Cabozantinib and Androgen Ablation in Patients With Androgen-Dependent Metastatic Prostate Cancer: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Cabozantinib and Androgen Ablation in Patients With Androgen-Dependent Metastatic Prostate Cancer (NCT01630590), a na phase 2 study. The primary outcome is Progression Free Survival.

2. Clinical Question

The study concerns whether cabozantinib used with androgen ablation is associated with a progression-free survival outcome in this patient group. Because it has a single treatment group, it can describe outcomes among enrolled participants but cannot establish how those outcomes compare with what would have occurred under a different treatment. The study’s title calls it observational, while its phase is listed as Phase 2. The registry record does not report a comparison that would separate the contribution of cabozantinib from the contribution of androgen ablation, or from other influences on participants’ outcomes.

3. Trial Design

The registry record describes a completed Phase 2 study titled as an observational study of XL-184 cabozantinib and androgen ablation in patients with androgen-dependent metastatic prostate cancer. The listed condition is prostate cancer, and M.D. Anderson Cancer Center is the sponsor. The study began on 2014-01-08, reached primary completion on 2021-04-06, and has a status of completed.

The design is recorded as single group, with allocation listed as NA and masking listed as none. The only described group received cabozantinib plus androgen ablation therapy. The record lists 62 participants enrolled. There is no separate group receiving a different treatment or no study treatment, so this design does not provide a like-for-like control comparison.

The treatment description states that cabozantinib began at 60 mg by mouth every day and that study cycles lasted 3 weeks. Patients were to remain on treatment as long as they were benefitting. Androgen ablation could be given using a luteinizing hormone-releasing hormone super-agonist, but the registry description ends before the permitted formulations are fully specified. Additional operational details, including a complete account of treatment duration and dose modification, are not reported in the registry record.

The record lists two outcome measures, but gives no analyses. It identifies progression-free survival as the primary outcome and defines progression using radiographic progression, additional anti-cancer therapy, or clinical progression resulting in treatment discontinuation. The registry record does not report the primary endpoint estimate, the number of participants included in its analysis, or a statistical analysis plan. The sample-size justification and any planned interim analyses are also not reported in the registry record.

These design features shape the scope of interpretation. A single-group study may describe the observed experience of participants receiving the combination, but the absence of a control group limits attribution of outcomes to either component of treatment. Its observational label, lack of masking, and unavailable analysis details should be kept in view alongside the reported enrollment and study status.

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

Reasons for not completing this period:

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.

6. Primary Endpoint

The registry lists the primary outcome as Progression Free Survival, measured over 31.2 months.

The primary endpoint is progression-free survival, a time-to-event measure. It concerns the time from an analysis starting point until progression, as defined in the study. The registry record defines progression as any of radiographic progression, receipt of additional anti-cancer therapy, or clinical progression that results in stopping treatment. Radiographic progression is assessed using RECIST 1.1 for visceral disease and PCWG2 for bone scans. These components make the endpoint broader than a radiographic finding alone: a treatment change or clinical deterioration leading to treatment discontinuation can also count as an event.

Time-to-event endpoints are useful when the timing of an event matters and participants may have different lengths of observation. A median can describe the time by which the estimated event-free proportion has reached the midpoint, while a confidence interval conveys uncertainty around that estimate. These are general statistical interpretations, not evidence that a particular analysis procedure was used in this study.

The registry record lists the endpoint timeframe as 31.2 months. That is a timeframe entry, not a reported median result. Neither the median progression-free survival estimate nor its 95% confidence interval is reported in the registry record. The event definition is available, but the numerical outcome and its precision cannot be evaluated from the record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Progression-free survival is a time-to-event endpoint. In general, time-to-event methods use both the timing of events and the duration of observation. A participant who experiences the defined event contributes an event time. A participant whose event has not been observed by the end of available follow-up may be censored, meaning that the event time is not known beyond that observation period. Censoring is not the same as confirming that an event will never occur. These are general descriptions; the registry record does not report how censoring was handled in this study.

What does a median time-to-event estimate describe?

In general, the median time-to-event estimate is the point at which the estimated proportion remaining event-free reaches the midpoint. It summarizes a feature of the event-time distribution rather than the experience of every participant. It does not say that all participants had an event at that time, nor does it describe the range of individual times. The registry record names the median as the summary measure for progression-free survival, but does not report its value.

Time-to-event estimates are often calculated with methods that can account for participants having different observation lengths. The choice and implementation of a method depend on the analysis plan and data. The registry record does not report the estimator used, the event counts, the censoring information, or the analysis population. It would therefore be inappropriate to state that a particular estimator or censoring procedure was used.

How should a confidence interval be read?

In general, a confidence interval expresses statistical uncertainty around an estimate under the assumptions of the method used. A narrower interval indicates greater precision than a wider interval, while an interval does not remove potential bias from study design, measurement, or missing data. A 95% confidence interval is listed as the dispersion measure for the primary endpoint, but its limits are not reported in the registry record. The precision of the median therefore cannot be assessed.

A confidence interval is not a range containing every participant’s outcome, and it does not establish that the result is free of bias. Its interpretation depends on the analysis method and the quality of the underlying data. In this study, the absence of the interval limits any assessment of uncertainty, and the single-group design separately limits causal and comparative interpretation.

What does the single-group design permit?

In general, a single-group study can describe outcomes observed among participants receiving a treatment combination. Without a concurrent comparator, however, it cannot directly estimate a contrast between that combination and an alternative. Changes in outcomes may reflect the treatment, the natural course of disease, other care, participant characteristics, or combinations of these factors. The design recorded for this study is single group, and allocation is listed as NA. A controlled treatment effect is not reported.

The combination includes cabozantinib and androgen ablation therapy. Since both are given in the described group, the study design cannot distinguish their separate contributions to an outcome. The registry record also does not report adjustment methods that might address differences in participant characteristics or other potential influences.

What are the planning assumptions?

The record describes sample-size planning illustrations using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It says that the effect to detect is a stated fraction of the observed effect. For time-to-event illustrations, the planning quantity is the total number of events; for other outcomes, it is participants per arm. These are planning assumptions, not features of the enrolled single-group study. In particular, the hypothetical equal allocation between two arms does not change the recorded design, which has one group.

Planning calculations explore what sample size might be needed under specified assumptions. They do not describe the number of participants actually enrolled, and they are not observed power. The registry record does not report the trial’s own sample-size justification or its original design assumptions. The numerical planning outputs and the effect values underlying them are not stated in the registry record; they should not be mistaken for observed trial results.

What can be said about analysis methods?

The record lists no analyses and does not provide a statistical analysis plan. It does not report a hazard ratio or another sponsor-reported comparative estimate. General descriptions of time-to-event methods cannot fill that gap, and a hazard ratio should not be inferred from a median endpoint or from the study description. The record’s endpoint label, summary measure, and timeframe do not disclose how the data were analyzed.

Over-dispersion is a general concern for count outcomes when variability is greater than a model assumes; it can make standard errors and uncertainty estimates unreliable if not addressed. The registry record does not indicate that a count model was used for the primary endpoint, and it does not report an over-dispersion assessment. The primary outcome is time-to-event, so count-model considerations should not be treated as the reported analysis method for this endpoint.

The same distinction applies to adjustment, subgroup analysis, and sensitivity analysis. Such methods can be useful in appropriate settings, but the registry record does not report their use in this study. With no analysis details or endpoint estimate, the statistical interpretation must remain focused on the recorded design and the information that is explicitly available.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists two outcome measures, but does not describe how multiple outcomes were handled statistically. No multiplicity adjustment, hierarchy of secondary endpoints, or prespecified testing strategy is reported in the registry record. Without that information, the role of any additional outcome in formal hypothesis testing cannot be assessed. The primary endpoint is identified as progression-free survival, but no analysis result is listed.

Missing-data methods are also not reported in the registry record. For a time-to-event outcome, incomplete observation may lead to censoring, but the record does not describe the censoring rules, the amount of follow-up available for each participant, or any sensitivity analyses. It also does not state whether endpoint information was missing for any participants. The absence of a reported method should not be read as evidence that there were no missing data.

The analysis population for progression-free survival is not reported in the registry record. Although 62 participants are listed as enrolled, the record does not state how many were included in the endpoint analysis or whether all enrolled participants were analyzed according to a prespecified principle. It also does not describe exclusions, protocol deviations, or handling of participants who stopped treatment.

These gaps matter because endpoint estimates depend on which participants and events are included and how incomplete observation is treated. The record lists no analyses, so neither the analysis population nor the statistical handling of missing information can be verified from it. No claim about multiplicity control or missing-data robustness is supported by the registry record.

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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: diarrhea (1.6%), dyspnea (1.6%), proteinuria (1.6%).

The registry record lists one treatment group, Cabozantinib + Androgen Ablation Therapy, with 62 participants at risk for serious adverse events and 62 at risk for other adverse events. It reports 3 participants affected by serious adverse events and 62 affected by other adverse events. These are counts of participants recorded in the respective categories; the registry record does not provide event-level detail sufficient to determine whether participants had more than one event.

The leading serious adverse event terms listed are Diarrhea, Dyspnea, and Proteinuria, each reported as 1.6%. These percentages are reproduced as reported. The record does not provide additional detail on timing, duration, outcome, or treatment attribution for these terms. The available information should not be used to infer that the listed events were caused by cabozantinib or androgen ablation.

The record also lists 24 deaths. It does not report causes of death or whether deaths were considered related to study treatment. A death count alone cannot establish treatment causality, and the registry information does not describe the follow-up or classification underlying that count. No comparison group is available to contextualize these safety figures against another treatment strategy.

Thus the safety entries describe recorded participant counts and selected serious-event terms, not a complete causal assessment of risk. The record does not report the full event details or attribution needed for broader conclusions.

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

The registry record identifies a completed study of cabozantinib combined with androgen ablation therapy in patients with androgen-dependent metastatic prostate cancer. It reports a single-group design, 62 participants enrolled, and progression-free survival as the primary endpoint. It also supplies a definition of progression and selected adverse event counts. These details clarify what the study was intended to examine and what kinds of events were recorded.

The primary endpoint result itself is not reported in the registry record. The median progression-free survival estimate and its 95% confidence interval are absent, while 31.2 months is listed as the endpoint timeframe. Accordingly, the record cannot show the observed median or how precisely it was estimated. It does not support a numerical account of progression-free survival among participants.

The single-group design also means that the registry record does not provide a controlled comparison. Even if outcomes were reported for the group, they could not be interpreted as a direct estimate of the difference between the treatment combination and an alternative. Because the two therapies were administered together, their separate contributions would not be identifiable from this design alone.

The safety entries should be read as registry-reported counts and terms, not as proof of treatment causation. The record lists 3 participants affected by serious adverse events, 62 affected by other adverse events, and 24 deaths, but does not report causes of death or event attribution. The serious terms listed each carry a reported value of 1.6%.

In general, clinical trial records can inform understanding of a study’s design and reported observations, while interpretation depends on results, analysis methods, and context. For this study, the endpoint definition and selected safety information are available, but the primary estimate, its precision, and the analysis details are not reported in the registry record. No conclusion that the treatment works or does not work follows from the information recorded.

13. Why This Trial Matters Statistically

This study is statistically notable because the record pairs a defined time-to-event primary endpoint with a single-group design and no reported endpoint estimate. The endpoint definition is explicit about several ways progression can be counted: radiographic progression, additional anti-cancer therapy, or clinical progression resulting in treatment discontinuation. That definition is important for understanding what the outcome represents, but the lack of component-level counts means the contribution of each criterion cannot be examined.

The single-group structure also highlights the difference between describing an outcome and estimating a comparative effect. A treatment group can be followed and characterized, but the absence of a concurrent control means the results cannot directly quantify a contrast with another strategy. The combination treatment further limits attribution to either cabozantinib or androgen ablation considered separately.

The record’s reporting gaps illustrate why an endpoint label is not a result. A median and its confidence interval would convey the estimated event-time summary and its precision; neither is reported. The timeframe entry of 31.2 months does not replace those statistics. Without event counts, follow-up details, analysis methods, or an analysis population, readers cannot assess the endpoint calculation or the degree of uncertainty.

The record also demonstrates the importance of separating planning exercises from trial conduct. Planning illustrations use stated assumptions, including a two-sided significance level of 0.05 and equal allocation between two hypothetical arms, whereas the actual recorded study has a single group. Such illustrations are not evidence of observed power, actual allocation, or a treatment effect.

Finally, safety counts require careful interpretation. Counts of affected participants and listed serious adverse event terms do not by themselves establish causation, especially without a control group, event-level detail, or reported attribution. Statistical reading therefore depends not only on the numbers that appear, but also on clear distinctions between design, observed data, uncertainty, and causal claims.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The principal limitation for interpreting efficacy is that the registry record does not report the median progression-free survival estimate or its 95% confidence interval. The timeframe is listed as 31.2 months, but this does not provide the endpoint result. The record lists no analyses, so the event count, censoring information, analysis population, and statistical estimator are also not reported in the registry record.

The single-group design has no concurrent control comparison. It cannot directly establish how outcomes differ from those under another treatment, and it cannot separate the contribution of cabozantinib from that of androgen ablation. Allocation is listed as NA and masking as none. The registry record does not report methods for addressing potential confounding or bias.

The endpoint combines radiographic progression, receipt of additional anti-cancer therapy, and clinical progression leading to treatment discontinuation. The record does not report the frequency of each component, assessment schedules, or details of endpoint adjudication. Those omissions limit assessment of how the composite endpoint was applied.

The treatment description is incomplete for androgen ablation: it mentions a luteinizing hormone-releasing hormone super-agonist but does not fully specify the permitted formulations. The record also does not report the sample-size justification, interim analyses, or a statistical analysis plan. It does not state the analysis population, missing-data approach, or multiplicity strategy.

Safety interpretation is limited by the absence of event-level descriptions, timing, causes of death, and treatment attribution. The registry record lists selected counts and serious terms but provides no comparator group for context. These limitations do not imply that unreported procedures or results were absent; they mean that they are not reported in the registry record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Cabozantinib and Androgen Ablation in Patients With Androgen-Dependent Metastatic Prostate Cancer — NCT01630590.
• Registry record last updated 2022-03-25; status last verified 2022-03.
• Results first posted 2022-03-25.
• 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

NCT01630590 is a completed Phase 2 study sponsored by M.D. Anderson Cancer Center. It is titled as an observational study of XL-184 cabozantinib and androgen ablation in patients with androgen-dependent metastatic prostate cancer. The registry record lists a single group, no masking, allocation as NA, and 62 participants enrolled. The study began on 2014-01-08 and reached primary completion on 2021-04-06.

Participants in the described group received cabozantinib with androgen ablation therapy. Cabozantinib was listed at a starting dose of 60 mg by mouth every day, with study cycles of 3 weeks and treatment continuing while participants were benefitting. Progression-free survival was the primary endpoint, with progression defined using radiographic, treatment-based, or clinical criteria. Its timeframe is listed as 31.2 months, but the median result and 95% confidence interval are not reported in the registry record.

The registry record lists 3 participants affected by serious adverse events, 62 affected by other adverse events, and 24 deaths. Diarrhea, Dyspnea, and Proteinuria are each listed at 1.6% among the leading serious terms. No analyses are listed, and analysis methods, event attribution, and the primary endpoint result are not reported.