) versus 2.3% (1/43) on control; risk difference -2.3 percentage points (95% CI -6.8 to 2.2); unadjusted two-proportion z-test p = 0.314.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between SRT Plus Enzalutamide and the control. The interval gives the range of effects that remain compatible with the data.

Feasibility of Achieving Stated Accrual

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • SRT Plus Enzalutamide: 89.6% (43/48) versus 89.6% (43/48) on control; risk difference 0.0 percentage points (95% CI -12.2 to 12.2), risk ratio 1.00 (0.87–1.15); unadjusted two-proportion z-test p = 1.000.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between SRT Plus Enzalutamide and the control. The interval gives the range of effects that remain compatible with the data.

The secondary outcome list spans disease recurrence, metastatic outcomes, treatment tolerability, quality of life, sexual health, and feasibility of reaching accrual. The registry record contains numerical results for metastatic-free survival and feasibility of achieving stated accrual. It does not report numerical results for the other listed secondary measures, including local recurrence and the listed questionnaire outcomes. The overall secondary picture is therefore incomplete: the available posted results cover only part of the range of questions the study set out to assess.

The two posted secondary results address different questions from the primary PSA endpoint. The metastatic outcome concerns a less frequent disease event, while the feasibility measure concerns whether the stated accrual target was reached. Neither directly replaces the primary measure of freedom from PSA progression. In general, an outcome farther downstream in the disease course may have fewer events during limited follow-up, while a feasibility measure assesses recruitment rather than treatment efficacy. These distinctions mean that the secondary outcomes can add context but should not be read as equivalent tests of the primary question.

The posted secondary analyses are unadjusted, and the record does not describe a multiplicity plan. When several outcomes are examined, the chance of at least one apparently unusual result can increase; this is a general statistical concern, not a claim about what happened in this trial. Without a prespecified hierarchy or adjustment method in the registry record, individual secondary p-values carry less weight than a clearly specified primary analysis. They are best treated as exploratory descriptions rather than independent confirmation.

The record reports no analyses for the secondary measures in its analysis entries. The numerical values that are posted can still be read descriptively, but the missing details limit inferences about how they were calculated and whether they were planned as formal tests. The absence of results for other listed outcomes also cannot be interpreted as evidence that those outcomes showed no difference. Their results are not reported in the registry record.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Number of Participants With Local Recurrence
• Metastatic Free Survival Rate
• How Well Participants Tolerate Treatment Assessed by European Organization for Research & Treatment of Cancer Quality of Life (Questionnaire (EORTC-QLQ-P25)
• How Well Participants Tolerate Treatment Assessed by the Functional Assessment of Cancer Therapy-Prostate (FACT-P).
• How Well Participants Tolerate Treatment Assessed by the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-C30).
• How Well Participants Tolerate Treatment Assessed by Sexual Health Inventory in Men (SHIM) Questionnaire.
• Feasibility of Achieving Stated Accrual

9. Statistical Interpretation

10. Statistical Methods Explained

Statistical concepts in this discussion are general explanations unless a result is explicitly attributed to the registry record. The primary contrast is an unadjusted recalculation from the posted group counts. It is not a sponsor-reported analysis, and the record does not provide a full statistical methods plan.

What does a group percentage describe?

A group percentage expresses the observed outcome for that group in relation to the participants represented in its result. Here, the registry posts freedom-from-PSA-progression values of 84.0% and 66.0% for the enzalutamide and placebo groups, respectively. The comparison is not based on the percentages alone: the recalculation uses posted counts of 36 of 43 and 28 of 43. A percentage is a concise summary, but it does not show which participants had missing measurements, the timing of progression, or how follow-up differed across individuals.

For a binary outcome, a risk difference is the outcome proportion in one group minus the outcome proportion in the comparison group, with the direction depending on which outcome is coded and which group is subtracted. The posted recalculation gives a risk difference of 0.186 for enzalutamide relative to placebo on the freedom-from-progression outcome. This is an absolute contrast on the proportion scale. It is not a relative risk, and it does not mean that each participant's outcome changes by that amount.

How should the p-value be read?

The unadjusted p-value for the recalculated primary contrast is 0.048. In general, a p-value measures how incompatible the observed data are with a specified null model, assuming the model and its conditions hold. It is not the probability that the observed difference arose by chance, and it does not measure how important the difference is. A value near a conventional threshold can be sensitive to analysis choices, outcome definitions, or additional comparisons. The registry record does not state the primary analysis plan or a multiplicity procedure, so this p-value should be read as an unadjusted result rather than as a documented confirmatory test.

Randomization helps make groups comparable on average, including with respect to factors that were not measured, but it does not guarantee exact balance in a small trial. The record gives no baseline table or adjusted primary analysis. Thus the recalculation is a simple comparison of posted summaries, not a model that accounts for participant-level characteristics, follow-up time, or other covariates.

What does censoring mean for this endpoint?

In general, censoring occurs when the exact event time is not observed during the available follow-up. The endpoint definition says that a participant without PSA progression at analysis is censored at the last PSA measurement. This preserves information that the participant remained progression-free through that measurement, without asserting what happened afterward. Time-to-event methods usually rely on assumptions about how censored follow-up relates to the event process. The registry does not report the specific estimator, model, or diagnostics used for a time-to-event analysis, and no sponsor-reported time-to-event analysis is posted.

The primary endpoint is described both as a rate at 2 years and as time from randomization to progression. Those concepts are related but not interchangeable in every analysis: a fixed-time percentage summarizes status at a target time, while a time-to-event method can use event timing and censoring over follow-up. The record's arm values provide percentages, but the absence of a posted analysis description prevents confirmation of how those values were derived from the time-to-event definition.

Why does the recalculation differ in status from a trial analysis?

A recalculation from summary counts is useful because its inputs and result are transparent. It cannot recover information that is not in the summary, such as event dates, censoring patterns, stratification variables, or participant-level missingness. A sponsor's planned and executed analysis, if reported, can use information and methods not represented in a simple count comparison. No such primary analysis is reported in this registry record. The record does not flag a discrepancy, but that does not convert the recalculation into a sponsor analysis.

The secondary metastatic result is also posted as group counts and an unadjusted contrast. The registry gives 0 participants in the enzalutamide group and 1 in the placebo group for that outcome, with an unadjusted p-value of 0.314. With so few recorded events, estimates based on the counts are inherently limited in precision; this is a general property of sparse binary data. The registry's title calls the outcome metastatic-free survival, while its posted unit is participants. Without a detailed analysis description, the counts should not be treated as a complete time-to-event analysis.

Finally, a confidence interval describes uncertainty under the calculation's assumptions, while a power calculation describes the sample size that a design would need under specified assumptions. Neither converts a small trial into a definitive answer. The registry's sample-size illustration uses the observed effect and stated planning assumptions; it is not the original design justification, which is not reported in the registry record.

11. Confidence Intervals and Precision

The unadjusted primary recalculation estimates a risk difference of 0.186, with an interval from 0.006 to 0.366. A confidence interval is a range of values compatible with the data under the statistical method and its assumptions. The record does not specify a confidence level for this interval, so no confidence level should be attached to it from the posted information alone.

The interval spans from a value close to no difference to a substantially larger positive difference. This means the point estimate is not precise enough to identify one narrow effect size. The lower endpoint is above zero, but close to it; modest changes in data or analysis could matter for a result near that boundary. The unadjusted p-value of 0.048 is also close to a commonly used threshold, but it should not be treated as a sharp divide between certainty and uncertainty.

Precision depends in part on the amount of information available. The primary comparison includes 43 participants per group, and the recalculation uses the posted outcome counts. No participant-level data, event timing, or detailed missingness information is reported. The registry provides no adjusted estimate or sponsor-reported interval for the primary outcome. Consequently, the interval characterizes the simple unadjusted contrast rather than all uncertainty that could arise from different analysis choices or limitations in follow-up.

The interval does not establish that the true effect lies within its endpoints with certainty, nor does it address whether a difference would be meaningful in another setting. It quantifies sampling uncertainty under the calculation's assumptions. The small number of participants and absent analysis details support reading the primary result as an estimate with meaningful uncertainty, rather than as a precise measure of the size of a treatment effect.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The sample-size display is a planning illustration based on the observed primary effect, not the trial's own original design assumptions. The figures are participants per arm for 80% power and participants per arm for 90% power; they are not total event counts. The listed assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is set to the stated fraction of the observed effect.

In plain terms, the 80% power column gives the number of participants per group that the illustration estimates would be needed for an 80% chance of detecting the specified effect under its assumptions, if that effect were present. The 90% power column applies the same idea with a higher target chance of detection. For the full observed effect, the display lists 86 participants per arm for 80% power and 114 participants per arm for 90% power. For planning for 75% of the observed effect, it lists 162 and 216 participants per arm. For planning for 50% of the observed effect, it lists 382 and 511 participants per arm.

Smaller effects are harder to distinguish from random variation, so the illustration requires more participants per arm as the target effect becomes smaller. These figures are not observed power: they do not report the probability that this completed trial detected an effect after the results were known. Because the calculation uses the observed effect, it is a hypothetical planning exercise, not a prospective justification for the trial's enrollment. The trial's own original sample-size justification is not reported in the registry record.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, p₀ and p₁ are the control and treatment proportions, and p̄ is their average.

Worked calculation for this trial

1. Control proportion p₀ = 0.651; treatment proportion p₁ = 0.837; average p̄ = 0.744.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.6170 = 1.2094.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.6029 = 0.5074.
4. n = (1.2094 + 0.5074)² / (0.1860)² = 85.1, rounded up to 86 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
p0 <- 0.651162790697674                          # control proportion
p1 <- 0.837209302325581                          # treatment proportion
n_per_arm <- function(power, frac = 1) {
  q1 <- p0 + (p1 - p0) * frac               # smaller effect = fraction of the observed difference
  pbar <- (p0 + q1) / 2
  z_b <- qnorm(power)
  ceiling(round((z_a * sqrt(2 * pbar * (1 - pbar)) + z_b * sqrt(p0 * (1 - p0) + q1 * (1 - q1)))^2 / (q1 - p0)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (unrounded n per arm)
cat("power.prop.test:", round(power.prop.test(p1 = p0, p2 = p1, power = 0.80)$n, 1), "\n")

# Simulation: how often does the z-test reject at the 80%-power sample size?
set.seed(2203695)
n    <- n_per_arm(0.80)
reps <- 20000
x0 <- rbinom(reps, n, p0); x1 <- rbinom(reps, n, p1)
ph <- (x0 + x1) / (2 * n)
z  <- ((x1 - x0) / n) / sqrt(ph * (1 - ph) * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE), reps))

Output from running the code

100% of observed effect: n per arm = 86 (80% power), 114 (90% power)
 75% of observed effect: n per arm = 162 (80% power), 216 (90% power)
 50% of observed effect: n per arm = 382 (80% power), 511 (90% power)
power.prop.test: 85.1 
Simulated power at n = 86 per arm: 0.814 (20000 replicates)

The simulation draws many pairs of event counts at the planned sample size and counts how often the two-proportion z-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Multiplicity, Missing Data and Analysis Populations

The primary outcome is identified in the registry record, but the record does not report a statistical analysis plan specifying how the primary comparison was to be conducted. It does not state whether the primary analysis was intended to use a fixed-time proportion, a time-to-event method, or an adjusted model. The endpoint definition explains censoring at the last PSA measurement, but the detailed analysis method is not reported in the registry record.

Multiplicity refers, in general, to the problem of interpreting results when several outcomes or comparisons are examined. If many tests are conducted, some may appear unusual even when there are no underlying differences. The registry lists several secondary outcomes, but it does not report a multiplicity adjustment, a testing hierarchy, or which secondary measures were designated as confirmatory. Therefore, the unadjusted secondary p-values should not be treated as if they were protected against the broader set of comparisons.

The record does not state whether interim analyses were planned or conducted, whether any analysis populations were defined, or how participants who discontinued or lacked outcome measurements were handled beyond the primary endpoint's censoring description. It does not describe a missing-data strategy for the quality-of-life questionnaires or other secondary outcomes. These details are not reported in the registry record. Their absence does not prove that no such procedures existed; it means they cannot be evaluated from the registry information.

The primary outcome's definition says participants without progression at analysis are censored at their last PSA measurement. In general, censoring is most straightforward to interpret when the reason follow-up ends does not systematically conceal a different event risk. The registry does not provide enough detail to assess censoring patterns or whether that assumption was examined. The posted arm percentages and recalculated comparison should consequently be understood alongside this uncertainty.

The primary recalculation is unadjusted, and the record has no sponsor-reported analysis entry. There is no discrepancy flagged between the recalculation and a sponsor analysis. Still, the lack of a reported sponsor analysis means the registry does not provide a direct basis for checking the simple comparison against the trial's intended inferential approach. These missing analysis details limit reproducibility and confidence in the interpretation of borderline or secondary findings.

15. 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 1% reporting threshold.

Most frequent non-serious adverse event terms

The adverse-event record lists 43 participants at risk for serious adverse events in each group and 0 participants affected in either group. It lists 43 participants at risk for other adverse events in each group, with 43 affected in each group. Deaths are listed for 2 participants in the SRT plus enzalutamide group and 0 in the SRT plus placebo group.

These counts describe the registry's posted safety summary. The presence of other adverse events for all participants does not mean that all events were alike in type or severity. The record gives no serious adverse-event terms and does not provide event-level descriptions, timing, attribution, or information about whether deaths were related to treatment. It also does not report a statistical comparison for these safety counts.

Zero recorded serious adverse events should not be interpreted as proof that serious harms are impossible, particularly in a study of this size. Likewise, the difference in death counts is descriptive and does not establish a causal relationship with assigned treatment. The registry safety information is limited to these counts, so it cannot support a detailed assessment of the nature or comparative risk of adverse events.

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

The primary posted data show a higher percentage of freedom from PSA progression in the SRT plus enzalutamide group than in the SRT plus placebo group. The simple unadjusted recalculation estimates a risk difference of 0.186, with an interval from 0.006 to 0.366 and p = 0.048. These figures describe the observed comparison and its statistical uncertainty under the recalculation's assumptions. They do not establish the exact size of an effect or guarantee that the same pattern would occur in another study.

The result does not establish that enzalutamide is beneficial for every participant, nor does it establish that the regimen should be used in clinical practice. It is a comparison from a phase II study with 43 participants per group, and the registry record does not report a sponsor analysis or the full statistical plan. No medical advice follows from this statistical summary.

Nor does the result show that the treatment has no risks. The safety record lists other adverse events for all participants at risk in both groups, no serious adverse events, and deaths in the enzalutamide group but not the placebo group. The registry does not provide enough event detail or attribution to interpret those counts causally or comprehensively.

The trial's stated purpose was to assess whether the addition of enzalutamide could support further study in a definitive phase III setting. The posted primary result offers a comparative estimate relevant to that research question, but the interval and missing analysis details leave substantial uncertainty about its magnitude and generalizability. The metastatic and feasibility results address different questions, and results for several other listed secondary outcomes are not reported in the registry record. A complete appraisal therefore requires attention to both what the posted outcomes show and what the registry does not describe.

17. Why This Trial Matters Statistically

This trial provides a useful statistical example of how an apparently encouraging point estimate can coexist with considerable uncertainty. The primary arm percentages differ, and the unadjusted recalculation produces an interval that extends from near no difference to a materially larger contrast. Reading only the point estimate or only the p-value would omit important information about precision.

The study also illustrates why the outcome definition matters. Freedom from PSA progression is framed as a time-to-event endpoint, with censoring at the last PSA measurement, while the posted arm results are percentages. A reader needs the analysis method and follow-up details to understand exactly how the percentages represent the time-to-event question. Those details are not reported in the registry record.

Several related statistical issues are visible in the record: a randomized design, a modest number of participants per group, a primary comparison that can be recalculated from summary counts, sparse metastatic events, multiple secondary outcomes, and limited safety detail. Each affects how much weight a result can carry. The study can inform the design and interpretation of later research, but the planning illustration based on its observed effect is not a replacement for a prospectively justified design.

Finally, the registry distinguishes between a posted outcome and a fully documented analysis. The arm-level primary percentages and recalculated contrast are informative, but the absence of a reported sponsor analysis, analysis populations, multiplicity procedures, and results for several secondary measures limits a complete statistical assessment. That distinction is important when interpreting registry results: a numerical finding can be described accurately while its broader evidential role remains uncertain.

18. 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.
• Participant counts were reconstructed from posted percentages and arm sizes, so small rounding differences are possible.

The principal limitation for interpreting the primary comparison is that the registry posts arm-level percentages and summary counts but no sponsor-reported primary analysis. The unadjusted recalculation does not incorporate event timing or individual follow-up information. Although the endpoint definition describes censoring, the registry does not report the time-to-event method, censoring distribution, or a survival curve. It is therefore difficult to determine from the record how closely the posted percentages reflect the endpoint's time-to-event definition.

The primary result includes 43 participants per group, and the interval around the recalculated risk difference is broad. The record does not report baseline characteristics or an adjusted analysis, so it is not possible to assess group balance or understand whether any adjustment was planned. The trial's own original sample-size justification is not reported; the posted planning illustration instead uses the observed effect and is not evidence of the assumptions used to design the study.

The secondary evidence is partial. Numerical results are posted for the metastatic outcome and accrual feasibility, but the record lists other secondary measures without reporting their results. It does not describe a plan for handling multiple outcomes, define analysis populations, or report missing-data methods for questionnaire outcomes. Consequently, the secondary outcome pattern cannot be evaluated comprehensively.

Safety interpretation is also limited. The registry provides summary counts, without serious-event terms, event descriptions, treatment attribution, or an inferential comparison. The recorded death counts likewise do not identify cause or relationship to treatment. These limitations prevent a detailed comparison of safety outcomes and are especially relevant when interpreting the absence of reported serious events in a trial of this size.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Randomized Salvage Radiation Therapy Plus Enzalutamide Post Prostatectomy — NCT02203695.
• Registry record last updated 2025-10-28; status last verified 2025-10.
• Results first posted 2025-10-24.
• 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.

22. Record Summary

The registry record describes a completed randomized, triple-masked, parallel phase II trial with enrollment of 86 participants. It compared salvage radiation therapy plus enzalutamide with salvage radiation therapy plus placebo in men with high-risk PSA-recurrent prostate cancer after radical prostatectomy. The primary endpoint was freedom from PSA progression at approximately 2 years.

The posted primary arm values are 84.0% and 66.0%, respectively. An unadjusted recalculation gives a risk difference of 0.186, an interval from 0.006 to 0.366, and p = 0.048. The registry also reports limited secondary and safety counts, but does not report a sponsor analysis, the full statistical plan, or results for several listed secondary measures. The findings are therefore best read as a phase II comparison with important uncertainty and incomplete analysis detail.