Effects of Sulforaphane on Normal Prostate Tissue: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Effects of Sulforaphane on Normal Prostate Tissue (NCT00946309), a randomized phase 1, phase 2 study. The primary outcome is Gene Expression of Phase II Enzymes.

2. Clinical Question

3. Trial Design

This was a randomized, triple-masked, parallel-group trial listed as Phase 1 and Phase 2. The registry reports an enrollment of 45 and a completed status. The study start is recorded as 2010-07, and primary completion as 2014-05. Fred Hutchinson Cancer Center is listed as the sponsor.

Participants were assigned to High Sulforaphane Extract, identified as broccoli sprout extract, or Microcrystalline Cellulose NF, identified as placebo. Randomization describes assignment by chance; a parallel-group design means the trial compared distinct groups rather than reporting a crossover. Triple masking indicates that the registry characterizes the study as masked at three levels, but it does not identify those levels. Further details of the masking procedures are not reported in the registry record.

The study’s stated purpose was to identify biological effects of high-sulforaphane broccoli sprout extract in normal prostate tissue. Its hypothesis was that consuming the extract every other day would inhibit growth of prostate cancer cells. The primary outcome, however, was a tissue gene-expression measure: change in Phase II enzyme expression from baseline to 5 weeks. The record does not describe a cancer-growth endpoint among the primary outcome details.

Although enrollment was 45, the registry states that outcome data were collected from only the first 20 participants because of budget restrictions. It does not explain how those participants were selected, whether outcome data were available for every one of them, or how the smaller outcome-data group was handled in analyses. The arm descriptions contain no further regimen details.

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: There were no pre-assignment events. Group assignment occurred at the time of participant enrollment.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Due to budget restrictions, outcome data from only collected from the first 20 participants

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.

Population: One participant enrolled to the placebo arm was determined to be ineligible, and was withdrawn from the study Two additional participants enrolled to the placebo arm became ineligible after enrollment, and were withdrawn from the study

6. Primary Endpoint

The registry lists the primary outcome as Gene Expression of Phase II Enzymes, measured over Baseline and 5 weeks.

The primary endpoint was titled Gene Expression of Phase II Enzymes. It measures change in expression, expressed as fold change, between baseline and 5 weeks. The registry describes the outcome as continuous and specifies a mean with standard deviation as its summary form. Phase II enzyme expression is a biological measure, so it addresses a tissue-level response to the intervention rather than a clinical event such as cancer diagnosis, progression, or survival. The record does not specify which individual enzymes were included or how expression was measured.

As a general statistical concept, a continuous endpoint can retain gradations of response rather than reducing measurements to categories such as improved or not improved. Reporting a mean describes the central value across observations, while a standard deviation describes spread among those observations. Neither summary, by itself, establishes the size or precision of a treatment-group contrast.

The registry gives baseline and 5 weeks as the assessment time points, but the primary outcome has several categories or time points and is not reduced to one comparison in the posted results. Numerical endpoint estimates are not reported in the registry record. Consequently, the direction, magnitude, and uncertainty of the primary outcome cannot be assessed from the available record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies a randomized, triple-masked, parallel-group study and describes a continuous primary outcome summarized as a mean and standard deviation. It does not report inferential analyses for that outcome. The following concepts explain how such methods are generally interpreted, without attributing unreported procedures or results to this trial.

What does randomization contribute?

In general, randomization assigns participants to treatment groups by chance. Its purpose is to reduce systematic differences between groups at the point of assignment, including differences that might otherwise be related to prognosis or response. It does not guarantee that groups are identical, particularly in a small study, and it does not correct problems that occur after assignment, such as missing outcome measurements. The registry identifies randomization but does not report the sequence-generation procedure, allocation concealment, or details of how assignments were implemented.

What does masking mean in this record?

The study is labeled triple-masked. In general, masking is intended to limit the influence of knowledge about assigned treatment on participants, care providers, or people assessing or analyzing outcomes. The registry does not identify the three masked parties or describe procedures for maintaining masking. It is therefore possible to report the study’s masking label, but not to assess how masking was implemented or whether it was maintained.

How should a mean and standard deviation be understood?

For a continuous outcome, the mean is a measure of the center of the observed values. The standard deviation describes how dispersed individual values are around that mean. The mean does not show the full shape of the data, and the standard deviation is not the same as the uncertainty in the estimated mean or in a difference between groups. General statistical practice may use a confidence interval to communicate uncertainty in an estimate, but no confidence interval for this endpoint is reported in the registry record.

The trial’s endpoint is change in Phase II enzyme expression, described in fold-change units, with baseline and 5 weeks as the time frame. The registry does not specify the exact endpoint calculation or identify the enzyme categories in the posted primary-outcome description. It also does not report group means, standard deviations, an effect estimate, or an inferential test. No particular statistical model, adjustment method, or assumption about the distribution of the outcome can therefore be assigned to the trial based on this record.

Why does over-dispersion matter in general?

For count outcomes, over-dispersion means that observed variability exceeds what a chosen model expects. If it is ignored, standard errors can be too small and confidence intervals too narrow. This is a general issue for count data; the primary endpoint in this record is described as a continuous expression measure, not a count outcome. The registry does not report an over-dispersion assessment or any model diagnostics.

What can be learned from a confidence interval?

In general, a confidence interval gives a range of estimates compatible with the data under the analysis method and its assumptions. Its width reflects precision: a wider interval indicates greater uncertainty than a narrower one. An interval is not a guarantee that the true value lies within its particular endpoints. No interval for the primary outcome is reported in the registry record, so precision cannot be evaluated for that outcome.

How should planning illustrations be read?

General sample-size planning asks how many participants per arm would be needed to detect a specified effect under chosen assumptions. The record describes a planning illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation; it says the effect to detect is a stated fraction of the observed effect. It also distinguishes participant counts per arm for non-time-to-event outcomes from total event counts for time-to-event outcomes. Such illustrations are not observed power and are not a report of the trial’s original design justification. Because numerical primary-outcome results are not reported in the registry record, the observed effect underlying the planning illustration cannot be evaluated from this record.

The registry does not report the statistical analysis plan, test used for the primary endpoint, handling of repeated measurements, covariate adjustment, or interim analyses. Those methods should not be inferred from the design label or from the outcome’s summary format. In this trial, the available registry entries support explanation of general statistical concepts, but not reconstruction of the actual primary-outcome analysis.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists six outcome measures and gives the primary outcome time frame as baseline and 5 weeks. It also indicates that the primary outcome has several categories or time points and is not reduced to one comparison in the posted results. No analysis results are reported. The record does not describe a multiplicity strategy, such as adjustment for multiple outcomes or comparisons, and it does not report a statistical analysis plan. It is therefore not possible to determine whether or how multiplicity was addressed.

Missing-data information is limited. The registry states that, because of budget restrictions, outcome data were collected from only the first 20 participants. This describes a restriction on outcome data collection; it does not establish why data may be absent for any individual or whether there were additional missing measurements among those participants. The record does not report the number with complete baseline and 5-week measurements, a missing-data method, or sensitivity analyses. It also does not explain how the first 20 participants were selected for outcome collection.

The record reports no analyses. It does not identify an intention-to-treat, per-protocol, or other analysis population, nor does it describe how participants were handled if they did not follow the assigned intervention. These omissions matter because analysis choices and missing-data assumptions can affect estimates and their uncertainty. They cannot be resolved from the posted registry entries.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent non-serious adverse event terms

The registry reports serious adverse events separately by group. In the Sulforaphane group, 0 serious adverse events were recorded among 21 participants at risk. In the Placebo group, 0 serious adverse events were recorded among 23 participants at risk. The record also lists other adverse events for 19 participants among 21 at risk in the Sulforaphane group and 18 participants among 23 at risk in the Placebo group.

These are counts with group-specific denominators, not measures of event severity or causality. The registry does not list serious adverse-event terms, and it does not describe the other adverse events by type or timing. The death fields are not reported in the registry record. The counts should therefore be read as the adverse-event information posted for the listed groups, not as a complete account of all possible safety outcomes or as evidence that an event was caused by the assigned intervention.

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

The record establishes that investigators conducted a randomized, triple-masked, parallel-group comparison of high-sulforaphane broccoli sprout extract with placebo. It identifies a biological primary endpoint—change in Phase II enzyme expression from baseline to 5 weeks—and notes that outcome data were collected from only the first 20 participants because of budget restrictions. It also posts group-specific adverse-event counts.

Those details do not establish whether the intervention changed gene expression relative to placebo. Numerical primary-outcome results, effect estimates, and uncertainty measures are not reported in the registry record. The direction and magnitude of any difference therefore remain unknown from the posted information. The record also does not report the results of an analysis testing the investigators’ hypothesis about prostate cancer cell growth.

Even if a difference in gene expression had been reported, a biological measure would not by itself demonstrate an effect on cancer growth, diagnosis, progression, or another clinical outcome. The primary endpoint is not a direct measure of those outcomes. The registry’s hypothesis and stated purpose should be distinguished from findings: they describe what the investigators sought to examine, not a result.

The safety counts show that no serious adverse events were recorded in either listed group, with other adverse events recorded in both groups. The record does not provide event details sufficient to compare types, timing, or attribution. Overall, the registry supports a description of the trial’s design and reported safety counts, but it does not permit a quantitative assessment of the primary endpoint or a conclusion about clinical benefit or harm.

13. Why This Trial Matters Statistically

This trial is statistically notable because its design information and endpoint definition are more complete than its posted primary-outcome results. Randomization, masking, and a parallel-group comparison describe how the study was structured. The continuous endpoint and its time frame describe what investigators intended to measure. Yet numerical results and analysis results are not reported in the registry record, limiting what can be learned about the treatment-group contrast.

The outcome-data restriction is also important for interpretation. Although enrollment was 45, the registry says outcome data were collected from only the first 20 participants because of budget restrictions. The record does not explain how that group was selected or how the restriction affected analysis. In general, a smaller set of outcome observations can make estimates less precise, while selection of participants for measurement may introduce bias if selection is related to outcomes. Whether either issue occurred cannot be determined from the posted information.

The trial also illustrates why endpoint meaning matters. Phase II enzyme expression is a biological measure, while the investigators’ hypothesis refers to growth of prostate cancer cells. A statistical result for the former would not automatically answer the latter question. Defining the endpoint and its relation to the scientific hypothesis is essential when interpreting study findings.

Finally, the adverse-event figures demonstrate the distinction between counts and a full safety interpretation. The record reports group denominators and event counts, but does not provide event descriptions or attribution. The study is therefore useful for considering how design, incomplete outcome reporting, and endpoint choice shape interpretation, without supporting a numerical efficacy conclusion.

14. 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 principal limitation for interpreting the primary endpoint is that numerical results are not reported in the registry record. The record gives the endpoint name, summary form, unit, and assessment time frame, but no group estimates, variability values, treatment contrast, confidence interval, or p-value. The lack of analysis results prevents evaluation of the direction, magnitude, and precision of any effect.

Outcome data were collected from only the first 20 participants because of budget restrictions, despite an enrollment of 45. The record does not state how those participants were chosen, whether data were complete at both baseline and 5 weeks, or how the restriction was addressed in analysis. The arm descriptions provide no further information about the treatment regimen. The registry also does not identify the Phase II enzymes or describe the measurement procedures.

The posted information does not report an analysis plan, a multiplicity approach, analysis populations, missing-data procedures, or interim analyses. It does not identify the three parties covered by the triple-masking label or explain how masking was implemented. These details should not be inferred from the design labels.

The registry lists Prostate Cancer as the condition while describing the study purpose as examining biological effects in normal prostate tissue. That context does not make the primary endpoint a clinical cancer outcome. The posted safety information lacks event terms, timing, and attribution, and deaths are not reported in the registry record. Together, these limitations restrict interpretation to the trial’s stated design, endpoint definition, outcome-data collection note, and posted event counts.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Effects of Sulforaphane on Normal Prostate Tissue — NCT00946309.
• Registry record last updated 2016-11-15; status last verified 2016-06.
• Results first posted 2016-11-15.
• 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.

18. Record Summary

NCT00946309 is titled “Effects of Sulforaphane on Normal Prostate Tissue,” with the official title “In Vivo Effects of Sulforaphane Supplementation on Normal Human Prostate.” The registry lists Phase 1 and Phase 2, randomized allocation, triple masking, a parallel model, enrollment of 45, and completed status. Fred Hutchinson Cancer Center is the listed sponsor; the study start is recorded as 2010-07 and primary completion as 2014-05.

The comparison was High Sulforaphane Extract, described as broccoli sprout extract, versus Microcrystalline Cellulose NF placebo. The primary endpoint was change in Phase II enzyme expression, measured at baseline and 5 weeks. Due to budget restrictions, outcome data were collected from only the first 20 participants. Numerical primary-outcome and analysis results are not reported in the registry record. The safety record lists no serious adverse events in either group and reports other adverse events in both groups.