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 Multicenter Trial of Abiraterone Acetate With or Without Cabazitaxel in Treatment of Metastatic Castration Resistant Prostate Cancer (NCT02218606), a randomized phase 2 study. The primary outcome is Progression Free Survival (rPFS).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02218606 |
| Phase | Phase 2 |
| Condition | Prostate Cancer |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 81 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Memorial Sloan Kettering Cancer Center |
| Results posted | Yes |
2. Clinical Question
Population
People with metastatic castration-resistant prostate cancer were eligible for this multicenter trial. The registry record lists prostate cancer as the condition and an enrollment of 81. Further eligibility criteria and details of the enrolled participants are not reported in the registry record.
Intervention
One randomized arm received cabazitaxel 25 mg/m2 intravenously with abiraterone acetate 1000 mg by mouth daily and prednisone 5 mg by mouth twice daily. The registry describes the purpose as examining treatment effects and the potential usefulness of tumor laboratory tests for predicting response.
Comparator
The other arm received abiraterone acetate 1000 mg by mouth daily with prednisone 5 mg by mouth twice daily, without cabazitaxel. The trial was randomized, open-label, and parallel-group; additional details about treatment assignment are not reported in the registry record.
Primary question
The primary endpoint was median progression-free survival assessed using RECIST criteria, with a timeframe of up to 100 weeks. The posted results give a median for each arm. They do not report a hazard ratio or another sponsor-reported comparative estimate, so the medians alone do not establish the size or precision of a treatment contrast.
3. Trial Design
This was an exploratory, randomized, phase II, multicenter trial with a parallel-arm design and no masking. The registry lists Memorial Sloan Kettering Cancer Center as the sponsor. The record gives an enrollment of 81 and marks the study as completed. It lists a start in 2014-08 and primary completion on 2023-10-13.
The comparison was between abiraterone acetate with prednisone and cabazitaxel added to abiraterone acetate with prednisone. The registry's arm descriptions specify cabazitaxel 25 mg/m2 intravenously, abiraterone acetate 1000 mg by mouth daily, and prednisone 5 mg by mouth twice daily. The posted primary-outcome records list 42 participants in the abiraterone-and-prednisone arm and 39 in the cabazitaxel-containing arm. These arm-level records need not be interpreted as a complete account of every analysis population.
Randomization is intended, in general, to reduce systematic differences between treatment groups at assignment. It does not guarantee that all prognostic characteristics are balanced in a trial of this size. With no masking, participants and study staff knew the assigned treatment; the registry record does not describe any masking of outcome assessment. The primary endpoint used RECIST criteria, but further details of assessment procedures are not reported in the registry record.
The study also listed PSA progression-free survival, objective response rate, and participants with maximum overall grade 3 or higher adverse events as secondary outcomes. The registry describes the trial's broader purpose as examining treatment effects and exploring whether tumor laboratory tests might predict response. Specific eligibility criteria, randomization procedures, treatment duration, and the laboratory-test analyses are not reported in the registry record.
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 1000 mg po Daily + Prednisone 5 mg po BID | Cabazitaxel 25 mg/m2 IV + Abiraterone Acetate 1000 mg po Daily |
|---|---|---|
| STARTED | 42 | 39 |
| COMPLETED | 17 | 7 |
| NOT COMPLETED | 25 | 32 |
Reasons for not completing this period:
| Reason | Abiraterone Acetate 1000 mg po Daily + Prednisone 5 mg po BID | Cabazitaxel 25 mg/m2 IV + Abiraterone Acetate 1000 mg po Daily |
|---|---|---|
| Adverse Event | 1 | 1 |
| Death | 15 | 28 |
| Physician Decision | 0 | 1 |
| Withdrawal by Subject | 4 | 0 |
| Noncompliance | 1 | 0 |
| Initiation of new drug for prostate cancer | 2 | 0 |
| Other | 2 | 1 |
| Never started treatment | 0 | 1 |
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 1000 mg po Daily + Prednisone 5 mg po BID | Cabazitaxel 25 mg/m2 IV + Abiraterone Acetate 1000 mg po Daily | Total |
|---|---|---|---|---|
| Participants analysed | 42 | 39 | 81 | |
| Age, Continuous | years | 69.5 (50 to 85) | 67 (49 to 81) | 67 (49 to 85) |
| Sex: Female, Male: Female | Participants | 0 | 0 | 0 |
| Sex: Female, Male: Male | Participants | 42 | 39 | 81 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 0 | 0 | 0 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 42 | 39 | 81 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Asian | Participants | 1 | 1 | 2 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Black or African American | Participants | 4 | 7 | 11 |
| Race (NIH/OMB): White | Participants | 34 | 29 | 63 |
| Race (NIH/OMB): More than one race | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 3 | 2 | 5 |
| Region of Enrollment: United States | Participants | 42 | 39 | 81 |
6. Primary Endpoint
The registry lists the primary outcome as Progression Free Survival (rPFS), measured over Up to 100 weeks.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Full Range |
| Unit | months |
| Endpoint classification | Time-to-Event Analysis |
The primary endpoint was progression-free survival assessed using RECIST criteria, reported as a median in months. In general, a time-to-event endpoint measures the time from a defined starting point until an event specified by the study. The registry's brief endpoint description does not give further details about the event definition or starting point, so those should not be inferred.
A median time-to-event result describes the time by which half of the observed participants in the relevant analysis have experienced the event, under the endpoint's analysis rules. It gives a central summary rather than a complete description of when events occurred. Participants who have not experienced the event by the end of observation may contribute censored follow-up in time-to-event analyses, but the registry record does not report how censoring was handled for this endpoint.
Time-to-event endpoints are useful in clinical trials because they account for the timing of events, rather than simply classifying participants as having or not having an event at a single fixed point. The timeframe listed for this endpoint is up to 100 weeks. The registry reports medians and ranges for the two arms; the listed ranges describe observed values and are not confidence intervals. No sponsor-reported hazard ratio or confidence interval for the between-arm comparison is reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry reports median progression-free survival of 6.4 months for abiraterone acetate with prednisone, with a range from 3.8 to 10.6 months. For the arm adding cabazitaxel to abiraterone acetate and prednisone, the reported median is 14.8 months, with a range from 10.6 to 16.4 months. These are arm-specific descriptive summaries for the primary endpoint.
A difference between arm medians is not, by itself, a complete estimate of the randomized treatment effect. Medians do not show the full distribution of event times, and they do not use all follow-up information in the same way as a time-to-event model. The ranges describe the reported spread of observed values, not the uncertainty around each median or around a comparison. The registry record does not report confidence intervals for the medians.
For a time-to-event comparison, a hazard ratio can describe the relative event rate over follow-up under the model used. The registry record does not report a sponsor hazard ratio, its confidence interval, or a corresponding comparative analysis. It also lists no posted analyses. Therefore, the registry results do not establish the precision or statistical significance of a between-arm contrast. No recalculated comparison is available for this median time endpoint because values are missing or not estimable for a two-arm comparison.
The randomized design is relevant to interpretation: random assignment supports a causal comparison in general, provided the study's conduct, follow-up, and analysis preserve the benefits of randomization. The registry record does not contain enough detail to assess those conditions fully. The open-label design may also matter for aspects of care and outcome ascertainment, although the endpoint is described as using RECIST criteria and details of assessment procedures are not reported.
These results should be read as the posted arm-level summaries, not as proof that either regimen is superior or inferior. The trial is identified as exploratory and phase II. Its reported medians are informative descriptions of the observed endpoint, but a comparative estimate with uncertainty and details of the analysis would be needed for a fuller statistical assessment.
9. Statistical Methods Explained
What does a median time-to-event result describe?
In general, a median is the middle of a distribution: the point at which half of the observations fall on either side, subject to the endpoint's analysis rules. For a time-to-event outcome, the median is commonly estimated from the event-time curve rather than by taking a simple average of observed times. This approach can accommodate participants whose event has not been observed by the end of their available follow-up, provided they are treated as censored according to the analysis plan. The registry record does not report the specific censoring rules or estimator used for this endpoint.
The posted medians are 6.4 months and 14.8 months for the respective arms. A median is a compact summary, but it does not show whether event times are concentrated near the center or spread unevenly across follow-up. Nor does a pair of medians reveal whether the relative difference between groups is steady over time. The record gives a range for each arm, but a range is a description of the observed endpoints, not an estimate of statistical uncertainty.
Why is a hazard ratio often used?
In general, a hazard is the instantaneous event rate among participants who have not yet experienced the event, conditional on the model and its assumptions. A hazard ratio compares those rates between groups over follow-up. It is not the same as a ratio of medians or a difference in median times. A hazard ratio is often paired with a confidence interval, which conveys the range of effect estimates reasonably compatible with the data under the model. The registry record does not report a hazard ratio or its confidence interval for this comparison.
Some time-to-event models assume that the hazard ratio is reasonably constant over time. If treatment effects change during follow-up, a single hazard ratio may not describe the pattern well. General methods for assessing that assumption include examining event-time curves and model diagnostics. The registry record does not report whether such checks were performed, and no sponsor comparative analysis is posted. These methods therefore cannot be used to infer an unreported result.
What do randomization and open-label conduct contribute?
In general, randomization assigns treatment by chance and aims to make the groups comparable at the start of a study, including with respect to measured and unmeasured prognostic factors. It does not guarantee balance in every trial, and it cannot by itself correct problems that arise after assignment, such as differential follow-up or departures from assigned treatment. Details about the randomization method, allocation concealment, adherence, and analysis population are not reported in the registry record.
The trial is listed as unmasked. In general, knowledge of assignment can influence care, reporting, or assessment. Using a defined response framework such as RECIST can promote consistency, but the registry does not describe assessor masking, review procedures, or other safeguards. The implications of open-label conduct therefore cannot be quantified from the posted record.
How should uncertainty and planning illustrations be understood?
In general, a confidence interval expresses uncertainty around an estimate; it is not a range containing a specified share of individual observations. The ranges reported with these medians are not confidence intervals. Without inferential estimates and their uncertainty, readers should avoid treating the arm-specific summaries as a precise estimate of comparative effect.
Sample-size calculations are planning illustrations, not observed trial outcomes and not observed power. In general, their results depend on assumptions about the effect to detect, significance level, allocation, outcome type, and statistical model. The registry's stated planning assumptions refer to an observed effect and equal allocation, but values for a two-arm comparison are missing or not estimable for this median time endpoint. No planning result for this endpoint should be inferred from the arm medians alone.
Over-dispersion is a general issue for count outcomes: it occurs when observed variation exceeds what a simple model assumes, and can make standard errors too small if ignored. It is not a reported feature of this trial's primary median endpoint. The record does not provide enough analysis detail to judge which modeling assumptions were used for the secondary outcomes or adverse events.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists three secondary outcomes: PSA progression-free survival, objective response rate, and participants with maximum overall grade 3 or higher adverse events. Along with the primary endpoint, these represent multiple questions. In general, testing several outcomes can increase the chance of at least one apparently positive finding by chance. Trials may address this through a prespecified testing sequence, adjusted significance thresholds, or by treating secondary analyses as exploratory. The registry record does not report a multiplicity strategy, so none should be assumed.
The record does not report results for the named secondary outcomes in the posted material described by these registry entries, nor does it provide sponsor-reported analysis estimates. It lists no posted analyses. The registry record does not report whether an analysis plan was prespecified, whether analyses were interim or final, or how analysis populations were defined.
Missing data and incomplete follow-up can affect clinical-trial estimates, particularly for time-to-event outcomes. In general, censoring is handled using assumptions about how follow-up ends and how that relates to event risk. The registry record does not report missingness, censoring rules, reasons for loss to follow-up, or sensitivity analyses. It also does not report whether the primary analysis followed an intention-to-treat principle or used another population. These omissions limit assessment of how robust the posted summaries are to missing data and analysis choices.
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 1000 mg po Daily + Prednisone 5 mg po BID | 22 | 42 | 52.4% |
| Cabazitaxel 25 mg/m2 IV + Abiraterone Acetate 1000 mg po Daily | 28 | 39 | 71.8% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Abiraterone Acetate 1000 mg po Daily + Prednisone 5 mg po BID | 15 of 42 |
| Cabazitaxel 25 mg/m2 IV + Abiraterone Acetate 1000 mg po Daily | 28 of 39 |
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 1000 mg po Daily + Prednisone 5 mg po BID | 27 of 42 |
| Cabazitaxel 25 mg/m2 IV + Abiraterone Acetate 1000 mg po Daily | 23 of 39 |
Most frequent serious adverse event terms
| Event term | Organ system | Abiraterone Acetate 1000 mg po Daily + Prednisone 5 mg po BID | Cabazitaxel 25 mg/m2 IV + Abiraterone Acetate 1000 mg po Daily |
|---|---|---|---|
| Death NOS | General disorders | 15 of 42 | 28 of 39 |
| Pain | General disorders | 6 of 42 | 6 of 39 |
| Febrile neutropenia | Blood and lymphatic system disorders | 2 of 42 | 4 of 39 |
| Anemia | Blood and lymphatic system disorders | 1 of 42 | 4 of 39 |
| Back pain | Musculoskeletal and connective tissue disorders | 4 of 42 | 1 of 39 |
| Abdominal pain | Gastrointestinal disorders | 2 of 42 | 2 of 39 |
| Acute kidney injury | Renal and urinary disorders | 2 of 42 | 2 of 39 |
| Fever | General disorders | 2 of 42 | 2 of 39 |
| Neutrophil count decreased | Investigations | 2 of 42 | 2 of 39 |
| Fatigue | General disorders | 1 of 42 | 2 of 39 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Abiraterone Acetate 1000 mg po Daily + Prednisone 5 mg po BID | Cabazitaxel 25 mg/m2 IV + Abiraterone Acetate 1000 mg po Daily |
|---|---|---|---|
| Fatigue | General disorders | 27 of 42 | 23 of 39 |
| Pain | General disorders | 25 of 42 | 23 of 39 |
| Nausea | Gastrointestinal disorders | 19 of 42 | 16 of 39 |
| Urinary frequency | Renal and urinary disorders | 16 of 42 | 17 of 39 |
| Diarrhea | Gastrointestinal disorders | 14 of 42 | 13 of 39 |
| Constipation | Gastrointestinal disorders | 16 of 42 | 10 of 39 |
| Cough | Respiratory, thoracic and mediastinal disorders | 10 of 42 | 14 of 39 |
| Dyspnea | Respiratory, thoracic and mediastinal disorders | 9 of 42 | 13 of 39 |
| Hypertension | Vascular disorders | 11 of 42 | 11 of 39 |
| Urinary incontinence | Renal and urinary disorders | 9 of 42 | 13 of 39 |
Serious events with the highest arm-level rate: death nos (71.8%), pain (15.4%), anemia (10.3%), febrile neutropenia (10.3%), back pain (9.5%).
The registry reports serious adverse events among 22 of 42 participants at risk in the abiraterone acetate and prednisone arm, and among 28 of 39 participants at risk in the cabazitaxel-containing arm. For other adverse events, it reports 27 of 42 participants at risk and 23 of 39 participants at risk, respectively. Death counts are listed as 15 and 28 in the same arm order. These are reported counts; they should not be read as a comparative safety estimate.
In general, an adverse-event count depends on how events were defined, collected, and attributed, as well as the observation period and the population monitored. The registry record does not report additional detail about event attribution, duration of exposure, or follow-up for these summaries. The listed serious-event terms include Death NOS at 71.8%, Pain at 15.4%, Anemia at 10.3%, Febrile neutropenia at 10.3%, Back pain at 9.5%, and Abdominal pain at 5.1%. The denominator and precise interpretation of those percentages are not reported in the registry record, so they should not be treated as arm-specific incidence estimates.
12. What the Result Does, and Does Not, Mean
The registry's primary-endpoint results describe median progression-free survival in each randomized arm. The medians are 6.4 months for abiraterone acetate with prednisone and 14.8 months for the arm that also received cabazitaxel. The reported ranges describe observed values, not uncertainty around an estimated treatment effect. A comparative hazard ratio, confidence interval, and sponsor-reported statistical analysis are not reported in the registry record.
That distinction matters because descriptive arm summaries do not answer every question about a randomized comparison. A formal time-to-event analysis can account for follow-up and censoring in a defined way and can quantify uncertainty around the relative effect. Without the registry's comparative estimate and analysis details, the precision and statistical significance of a treatment contrast cannot be established from the posted medians.
The adverse-event records likewise provide counts, not a complete comparison of safety. The figures do not by themselves account for exposure duration, event severity beyond the reported categories, attribution, or differences in observation. The serious-event term percentages have no reported denominator in the registry record, which limits their interpretation.
The record identifies an exploratory phase II trial and states that tumor laboratory tests were also of interest as potential predictors of response. It does not report findings for that exploratory objective in the registry record. The results therefore characterize selected registry entries; they do not establish a general treatment recommendation, settle all benefit-risk questions, or show whether a laboratory test can predict response.
13. Why This Trial Matters Statistically
This trial is statistically notable for the contrast between a randomized design and the limited comparative information in the posted registry results. Randomization is intended to support a fair treatment comparison, but arm-level medians alone do not convey the estimated relative effect or its uncertainty. A clearly reported hazard ratio with a confidence interval, along with details of the analysis population and censoring, would help readers judge the strength and precision of the comparison. Those details are not reported in the registry record.
The endpoint also illustrates why the type of summary matters. Median time-to-event results are easy to interpret as central summaries, while a range describes observed spread. Neither is a substitute for an uncertainty interval around a comparison. Readers who distinguish these quantities are less likely to mistake the extremes of observed values for statistical precision or to infer a comparative result from two separate arm summaries.
The study also lists several secondary outcomes and adverse-event measures. In general, multiple outcomes raise questions about prespecification and multiplicity, while safety counts require attention to denominators and follow-up. The registry record does not report enough analytical detail to resolve those questions. This makes transparent reporting especially important when interpreting an exploratory phase II study.
Finally, the stated interest in tumor laboratory tests points to a separate statistical challenge: a marker may be associated with outcome without reliably predicting differential response between treatments. The registry record does not report results for that objective. The distinction between describing an outcome, estimating a treatment effect, and evaluating a predictive marker is central to interpreting clinical-trial evidence.
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.
Several trial-specific details needed for a fuller assessment are not reported in the registry record. These include eligibility criteria, participant characteristics, the method of randomization, allocation concealment, treatment adherence, and definitions of the analysis populations. The record identifies the study as open-label but does not describe whether outcome assessors were masked or how RECIST assessments were reviewed.
The primary result is reported as arm-specific medians and ranges. The registry record does not report a hazard ratio, confidence interval, formal comparative analysis, or details of censoring and follow-up. Consequently, the reported summaries do not establish the precision of the between-arm result. The range is not a confidence interval and should not be used as one.
The registry lists secondary outcomes, but the record does not report their results or a multiplicity strategy. It also does not report missing-data summaries, reasons for incomplete follow-up, sensitivity analyses, or a statistical analysis plan. Such information would help assess whether the findings could be affected by selective outcome reporting, analysis choices, or missing observations.
The adverse-event records give counts and list selected serious-event terms with percentages, but the denominator for those percentages is not reported. Additional context on event attribution, exposure, observation time, and collection procedures is not reported in the registry record. The study's exploratory laboratory-test objective is also not accompanied by results or analysis details in the registry record. These limitations constrain interpretation without changing the descriptive values that the registry does report.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Multicenter Trial of Abiraterone Acetate With or Without Cabazitaxel in Treatment of Metastatic Castration Resistant Prostate Cancer — NCT02218606.
- Registry record last updated 2024-12-10; status last verified 2023-10.
- Results first posted 2024-12-10.
- 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 identifies NCT02218606 as a completed, exploratory randomized phase II multicenter trial in metastatic castration-resistant prostate cancer. It compared abiraterone acetate with prednisone against cabazitaxel added to abiraterone acetate and prednisone. The listed primary outcome was RECIST-based progression-free survival, reported as a median in months over a timeframe of up to 100 weeks.
The posted medians are 6.4 months, with a range of 3.8 to 10.6 months, for abiraterone acetate with prednisone, and 14.8 months, with a range of 10.6 to 16.4 months, for the cabazitaxel-containing arm. The registry also reports adverse-event counts. A comparative hazard ratio, confidence interval, and detailed statistical analysis are not reported in the registry record.