This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Clinical Trial of Two Study Drinks in Detoxification of Environmental Toxicants and Carcinogens (NCT03978117), a randomized phase 2 study. The primary outcome is Carcinogen Detoxification of Metabolites in Urine..
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT03978117 |
| Phase | Phase 2 |
| Condition | Healthy |
| Allocation | Randomized |
| Design model | Crossover |
| Masking | Single |
| Enrollment | 300 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Masonic Cancer Center, University of Minnesota |
| Results posted | Yes |
2. Clinical Question
Population
Healthy participants. The registry lists an enrollment of 300 and notes that the number analyzed differs because some markers were incomplete.
Intervention
Freeze Dried Watercress Preparation, a dietary supplement.
Comparator
Placebo Preparation, also listed as a dietary supplement.
Primary question
Whether urine concentrations of carcinogen-detoxification metabolites differ under the study drinks. The registry does not report numerical outcome results or an analysis answering this question.
The study asks whether consuming the watercress preparation is associated with a change in biomarkers related to the processing of environmental toxicants and carcinogens, compared with placebo. Its stated interest includes participants who are null for GSTM1, GSTT1, or both. The record does not report results by these genetic groups, so it does not establish whether the biomarker pattern differed across them.
The primary outcome is described as a set of urine metabolites measured at two months. Because the record does not give the marker-specific results, it is not possible to tell from the registry whether the watercress and placebo conditions differed, how large any difference was, or how precisely it was estimated. The statistical question is therefore identifiable from the study description, but its answer is not reported in the registry record.
3. Trial Design
The registry classifies this as a randomized, single-masked, Phase 2 crossover trial. The listed interventions are a freeze dried watercress preparation and a placebo preparation. The study population is described as healthy, and the registry lists enrollment of 300. The record marks the trial as completed.
In general, randomization is intended to make treatment assignment less dependent on participant characteristics, while masking can reduce some expectations-related influences on behavior or assessment. The record says the trial was single-masked but does not report who was masked or how masking was maintained. It also does not describe the randomization method, allocation sequence, or allocation concealment.
A crossover design generally compares interventions within participants across different periods or sequences. This can allow each participant to contribute information under more than one condition, but the analysis must account for the paired structure. The registry does not report the treatment sequences, period lengths, washout procedures, timing of measurements beyond the primary outcome timeframe, or how period and sequence effects were handled. Those details should not be inferred from the design label alone.
The registry gives a two-month timeframe for the primary outcome. The arm descriptions contain no additional details. Although the study is marked completed, the record lists no analyses and does not provide numerical primary-outcome findings. Consequently, the design and intended comparison can be described, but the reported information is insufficient to reconstruct the conduct of each crossover period or evaluate the primary comparison.
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
| Stage | Freeze Dried Watercress Preparation Then Placebo | Placebo Then Freeze Dried Watercress Preparation |
|---|---|---|
| STARTED | 155 | 145 |
| COMPLETED | 125 | 115 |
| NOT COMPLETED | 30 | 30 |
Reasons for not completing this period:
| Reason | Freeze Dried Watercress Preparation Then Placebo | Placebo Then Freeze Dried Watercress Preparation |
|---|---|---|
| self- withdrawal or PI withdrawal | 26 | 26 |
| Lost to Follow-up | 4 | 4 |
Analysis population for the primary outcome, as defined in the registry: Number analyzed differs due to incomplete markers in analysis.
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.
| Characteristic | Unit | Freeze Dried Watercress Preparation Then Placebo | Placebo Then Freeze Dried Watercress Preparation | Total |
|---|---|---|---|---|
| Participants analysed | 108 | 80 | 188 | |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 108 | 80 | 188 |
| Age, Categorical: >=65 years | Participants | 0 | 0 | 0 |
| Sex: Female, Male: Female | Participants | 69 | 57 | 126 |
| Sex: Female, Male: Male | Participants | 39 | 23 | 62 |
| Race/Ethnicity, Customized: Non-White | participants | 25 | 14 | 39 |
| Race/Ethnicity, Customized: White | participants | 83 | 66 | 149 |
| Region of Enrollment: United States | participants | 108 | 80 | 188 |
6. Primary Endpoint
The registry lists the primary outcome as Carcinogen Detoxification of Metabolites in Urine., measured over 2 Months.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Inter-Quartile Range |
| Unit | ng/mL |
| Endpoint classification | not reduced to a single comparison |
The primary outcome is described as carcinogen-detoxification metabolites in urine, with results intended to be expressed in ng/mL. The registry specifies medians and inter-quartile ranges and gives a timeframe of two months. The listed biomarkers are CEMA, HPMA1, HPMA2, SPMA, HMPMA1, HMPMA2, and HMPMA3.
These metabolites are used as biomarkers of exposure processing: they can indicate the presence of products associated with the metabolism and elimination of particular compounds. Measuring them provides a biological outcome rather than relying only on reported intake or symptoms. That makes the endpoint relevant to the study’s stated question about detoxification, but a biomarker remains an indirect measure. A change in a urine metabolite alone does not establish a change in long-term health or cancer risk.
The median describes the central value of a distribution, while the inter-quartile range describes its spread across the middle portion. In general, these summaries can be useful when biomarker values are skewed or contain extreme observations. The registry does not report the actual median or inter-quartile range for any marker, nor does it report marker-specific comparisons. It therefore documents what was intended to be measured, not the observed biomarker response.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies a randomized comparison of freeze dried watercress and placebo and names urine carcinogen-detoxification metabolites as the primary outcome. It does not report numerical results for those metabolites. There are no posted medians, inter-quartile ranges, effect estimates, confidence intervals, or p-values for the primary outcome, and the record lists no analyses. As a result, the direction, size, and precision of any biomarker difference cannot be determined from the registry results.
The outcome description includes multiple biomarkers and notes that the primary outcome has several categories or time points and was not reduced to one comparison. This means there is no single reported contrast that can be interpreted as the trial’s numerical result. It would be inappropriate to select one marker, assume a common effect across markers, or infer a favorable or unfavorable finding from the study’s stated purpose.
The enrollment figure of 300 is a design or recruitment record, not a statement that every enrolled participant contributed usable data for each marker. The registry explicitly notes that the number analyzed differs because of incomplete markers. It does not report the analyzed count for each biomarker or condition. Thus, the amount of information underlying any particular marker comparison is not reported in the registry record.
The record’s adverse-event entries are separate from the primary biomarker outcome. It lists zero serious adverse events in each displayed group, alongside other adverse-event counts. These entries do not supply evidence about whether the primary biomarker outcome differed, and the registry does not state that the other adverse events were caused by either preparation.
Any planning illustration based on an observed effect should not be mistaken for an observed treatment result or for the trial’s actual design justification. The registry describes a planning approach using a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation, with the effect to detect expressed as a fraction of the observed effect. The relevant biomarker effect estimates are not reported, so the illustration cannot substitute for an analysis of trial outcomes. Overall, the record defines a research question and design but leaves the primary statistical finding unavailable.
9. Statistical Methods Explained
As a general statistical point, randomized allocation is intended to reduce systematic differences between treatment groups at the start of a study. It does not guarantee that all participant characteristics will be balanced, and it does not resolve problems caused by missing measurements, incomplete follow-up, or an analysis that does not respect the study design. The registry labels this study randomized but does not report the sequence-generation or allocation-concealment methods.
What does a crossover design require statistically?
In general, crossover data contain repeated measurements from participants across intervention periods. Measurements from the same participant are usually more alike than measurements from unrelated participants. An analysis should account for that within-participant relationship rather than treating every period measurement as independent. The paired structure can improve precision when the analysis is appropriate, but the validity of a crossover comparison also depends on assumptions about period effects, sequence effects, and persistence of an earlier intervention into a later period.
The record identifies a crossover model but does not report the sequences, period structure, washout, or statistical model. It is therefore not possible to tell whether the posted analysis accounted for within-participant correlation, period, sequence, or possible carryover. The record lists no analyses, so there is no reported method to assess. These are general design and analysis considerations, not claims about procedures used in this trial.
Why report medians and inter-quartile ranges?
In general, a median gives a distribution’s central point without being pulled as strongly by unusually high or low observations as a mean can be. The inter-quartile range describes variability across the middle of the data. These summaries are often informative for biological measurements that may be skewed. They do not, by themselves, test whether two conditions differ. A comparison needs an appropriate estimate and inferential method that reflects the outcome distribution and the crossover structure.
The registry specifies medians and inter-quartile ranges in ng/mL, but gives none of their values. It also does not name a test or model, state whether estimates were adjusted, or provide confidence intervals. No inferential result can therefore be reproduced from the posted record. In general, a confidence interval communicates the range of effect values reasonably compatible with the data and analysis assumptions. Its width conveys precision; it is not a guarantee that the true effect lies within the interval.
How should multiple biomarkers be handled?
The endpoint description names several urinary metabolites. In general, testing multiple outcomes creates a multiplicity issue: even when there is no underlying effect, a larger collection of tests creates more opportunities for an apparently notable result. Analysts may define a primary marker, use a prespecified hierarchy, adjust for multiple comparisons, or treat findings as exploratory. The registry does not report a multiplicity plan or identify a single marker-specific contrast as the primary statistical comparison. It explicitly says the outcome was not reduced to one comparison because it has several categories or time points.
Without a reported plan and results, readers cannot determine whether any marker-level findings were confirmatory or exploratory, or how uncertainty across the collection of biomarkers should be interpreted. This does not establish that multiplicity was mishandled; the relevant analysis details are not reported in the registry record.
What does the planning illustration mean?
In general, a sample-size calculation estimates how many observations would be needed under specified assumptions to detect a target effect with a chosen type I error rate and power. The registry describes a planning illustration based on the observed effect, a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The target effect is described as a stated fraction of the observed effect. Such an illustration is not the trial’s original design justification unless the record says so; that justification is not reported.
A planning calculation is also not observed power. Observed power is not a substitute for reporting an effect estimate and its uncertainty. Because the registry does not report the primary marker results or observed effect estimates, the basis and numerical output of a planning illustration cannot be evaluated from this record. Any sample-size figure should be read as a conditional planning scenario, not as evidence that the study detected or failed to detect an effect.
10. Multiplicity, Missing Data and Analysis Populations
The primary outcome covers several urine biomarkers, and the registry notes that it has several categories or time points rather than a single reduced comparison. This creates a need to distinguish the overall study question from marker-specific analyses. In general, evaluating multiple outcomes without a prespecified approach can make isolated findings difficult to interpret because the chance of apparently notable results increases as the set of comparisons grows.
The record does not report a multiplicity adjustment, a hierarchy among biomarkers, a prespecified primary marker, or an analysis plan. It lists one outcome measure but zero analyses; the outcome measure’s broad description does not establish how many statistical tests were intended or performed. The registry therefore does not allow a reader to assess how multiplicity was addressed.
Missingness is also relevant. The population description says the number analyzed differs because of incomplete markers in analysis. The record does not give marker-specific analyzed counts, reasons for missing measurements, patterns of missingness, or any imputation or sensitivity-analysis approach. It does not report whether analyses included all randomized participants, only participants with complete measurements, or another defined population. Those analysis-population details are not reported in the registry record.
These omissions limit interpretation, but they do not establish that the study had no analysis plan or that any particular method was used. They mean only that the registry record does not describe those methods or provide the results needed to evaluate them.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Freeze Dried Watercress | 0 | 300 | 0.0% |
| Placebo | 0 | 300 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Freeze Dried Watercress | 0 of 300 |
| Placebo | 0 of 300 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Freeze Dried Watercress | 188 of 300 |
| Placebo | 50 of 300 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Freeze Dried Watercress | Placebo |
|---|---|---|---|
| Increased gas, belching and changes to stool | Gastrointestinal disorders | 37 of 300 | 8 of 300 |
| Nausea | General disorders | 30 of 300 | 5 of 300 |
| Oral dysesthesia (burning/tingling/numbness/pain) | General disorders | 21 of 300 | 1 of 300 |
| Stomach Pain | Gastrointestinal disorders | 18 of 300 | 4 of 300 |
| Bloating | Gastrointestinal disorders | 16 of 300 | 3 of 300 |
| Diarrhea | Gastrointestinal disorders | 15 of 300 | 3 of 300 |
| Increased Urination | Gastrointestinal disorders | 7 of 300 | 11 of 300 |
| Gastroesophageal Reflux (GERD/heartburn/acid) | Gastrointestinal disorders | 7 of 300 | 3 of 300 |
| Vomiting | Gastrointestinal disorders | 7 of 300 | 0 of 300 |
| Constipation | Gastrointestinal disorders | 5 of 300 | 1 of 300 |
The registry lists serious adverse events as zero in the freeze dried watercress group and zero in the placebo group. Each displayed group has 300 at risk in the serious-event entry. These are the counts recorded in the registry; they should not be read as proof that no serious event occurred outside the record’s reporting definitions or observation process.
For other adverse events, the registry lists 188 affected in the freeze dried watercress group and 50 affected in the placebo group, with 300 at risk in each displayed group. The record does not describe the event types, severity breakdown, timing, relationship to the study preparations, or the method used to collect and classify these events. It also does not explain how adverse-event group denominators relate to the crossover periods or participant overlap. The figures should therefore be read as registry entries, not as causal comparisons between preparations.
These safety entries are not a substitute for the primary outcome analysis, and they do not establish whether either preparation caused or prevented an event. The registry lists zero deaths in both groups. Further detail about safety definitions and analysis is not reported in the registry record.
12. What the Result Does, and Does Not, Mean
The record establishes that a randomized, single-masked Phase 2 crossover study compared a freeze dried watercress preparation with placebo in healthy participants. It identifies urine carcinogen-detoxification metabolites as the primary outcome and specifies medians and inter-quartile ranges at two months. These details explain the intended comparison and the type of measurement, but they do not reveal the observed result.
No numerical primary-outcome findings or analysis are reported. Accordingly, the record cannot establish whether biomarker values were higher or lower under either preparation, whether a difference was large or small, or how precise an estimate might be. It also cannot show whether findings were consistent across the named biomarkers or differed in the genetic groups mentioned in the study summary.
Even if a registry reported a biomarker difference, such a result would need to be interpreted as a change in a measured biological marker. A biomarker is not itself a direct measure of long-term disease outcomes. The study summary describes an interest in environmental toxicants and cancer-causing agents, but the primary endpoint listed is urinary metabolites, not cancer incidence or a clinical health outcome.
The registry’s adverse-event entries provide counts but no event descriptions or causal assessments. They should not be used to claim that a preparation is safe, harmful, effective, or ineffective. The reported record is incomplete for those judgments, and no medical advice follows from these statistics. The appropriate conclusion is limited: the registry describes the study question and selected design features, while its posted primary results and analysis are not reported.
13. Why This Trial Matters Statistically
This trial raises several statistical issues that commonly matter when evaluating biomarker studies. Its crossover design makes it important to distinguish within-participant comparisons from independent-group comparisons. A valid analysis needs to reflect repeated measurements and should address the possibility that period, sequence, or carryover effects influence the result. The registry identifies the design but does not report the details needed to assess those choices.
The endpoint also includes several metabolites rather than a single marker. That makes it important to know which comparisons were prespecified and how multiplicity was handled. Without a reported analysis plan or marker-level results, readers cannot separate a primary confirmatory finding from a pattern of exploratory comparisons. Missing marker measurements further matter because the registry says the number analyzed differs due to incomplete markers, but it does not describe the extent or handling of that missingness.
The distinction between a biological marker and a clinical outcome is also central. Urine metabolites can address a biological process relevant to the study’s rationale, but they do not automatically establish a change in health outcomes. Statistical interpretation must stay aligned with what was actually measured.
Finally, the registry’s planning assumptions should be distinguished from evidence. A planning illustration based on an observed effect is conditional on assumptions and does not report how the trial’s outcomes turned out. Since the primary estimates and analyses are absent, the record is more informative about the intended question than about its answer.
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 of the registry record is that it does not report numerical results or analyses for the primary endpoint. Without marker-specific summaries or effect estimates, readers cannot evaluate the direction, magnitude, precision, or consistency of the biomarker findings. The record also does not provide confidence intervals or p-values.
The outcome combines multiple biomarkers and refers to several categories or time points, but no single comparison is reported. The registry does not describe a statistical plan for multiplicity or indicate how marker-level comparisons were prioritized. The number analyzed is said to differ because of incomplete markers, without marker-specific counts, reasons for missingness, or a description of how incomplete data were handled.
Important crossover details are not reported, including the treatment sequences, period structure, washout, and the method used to account for repeated measurements, period effects, sequence effects, or carryover. The masking description does not identify who was masked. The randomization method and allocation concealment are also not described. These gaps prevent reconstruction of the analysis from the registry record.
The safety entries lack descriptions of event definitions, timing, severity beyond the serious-event category, and attribution. The record does not explain the relationship between the displayed group counts and crossover periods. These limitations do not show that the study was conducted improperly; they identify information that is not reported in the registry record and therefore cannot be evaluated from it.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Clinical Trial of Two Study Drinks in Detoxification of Environmental Toxicants and Carcinogens — NCT03978117.
- Registry record last updated 2025-11-21; status last verified 2025-11.
- Results first posted 2025-09-05.
- 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.
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18. Record Summary
The registry describes a completed randomized, single-masked Phase 2 crossover trial in healthy participants, comparing a freeze dried watercress preparation with placebo. Enrollment is listed as 300. The primary outcome concerns urinary carcinogen-detoxification metabolites, summarized by median and inter-quartile range in ng/mL at two months.
The record names CEMA, HPMA1, HPMA2, SPMA, HMPMA1, HMPMA2, and HMPMA3, and notes that the number analyzed differs because of incomplete markers. It does not report numerical primary-outcome results, marker-specific analyses, or a statistical analysis plan. Serious adverse events are listed as zero in both groups; other adverse-event counts are listed as 188 for freeze dried watercress and 50 for placebo. The event details and relationship to treatment are not reported in the registry record.