Hormone Suppression and Radiation Therapy for 6 Months With/Without Docetaxel for High Risk Prostate Cancer: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Hormone Suppression and Radiation Therapy for 6 Months With/Without Docetaxel for High Risk Prostate Cancer (NCT00116142), a randomized phase 3 study. The primary outcome is 10-Year Restricted Mean Survival Time for Overall Survival.

2. Clinical Question

The clinical question is about the added contribution of docetaxel within a combined treatment strategy for high-risk prostate cancer. The comparison does not isolate the effect of androgen suppression or radiation, because both groups received those treatments. The registry identifies biochemical recurrence, prostate cancer mortality, and adverse events among the secondary outcomes, so the study also records disease-related outcomes and safety events. The primary endpoint is overall survival, measured from random assignment, and its restricted mean summary focuses on survival through the stated horizon rather than on survival beyond it. The registry record does not report more detailed eligibility criteria or a separate primary research hypothesis.

3. Trial Design

This was a randomized, phase 3, parallel-group trial with no masking. The registry lists enrollment of 350 participants and 175 participants in each treatment group. One group received androgen suppression therapy and radiation therapy; the other received those treatments plus docetaxel. Dana-Farber Cancer Institute is listed as the sponsor. The condition is prostate cancer, and the registry status is completed.

The registry records a start date of 2005-06 and a primary completion date of 2020-06-29. The primary outcome was 10-year restricted mean survival time for overall survival. Its timeframe describes follow-up after radiation therapy, with visits every 6 months for 5 years and annually thereafter, through 10 years. Overall survival was defined from random assignment to death from any cause, with surviving participants censored at their last follow-up date.

Random allocation supports a comparison between groups that is less dependent on clinicians or participants choosing their treatment, although the registry does not provide the method used to generate or conceal the allocation sequence. With no masking, participants and study personnel were not blinded to group assignment according to the registry entry. Details about treatment delivery, adherence, crossover, and concomitant care are not reported in the registry record.

The registry lists secondary outcomes including biochemical recurrence, prostate cancer mortality, and acute and late adverse events. It reports no analyses in the analyses listing. The original statistical design, including any target effect, sample-size justification, planned adjustment strategy, and planned analysis population, is not reported in the registry record. The fact that enrollment was 350 does not by itself explain how that number was chosen or what precision the investigators expected.

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 10-Year Restricted Mean Survival Time for Overall Survival, measured over Following the end of RT patients were seen for follow up every 6 months for 5 years and annually thereafter, 10 years..

The primary endpoint is 10-year restricted mean survival time for overall survival, measured in years. Overall survival starts at random assignment and ends at death from any cause; participants still alive at their last follow-up are censored at that date. The registry says the restricted mean was calculated as the area under the Kaplan-Meier overall-survival curve from randomization to 10 years.

General explanation: a restricted mean survival time is the average survival time accumulated within a fixed time horizon. It summarizes survival over that interval without requiring the result to be expressed as a hazard ratio or as a difference in median survival. The 10-year restriction sets the period being summarized; it does not describe survival after that horizon.

This measure is useful when the scientific question concerns average time alive during a stated period, and it can be interpreted in years. It also depends on the follow-up information available to construct the survival curve, including how censoring is handled. The registry describes the censoring rule for surviving participants but does not give further detail about the survival-analysis model, confidence-interval method, or handling of incomplete follow-up.

7. Results Posted in the Registry

• Arm2: Docetaxel + Androgen Suppression Therapy + Radiation Therapy: mean 9.11 versus 8.82 on control; difference 0.29 (95% CI -0.18 to 0.76), standardized effect d = 0.13; z-test p = 0.231.

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.

10-year Biochemical Recurrence (PSA Failure)

• Endpoint type: Binary: the percentage of participants with the event (counts rebuilt from the posted percentages and group sizes).
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Arm2: Docetaxel + Androgen Suppression Therapy + Radiation Therapy: 53.7% (94/175) versus 48.0% (84/175) on control; risk difference 5.7 percentage points (95% CI -4.7 to 16.2), risk ratio 1.12 (0.91–1.38); unadjusted two-proportion z-test p = 0.285.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Arm2: Docetaxel + Androgen Suppression Therapy + Radiation Therapy and the control. The interval gives the range of effects that remain compatible with the data.

10-year Prostate Cancer Mortality

• Endpoint type: Binary: the percentage of participants with the event (counts rebuilt from the posted percentages and group sizes).
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Arm2: Docetaxel + Androgen Suppression Therapy + Radiation Therapy: 14.9% (26/175) versus 10.9% (19/175) on control; risk difference 4.0 percentage points (95% CI -3.0 to 11.0), risk ratio 1.37 (0.79–2.38); unadjusted two-proportion z-test p = 0.264.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Arm2: Docetaxel + Androgen Suppression Therapy + Radiation Therapy and the control. The interval gives the range of effects that remain compatible with the data.

The posted secondary outcome estimates do not form a uniformly favorable pattern for the group assigned docetaxel. The point estimates for biochemical recurrence and prostate cancer mortality are higher in that group, while the primary restricted mean survival estimate is also higher in that group. These outcomes represent different aspects of disease course and survival, so their directions need not coincide. Their differing patterns do not resolve the uncertainty in the primary comparison.

Secondary endpoints can add context, but they are not substitutes for the primary endpoint. Biochemical recurrence, prostate cancer mortality, and overall survival measure distinct events or summaries. Event definitions, follow-up, and the amount of information available can differ across outcomes. The registry lists adverse-event outcomes as well, which address safety rather than the same efficacy question as restricted mean survival time.

The registry reports no analyses in the analysis listing, and the secondary comparisons shown are unadjusted recalculations from posted summary information. Unadjusted secondary comparisons carry less weight when many outcomes may be examined: the more comparisons made, the greater the chance that some results appear notable by chance alone. The registry record does not report a multiplicity adjustment, a hierarchy for interpreting secondary outcomes, or which secondary comparisons were prespecified.

For that reason, the overall secondary pattern is best treated as descriptive context rather than as a set of independent confirmatory findings. It neither overturns the primary estimate nor establishes a consistent treatment effect across outcomes. A full interpretation would require the prespecified analysis plan, outcome definitions, and details about completeness of follow-up and statistical adjustment, which are not reported in the registry record.

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

• 10-year Biochemical Recurrence (PSA Failure)
• 10-year Prostate Cancer Mortality
• Number of Participants With Acute Adverse Events
• Number of Participants With Late Adverse Events, Any Grade and Attribution

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is continuous: each treatment group has a mean restricted survival time, reported with a standard error. The between-group estimate is a mean difference, with the docetaxel group compared against androgen suppression and radiation alone. A positive difference means the estimated restricted mean is higher in the docetaxel group; a negative difference would mean it is higher in the comparison group. The estimate is expressed in years because that is the endpoint’s unit.

What does restricted mean survival time summarize?

General explanation: survival methods account for the fact that some participants may not have experienced the event by the time their observation ends. A Kaplan-Meier curve estimates the proportion surviving over time while incorporating the timing of observed events and censoring. The area under that curve through a chosen horizon corresponds to restricted mean survival time. It can be understood as the average time alive accumulated within that horizon, subject to the observed follow-up and analysis assumptions.

The registry defines overall survival as time from random assignment to death from any cause. It says participants alive at last follow-up were censored on that date and that the restricted mean was calculated through 10 years. It does not report further details about the Kaplan-Meier estimation, the handling of participants with incomplete follow-up, or the method used to calculate the uncertainty around the restricted means.

How should the mean difference and p-value be read?

The mean difference is the direct contrast between the two group estimates. The unadjusted difference is 0.29 years. The reported unadjusted p-value is 0.231. General explanation: a p-value describes how unusual data at least as incompatible with a specified null hypothesis would be if that hypothesis and the test assumptions were correct. It is not the probability that the null hypothesis is true, and it does not measure the size or clinical importance of an effect. A p-value also does not show whether an estimate is precise; the confidence interval is useful for that.

The comparison is labeled unadjusted. That means the posted calculation does not reflect an adjustment for other covariates in the reported summary. The registry record does not identify a covariate-adjusted primary analysis, a stratification factor, or a model specification. The unadjusted comparison should therefore be read as a simple contrast of the posted group summaries, not as a complete description of every analysis that may have been conducted outside the registry.

What does uncertainty in the interval convey?

General explanation: a confidence interval is a range produced by a procedure designed to have a stated coverage property over repeated studies under its assumptions. For an effect difference, an interval containing zero indicates that values on both sides of no difference remain compatible with the data at the interval’s stated confidence level. The interval does not assign a probability to each possible effect value, and its limits are not guaranteed bounds on the true effect.

For this primary comparison, the interval crosses zero. That is consistent with the unadjusted p-value not indicating a clear difference. Neither result proves that the groups are the same. The interval’s width also matters: a range that includes potentially meaningful differences in both directions leaves substantial uncertainty about the size and direction of the effect. The registry’s posted summary does not specify whether the primary comparison was prespecified in exactly this form or whether other analyses were planned.

Why can survival data need special handling?

General explanation: standard methods for a continuous endpoint can be inadequate when follow-up time differs among participants or when some event times are not observed. Survival methods use the event and censoring information rather than treating every participant as if the same complete follow-up were available. Their interpretation depends on appropriate handling of censoring and the observed follow-up pattern. The record provides the event definition and censoring rule, but it does not give enough detail to evaluate all assumptions or the completeness of follow-up.

The registry lists no reported analyses in its analysis listing. It also does not report multiplicity procedures, missing-data methods, protocol deviations, or analysis-population definitions. Accordingly, the figures can be interpreted as the posted estimates and unadjusted comparisons, but the record does not support a fuller reconstruction of the trial’s statistical analysis plan.

11. Confidence Intervals and Precision

The primary estimate is a mean difference of 0.29 years. Its posted confidence interval has a lower limit below zero and an upper limit above zero. The interval therefore includes no difference as well as effects in either direction. The unadjusted p-value is 0.231, which is consistent with the interval’s failure to exclude zero under the reported comparison.

General explanation: a confidence interval expresses uncertainty about an estimated effect under a specified statistical procedure. Its width reflects both the variability in the data and the amount of information available. A narrow interval would indicate greater precision than a wide interval, but precision is not the same as clinical importance. An interval that includes zero does not prove that the true effect is zero; it indicates that the data do not rule out zero at the interval’s confidence level.

The group estimates are based on 175 participants in each arm, but the registry does not report the number with complete 10-year follow-up, the number censored before that point, or the distribution of follow-up time. Those details affect how the survival curve and restricted mean are supported by observed data. Enrollment alone cannot describe the information available at the end of follow-up.

The posted interval allows a range of possible effects, rather than a single definitive conclusion about the direction or size of the difference. The registry record does not give a clinically important difference threshold for restricted mean survival time, so statistical precision cannot be translated into a judgment about clinical importance from this record alone.

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 illustrations based on the observed effect, not a reconstruction of the trial’s original sample-size calculation. For this continuous primary outcome, the listed figures are participants per arm. The planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation; each scenario targets a stated fraction of the observed effect. The registry’s own design assumptions are not reported in the registry record.

The 80% power column gives the planned number of participants per arm for a hypothetical study to have an 80% chance of detecting the selected effect under those assumptions, if that effect and the assumptions were correct. The 90% power column gives the corresponding planning number for a 90% chance. These are design probabilities for hypothetical repeated studies, not probabilities that the observed result is true and not a measure of the chance that this completed trial found an effect.

The rows plan for 100%, 75%, and 50% of the observed effect. A smaller target effect requires more participants because it is harder to distinguish from random variation. The displayed curve visualizes the planning relationship under the same assumptions; it does not supply a separate estimate of the treatment effect. These figures are not observed power.

For outcomes with time-to-event planning calculations, the stated convention is total events using the Schoenfeld approach; other planning figures are participants per arm. The primary endpoint’s listed calculation is continuous, so its figures should be read as participants per arm, not as total events. The original trial’s enrollment should not be compared mechanically with the illustrative requirements to infer what the investigators planned, since the registry does not report the original design rationale.

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, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 0.290; pooled standard deviation σ = 2.264.
2. n = 2 × (1.96 + 0.842)² × 2.264² / 0.290² = 957.1, rounded up to 958 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
delta <- 0.289999999999999                      # observed difference in means
sigma <- 2.26439837484485                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^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 (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(116142)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 958 (80% power), 1,282 (90% power)
 75% of observed effect: n per arm = 1,702 (80% power), 2,278 (90% power)
 50% of observed effect: n per arm = 3,829 (80% power), 5,126 (90% power)
power.t.test: 958 
Simulated power at n = 958 per arm: 0.796 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-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

Multiplicity arises when a study evaluates more than one outcome, time point, subgroup, or statistical comparison. General explanation: as the number of unadjusted tests grows, so does the chance that at least one result appears statistically notable even when the underlying effects are absent. Prespecifying a primary endpoint and a testing hierarchy can help distinguish confirmatory questions from exploratory ones. The registry identifies a primary endpoint and several secondary outcomes, but a multiplicity procedure or testing hierarchy is not reported in the registry record.

The analysis listing reports zero analyses. That does not establish that no analyses were performed; it means the registry does not include analyses in that listing. The posted comparisons are unadjusted recalculations from the available summary statistics. The record does not describe whether these match the trial’s original analysis plan, whether other analyses were performed, or how any deviations from a plan were handled.

Missing-data and analysis-population details are also not reported in the registry record. The primary outcome description says that surviving participants were censored at last follow-up, but it does not report how many participants were censored, the reasons for censoring, follow-up completeness, or any method for handling missing outcome information. It also does not specify whether the reported groups follow an intention-to-treat, per-protocol, or other analysis population.

These omissions limit assessment of whether the posted estimates reflect the planned analysis and whether all randomized participants contributed as intended. They do not invalidate the posted figures by themselves, but they prevent a complete audit of analysis choices, missingness, and the potential effect of multiple testing. The registry record does not report enough information to determine whether multiplicity or missing-data procedures were used elsewhere.

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: renal/gu-other (15.8%), urinary frequency/urgency (10.5%), diarrhea w/o prior colostomy (9.9%), incontinence urinary (6.3%), gi-other (5.7%).

The registry lists serious adverse events affecting 63 of 174 participants in the androgen suppression and radiation group and 87 of 171 participants in the group that also received docetaxel. Other adverse events are reported for 128 of 174 and 142 of 171 participants, respectively. These are posted counts with the listed at-risk denominators; they are not adjusted comparisons and should not be treated as evidence of causation on their own.

The registry also lists 45 deaths in the first group and 44 in the docetaxel group under the adverse-event summary. Those counts are not a replacement for the primary survival analysis, which uses time from random assignment to death and accounts for censoring. The registry does not provide enough detail in the adverse-event summary to determine the timing, duration, or relationship of each event to treatment.

Listed serious-event terms include renal/GU-other, urinary frequency/urgency, diarrhea without prior colostomy, urinary incontinence, GI-other, and bladder hemorrhage. The registry provides percentages for these terms but does not clarify their denominator in the summary. They should therefore be read as listed safety descriptions, not as comparative risk estimates. Further details about event grading, attribution, and collection methods are not reported in the registry record.

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

The primary result is an estimate of the difference in average survival time accumulated through 10 years, not a complete account of every possible benefit or harm. The docetaxel group’s estimated restricted mean is higher by 0.29 years, but the confidence interval crosses zero and the unadjusted p-value is 0.231. The result is therefore uncertain about both the direction and size of the underlying difference.

This does not demonstrate that the two treatment strategies are equivalent, and it does not establish that either strategy is superior. Equivalence or non-inferiority requires a prespecified margin and an analysis designed for that question; such a margin is not reported in the registry record. Likewise, a non-significant comparison is not proof of no effect. It indicates that the posted data do not establish a difference in the reported analysis.

The primary endpoint does not measure quality of life, symptom burden, or all aspects of disease control. Secondary outcomes provide additional information about recurrence, prostate cancer mortality, and adverse events, but the registry does not report a multiplicity plan or detailed analyses for interpreting the full set of outcomes together. Safety counts also require context about event severity, timing, attribution, and follow-up that is not fully available in the registry summary.

Interpretation is constrained by missing information about the original sample-size justification, statistical plan, missing data, analysis populations, and follow-up completeness. The randomized design is an important feature for comparing assigned groups, but it does not remove uncertainty arising from limited precision or incomplete reporting. The posted findings describe the trial’s registry results and should not be extended beyond the outcomes, follow-up horizon, and analyses recorded there.

17. Why This Trial Matters Statistically

This trial illustrates why the choice of estimand matters in survival research. Restricted mean survival time expresses the comparison as time alive accumulated through a fixed horizon, in years. That makes the endpoint more directly interpretable as a difference in average survival time over the chosen period than a relative measure alone. The horizon is essential to the meaning: the result concerns survival through 10 years, not unrestricted lifetime survival.

It also shows why the estimate, interval, and p-value should be read together. The point estimate favors a higher restricted mean in the docetaxel group, but the interval includes zero and the unadjusted p-value is 0.231. Reporting only the point estimate would conceal uncertainty, while reporting only whether a p-value crosses a threshold would hide the range of effects compatible with the data.

The registry’s multiple outcomes create another statistical lesson. Overall survival, recurrence, prostate cancer mortality, and adverse events answer different questions. Secondary comparisons can help describe the evidence, but without a reported testing hierarchy or multiplicity procedure they should not be treated as a collection of independent confirmatory claims. The empty analyses listing and limited analysis-plan details also show how registry reporting affects independent assessment.

Finally, the planning illustrations demonstrate that the number of participants needed depends on the effect a future study aims to detect. Smaller target effects require larger planned sample sizes under the stated assumptions. Those calculations are not a retrospective measure of the completed trial’s power and do not reveal the trial’s original design rationale. Together, these points emphasize careful interpretation of the estimand, precision, multiple outcomes, and planning assumptions.

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.

Several trial-specific limitations of interpretation follow from the information recorded. The registry identifies the study as unmasked, so participants and study personnel were not blinded to assignment. The potential consequences of this for outcome assessment depend on how outcomes were collected; further assessment procedures are not reported in the registry record. Overall survival is less dependent on subjective outcome judgment than some outcomes, but the record does not describe independent adjudication or other safeguards.

Although the primary endpoint is defined through 10 years and the record gives a follow-up schedule, it does not report the number of participants with complete follow-up, the number censored, or the distribution of follow-up. The precision and robustness of the restricted mean estimate cannot be fully assessed without those details. The record also does not report the protocol’s original sample-size assumptions, so the enrolled total cannot be judged against a documented target effect or precision goal.

The registry does not provide detailed eligibility criteria beyond the high-risk localized or locally advanced population description. It also does not report treatment adherence, crossover, protocol deviations, or the analysis population. These omissions limit assessment of how closely the posted comparisons reflect the randomized assignment and the intended treatment strategies.

Finally, the registry reports no analyses in its analysis listing and does not describe multiplicity control or missing-data procedures. The posted unadjusted recalculations are useful summaries, but they cannot establish that all planned analyses are represented. These reporting limitations restrict the strength of conclusions that can be drawn from the registry record alone.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Hormone Suppression and Radiation Therapy for 6 Months With/Without Docetaxel for High Risk Prostate Cancer — NCT00116142.
• Registry record last updated 2022-01-11; status last verified 2022-01.
• Results first posted 2021-07-28.
• 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

NCT00116142 is a completed randomized phase 3 parallel-group trial sponsored by Dana-Farber Cancer Institute. It enrolled 350 participants with high-risk localized or locally advanced prostate cancer and compared androgen suppression therapy plus radiation with the same combination plus docetaxel. The trial was unmasked.

The primary outcome was 10-year restricted mean survival time for overall survival. The posted group estimates were 8.82 and 9.11 years, with an unadjusted mean difference of 0.29 years; the confidence interval crosses zero and the unadjusted p-value is 0.231. Secondary outcomes include biochemical recurrence, prostate cancer mortality, and adverse events. Further details about the original statistical plan, missing data, analysis populations, and multiplicity are not reported in the registry record.