Treating Patients With Metastatic Prostate Cancer Not Responding to Hormone and Chemotherapy: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Treating Patients With Metastatic Prostate Cancer Not Responding to Hormone and Chemotherapy (NCT00331344), a registered phase 1, phase 2 study. The primary outcome is Dose Limiting Toxicities for Each Dose Level of Ixabepilone, Mitoxantrone Hydrochloride, and Prednisone in Patients With Hormone-refractory Metastatic Prostate Cancer That Progressed During or After Taxane-based Chemotherapy (Phase I)..

2. Clinical Question

The trial addressed treatment in patients with metastatic prostate cancer that had not responded to hormone therapy and chemotherapy. Its Phase I population was more specifically described as having hormone-refractory metastatic prostate cancer that progressed during or after taxane-based chemotherapy. The central early-phase question was whether dose-limiting toxicities occurred at each dose level of the three-drug regimen, and how those observations would guide dose escalation and selection of a maximum tolerated dose. The record also lists time to progression as a Phase II secondary outcome. It does not report a Phase II result for that outcome.

This is principally a dose-finding and safety question, not a randomized test of the regimen against another treatment. The primary endpoint concerns the first course, defined as the first 21 days. The Phase II time-to-progression outcome addresses a different question, but its definition, estimates, and uncertainty are not reported in the registry record.

3. Trial Design

The record describes a Phase I/II, sequential study with no masking. The sponsor was the National Cancer Institute (NCI). The listed start date is 2006-04, primary completion is 2010-11, and status is completed. The registry lists enrollment of 100; it does not state in this information whether that figure is an actual or planned enrollment.

The Phase I component was a dose-escalation safety study. The endpoint description says cohorts of 3 patients would be enrolled at each dose level. If 1 dose-limiting toxicity was observed, the cohort would expand to 6 patients. If a second dose-limiting toxicity was observed, the previous dose level would be considered the maximum tolerated dose. The description includes a separate rule for neuropathy attributed specifically to ixabepilone: if all observed dose-limiting toxicities were neuropathy, the previous ixabepilone dose level would be considered that drug's maximum tolerated dose while mitoxantrone escalation continued, up to 12 mg/m^2.

The treatment arm description specifies mitoxantrone hydrochloride intravenously over 30 minutes and ixabepilone intravenously over 3 hours on day 1, with oral prednisone twice daily on days 1-21. Courses repeat every 21 days for at least 3 courses in the absence of disease progression or unacceptable toxicity. The record identifies adenocarcinoma, recurrent prostate cancer, and stage IV prostate cancer among the conditions.

Time to progression is listed as a Phase II secondary outcome. The record does not explain how the Phase I and Phase II components were operationally sequenced, give results by dose level, or report a randomized control group. Allocation details are not stated, and the listed treatment is not described as a comparison between like-for-like arms.

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.

Only the first 6 of 9 groups are shown.

Phase I

Reasons for not completing this period:

Phase II

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 Dose Limiting Toxicities for Each Dose Level of Ixabepilone, Mitoxantrone Hydrochloride, and Prednisone in Patients With Hormone-refractory Metastatic Prostate Cancer That Progressed During or After Taxane-based Chemotherapy (Phase I)., measured over Course 1 (first 21 days).

The primary endpoint counts participants with dose-limiting toxicities at each dose level during Course 1, the first 21 days. In a dose-finding study, this endpoint is used to identify dose levels at which treatment-related toxicity becomes a constraint on further escalation. The registry description outlines rules for expanding cohorts and choosing a maximum tolerated dose based on observed dose-limiting toxicities. It also describes how neuropathy could lead to a separate decision for ixabepilone while mitoxantrone escalation continued.

The endpoint is a participant count, not a measure of the total number of toxicity episodes. The registry says toxicities would be tabulated by grade for each dose cohort and overall for participants accrued to Phase I. Those statements describe the planned assessment; they do not establish what was observed. The number of participants with dose-limiting toxicity at each level, the toxicity grades, and the resulting maximum tolerated dose are not reported in the registry record.

Restricting the primary assessment to the first course provides a defined early period for dose-limiting toxicity evaluation. It does not capture the full range of later toxicity or establish the frequency of adverse effects over all treatment courses. The registry record does not report the operational criteria used to classify a toxicity as dose-limiting, beyond the dose-escalation rules in the endpoint description.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The methods described in the registry record are most informative as a planned dose-escalation framework. They should not be mistaken for a complete statistical analysis plan or for evidence that a particular dose was selected. Actual dose-level outcomes and the final dose decision are not reported in the registry record.

What does the dose-escalation rule do?

The Phase I description assigns cohorts to dose levels and uses observed dose-limiting toxicities to decide whether to expand a cohort or consider a lower dose as the maximum tolerated dose. This is a sequential design: information from an earlier cohort informs what happens next. The described rules are operational thresholds for dose decisions, rather than a conventional randomized comparison of treatment groups. A cohort expansion can gather more safety observations at a dose level where an initial toxicity was seen. The record describes the rules, but does not report how many dose levels were tested, how many participants entered each cohort, or which rule was ultimately triggered.

The special neuropathy rule separates the dose decision for ixabepilone from escalation of mitoxantrone. This matters because the regimen contains multiple drugs and toxicities may constrain different components. The description specifies a mitoxantrone ceiling of 12 mg/m^2 in that circumstance. It does not report the observed neuropathy pattern or whether this ceiling was reached.

Why is the primary outcome a participant count?

The primary outcome is the number of participants with a dose-limiting toxicity, assessed in the first course. A count answers how many participants experienced the specified event within the defined assessment group. When a denominator is available, a proportion can also describe the share of participants affected, but the primary endpoint results by dose level and their denominators are not reported. A count should not be confused with the total number of toxicity episodes: one participant might experience more than one event, and a participant count does not convey that event burden.

The registry says toxicities would be tabulated by grade for each dose cohort and overall in Phase I. Grading can distinguish levels of severity, while a cohort summary can make differences across dose levels visible. Neither a grade-specific result nor the grading criteria themselves are reported in the registry record. The dose-limiting toxicity classification criteria are also not fully described, so the registry account does not allow an independent reconstruction of endpoint classification.

How does time to progression differ?

Time to progression is listed as a secondary Phase II outcome. Unlike a simple count measured within a fixed course, a time-to-event outcome concerns the time until a defined event. General methods for these outcomes can account for participants whose event has not been observed by the end of their available follow-up, but the registry record does not state the event definition, censoring rules, follow-up schedule, estimator, or model used. It does not report a time-to-progression result or its uncertainty. The listed outcome alone is not enough to determine how the analysis was conducted.

What do the planning illustrations mean?

The planning illustrations are described as calculations based on the observed effect, with two-sided significance level 0.05, equal allocation between two arms, and a normal approximation. They describe the effect to detect as a stated fraction of the observed effect. For time-to-event outcomes, the illustration uses a total event count; for other outcomes, it gives participants per arm. These are planning assumptions, not the study's own design justification. The registry record does not report the trial's sample-size justification, and the illustrations are not observed power. A planning calculation estimates requirements under chosen assumptions; it does not measure the probability that a completed trial has produced a reliable conclusion.

Because no like-for-like randomized comparison is reported, the equal-allocation, two-arm assumption in a planning illustration should not be read as a description of the trial's actual design. Nor does a calculation based on an observed effect convert the study into a comparative trial. The registry record does not report the effect value used for that illustration or a corresponding comparative result.

What information would support statistical interpretation?

For the primary endpoint, interpretation would require dose-level participant counts, denominators, and a clear account of which toxicities met the dose-limiting definition. For time to progression, readers would need the outcome definition, follow-up information, event count, analysis method, and an estimate with its uncertainty. A confidence interval is a general way to express the precision of an estimate; a wider interval indicates less precision than a narrower interval, all else equal. No such intervals are reported for these outcomes.

Over-dispersion is a general concern when count data vary more than a chosen statistical model expects. It is not possible to assess whether it applies to an analysis from the registry information because the primary outcome is a participant count, the actual distribution is unreported, and the analysis model is not stated. In general, a model that fails to account for extra variation can produce uncertainty estimates that are too small. The registry record does not report a model choice or diagnostic assessment.

The number of outcome measures listed is 4, and the record lists 1 analysis. The names and details of all measures and the analysis are not available in the registry description. No statistical plan, model specifications, covariate adjustments, interim analysis details, or multiplicity procedure are reported. Those omissions limit the ability to assess how outcomes were selected and analyzed.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Phase I Group I", "Phase Group II", "Phase I Group III", "Phase I Group IV", "Phase I Group V", "Phase I Group VI")
n      <- c(3, 3, 3, 6, 6, 5)
events <- c(0, 0, 0, 1, 2, 2)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Phase I Group I  3  0  0.0  0.0  70.8  0.0  56.1  0.6  60.2
ARM  Phase Group II  3  0  0.0  0.0  70.8  0.0  56.1  0.6  60.2
ARM  Phase I Group III  3  0  0.0  0.0  70.8  0.0  56.1  0.6  60.2
ARM  Phase I Group IV  6  1  16.7  0.4  64.1  3.0  56.4  3.7  57.9
ARM  Phase I Group V  6  2  33.3  4.3  77.7  9.7  70.0  9.9  71.0
ARM  Phase I Group VI  5  2  40.0  5.3  85.3  11.8  76.9  11.8  77.7

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists 4 outcome measures and 1 analysis, but does not report the names and analysis details for all measures. It identifies dose-limiting toxicities as the primary Phase I outcome and time to progression as a Phase II secondary outcome. A planned approach to multiplicity, such as whether or how inference across multiple outcomes or dose levels would be controlled, is not reported in the registry record. No interim analysis plan is reported.

Missing-data methods are not reported. The record does not explain how participants who did not complete the first course, had incomplete toxicity assessment, or lacked time-to-progression follow-up would be handled. It also does not state which participants were included in each analysis population, or how those populations were defined. Those details matter because the number enrolled, the number evaluable for an endpoint, and the number included in a particular analysis may differ.

The registry lists enrollment of 100, while the cumulative adverse event summary lists 88 participants at risk. The record does not explain this difference, and it should not be treated as evidence of a particular number of withdrawals, exclusions, or missing outcomes. Similarly, the 88 participants at risk in the serious and other adverse event summaries do not establish the denominator for the primary dose-limiting toxicity endpoint or the Phase II time-to-progression analysis.

Without reported analysis populations, missing-data procedures, multiplicity handling, and endpoint results, readers cannot determine whether the reported summaries account for all relevant participants or how uncertainty from incomplete observation was handled.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: neutrophil count decreased (4.5%), adrenal insuffiency (3.4%), atrial fibrillation (3.4%), leucocytes (3.4%), cardiac ischemia/infarction (2.3%).

The cumulative Phase I and Phase II adverse event summary lists 88 participants at risk for serious adverse events and 19 participants with a serious adverse event. For other adverse events, it lists 88 at risk and 56 affected. The same cumulative group lists 29 deaths. These are registry counts; they should not be interpreted as dose-level or phase-specific results because the summary combines Phase I and Phase II.

The listed serious adverse event terms and percentages are neutrophil count decreased, 4.5%; adrenal insufficiency, 3.4%; atrial fibrillation, 3.4%; leucocytes, 3.4%; cardiac ischemia/infarction, 2.3%; and renal failure, 2.3%. The record does not specify the denominator or calculation details for each term-specific percentage in this summary. It also does not report whether events were judged related to treatment, how long participants were monitored, or whether one participant could contribute to multiple terms.

Serious adverse event summaries describe events meeting a seriousness category; they do not by themselves establish that treatment caused the events. The combined counts also do not show the frequency at a particular dose or distinguish outcomes among treatment components. The record does not supply a control-group safety comparison, so these figures cannot estimate a difference in risk versus another regimen.

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

The registry record establishes that the trial was designed as a sequential Phase I/II study of ixabepilone, mitoxantrone hydrochloride, and prednisone in metastatic prostate cancer after prior treatment. It describes a Phase I dose-escalation approach focused on dose-limiting toxicities in the first course, along with a Phase II time-to-progression outcome. It also presents cumulative adverse event counts for participants at risk in both phases.

The record does not report the actual primary endpoint results by dose level, the resulting maximum tolerated dose, or the Phase II time-to-progression estimate. It therefore does not permit a quantitative conclusion about these endpoints. The absence of a reported result is not evidence that an event did or did not occur, and it is not evidence for or against a treatment effect.

The cumulative adverse event counts describe the registry's safety summary, but they do not identify the contribution of a particular drug, dose, or study phase. They also do not establish causality. Without a reported like-for-like control comparison, the safety counts cannot show how outcomes compare with another treatment. The record states that allocation was not stated and that the arms are not a like-for-like control comparison.

Statistical precision also cannot be judged for the primary and secondary endpoints because estimates and confidence intervals are not reported. General interpretation of a confidence interval depends on both its location and width: the estimate describes the data under the analysis, while the interval conveys uncertainty. Neither can be assessed for these endpoints from the registry information. The enrollment listing and adverse event denominators do not resolve the missing endpoint results or define the analysis populations.

Any sample-size planning illustrations are hypothetical calculations under stated assumptions, not observed power and not proof that the original study was designed to detect a particular effect. Overall, the record supports describing the trial's aims, planned dose-escalation rules, treatment schedule, and cumulative safety counts. It does not support claims about a comparative treatment effect or an unreported clinical outcome.

14. Why This Trial Matters Statistically

This study illustrates why early-phase dose-finding and later-phase outcome assessment should be interpreted separately. The Phase I endpoint was designed to inform dose escalation by recording dose-limiting toxicities at each level during the first course. That is a different statistical purpose from estimating a comparative treatment effect or analyzing time to progression in Phase II.

The sequential design also makes dose-level context important. Toxicity counts are interpreted in relation to the cohort and dose at which they were observed; a cumulative safety summary across Phase I and Phase II cannot substitute for those dose-specific results. The registry describes cohort-expansion and maximum-tolerated-dose rules, but does not report the observations needed to see how those rules operated.

The record highlights the value of complete outcome reporting. Without dose-level endpoint results, analysis populations, and uncertainty estimates, readers cannot assess the precision of the planned dose-finding outcome. Without a time-to-progression estimate and analysis details, the listed secondary outcome remains an aim rather than an interpretable result. The same distinction applies to planning illustrations: design calculations do not establish what a completed study observed.

Finally, a completed registry entry can still leave key statistical questions unresolved. The enrollment listing, cumulative adverse event denominators, and outcome descriptions provide useful context, but the record does not explain their relationship or report all analysis details. Keeping those limits explicit prevents descriptive safety counts or protocol rules from being mistaken for comparative evidence.

15. Limitations

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

The registry record does not report the primary dose-limiting toxicity counts by dose level, toxicity grades, or the maximum tolerated dose. It also does not report the Phase II time-to-progression estimate. These missing outcome results prevent assessment of the study's stated primary and secondary questions.

The record describes a cumulative safety group combining Phase I and Phase II, but does not provide phase-specific or dose-specific adverse event results. It does not report the relationship between the enrollment listing of 100 and the 88 participants at risk in the adverse event summaries. The record also does not state whether the safety percentages use a particular denominator or explain event attribution and monitoring duration.

Allocation is not stated, and the record indicates that the arms are not a like-for-like control comparison. There is therefore no reported randomized comparison from which to estimate a relative treatment effect. The record does not identify all analysis populations, describe missing-data handling, or provide a complete statistical analysis plan, including multiplicity procedures, interim analyses, endpoint definitions beyond the described dose-escalation rules, or model specifications.

The dose-escalation description gives general rules but not the actual sequence of dose levels or cohort outcomes. The time-to-progression listing lacks its event definition, follow-up information, censoring rules, and analysis method. As a result, readers cannot independently reconstruct either endpoint analysis. These limitations reflect what is not reported in the registry record; they do not establish that the information was absent from trial conduct outside the record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Treating Patients With Metastatic Prostate Cancer Not Responding to Hormone and Chemotherapy — NCT00331344.
• Registry record last updated 2017-10-31; status last verified 2017-10.
• Results first posted 2017-10-31.
• 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.

19. Record Summary

NCT00331344 is a completed Phase I/II, sequential trial sponsored by the National Cancer Institute (NCI), with no masking. It studied ixabepilone, mitoxantrone hydrochloride, and prednisone in patients with metastatic prostate cancer previously treated with hormone therapy and chemotherapy. The record lists enrollment of 100, a start date of 2006-04, and primary completion of 2010-11.

The primary Phase I endpoint was the number of participants with dose-limiting toxicities at each dose level during the first 21 days. The record describes cohort expansion and dose-selection rules, but does not report the endpoint results or maximum tolerated dose. Time to progression is listed as a Phase II secondary outcome, with no result reported.

The cumulative Phase I and Phase II safety summary lists 19 of 88 participants with a serious adverse event, 56 of 88 with another adverse event, and 29 deaths. These combined counts are descriptive and are not a like-for-like comparison. The registry record does not report a randomized control comparison, complete analysis populations, missing-data handling, or a statistical analysis plan.