Abiraterone Acetate Plus LHRH Agonist and Abiraterone Acetate Plus LHRH Agonist and Enzalutamide: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Abiraterone Acetate Plus LHRH Agonist and Abiraterone Acetate Plus LHRH Agonist and Enzalutamide (NCT01946165), a randomized phase 2 study. The primary outcome is Proportion of Participants With Pathologic Stage Less Than or Equal to ypT2N0.

2. Clinical Question

The registry describes a pre-operative study of treatment for prostate cancer at high risk for recurrence. Its stated goal was to learn whether adding abiraterone acetate and prednisone, with or without enzalutamide, to hormonal therapy could help control cancer before surgery; safety was also to be studied. The statistical comparison focuses on a pathology finding at surgery, rather than a long-term outcome such as recurrence or survival.

The posted primary results count 13 participants in Group A and 11 in Group B with the specified pathologic stage. The corresponding endpoint denominators are 43 in Group A and 21 in Group B. Those denominators are for the evaluable participants used in this outcome, not a statement that every person enrolled contributed to the endpoint. The registry describes the primary outcome population as evaluable participants and specifies that the proportion is calculated among participants who underwent surgery in the same arm.

The comparison is between the two complete treatment regimens as assigned in this trial. It does not isolate the effect of enzalutamide from every other feature of treatment, and the registry record does not report enough detail to assess whether treatment exposure or surgery timing differed between participants. The clinical question is therefore about the observed endpoint comparison between these regimens in this study population.

3. Trial Design

This was a Phase 2, randomized, parallel-group trial with no masking. The registry lists enrollment as 69 and the study status as completed. The listed start date is 2013-10-31, and the primary completion date is 2017-07-28. The sponsor was M.D. Anderson Cancer Center.

The treatment arms differed by the addition of enzalutamide to abiraterone acetate, prednisone and LHRHa in Group A. Group B received abiraterone acetate, prednisone and LHRHa. The arm descriptions say that LHRHa was given as a monthly or three-month injection for a maximum of 7 months before prostatectomy. The official study title describes treatment for six months, while the arm descriptions state a maximum of 7 months; the registry record does not explain this difference.

Randomization means that the study used an allocation process intended to assign participants to treatment groups by chance. The record does not report the randomization method, whether allocation was concealed, or whether any stratification was used. With no masking, participants and study personnel were not masked according to the registry classification. The record does not report details about pathology assessors’ knowledge of treatment assignment.

The primary outcome was a binary count: whether a participant had a pathologic stage less than or equal to ypT2N0. The stated timeframe was from treatment start until surgery was completed, among participants who underwent surgery. Positive surgical margins were posted as a secondary outcome. Safety results were also reported. The registry record does not report the trial’s original sample-size justification, the intended analysis plan, or a detailed account of the methods used to compare arms.

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: Out of 69 participants, due to a screen failure, no arm assignment was made for 1 participant; therefore, only 68 participants were treated and evaluable for outcome analysis.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Patients that are evaluable are included in these values.

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 Proportion of Participants With Pathologic Stage Less Than or Equal to ypT2N0, measured over For all participants who underwent surgery, from start of treatment until surgery is completed.

The primary endpoint is the proportion of participants whose pathologic stage after pre-operative treatment and surgery was less than or equal to ypT2N0. The registry describes it as a count of participants and says the proportion was calculated by dividing the number meeting the stage criterion in an arm by the number who underwent surgery in that arm. The endpoint was assessed from treatment start through completion of surgery.

Pathologic stage is determined from examination of surgical tissue. As a general explanation, a threshold endpoint groups participants according to whether their findings fall on one side of a prespecified stage boundary. It can provide a direct summary of pathology at surgery and make the outcome comparable between treatment arms. The “less than or equal to” wording is important: the endpoint includes stages at the stated threshold as well as stages below it.

This endpoint is not itself a measure of time to recurrence or survival. Nor does the posted primary result report every aspect of pathology or subsequent clinical course. It answers the narrower question of how many evaluable surgical participants in each arm met the stated stage criterion. The registry does not report why this particular stage boundary was chosen or whether it was supported by a sample-size calculation.

7. Results Posted in the Registry

• Group B: Abiraterone + LHRHa + Prednisone: 52.4% (11/21) versus 30.2% (13/43) on control; risk difference 22.1 percentage points (95% CI -3.2 to 47.5), risk ratio 1.73 (0.94–3.19); unadjusted two-proportion z-test p = 0.086.

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.

Proportion of Participants With Positive Surgical Margins

• 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:
  • Group B: Abiraterone + LHRHa + Prednisone: 9.5% (2/21) versus 20.9% (9/43) on control; risk difference -11.4 percentage points (95% CI -28.9 to 6.1), risk ratio 0.46 (0.11–1.92); unadjusted two-proportion z-test p = 0.256.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Group B: Abiraterone + LHRHa + Prednisone and the control. The interval gives the range of effects that remain compatible with the data.

The posted secondary outcome is the proportion of participants with positive surgical margins. It concerns a different pathology feature from the primary stage threshold, but it is still assessed in relation to surgical tissue. Read together, these outcomes offer more than one view of pathology at surgery; they do not amount to independent confirmation of a treatment effect or a comprehensive account of later clinical outcomes.

The registry reports an unadjusted comparison for the secondary endpoint, but it does not report a prespecified hierarchy of outcomes, an adjustment for multiple testing, or a plan for interpreting several endpoint results together. When several outcomes are examined, the chance of encountering a seemingly notable result can increase. This is a general statistical concern, not a claim that a particular posted result is false. Without a reported multiplicity strategy, secondary findings generally carry less confirmatory weight than a prespecified primary outcome.

The primary endpoint and the margin endpoint are related in that both use pathology from surgery, but they capture different features and may have different denominators or clinical meaning. A pattern across them should not be reduced to a single “overall” effect without a defined method for combining outcomes. The registry record does not report such a composite analysis, nor does it report formal analyses for the secondary outcome beyond the posted comparison.

These results can be used to describe what was observed in this study, but they do not establish consistency across settings or settle whether treatment differences exist. Interpretation should take account of uncertainty, the population with evaluable surgical outcomes, and the lack of a reported multiplicity plan. The registry record does not report long-term outcomes that would connect these surgical findings to recurrence or survival.

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

• Proportion of Participants With Positive Surgical Margins

9. Statistical Interpretation

10. Statistical Methods Explained

What does a risk difference describe?

General statistical explanation: A risk difference subtracts the event proportion in one group from the event proportion in another. It is expressed on the proportion scale, so zero represents no difference. A positive or negative value indicates the direction of the contrast according to the order in which groups are compared. In this registry comparison, Group B is compared with Group A. The reported point estimate is positive, but its confidence interval includes zero, which means the estimated contrast is uncertain.

The endpoint is recorded as participants meeting a binary criterion: the stage is either within the stated threshold or it is not. A binary outcome can be summarized with counts and denominators, and then with proportions or contrasts between proportions. The posted counts are the observed data for this endpoint; the comparison measures are statistical summaries of those data. A difference in proportions is not the same as a difference in the number of participants, particularly when group denominators differ.

What do relative measures add?

General statistical explanation: A risk ratio compares one group’s event proportion with another group’s proportion by division. An odds ratio compares the odds of the event between groups. These relative measures use different scales from a risk difference, so their numerical values should not be read as interchangeable. A relative measure with a null value of one indicates no relative difference, whereas a risk difference has a null value of zero. The registry reports relative-effect estimates for the primary comparison as well as the risk difference, but no adjustment for other variables is described.

Relative measures can sometimes appear large even when the underlying data are sparse. Their precision depends on how many events and non-events contribute to the comparison. For this reason, estimates should be read alongside the denominators and confidence intervals, rather than interpreted as stand-alone measures of importance. The registry does not report a clinical threshold for a meaningful difference on this endpoint.

How should the p-value be understood?

General statistical explanation: A p-value describes how unusual results at least as extreme as those observed would be under a specified null model and its assumptions. It is not the probability that the observed result arose by chance, nor is it a direct measure of effect size. The registry posts an unadjusted p-value of 0.086 for the primary comparison. The record does not describe the test used to obtain it, so the test procedure and its assumptions cannot be evaluated from the posted information.

“Unadjusted” means that the reported p-value is not presented as adjusted for other variables or for multiple comparisons. The registry record does not report a multiplicity plan. A single p-value should not be treated as a complete account of evidence, particularly when other outcomes are also assessed. The estimate’s direction, its interval, the endpoint definition and the population contributing data all matter to interpretation.

Why does randomization matter, and what can it not tell us?

General statistical explanation: Random allocation aims to make treatment groups comparable on average with respect to measured and unmeasured characteristics at the time of assignment. It supports a causal comparison when the trial is conducted and analyzed as intended. Randomization does not guarantee that every group characteristic will be exactly balanced, especially when the amount of outcome information is limited. Nor does the registry classification by itself explain how randomization was implemented or whether the analysis followed the original assignment for all participants.

The registry reports randomized allocation and parallel groups, but it does not describe an intention-to-treat analysis, a per-protocol analysis, or a prespecified adjustment model. The primary endpoint description instead identifies evaluable participants who underwent surgery. That is a relevant population restriction: a comparison among surgical participants may not represent all enrolled participants if some did not undergo surgery or did not have evaluable pathology. Why any participant is absent from the endpoint denominator is not reported in the registry record.

What does the outcome count represent?

General statistical explanation: For a binary endpoint, each participant contributes an outcome classification if the outcome is observed. The count of participants meeting the definition and the denominator used to calculate the proportion are both needed to understand the result. The denominator is not necessarily the total enrollment. In this trial the primary outcome is described among participants who underwent surgery, and the record also says that evaluable participants are included in the values. The posted outcome counts and denominators should therefore be interpreted according to that definition.

Statistical methods for binary outcomes can include several possible models or tests, but the registry does not identify which method was used for the posted primary comparison. It would be inappropriate to infer a specific test, covariate adjustment, or missing-data method from the numerical result alone. No over-dispersion parameter is reported; as a general point, over-dispersion is a concern when observed variability exceeds what a chosen model assumes, but the posted information does not establish that it applies to this binary endpoint.

How do confidence intervals complement the analysis?

General statistical explanation: A confidence interval gives a range of effect estimates compatible with the observed data under a specified method and its assumptions. It conveys precision as well as direction. For a risk difference, an interval that crosses zero includes values corresponding to no difference. For a risk ratio or odds ratio, the corresponding null value is one. The registry’s primary risk-difference interval crosses zero, and the relative-measure intervals cross their null value. These features are consistent with uncertainty about the direction and size of the between-arm contrast.

The record does not identify the confidence-interval construction method. Different methods can behave differently when event counts are limited, so the interval should be read as the registry’s posted estimate rather than as a uniquely determined description of uncertainty. The interval also does not account for every possible source of uncertainty, such as missing outcomes, choice of endpoint, or multiple testing, unless the method explicitly incorporates them. The registry does not report such adjustments.

11. Confidence Intervals and Precision

The precision of the primary comparison is limited. The risk-difference confidence interval extends from a negative value to a positive value, crossing the no-difference value of zero. The relative-effect intervals also include their respective null value of one. This means the posted data are compatible with more than one interpretation of the direction of the association. The point estimate alone gives a direction, but the interval indicates that the estimate is not precise enough to rule out no difference.

General statistical explanation: A confidence interval is a range produced by a statistical procedure that, under its assumptions, reflects uncertainty about an effect estimate. A wide interval represents lower precision than a narrow interval. It does not mean that every value inside the range is equally likely, and it does not establish that the true effect lies within the interval with certainty. The registry does not identify the method used to construct these intervals, so their exact operating properties cannot be assessed from the record.

The endpoint uses fewer participants than the overall enrollment figure, and the denominators differ between arms. The registry’s primary population is evaluable participants who underwent surgery. These details matter because precision depends on the amount of outcome information, not simply the enrollment label. The registry record does not report a detailed participant flow explaining how people moved from enrollment to the endpoint population.

The p-value of 0.086 is consistent with the interval’s inclusion of the null value, but the p-value and interval are not substitutes for considering the estimate’s scale, uncertainty, study design and endpoint. No interval can address unreported analysis choices or missing-data processes. The available precision supports caution rather than a firm conclusion about the size or direction of a difference.

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 planning figures are participants per arm for the primary binary endpoint. They are not total event counts. The calculation is an illustration based on the observed effect, not the trial’s original design assumptions. Its stated assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, a normal approximation, and an effect to detect set to a stated fraction of the observed effect. The trial’s own original sample-size assumptions and justification are not reported in the registry record.

The planning entries for 100% of the observed effect are 77 participants per arm for 80% power and 102 participants per arm for 90% power. For 75% of the observed effect, the corresponding figures are 134 participants per arm for 80% power and 179 participants per arm for 90% power. For 50% of the observed effect, they are 293 participants per arm for 80% power and 392 participants per arm for 90% power.

General statistical explanation: Power is the probability that a planned statistical procedure will reject its null hypothesis under a particular assumed effect and other design conditions. The 80% and 90% columns represent different target probabilities under those assumptions; they do not describe the probability that the trial’s observed result is correct. These planning figures are not observed power.

The rows illustrate that smaller effects require more participants to detect under the same planning framework. The figures also rely on the observed effect as their starting point. An observed effect from a limited study can be uncertain, so planning based on it should not be treated as a reliable estimate of what a future study will observe. The calculation does not replace the trial’s original design justification, which 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 = 0.302; treatment proportion p₁ = 0.524; average p̄ = 0.413.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.6963 = 1.3648.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.6785 = 0.5710.
4. n = (1.3648 + 0.5710)² / (0.2215)² = 76.4, rounded up to 77 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 <- 0.302325581395349                          # control proportion
p1 <- 0.523809523809524                          # 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(1946165)
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 = 77 (80% power), 102 (90% power)
 75% of observed effect: n per arm = 134 (80% power), 179 (90% power)
 50% of observed effect: n per arm = 293 (80% power), 392 (90% power)
power.prop.test: 76.4 
Simulated power at n = 77 per arm: 0.808 (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 registry posts one primary outcome and one secondary outcome. It does not report a statistical analysis plan describing how outcomes were prioritized, whether any interim analyses were planned, or how multiplicity was handled. The fact that the primary comparison has an unadjusted p-value does not establish whether a broader testing strategy was prespecified. The registry record does not report whether any adjustment for multiple comparisons was performed.

General statistical explanation: Testing multiple outcomes can increase the chance of at least one small p-value even when there is no true effect on any outcome. Prespecifying a primary endpoint and an approach to multiplicity helps clarify how much weight to place on findings across outcomes. Without a reported plan, the primary result remains the main endpoint to consider, while secondary findings should be treated as less definitive.

The primary endpoint description says that evaluable participants are included and defines the proportion among participants who underwent surgery in each arm. This is not the same as saying that all enrolled participants contributed a primary outcome. The registry record does not report the reasons participants may have been excluded from the evaluable population, the number without surgery or evaluable pathology, or a participant-flow account. It also does not report whether missing outcomes were imputed, treated as failures, or handled in another way.

The record lists enrollment as 69, while the posted primary endpoint denominators are 43 in Group A and 21 in Group B. Safety results use different at-risk denominators, 45 in Group A and 23 in Group B. These figures describe different reported populations and should not be combined or assumed to be interchangeable. The record does not explain the differences in denominators or provide enough information to determine their causes.

The registry does not report whether the primary analysis followed randomized assignment for all participants, was restricted to those who received treatment, or used another analysis population. It also does not report sensitivity analyses for missing data. Those omissions limit assessment of how robust the posted comparison is to population definitions and outcome availability.

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 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: pe (4.3%), pancreatitis (2.2%), possible mini stroke (2.2%), abdominal pain (2.2%), neoplasm (2.2%).

The registry reports serious adverse events among participants at risk in each arm. In Group A, 4 participants were reported with a serious adverse event among 45 at risk; in Group B, 1 participant was reported with a serious adverse event among 23 at risk. The registry reports zero deaths in each group. Other adverse events were reported for 45 participants among 45 at risk in Group A and 23 among 23 at risk in Group B.

The listed serious adverse event terms and percentages include PE at 4.3%, pancreatitis at 2.2%, possible mini stroke at 2.2%, abdominal pain at 2.2%, neoplasm at 2.2%, and hematoma at 2.2%. The registry does not provide event-level counts for each listed term in the information available for this summary, so these percentages should be read as the posted descriptions rather than recalculated counts.

General statistical explanation: Safety counts describe events recorded during the specified study observation and do not by themselves establish that treatment caused an event. The registry record does not report additional detail about event timing, severity grading, relatedness assessments, or exposure-adjusted rates. The different safety and primary endpoint denominators also mean the safety results should not be treated as if they came from the same analysis population as the primary outcome.

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

The primary result describes the proportion of evaluable surgical participants in each arm whose pathology met the stated stage threshold. In the observed data, 13 participants in Group A and 11 in Group B met that criterion. The estimated risk difference is positive for Group B relative to Group A, but its confidence interval crosses zero, and the unadjusted p-value is 0.086. The data therefore do not provide a precise, conclusive estimate of the between-arm difference.

This does not show that the arms are equivalent. A non-significant comparison cannot demonstrate equivalence unless the study is designed around an equivalence or non-inferiority question with suitable margins and methods; such a design is not reported in the registry record. Nor does the result establish that one regimen is superior. The interval permits uncertainty about both the direction and size of the association.

The endpoint is pathology at surgery, not recurrence, survival, quality of life, or long-term disease control. The registry’s goal statement mentions controlling cancer before surgery, but the posted primary measure answers a narrower question about pathologic stage. The results should not be extended to outcomes that were not reported or to patients outside the described high-risk pre-operative setting.

General statistical explanation: Statistical evidence is best interpreted through the endpoint definition, observed data, effect estimate, interval, study design and potential limitations together. A p-value alone cannot establish clinical importance or causation. Randomization supports a comparison between assigned groups, but missing outcome information, treatment adherence, analysis population and implementation details can affect how that comparison should be interpreted. Several of these details are not reported in the registry record.

The posted results are a record of what was observed and how the registry summarized it. They do not constitute medical advice, and they do not establish whether an individual should receive any treatment. A clinical decision would require evidence and considerations beyond this statistical comparison.

17. Why This Trial Matters Statistically

This trial illustrates why the denominator and endpoint definition matter as much as the event count. The primary outcome is not a count from everyone enrolled; it is defined for evaluable participants who underwent surgery. Reading the counts without that population definition could misrepresent what the comparison estimates. The difference between endpoint denominators and safety denominators further shows that different outcomes can be reported for different populations.

It also demonstrates the value of reading an effect estimate with its interval. The primary point estimate has a direction, but the interval includes the null value and the unadjusted p-value is 0.086. The central statistical issue is not simply whether a threshold is crossed; it is how much uncertainty remains about the size and direction of the effect. The result is not precise enough to support a firm conclusion about a between-arm difference.

The registry combines randomized treatment assignment with a surgical pathology outcome. That makes the trial a useful example of how randomization and outcome availability are distinct considerations. Randomization helps support a fair comparison at assignment, while a surgery-based analysis population can differ from the randomized population. The record does not explain how that transition occurred for each participant, limiting assessment of possible selection effects.

Finally, the secondary pathology outcome and safety information reinforce that no single statistic captures every aspect of a trial. Secondary results require caution when the multiplicity strategy is not reported, and safety counts need their own denominators and context. Clear descriptions of analysis populations, missing data, and prespecified methods are essential for readers to judge precision and evidential strength.

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.

The primary outcome is restricted to evaluable participants who underwent surgery, while the overall enrollment and safety populations have different reported denominators. The registry does not provide a participant-flow explanation for these differences, reasons for missing or unevaluable pathology, or details of how such data were handled. This limits assessment of whether the endpoint population reflects all randomized participants.

The statistical analysis plan is not reported in the registry record. The record does not identify the test used for the primary comparison, the construction method for confidence intervals, any covariate adjustment, or whether the analysis followed randomized assignment. It also does not report the original sample-size justification, interim-analysis plans, or a multiplicity strategy. The planning illustration based on the observed effect should not be confused with the trial’s original design.

The study was Phase 2 and the posted primary comparison has limited precision. The confidence interval crosses the null value, leaving substantial uncertainty about the magnitude and direction of the contrast. The sample-size illustration itself shows that the number of participants needed depends on the assumed effect; a smaller effect requires more participants under the listed assumptions.

The outcome measures pathology at surgery. The registry does not report long-term recurrence or survival results in the registry record for this trial, so the primary endpoint cannot answer those questions. Safety reporting includes serious-event counts and selected terms, but further information about timing, relatedness, severity grading and exposure is not reported in the registry record.

The official title describes six months of treatment, whereas the arm descriptions specify a maximum of 7 months before prostatectomy. The record does not explain that difference. It also does not report details of randomization implementation, adherence, or masking of pathology assessment. These gaps restrict how fully the design and conduct can be evaluated.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Abiraterone Acetate Plus LHRH Agonist and Abiraterone Acetate Plus LHRH Agonist and Enzalutamide — NCT01946165.
• Registry record last updated 2019-12-06; status last verified 2019-11.
• Results first posted 2019-12-06.
• 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

NCT01946165 was a completed Phase 2 randomized, unmasked, parallel-group pre-operative study sponsored by M.D. Anderson Cancer Center. It compared abiraterone acetate, prednisone and LHRHa with the same regimen plus enzalutamide in people with prostate cancer at high risk for recurrence. The registry lists enrollment as 69.

The primary endpoint was the proportion of evaluable participants who underwent surgery and had pathologic stage less than than or equal to ypT2N0. The posted counts were 13 among 43 in Group A and 11 among 21 in Group B. The registry reports an unadjusted p-value of 0.086, and the risk-difference interval crosses zero, indicating uncertainty about the comparison.

Positive surgical margins were posted as a secondary outcome, and safety results included serious adverse events, other adverse events and deaths. The registry record does not report the original sample-size justification, a detailed statistical analysis plan, multiplicity handling, or a participant-flow explanation for the different outcome denominators.