Green Tea, Black Tea, or Water in Treating Patients With Prostate Cancer Undergoing Surgery: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Green Tea, Black Tea, or Water in Treating Patients With Prostate Cancer Undergoing Surgery (NCT00685516), a randomized na study. The primary outcome is Effect of Green Tea (GT) and Black Tea (BT) Consumption on Percentage of Cells With Positive Staining for Apoptosis, Proliferation, Oxidation, and Inflammation in Malignant Radical Prostatectomy Tissue Compared to Water Control Using Immunohistochemistry..

2. Clinical Question

The trial was designed to examine whether consuming brewed tea before surgery was associated with differences in biological markers measured in malignant prostate tissue. The registry describes the primary outcome as the mean percentage of cells with positive staining, assessed using immunohistochemistry. The planned timeframe for this endpoint is 6 weeks.

This is a biological tissue question, not a question about whether tea changes cancer symptoms, recurrence, survival, or other clinical outcomes. The registry record lists additional outcomes involving tea-related compounds in prostate tissue and urine, as well as prostate specific antigen (PSA) after green or black tea consumption. Numerical findings for these outcomes are not reported in the registry record.

3. Trial Design

The registry describes a randomized, parallel-group trial with no masking. The brief summary calls it a randomized phase II trial, while the formal phase field is recorded as NA. The record lists an enrollment of 113. It identifies prostate cancer as the condition and Jonsson Comprehensive Cancer Center as the sponsor.

Participants were assigned to one of three regimens: green tea, water, or decaffeinated black tea. Each arm description specifies 6 cups daily for 2-8 weeks, subject to the absence of unacceptable toxicity. Water served as the control. Although a placebo intervention is also listed in the record, the arm descriptions identify the comparator group as receiving water.

The primary endpoint is described for subjects who completed the study, using malignant tissue collected at radical prostatectomy. Its stated timeframe is 6 weeks. The record lists the study start as 2007-09-01, primary completion as 2012-01-12, and status as completed.

Random allocation and parallel groups establish the broad design, but details of sequence generation, allocation concealment, stratification, adherence measurement, and the timing of randomization are not reported in the registry record. The record also does not report a sample-size justification or a detailed protocol-level statistical analysis plan. The registry’s phase designation and the summary wording should therefore be read as recorded, without inferring additional design 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.

Overall Study

Analysis population for the primary outcome, as defined in the registry: subjects that completed study

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: 93 subjects completed the intervention (Arm I, GT: 34, Arm II, control: 33, Arm III, BT: 26).

6. Primary Endpoint

The registry lists the primary outcome as Effect of Green Tea (GT) and Black Tea (BT) Consumption on Percentage of Cells With Positive Staining for Apoptosis, Proliferation, Oxidation, and Inflammation in Malignant Radical Prostatectomy Tissue Compared to Water Control Using Immunohistochemistry., measured over 6 weeks.

The primary endpoint concerns the proportion of malignant prostate tissue cells that stain positively for markers of apoptosis, proliferation, oxidation, and inflammation. Immunohistochemistry uses staining to identify biological features in tissue. The endpoint is expressed as a mean percentage of total cells with positive staining, with standard deviation named as the measure of dispersion. The stated assessment timeframe is 6 weeks.

These markers address different biological processes. In general, apoptosis refers to programmed cell death, proliferation to cell growth and division, oxidation to chemical processes involving oxidation, and inflammation to a tissue response. Measuring them in prostatectomy tissue allows researchers to examine whether the assigned tea regimens are associated with differences in tissue-level biology at surgery.

The endpoint is not itself a measure of symptoms, tumor shrinkage, recurrence, or survival. A change in a staining measure would describe a difference in the marker as measured, not by itself establish a clinical benefit. The registry record does not report the observed means, standard deviations, group comparisons, or uncertainty estimates for this primary endpoint.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Several statistical ideas help explain what the trial’s endpoint is intended to capture and what would be needed to interpret a comparison. The registry record names a mean and standard deviation for a continuous outcome. It does not report the observed values or a statistical analysis, so the explanations below are general and do not imply that a particular method was used in this trial.

What does a mean percentage describe?

For each tissue marker, the percentage of cells staining positive describes how common positive staining is among the cells assessed. A group mean summarizes the average measurement across participants with data. The standard deviation describes the spread of individual measurements around that mean. A mean alone cannot show whether participants had similar measurements or a wide range of values; the standard deviation gives information about that variability.

The endpoint is measured at the participant level through tissue sampling, even though cells contribute to the percentage. Treating every cell as an independent participant would ignore that cells from the same tissue specimen are grouped together. In general, analyses should respect the unit of randomization and the structure of the measurements. The registry record does not describe the detailed data structure or the statistical model.

What would a group comparison mean?

A comparison of group means would estimate how the average staining percentage differs between assigned regimens. A confidence interval, in general, describes a range of values that are reasonably compatible with the data and the method used to calculate it. Its width conveys precision: a wider interval indicates less precise estimation than a narrower interval. The registry record does not report confidence intervals, so the precision of any contrast cannot be assessed.

A p-value, in general, measures how surprising data at least as incompatible with a specified null hypothesis would be under the assumptions of a statistical test. It does not quantify the clinical importance of a difference, nor does it measure the probability that the null hypothesis is true. No p-values or test results are reported in the registry record. Without estimates and uncertainty measures, neither statistical significance nor the range of plausible differences can be assessed.

Why do the multiple markers matter?

The primary endpoint names apoptosis, proliferation, oxidation, and inflammation, and the record lists 4 outcome measures. Testing multiple outcomes can increase the chance of at least one apparently notable result when all are considered together. In general, a prespecified multiplicity strategy can address that issue, for example by controlling the overall error rate or by defining a hierarchy of tests. The registry record does not report whether such a strategy was planned or used. Since no analyses are listed, it is also not possible to determine how the outcomes were handled analytically.

Multiple arms create another design consideration. A comparison of green tea with water addresses a different contrast from a comparison of decaffeinated black tea with water, or from a direct comparison between the teas. The registry identifies all three groups but does not report a prespecified hierarchy or set of primary contrasts. A reader should not assume which pairwise comparisons were intended to carry the main inferential claim.

What does a planning illustration show?

In general, a sample-size calculation estimates how many participants would be needed to detect a specified effect under stated assumptions. The record describes planning illustrations based on the observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It says the target effect is a stated fraction of the observed effect. These assumptions describe illustrations rather than a documented design calculation for this trial. They should not be interpreted as observed power. Power is a prospective design quantity under chosen assumptions; after results are collected, estimates and confidence intervals are more informative about what the data show.

The record does not report the effect estimate on which those illustrations depend in the information available for interpretation, nor does it report the original sample-size justification. The illustrations therefore cannot establish that the trial was designed to detect a particular difference. In addition, their two-arm framing does not by itself resolve how comparisons across three randomized groups or multiple biological outcomes were planned.

What cannot be inferred from the analysis fields?

The registry lists no analyses. That absence means there are no reported statistical findings to interpret in the registry record; it does not establish that no analysis was performed outside the record. Details such as covariate adjustment, distributional checks, transformations, handling of outliers, and missing-data methods are not reported in the registry record. In general, such choices can affect estimates and their uncertainty, particularly for biological measurements that may have skewed distributions or varying precision.

The named outcome is a mean of a continuous measure, but that label alone does not identify the full analysis model. It does not say whether groups were compared using an unadjusted method, a regression model, or another approach. The reader therefore cannot reconstruct an analysis or judge its assumptions from the endpoint description alone.

10. Multiplicity, Missing Data and Analysis Populations

The primary outcome description includes staining measures for apoptosis, proliferation, oxidation, and inflammation, and the record lists 4 outcome measures. These are multiple biological outcomes. If each is tested separately, the possibility of a chance-positive result across the set is generally greater than for a single prespecified test. A multiplicity plan might define a primary marker, adjust inference across tests, or treat findings as exploratory. Whether any such plan was specified or used is not reported in the registry record.

The trial also has three randomized arms, so more than one pairwise comparison is possible. The registry record does not identify a primary pairwise contrast, a testing hierarchy, or an adjustment for comparisons among arms. The record lists no analyses, so it offers no results from which to assess how comparisons were conducted.

The primary endpoint population is described as subjects who completed the study. This wording does not establish whether the analysis followed intention-to-treat principles, used a per-protocol population, or applied another definition. The number of participants with primary endpoint data by arm, reasons for missing measurements, and any method for addressing missing data are not reported in the registry record. The record also does not report whether participants who discontinued tea consumption or did not undergo the planned tissue assessment remained in an analysis population.

These omissions limit assessment of selection bias and robustness. In general, if completion or availability of tissue measurements is related to assigned group or participant characteristics, an analysis limited to completers can differ from an analysis of all randomized participants. That is a general concern, not evidence that such bias occurred in this trial. With no posted endpoint estimates or analysis details, the impact of missing data and multiplicity cannot be determined.

11. 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.

The registry reports serious adverse events, other adverse events, and deaths for the three arms. For green tea, the serious-event group lists 34 at risk and 0 affected; the other-event group lists 34 at risk and 0 affected; deaths are 0. For water, the corresponding at-risk counts are 33 for serious and other events, with 0 affected in each category and 0 deaths. For decaffeinated black tea, the at-risk counts are 26 for serious and other events, with 0 affected in each category and 0 deaths.

These figures mean that the registry reports no affected participants in the listed adverse-event categories among the stated at-risk counts. They do not establish that no symptoms or non-serious events of any kind occurred, and they do not describe event severity beyond the listed categories. The record’s top serious-event terms list is empty. Follow-up duration for safety collection, event definitions, attribution, and completeness of reporting are not reported in the registry record.

Zero reported events should not be read as proof of zero risk. In general, safety estimates depend on the number of people observed, how long they were followed, and how events were defined and collected. The registry entries alone do not support a detailed comparison of safety between regimens.

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

The registry record shows that the study asked a focused biological question: whether green tea or decaffeinated black tea consumption, compared with water, was associated with differences in staining markers in malignant prostate tissue at surgery. It describes randomized parallel groups, the beverage regimens, a 6-week endpoint timeframe, and the intended tissue measures.

It does not report numerical primary endpoint findings. There are no group-specific means, standard deviations, differences, confidence intervals, or p-values in the registry record, and no analyses are listed. Consequently, the posted information does not establish whether the groups differed, how large any differences were, or how precisely they could be estimated. The same absence of numerical results applies to the listed secondary outcomes.

Even a documented difference in these tissue markers would have a limited interpretation. It would describe a difference in measured biological features, not necessarily a change in a patient-centered outcome such as symptoms, recurrence, or survival. The record does not list such clinical outcomes as results to interpret.

The safety entries report 0 affected participants for serious and other adverse events in each arm, and 0 deaths. Those are the counts as recorded, not proof that adverse effects are impossible or that the regimens have equivalent safety. The size and duration of safety observation, event definitions, and methods of collection are not reported in the registry record.

Accordingly, the registry information supports understanding the trial’s question and broad design, but it is insufficient to reach a statistical conclusion about the primary comparison. Any claims about the magnitude, direction, or certainty of an effect would require results and analysis details not reported in the registry record.

13. Why This Trial Matters Statistically

This trial is statistically notable for its combination of a randomized three-arm design and a tissue-based primary endpoint spanning several biological processes. The design asks readers to distinguish among different contrasts: each tea regimen versus water, and potentially green tea versus decaffeinated black tea. Those comparisons need not yield the same estimate or answer the same question.

The endpoint also contains several marker domains. Multiplicity matters because conclusions drawn from many outcomes and comparisons can be more vulnerable to chance findings unless the analysis plan addresses that structure. The registry record does not report a multiplicity strategy or list any analyses, so it is not possible to assess how these considerations were handled.

The outcome is a continuous percentage summarized as a mean and standard deviation. That makes the scale of measurement and the distribution of participant-level values relevant to analysis. In general, means describe average levels, while standard deviations describe variation; neither alone provides the uncertainty of a group comparison. Confidence intervals and an explicit analysis model would help readers understand the precision and assumptions of a contrast, but these are not reported in the registry record.

Finally, the endpoint population is described as study completers. This highlights the importance of knowing who contributed data and how missing tissue measurements were handled. Randomization provides a strong framework for comparison, but interpretation still depends on transparent reporting of analysis populations, missingness, and results. The record’s omissions make the study’s question clear while leaving its statistical findings unresolved.

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 registry record provides design and endpoint descriptions but no numerical primary outcome results or analyses. This is the central limitation for statistical interpretation: there is no basis in the record for estimating the size, direction, or precision of differences between the beverage groups.

The primary outcome covers several staining domains, but outcome-specific estimates and a prespecified comparison hierarchy are not reported in the registry record. The number of endpoint observations in each arm is also not reported. The primary population is described as subjects who completed the study, while definitions of completion, analysis populations, and missing-data procedures are not reported in the registry record.

Important design and analysis details are absent, including the randomization sequence and concealment methods, adherence assessment, any adjustment for baseline characteristics, and methods for evaluating model assumptions. A sample-size justification and the original statistical plan are not reported in the registry record. Planning illustrations based on observed effects do not replace those details and should not be read as observed power.

The record’s safety counts are limited to the listed categories and at-risk groups. Event definitions, follow-up duration, and collection procedures are not reported in the registry record. Finally, the primary endpoint concerns tissue markers; the record does not provide results for clinical outcomes such as recurrence or survival. These limitations constrain both statistical interpretation and the scope of conclusions that can be drawn.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Green Tea, Black Tea, or Water in Treating Patients With Prostate Cancer Undergoing Surgery — NCT00685516.
• Registry record last updated 2020-12-31; status last verified 2020-09.
• Results first posted 2016-06-06.
• 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.

18. Record Summary

NCT00685516 is a completed randomized, unmasked, parallel-group trial of green tea, water, and decaffeinated black tea in patients with prostate cancer undergoing surgery. The registry lists an enrollment of 113. Each arm description specifies 6 cups daily for 2-8 weeks, in the absence of unacceptable toxicity.

The primary endpoint is the mean percentage of malignant prostate tissue cells with positive staining for apoptosis, proliferation, oxidation, and inflammation, assessed by immunohistochemistry at 6 weeks. The endpoint population is described as subjects who completed the study. The registry record lists secondary outcomes concerning tea-related compounds in prostate tissue and urine, and PSA.

Numerical primary endpoint results and statistical analyses are not reported in the registry record. The adverse-event entries list 0 affected participants in the serious and other event categories for each arm, and 0 deaths.