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 An Observational Study of Continuous Oral Dosing of Abiraterone Acetate in Castration-Resistant Prostate Cancer Patients Evaluating Androgens and Steroid Metabolites in Bone Marrow Plasma (NCT00544440), a na phase 2 study. The primary outcome is Number of Participants With Detectable Bone Marrow Testosterone Level (>1 Picograms/Mililiter).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00544440 |
| Phase | Phase 2 |
| Condition | Prostate Neoplasms |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 57 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Janssen Research & Development, LLC |
| Results posted | Yes |
2. Clinical Question
Population
The study concerned patients with metastatic castration-resistant prostate cancer. The registry lists Prostate Neoplasms as the condition and records enrollment of 57 participants. Bone marrow aspirates were collected from 49 participants at baseline, defined as predose Week 1 Day 1, and from 44 participants at Week 8. The record does not provide further eligibility criteria or explain why aspirate counts differ across these time points.
Intervention
The study evaluated oral abiraterone acetate alongside prednisone. The arm description specifies abiraterone acetate 1000 mg daily and prednisone 5 mg twice a day, with treatment described as continuing until clinical disease progression. The study purpose was to investigate effects on androgen and steroid-metabolite levels in bone marrow plasma.
Comparator
There was no separate comparator group: the study is recorded as single-group, with allocation listed as NA. It is therefore not a randomized comparison, and the treatment group cannot be compared with a like-for-like control group in this record. Baseline and Week 8 are measurement times, not independent treatment arms.
Primary question
The primary endpoint asks how many participants had a detectable bone marrow testosterone level, defined in the outcome title as >1 Picograms/Mililiter, at baseline and Week 8. The record names the outcome and the time points but does not report the participant counts at either time point or a numerical change between them. It therefore does not establish from the posted primary outcome whether the number with detectable testosterone changed.
3. Trial Design
This completed study is registered as Phase 2 and observational. Its model is single-group, allocation is listed as NA, and masking is recorded as none. Those design features distinguish it from a randomized, masked comparison: the registry does not describe assignment to different treatment groups or a control arm. Accordingly, changes across time in this group would not by themselves supply a like-for-like comparison against an untreated or differently treated group.
The registry records enrollment of 57 participants and lists abiraterone acetate and prednisone as drug interventions. The arm description specifies oral abiraterone acetate 1000 mg daily together with prednisone 5 mg twice a day, continuing until clinical disease progression. This is the regimen described in the record; details about adherence, dose modifications, or actual treatment duration are not reported in the registry record.
The study purpose was to investigate the effect of abiraterone acetate on androgen and steroid-metabolite levels in bone marrow plasma in patients with metastatic castration-resistant prostate cancer. The primary endpoint concerns the number of participants whose bone marrow testosterone level was above the stated detection threshold at baseline and Week 8. The registry says bone marrow aspirates were collected from 49 participants at baseline and 44 at Week 8. It does not report why those numbers differ or how participants without a measurement at a given time point were handled.
The record lists one secondary outcome, the number of participants with change in markers of bone metabolism, and four outcome measures in total. It records zero analyses. Specific analysis populations, statistical tests, adjustment methods, and the timing or conduct of any interim analyses are not reported in the registry record. The study start is recorded as 2007-10, primary completion as 2012-08, and status as completed.
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 | Abiraterone Acetate |
|---|---|
| STARTED | 57 |
| COMPLETED | 0 |
| NOT COMPLETED | 57 |
Reasons for not completing this period:
| Reason | Abiraterone Acetate |
|---|---|
| Other | 1 |
| Adverse Event | 1 |
| Withdrawal by Subject | 2 |
| Subject Non-compliance | 1 |
| Progressive Disease | 47 |
| Other | 5 |
Analysis population for the primary outcome, as defined in the registry: Bone marrow aspirates were collected at baseline (predose Week 1 Day 1) in 49 participants and in 44 participants at Week 8.
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 | Abiraterone Acetate |
|---|---|---|
| Participants analysed | 57 | |
| Age, Continuous | years | 69.1 (SD 8.93) |
| Sex: Female, Male: Female | Participants | 0 |
| Sex: Female, Male: Male | Participants | 57 |
6. Primary Endpoint
The registry lists the primary outcome as Number of Participants With Detectable Bone Marrow Testosterone Level (>1 Picograms/Mililiter), measured over Baseline (predose Week 1 Day 1) and Week 8.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | Number of Participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is a count: the number of participants with a detectable bone marrow testosterone level, with the outcome title defining detectable as >1 Picograms/Mililiter. The registry specifies measurements at baseline, predose Week 1 Day 1, and Week 8. It reports that bone marrow aspirates were collected at baseline in 49 participants and at Week 8 in 44 participants.
A threshold-based endpoint turns a laboratory measurement into a classification: a value is either above the specified threshold or it is not. Counts can describe how many participants meet that definition at each time point. Such an endpoint can be useful when the scientific question focuses on whether a measurable level remains detectable, rather than on the full range of measured concentrations. That is a general description of threshold endpoints, not a claim about why this particular endpoint was selected; the rationale is not reported in the registry record.
The registry names the endpoint and collection times but does not report the actual numbers of participants above the threshold, the underlying testosterone measurements, or a statistical comparison between baseline and Week 8. It also does not state how values at or below the threshold were recorded, or how a participant with a missing aspirate was included in any analysis. Consequently, the endpoint definition can be described, but the amount or direction of change cannot be determined from the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies a clinically specific biological question: whether bone marrow testosterone was detectable, under the stated threshold, at baseline and Week 8 during treatment with abiraterone acetate plus prednisone. It also identifies the numbers of participants with aspirate collections at those two times. However, it does not report the endpoint counts or a numerical estimate of change. Without those values, the primary outcome cannot be interpreted as showing an increase, decrease, or lack of change.
The design matters for interpreting any within-group change that might be reported elsewhere. This is an observational, single-group study with allocation listed as NA and no masking. There is no randomized comparison group in the registry record. A difference between measurements over time in one group could describe a temporal pattern among measured participants, but it would not, on its own, separate treatment-related change from other explanations. This is a general limitation of single-group before-and-after comparisons, not a finding about what occurred in this study.
The measurement counts also require care. The record reports aspirates from 49 participants at baseline and 44 at Week 8, while enrollment was 57. These counts do not reveal whether the same participants contributed measurements at both times, why measurements were unavailable, or what analysis population was used. A comparison of counts at each time point is not necessarily the same as a paired comparison among participants measured at both times. The registry does not provide the participant-level pairing or missing-data handling needed to resolve that issue.
No confidence interval, p-value, or other numerical analysis for the primary endpoint is reported in the registry record. A confidence interval, as a general statistical concept, describes the uncertainty around an estimated quantity under the assumptions of the analysis. Without a reported estimate and interval, precision cannot be assessed. Likewise, the record does not report a test of change or a prespecified statistical decision rule, so it is not possible to determine whether the study’s primary result met any formal criterion.
The registry lists four outcome measures and one secondary outcome, but does not report analysis details. The existence of several outcomes can raise multiplicity questions when multiple statistical tests are conducted; whether such tests were conducted, and whether any adjustment was planned, is not reported. The registry’s entry of zero analyses does not provide a numerical analysis of the primary endpoint. Overall, the posted information describes the study question, design, treatment regimen, and specimen counts, but does not provide primary outcome results from which a treatment effect or its precision could be judged.
9. Statistical Methods Explained
What does the endpoint count?
The primary outcome is expressed as a number of participants, rather than as an average concentration. The outcome title defines a detectable bone marrow testosterone level as >1 Picograms/Mililiter. In general, a threshold converts a continuous measurement into a binary classification: each measured value falls on one side or the other of the cutoff. The resulting count is straightforward to describe, but it does not retain all information about how far individual measurements lie from the threshold. The registry record does not report the underlying measurements or the counts classified as detectable.
The endpoint is specified at baseline and Week 8. A before-and-after analysis could in general compare the two measurements within participants who contributed both. A separate comparison of the number meeting the threshold at each time point would instead summarize each time point’s available measurements. These approaches answer related but not identical questions. The registry record does not report which approach was used, whether measurements were paired in analysis, or what statistical test was applied.
How should the study design shape interpretation?
This is recorded as an observational, single-group study, with allocation listed as NA and masking as none. In general, a single-group study can describe measurements during a treatment course, but it has no randomized control group to provide a concurrent comparison. A change over time can be associated with the period of treatment without proving that treatment alone caused the change. This distinction is about what the design can establish; it does not imply that any particular alternative explanation occurred in this study.
Masking refers generally to whether participants, clinicians, or outcome assessors are kept unaware of assigned treatment. The registry lists masking as none, but does not specify further details about who knew what or whether laboratory assessors were masked. Because the endpoint is a laboratory measurement, general concerns about subjective assessment may differ from those for a judgment-based outcome, but measurement procedures and quality-control details are not reported in the registry record.
What do uncertainty measures usually add?
For a numerical outcome estimate, a confidence interval communicates statistical uncertainty around that estimate. A narrower interval generally indicates greater precision under the analysis assumptions, while a wider interval indicates less precision. A p-value, when reported, addresses compatibility between data and a specified null model; it does not itself measure the size or practical importance of a difference. These are general explanations. No confidence interval, p-value, or primary endpoint estimate is reported in the registry record, so no trial-specific uncertainty or statistical significance can be described.
For a binary count, uncertainty depends on the number of observations and the number classified in each category, among other features. If measurements are paired, the within-participant pattern is relevant; the two marginal counts alone do not capture which participants changed classification. If measurements are not paired, the assumptions and interpretation differ. The available record gives the number of aspirates at each time point but not the joint participant-level classifications or analysis method.
How do the planning illustrations differ from trial results?
The stated sample-size assumptions describe a planning illustration based on a fraction of an observed effect, a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The assumptions specify participants per arm for non-time-to-event outcomes. Such calculations are hypothetical planning exercises, not a report of the trial’s design justification or an observed power calculation. The study itself is single-group, not a two-arm randomized comparison. No sample-size justification for the actual trial is reported in the registry record, and no numerical planning result or observed primary effect is included among the registry entries.
In general, power is a property of a planned design under specified assumptions about the effect, variability, and analysis. It is not a measure of whether the result is true, and calculating power after observing an outcome does not replace reporting an estimate and its uncertainty. Here, the planning assumptions should not be read as evidence that the study was designed around a particular effect or that it had a particular probability of detecting one. Those protocol details are not reported in the registry record.
What is not available about the analysis?
The registry lists four outcome measures, one secondary outcome, and zero analyses. It does not describe the analysis population, statistical model, treatment of incomplete measurements, covariates, or any method for adjusting comparisons. It also does not report whether interim analyses were conducted. These omissions mean that the statistical method used for the primary outcome cannot be reconstructed from the registry record. General statistical principles can explain why such details matter, but they cannot substitute for the trial’s unreported analysis plan.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists four outcome measures and identifies one secondary outcome: the number of participants with change in markers of bone metabolism. It does not report a multiplicity strategy or specify how many statistical hypotheses were tested. When several outcomes or repeated comparisons are tested, the chance of at least one nominally unusual result can increase; methods such as prespecifying a primary hypothesis or adjusting for multiple tests can address that issue in some settings. This is a general explanation, not a description of a method used in this study. Whether any adjustment was planned or applied is not reported in the registry record.
The registry records zero analyses, and it does not provide a statistical analysis plan or numerical test results for the primary endpoint. That entry does not establish that no analyses were conducted; it means no analysis details are available in this record. The method for handling multiple outcomes, time points, or any other comparisons is therefore not reported in the registry record.
For missing data, the record states that aspirates were collected from 49 participants at baseline and 44 at Week 8, with enrollment of 57. It does not explain why specimens were not recorded for all enrolled participants, whether the same participants contributed at both times, or how incomplete observations were handled. In general, missing-data methods rely on assumptions about why values are absent. Without the reasons for absent measurements or the analysis approach, those assumptions cannot be evaluated. The analysis populations, exclusions, and any sensitivity analyses are not reported in the registry record.
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 |
|---|---|---|---|
| Abiraterone Acetate | 29 | 57 | 50.9% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Abiraterone Acetate | 56 of 57 |
Most frequent serious adverse event terms
| Event term | Organ system | Abiraterone Acetate |
|---|---|---|
| Back pain | Musculoskeletal and connective tissue disorders | 7 of 57 |
| Pneumonia | Infections and infestations | 5 of 57 |
| Dyspnoea | Respiratory, thoracic and mediastinal disorders | 5 of 57 |
| Abdominal pain | Gastrointestinal disorders | 4 of 57 |
| Anaemia | Blood and lymphatic system disorders | 3 of 57 |
| Disease progression | General disorders | 3 of 57 |
| Fatigue | General disorders | 3 of 57 |
| Anorexia | Metabolism and nutrition disorders | 3 of 57 |
| Arthralgia | Musculoskeletal and connective tissue disorders | 3 of 57 |
| Hypotension | Vascular disorders | 3 of 57 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Abiraterone Acetate |
|---|---|---|
| Hyperglycaemia | Metabolism and nutrition disorders | 47 of 57 |
| Fatigue | General disorders | 36 of 57 |
| Blood alkaline phosphatase increased | Investigations | 36 of 57 |
| Anaemia | Blood and lymphatic system disorders | 30 of 57 |
| Hypoalbuminaemia | Metabolism and nutrition disorders | 26 of 57 |
| Hypertension | Vascular disorders | 24 of 57 |
| Back pain | Musculoskeletal and connective tissue disorders | 23 of 57 |
| Arthralgia | Musculoskeletal and connective tissue disorders | 22 of 57 |
| Oedema peripheral | General disorders | 20 of 57 |
| Hypokalaemia | Metabolism and nutrition disorders | 20 of 57 |
Serious events with the highest arm-level rate: back pain (12.3%), pneumonia (8.8%), dyspnoea (8.8%), abdominal pain (7.0%), anaemia (5.3%).
The registry lists 57 participants at risk in the Abiraterone Acetate group for serious adverse events and records 29 participants affected. For other adverse events, it lists 57 at risk and 56 affected. These are participant counts, not counts of the total number of event episodes. A participant may experience more than one event, so the affected-participant count should not be read as the total event count.
The listed serious adverse event terms and percentages are Back pain, 12.3%; Pneumonia, 8.8%; Dyspnoea, 8.8%; Abdominal pain, 7.0%; Anaemia, 5.3%; and Disease progression, 5.3%. These are the terms and percentages recorded in the registry; the available information does not define further how each term’s percentage was calculated or whether participants could appear under more than one term. They should not be added together to estimate a proportion of participants.
The deaths value is not reported in the registry record. The safety figures do not establish a comparison with another treatment group, because this is a single-group study without a like-for-like control arm. They also do not establish whether an event was caused by a study drug. The record’s group label is Abiraterone Acetate, while the described regimen includes prednisone as well; attribution details are not reported in the registry record.
12. What the Result Does, and Does Not, Mean
The registry record establishes that the study was designed to investigate androgen and steroid-metabolite levels in bone marrow plasma during treatment of patients with metastatic castration-resistant prostate cancer. It identifies a primary endpoint based on the number of participants with bone marrow testosterone above >1 Picograms/Mililiter at baseline and Week 8. It also records the number of aspirate collections at each time point and describes a regimen of abiraterone acetate plus prednisone.
Those details do not establish what happened to the primary endpoint. The actual numbers meeting the threshold at baseline and Week 8, an estimate of change, and uncertainty around that estimate are not reported in the registry record. It is therefore not possible to state from these registry entries whether detectability became more or less common, or how precise any change might be. The absence of reported primary results is not evidence that no change occurred in either direction.
The design also limits what a temporal pattern could mean. As a single-group observational study without a randomized comparator, it cannot provide the same treatment contrast as a controlled randomized trial. In general, within-group measurements may describe a change over time, but a causal interpretation requires assumptions and evidence that this record does not supply. This is a design qualification, not a claim that the regimen did or did not affect the biomarker.
The study enrolled 57 participants, but aspirates were recorded for 49 at baseline and 44 at Week 8. Because the registry does not explain the difference, or identify the participants with measurements at both visits, it is not possible to determine how complete the paired primary endpoint data were. The analysis population and missing-data methods are also not reported.
Thus, the record supports a description of the research question, regimen, design, and available specimen counts. It does not support a conclusion about the size, direction, statistical significance, or causal interpretation of a primary endpoint result. These distinctions are important: a clearly specified biological endpoint is not itself a reported result, and an observed within-group pattern would not by itself constitute a controlled treatment comparison.
13. Why This Trial Matters Statistically
This study illustrates why interpreting a biomarker endpoint requires attention to both its definition and its analysis. The primary endpoint is not the full testosterone concentration distribution; it is the number of participants whose bone marrow level exceeds a stated threshold. That distinction matters because a threshold count can be easy to interpret as a classification while concealing variation in values within each category. The registry record does not report the underlying concentrations or the number above the threshold, so neither the distribution nor the classified outcome can be assessed.
It also highlights the importance of distinguishing repeated measurements from treatment groups. Baseline and Week 8 are time points in one group, not separate comparator arms. In general, a within-person comparison may use the relationship between a participant’s measurements, whereas a comparison of separate time-point totals does not necessarily preserve that information. The record reports specimen counts at each time but not the pairing or analysis method.
The difference between enrollment and the stated aspirate counts makes transparent reporting of analysis populations important. Knowing who contributed at each time, why other measurements were unavailable, and how missing values were handled would help readers evaluate the scope and precision of an estimate. Those details are not reported in the registry record.
Finally, this record demonstrates that a stated endpoint and a completed study do not ensure that numerical outcome results are available in the registry entry. Without counts, estimates, uncertainty intervals, and an analysis description, readers cannot evaluate the magnitude or precision of the primary finding. These are general statistical reporting considerations, not evidence about the unreported result of this study.
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 most direct limitation for interpretation is that the registry record does not report the primary endpoint counts or a numerical comparison between baseline and Week 8. It therefore provides no estimate of the direction, magnitude, or precision of change in detectable bone marrow testosterone. The laboratory values underlying the threshold classification are also not reported.
The design is observational and single-group, with allocation listed as NA and masking as none. There is no like-for-like control group in the record, so a within-group change would not by itself isolate a treatment effect. The record does not report eligibility criteria in detail, recruitment methods, or participant characteristics that could help assess who the findings might describe.
Although 57 participants were enrolled, the record reports bone marrow aspirates from 49 participants at baseline and 44 at Week 8. It does not explain these differences, state whether the same participants posted samples at both time points, or describe how incomplete measurements were handled. The analysis population is not reported in the registry record.
The record does not report the statistical test, model, confidence interval, p-value, covariate adjustment, multiplicity approach, or sensitivity analyses. It also does not report a sample-size justification for the actual study, interim analyses, adherence, treatment duration as observed, dose changes, or laboratory assessment procedures. These protocol and analysis details are not reported in the registry record.
Safety interpretation is also constrained: the registry provides participant counts and selected serious adverse event terms, but does not report deaths, causal attribution, or a control-group comparison. The listed safety information should therefore be read as descriptive record information rather than as a comparative estimate.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: An Observational Study of Continuous Oral Dosing of Abiraterone Acetate in Castration-Resistant Prostate Cancer Patients Evaluating Androgens and Steroid Metabolites in Bone Marrow Plasma — NCT00544440.
- Registry record last updated 2014-07-17; status last verified 2014-07.
- Results first posted 2013-11-01.
- 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
NCT00544440 is a completed Phase 2 observational study in patients with metastatic castration-resistant prostate cancer. It is recorded as single-group, with allocation listed as NA and masking as none. Enrollment was 57. The described oral regimen was abiraterone acetate 1000 mg daily and prednisone 5 mg twice a day, continuing until clinical disease progression.
The primary endpoint was the number of participants with a bone marrow testosterone level >1 Picograms/Mililiter at baseline and Week 8. Aspirates were collected from 49 participants at baseline and 44 at Week 8. The registry record does not report the primary endpoint results, statistical analysis details, or explanation of the different specimen counts. The record lists one secondary outcome and four outcome measures.
The study start is recorded as 2007-10, primary completion as 2012-08, and status as completed. The study’s single-group design does not provide a randomized control comparison, and the missing endpoint results preclude an assessment of the direction or precision of the primary outcome.