A Study of IMC-A12 or Ramucirumab Plus Mitoxantrone and Prednisone in Prostate Cancer: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study of IMC-A12 or Ramucirumab Plus Mitoxantrone and Prednisone in Prostate Cancer (NCT00683475), a randomized phase 2 study. The primary outcome is Composite Progression-free Survival (cPFS).

2. Clinical Question

This was a phase 2 randomized study in a specific clinical setting: metastatic disease after progression on docetaxel-based chemotherapy. It compares two combinations that share mitoxantrone and prednisone but differ in the additional biological agent. The clinical question is therefore about the contrast between those complete regimens, not the isolated effect of either biological agent.

The outcome definition is broader than radiographic tumor growth alone. It includes radiographic progression, bone-scan evidence, skeletal events, symptomatic progression for participants without measurable disease, other prostate-cancer-related clinical events requiring major interventions, and death from any cause. That composite aims to capture clinically relevant worsening across different forms of disease progression. It also means the endpoint can be reached through different types of events, which should be kept in mind when interpreting the median.

3. Trial Design

The registry describes a randomized, unmasked, parallel-group phase 2 trial. Participants were assigned to IMC-A12 plus mitoxantrone and prednisone or to IMC-1121B (ramucirumab) plus mitoxantrone and prednisone. The record gives an enrollment of 138. It reports 66 participants per arm for the primary outcome population, defined as modified intent to treat: all participants who received any quantity of study drug. The record does not provide further arm-level descriptions of treatment delivery.

The trial was conducted in metastatic androgen-independent prostate cancer after progression on docetaxel-based chemotherapy. The registry lists a start of 2008-08, primary completion of 2011-09, and status of completed. These dates describe the registered study timeline; they do not establish when individual participants were followed or when each outcome was assessed. The primary outcome timeframe is randomization to composite progressive disease, up to 23.4 months.

The primary endpoint was median composite progression-free survival. The registry also lists secondary outcomes including treatment-emergent adverse events, time to radiographic progression, prostate specific antigen response, composite progression-free survival at specified follow-up times, overall survival, and objective response rate. The record identifies 17 outcome measures and 16 posted secondary outcomes, but detailed results for every listed outcome are not available in the record.

The registry does not report the randomization method, allocation concealment, blinding of outcome assessment, protocol deviations, or a statistical analysis plan. It also does not report why enrollment was set at its recorded level or whether interim analyses were planned. These design details should not be inferred from the phase, the group sizes, or the observed outcomes.

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:

Analysis population for the primary outcome, as defined in the registry: Modified intent to treat population (mITT): All participants who received any quantity of study drug. 11 participants were censored in the IMC-A12 + Mitoxantrone + Prednisone arm. 15 participants were censored in the IMC-1121B (ramucirumab) + Mitoxantrone + Prednisone arm.

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.

Population: Modified intent to treat population (mITT): All participants who received any quantity of study drug.

6. Primary Endpoint

The registry lists the primary outcome as Composite Progression-free Survival (cPFS), measured over Randomization to composite progressive disease, up to 23.4 months.

Composite progression-free survival measures time from randomization until the earliest event in a prespecified composite. Events include tumor progression by RECIST, qualifying new bone-scan lesions after completion of the first 3 cycles, specified new skeletal events, symptomatic progression for participants without measurable disease, other prostate-cancer-related clinical events requiring major interventions, or death from any cause. The measure reported for the primary outcome is the median time to an event.

A composite endpoint can reflect several ways that disease may worsen, rather than relying on a single imaging measure. That can make the endpoint more inclusive of clinically important progression, particularly when participants have different patterns of disease. At the same time, the components are not interchangeable: a radiographic change, a skeletal event, and death differ in nature and importance. The registry record does not report the component-specific results, so the median cannot show which event types chiefly contributed to the endpoint.

Participants who remained ongoing without progression, discontinued treatment for reasons other than progression, or began new anticancer treatment before progression were censored according to the stated rules. In general, censoring means that the event time is not observed after a specified point, and the analysis uses the available follow-up up to that point. The registry reports 11 censored participants in the IMC-A12 arm and 15 in the ramucirumab arm. The median therefore summarizes the time-to-event experience under the study’s event and censoring definitions; it is not the duration of benefit for every participant.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is a time-to-event measure. Each participant contributes follow-up from randomization until a qualifying composite progression event, death, or censoring. The endpoint combines several types of disease progression with death from any cause. In general, time-to-event methods are useful when participants have different lengths of follow-up or when some have no observed event by the end of their available observation.

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

The median is the point in the estimated event-time distribution at which half of the group is estimated to have experienced the event. It is not an average, and it does not mean that every participant had an event at that time. The reported medians are 4.1 months for IMC-A12 plus mitoxantrone and prednisone, and 6.7 months for ramucirumab plus mitoxantrone and prednisone. Their 95% confidence intervals are 2.2 to 5.6 months and 4.5 to 8.3 months, respectively. These intervals describe uncertainty around each group’s median; the registry record does not report a confidence interval for a direct contrast between the medians.

Why is censoring important?

Censoring occurs when a participant’s event time is not observed beyond a particular point. Under the registry definition, participants who were ongoing without progression or who discontinued treatment for reasons other than progression were censored at their last assessment. Participants who started new anticancer treatment before progression were censored at their last assessment before that therapy began. In general, valid time-to-event interpretation depends on how censoring is handled and on assumptions about the relationship between censoring and future event risk. The record states the censoring rules and gives the arm-specific censored counts, but it does not report diagnostic checks or further details about those assumptions.

The reported censoring counts are 11 in the IMC-A12 combination arm and 15 in the ramucirumab combination arm. They indicate that event times were not observed for some participants through the endpoint definition. The registry does not provide further participant-level follow-up information or a breakdown of censoring reasons by arm. That limits assessment of whether follow-up and censoring patterns were comparable.

What do the binary secondary comparisons show?

For PSA response and composite progression-free survival at specified follow-up times, the record reports percentages with 95% confidence intervals. A risk difference expresses the difference between the two groups’ event proportions on an absolute scale. The posted comparisons give the risk difference and an unadjusted p-value. A p-value evaluates compatibility of the observed data with a no-difference hypothesis under the test assumptions; it is not the probability that the hypothesis is true, and it does not measure clinical importance.

Confidence intervals add information about precision. For example, an interval that includes zero for a risk difference is compatible with no difference under the interval method, while an interval entirely on one side of zero is less compatible with a null difference at the corresponding confidence level. Such interpretations remain conditional on the analysis method and do not account for multiple secondary comparisons unless an adjustment is specified. The registry does not report adjusted secondary analyses.

Why can over-dispersion matter?

In general, over-dispersion arises when outcome variability exceeds what a statistical model assumes. If it is ignored, standard errors can be too small and confidence intervals or tests can appear more certain than warranted. The posted outcomes include binary response proportions and a time-to-event primary endpoint; the registry record does not describe an over-dispersion model or report model-based adjustments. No such method should be presumed to have been used.

What do planning illustrations mean?

Planning illustrations based on an observed effect are not observed power and do not show that the trial was adequately or inadequately powered. They depend on assumptions, including a two-sided significance level of 0.05, equal allocation, a normal approximation for the binary outcomes, and an effect set to a stated fraction of the observed effect. The record labels the illustrations as planning calculations rather than the trial’s own design justification. It does not report the trial’s original sample-size assumptions or justification.

For binary outcomes, the illustrations express participants per arm for 80% power and participants per arm for 90% power under the stated assumptions. The illustrations are sensitive to the observed effect used as their starting point; smaller assumed effects require larger planning group sizes. They should not be read as a retrospective claim about power in the completed trial. The registry record does not provide a corresponding reported sponsor analysis for the primary time-to-event comparison in the available results.

What is not available for the primary comparison?

The registry record reports arm-specific median times and confidence intervals but no primary hazard ratio or formal test result. A hazard ratio, when reported, compares event rates over follow-up under a time-to-event model; it is not the same quantity as a ratio of medians. Since the record does not report a primary hazard ratio or other direct contrast, none should be inferred from the arm medians. The record also does not describe model covariates, stratification factors, or sensitivity analyses for the primary outcome.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists a broad set of outcomes, including the primary composite progression-free survival measure and secondary measures of adverse events, radiographic progression, PSA response, fixed-time composite progression-free survival, overall survival, and objective response. It identifies 17 outcome measures and 16 posted secondary outcomes. Testing multiple outcomes increases the chance that at least one comparison may appear statistically notable by chance. In general, multiplicity procedures can control that risk, or an analysis plan can designate a hierarchy of outcomes. Neither a multiplicity adjustment nor such a hierarchy is reported in the registry record.

The posted secondary comparisons are unadjusted. Their p-values and confidence intervals should be interpreted as separate exploratory summaries, not as a family-wise confirmatory evaluation. The registry record does not report which secondary comparisons were prespecified, how missing secondary observations were handled, or whether any sensitivity analyses were performed. Results for several listed outcomes are not reported in the registry record, limiting assessment of the full set of planned or collected measures.

The primary population is defined as modified intent to treat, including participants who received any quantity of study drug. The primary outcome arm counts are 66 and 66. The registry gives the overall enrollment as 138 but does not provide a participant disposition accounting that explains how enrollment relates to the primary outcome population. The PSA response denominators are 54 and 56; the record does not explain the difference between those denominators and the primary outcome group counts.

Censoring is described for the primary outcome, with participants censored at their last assessment in specified circumstances. The record reports the arm-specific numbers censored but not detailed reasons or further analysis of censoring. It does not report the missing-data approach for the secondary outcomes. The record also does not report an analysis plan, sample-size justification, interim-analysis plan, or detailed procedures for handling protocol deviations. These omissions limit evaluation of prespecification and robustness.

11. Safety Results

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

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: disease progression (12.1%), medication error (6.1%), dehydration (6.1%), back pain (6.1%), diarrhoea (4.5%).

The registry reports serious adverse events in 40 of 66 participants in the IMC-A12 combination arm and 36 of 66 participants in the ramucirumab combination arm. It reports other adverse events in 65 of 66 and 66 of 66 participants, respectively. These are participant counts for the recorded categories; they do not indicate how many events each participant experienced, their duration, severity beyond the serious classification, or causal relationship to study treatment.

The registry lists serious adverse-event terms with percentages, including disease progression at 12.1%, medication error at 6.1%, dehydration at 6.1%, back pain at 6.1%, diarrhoea at 4.5%, and expired drug administered at 4.5%. The record does not identify an arm for these terms in the listed summary. These percentages should therefore not be attributed to a particular treatment group. The reported deaths count is not reported in the registry record.

Safety comparisons require context about event definitions, exposure duration, collection procedures, and attribution. Those details are not reported in the registry record. The counts alone cannot establish whether an event was caused by treatment or whether the regimens differ in safety. They describe reported participants with events in the registry categories, not a complete clinical assessment.

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

The posted primary results describe median composite progression-free survival of 4.1 months in the IMC-A12 combination arm and 6.7 months in the ramucirumab combination arm, each with a 95% confidence interval. The estimates provide an arm-level summary under the registered endpoint definition and censoring rules. Their ordering is a descriptive observation; the registry record does not report a formal primary between-arm test or direct comparative estimate.

This result does not establish that one regimen is effective or ineffective, nor does it establish that the observed difference is caused by the added biological agent. Participants were assigned to treatment combinations that also included mitoxantrone and prednisone, and the registry record does not report a formal comparison isolating the contribution of one component. The result also does not indicate how long any particular participant remained progression-free.

The primary composite includes several kinds of progression and death. Without component-specific results, the median does not indicate which event type drove the observed times. It also does not capture every dimension of disease experience, such as quality of life, unless separately measured and reported. The record lists other outcomes, but detailed results are not reported for all of them.

The confidence intervals indicate uncertainty around the individual medians, while the absence of a direct primary comparison leaves uncertainty about the difference between arms. Unadjusted secondary findings add context but should not be treated as definitive confirmation, particularly because multiple outcomes are listed and no multiplicity plan is reported. The safety counts likewise describe reported events but cannot establish causation or comparative safety from the available information.

Interpretation should remain specific to the population and design in the registry: participants with metastatic androgen-independent prostate cancer after progression on docetaxel-based chemotherapy, in a randomized, unmasked phase 2 study. The registry findings do not, by themselves, support conclusions about other populations, treatment settings, or regimens.

13. Why This Trial Matters Statistically

This trial is statistically informative because the primary outcome is a composite time-to-event measure, while the posted secondary outcomes include fixed-time proportions and response measures. These outcomes summarize different features of disease progression. Reading them together requires attention to their distinct estimands rather than treating them as repeated measurements of the same quantity.

The primary results illustrate why arm-specific medians alone are not enough for a comparative conclusion. The registry gives a median and confidence interval for each group, but does not report a direct primary contrast, such as a hazard ratio or formal test. A descriptive ordering can be reported accurately, yet the precision of the between-group effect remains unresolved in the posted primary analysis.

The record also highlights the role of censoring. The primary outcome uses defined rules for participants without observed progression and for those beginning new anticancer treatment. Since time-to-event estimates depend on observed follow-up and censoring, reporting the rules and the numbers censored helps readers understand what the medians represent. More detailed information on censoring reasons and follow-up would be needed for a fuller assessment.

Finally, the secondary outcomes demonstrate the interpretive challenge of multiple unadjusted comparisons. Some estimates point in the same direction as the primary medians, but the record does not report a multiplicity strategy or a hierarchy that would establish which comparisons were confirmatory. The trial therefore offers useful descriptive estimates while leaving important questions about comparative inference and the complete outcome profile unanswered in the registry record.

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 registry record does not report a formal between-arm analysis for the primary composite progression-free survival outcome. It provides arm-specific medians and confidence intervals, but no direct comparative estimate, primary p-value, or hazard ratio. This limits the strength of statistical interpretation beyond describing the observed group estimates.

The primary endpoint combines different types of progression and death. Component-specific event counts or analyses are not reported, so it is not possible to determine which elements contributed most to the results. Censoring rules and arm-specific counts are stated, but detailed censoring reasons, follow-up distributions, and sensitivity analyses are not reported. Those omissions limit assessment of how censoring may affect the estimates.

There is no participant disposition account explaining the relation between the registered enrollment of 138 and the 66 participants per arm in the primary outcome population. PSA response denominators differ from the primary outcome group counts, and the reasons are not reported. The registry also does not report the missing-data methods for secondary outcomes.

The record does not report the randomization method, allocation concealment, outcome-assessment blinding, statistical analysis plan, sample-size justification, or interim-analysis plan. It lists multiple secondary outcomes, but no multiplicity approach or hierarchy is reported. Several listed outcomes do not have detailed results in the record. These gaps limit assessment of prespecification, the risk of selective reporting, and the robustness of secondary findings.

The study was unmasked and phase 2, and its population was specific to metastatic androgen-independent prostate cancer after progression on docetaxel-based chemotherapy. The registry results should not be generalized beyond that setting without additional evidence. Safety summaries also lack arm attribution for the listed serious-event terms and do not report a death count.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: A Study of IMC-A12 or Ramucirumab Plus Mitoxantrone and Prednisone in Prostate Cancer — NCT00683475.
• Registry record last updated 2014-10-16; status last verified 2014-10.
• Results first posted 2014-06-18.
• 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

NCT00683475 is a completed randomized, unmasked, parallel-group phase 2 study in metastatic androgen-independent prostate cancer after progression on docetaxel-based chemotherapy. It compared IMC-A12 plus mitoxantrone and prednisone with IMC-1121B (ramucirumab) plus mitoxantrone and prednisone. The registry reports enrollment of 138, a start of 2008-08, and primary completion of 2011-09.

The primary outcome was median composite progression-free survival from randomization to a qualifying progression event or death, with censoring under specified rules. The reported medians were 4.1 months for the IMC-A12 combination and 6.7 months for the ramucirumab combination. A formal primary comparison is not reported in the registry record.

Secondary outcomes include PSA response, fixed-time composite progression-free survival, overall survival, objective response, radiographic progression, and adverse events. Results are available for selected secondary outcomes, but not for every listed measure. The record does not report a multiplicity plan, sample-size justification, or detailed statistical analysis plan.