A Phase II Trial of MLN8237 in Patients With Metastatic Castrate Resistant and Neuroendocrine Prostate Cancer: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Phase II Trial of MLN8237 in Patients With Metastatic Castrate Resistant and Neuroendocrine Prostate Cancer (NCT01799278), a na phase 2 study. The primary outcome is Response Rate, as Assessed by CT/MRI and Bone Scan, of Treatment With MLN8237 for Patients With Neuroendocrine Prostate Cancer.

2. Clinical Question

3. Trial Design

This was a Phase II study of MLN8237 in patients with metastatic castrate resistant and neuroendocrine prostate cancer. The registry records an enrollment of 60 and a completed status. Its design is listed as single group, with allocation recorded as NA and masking as none. In practical terms, the record describes one treatment group rather than randomized treatment arms, and it does not describe blinding.

The treatment description specifies MLN8237 at 50 mg twice daily for 7 days, repeated every 21 days. Therapy was to continue until disease progression, unacceptable toxicity as a result of MLN8237, or withdrawal of patient consent. This describes the intended regimen; the registry record does not report individual treatment exposure, adherence, dose modifications, or how many participants stopped treatment for each reason.

The primary outcome was the response count assessed by CT/MRI and bone scan over one year. The listed secondary outcomes were progression-free survival, overall survival, prostate-specific antigen response rate, and circulating tumor cell response. Although those outcomes are named, their results and the analysis details are not reported in the registry record.

A single-group design can describe outcomes observed among people who received the study treatment, but it does not by itself establish how those outcomes compare with what would have occurred under another treatment or without the study treatment. Without a concurrent comparator, changes over time may also reflect features of the disease, patient selection, other care, or assessment practices. Those considerations limit comparative interpretation even if an outcome estimate is available. Here, the primary response estimate itself is not reported in the registry record.

The registry lists a start date of 2013-02 and a primary completion date of 2016-07. It does not report a detailed protocol, the statistical analysis plan, the response-assessment schedule beyond the one-year timeframe, or whether any interim analyses took place.

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

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 Response Rate, as Assessed by CT/MRI and Bone Scan, of Treatment With MLN8237 for Patients With Neuroendocrine Prostate Cancer, measured over one year.

The primary endpoint is a count of participants with a response to treatment, assessed by CT/MRI and bone scan over one year. A response count is a binary-outcome summary at the participant level: each participant is classified according to whether the recorded response criteria were met. The registry identifies RECIST 1.1 as the basis for defining complete response, partial response, stable disease, and disease progression. It also refers to PCWG2 criteria for bone scan progression in evaluable disease.

These imaging-based categories provide a structured way to describe whether measurable lesions change, remain stable, or progress during assessment. The endpoint is relevant to a Phase II evaluation because it focuses on observable tumor response rather than relying solely on a laboratory measure or a time-to-event outcome. The record also includes PSA normalization in its definition of complete response and specifies a minimum period without new lesions for complete response and stable disease.

The registry wording for partial response is recorded as a 30% 56 or greater reduction in the sum longest unidimensional diameter of measurable lesions. That phrase is unclear as written, and the record does not resolve the ambiguity. It further describes measurable lymph nodes using size criteria and notes that bone scan progression is assessed under PCWG2 criteria.

The endpoint’s reported result would be needed to know how many participants met the response definition. That count and a response rate are not reported in the registry record. The one-year timeframe identifies the stated period for outcome assessment, but details about assessment timing, missing scans, and how unevaluable participants were handled are also not reported.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What kind of endpoint was planned?

The primary endpoint is a participant count for response, which is a binary outcome: a participant either meets the response definition or does not. The record names imaging assessments by CT/MRI and bone scan and references RECIST 1.1 criteria, alongside PCWG2 criteria for bone scan progression in evaluable disease. The registry reports the endpoint timeframe as one year. It does not report a primary response count or rate, so there is no endpoint estimate to interpret statistically.

In general, a binary outcome can be summarized by a count and a proportion. A confidence interval around a proportion describes statistical uncertainty in the estimated response frequency under the analysis assumptions. It does not account automatically for sources of bias, such as missing assessments, selection into the study, or outcome classification problems. No confidence interval for the primary endpoint is reported in the registry record, and the record does not specify how unevaluable or missing assessments were treated.

Why does the single-group design affect inference?

In general, a single-group study estimates outcomes within the participants who receive the intervention. It does not directly estimate a treatment contrast against a concurrent control. A comparison with a historical expectation would require a defined external benchmark and assumptions about whether populations, outcome definitions, follow-up, and care are sufficiently comparable. No such benchmark or comparison is reported in the registry record.

The registry lists allocation as NA and the model as single group. It also lists masking as none. These design features mean that the registered record does not describe random assignment or masking. Randomization can help balance known and unknown prognostic factors between groups, while masking can reduce some forms of assessment or reporting bias. Those are general methodological principles; the record does not describe an allocation procedure, comparator group, or masked outcome review.

What do adverse-event counts represent?

The safety information reports participants at risk and participants affected in separate fields. The serious adverse event entry gives 23 affected among 60 at risk. The other adverse event entry gives 60 affected among 60 at risk. The record also lists 48 deaths. These entries are descriptive counts, not comparative treatment effects. The registry does not report event-level timing, severity grading beyond the serious-event classification, treatment attribution for each event, or the relationship between the deaths and study treatment.

In general, adverse-event counts can be influenced by the length and completeness of follow-up, definitions used to classify events, and whether repeat events in one participant are counted separately. The registry record does not give enough detail to determine how repeat events were handled or to reconstruct exposure-adjusted event rates. The listed percentages for serious adverse event terms should be read as reported in the record, rather than recalculated or interpreted as evidence of a comparative risk.

What can a confidence interval tell a reader?

In general, a confidence interval expresses the precision of an estimated quantity under a statistical model. A narrow interval indicates greater statistical precision than a wide interval, but precision is not the same as validity or clinical importance. The interval does not remove design limitations, and it cannot correct for systematic differences between groups or biased outcome ascertainment. No primary endpoint interval is reported in the registry record.

How should planning calculations be understood?

The registry includes assumptions for a planning illustration based on an observed effect: a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It describes the effect to detect as a stated fraction of the observed effect. Those assumptions describe an illustrative calculation, not the registered single-group design. They should not be read as the trial’s own design justification or as evidence that the trial had a particular probability of detecting an effect. No sample-size justification or statistical power calculation for the actual single-group trial is reported in the registry record.

In general, a sample-size calculation is conditional on assumptions about the target effect, variability or event frequency, error rates, and design. A planning number does not become an observed result after a study is completed. Nor does a retrospective calculation establish observed power. The registry record does not provide the trial’s own sample-size rationale, and no actual planning-calculation output is included in the statistical details.

How do multiple outcomes affect interpretation?

The record names a primary response outcome and secondary outcomes covering progression-free survival, overall survival, PSA response, and circulating tumor cell response. In general, testing or emphasizing multiple outcomes can increase the chance that at least one result appears notable by chance, depending on the analyses and selection process. Statistical approaches can address multiplicity, but the appropriate approach depends on the prespecified analysis strategy. The registry record does not report such a strategy, adjusted significance thresholds, or outcome-specific analysis details. No p-values or outcome estimates are reported for those named outcomes.

What is not specified?

The registry does not report the analysis population for the primary endpoint, the handling of missing data, the statistical model, an analysis plan, or whether interim analyses occurred. In general, these details help readers understand which participants contributed to an estimate and whether conclusions depend on assumptions about missing observations. Without them—and without a reported primary outcome estimate—the response endpoint cannot be quantitatively assessed from the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry record names the response assessment as the primary outcome and lists progression-free survival, overall survival, PSA response rate, and circulating tumor cell response as secondary outcomes. It does not report the statistical plan for these outcomes, whether hypotheses were tested, or whether any adjustment for multiple comparisons was planned. In general, when several outcomes or analyses are examined, an explicit prespecified strategy helps readers distinguish confirmatory questions from exploratory findings. No such strategy is reported in the registry record.

The record does not report how missing data were handled. For the imaging-based primary outcome, relevant details would include what happened when a scan was unavailable, a participant withdrew, or disease status could not be classified. The registry’s endpoint description includes criteria for response and progression but does not describe an analysis rule for incomplete or unevaluable assessments. No imputation method, sensitivity analysis, or missingness summary is reported.

The analysis population is also not reported. The record gives an enrollment of 60, but does not state how many participants were included in the primary endpoint analysis or whether the analysis was based on all enrolled participants, treated participants, or another group. The number enrolled should therefore not be treated as the denominator for an unreported response estimate.

In general, missingness can affect interpretation if participants without outcome data differ systematically from those with observed data. Statistical methods can address some forms of missingness only under assumptions, and those assumptions need to be made explicit. The registry record does not provide information to assess them. It also does not report interim analyses or stopping rules, so those aspects of outcome monitoring cannot be evaluated from the 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: fatigue (10.0%), febrile neutropenia (6.7%), anemia (6.7%), electrolyte abnormalities (6.7%), thrombocytopenia (5.0%).

The registry reports 23 participants affected by serious adverse events among 60 at risk, and 60 participants affected by other adverse events among 60 at risk. It also reports 48 deaths. These are descriptive safety figures from the registry record. They do not, by themselves, establish that MLN8237 caused an event or death, and they do not compare the treatment with a control group.

The serious adverse event terms listed include fatigue at 10.0%, febrile neutropenia at 6.7%, anemia at 6.7%, electrolyte abnormalities at 6.7%, thrombocytopenia at 5.0%, and infection (urinary tract, skin) at 5.0%. The figures should be read as the registry reports them. The record does not explain the follow-up period associated with these counts, the event definitions beyond the serious-event classification, or whether terms could overlap within a participant.

The death count is reported separately. The record does not state whether deaths were attributed to treatment, the disease, or other causes, nor does it specify the timing of deaths relative to treatment or the follow-up period. Accordingly, these safety entries describe what is recorded, but do not support causal attribution or a comparison of safety risks.

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

The registry record describes a Phase II, single-group evaluation of MLN8237 and specifies a one-year response endpoint assessed by CT/MRI and bone scan. It also reports selected adverse-event counts and names several secondary outcomes. Those details clarify what the study set out to measure and what safety information appears in the record.

The primary response result is not reported in the registry record. There is no response count, rate, confidence interval, or p-value available to characterize the observed response outcome. The planned enrollment of 60 does not fill that gap, because enrollment is not an outcome result and the analyzed population is not stated. The registry’s endpoint definitions alone cannot establish what happened to participants during the study.

Even if a response estimate were available, the single-group design would describe an outcome within the treated group rather than a randomized contrast. Without a concurrent comparator, the study cannot separate the effect of treatment from other influences on outcomes. This limitation should not be confused with proof that treatment did or did not produce an effect; the record lacks the comparative design needed for a direct treatment contrast.

The serious adverse event and death figures are also descriptive. Their timing, attribution, and relation to treatment are not reported, so they cannot establish that treatment caused those events. The registry lists adverse-event terms and percentages, but does not provide enough analysis detail to evaluate comparative risk or event patterns over time.

Thus, the record supports a description of the planned treatment, design, endpoint, and selected safety information. It does not support a quantitative conclusion about the primary response outcome, a comparative efficacy conclusion, or a causal safety conclusion. Those boundaries are important when interpreting a trial record that contains outcome definitions and safety counts but does not report the principal outcome estimate.

13. Why This Trial Matters Statistically

This study illustrates an important distinction in clinical-trial interpretation: a clearly defined endpoint is not the same as a reported result. The registry describes an imaging-based response outcome, its assessment timeframe, and disease-response criteria. Yet without the response count or rate, readers cannot quantify the primary outcome or its precision from this record.

The design also makes the scope of inference especially important. A single-group Phase II study can provide descriptive evidence about outcomes among participants receiving a specified regimen. It does not supply a randomized comparison with another treatment or control. Statistical interpretation must therefore distinguish a within-group observation from a treatment effect defined by a between-group contrast. The registry record does not report a comparator or such a contrast.

The endpoint definition combines imaging assessment with clinical criteria, including PSA normalization for complete response and PCWG2 criteria for bone scan progression in evaluable disease. This shows why endpoint definitions matter: they determine how participant outcomes are classified. At the same time, the partial-response wording is unclear as recorded, and the registry does not explain how missing or unevaluable assessments were handled. These reporting details affect whether an endpoint can be reproduced and interpreted consistently.

The record also demonstrates why safety counts need context. It reports serious adverse events, other adverse events, and deaths, but does not describe their timing or attribution. A count can be informative as a record of reported events while remaining insufficient to establish causation or comparative risk.

Finally, named secondary outcomes and planning assumptions do not replace a reported analysis plan or outcome estimates. Without analysis populations, missing-data procedures, multiplicity methods, and the primary result, readers cannot assess the statistical evidence for the study’s central question. These limitations are not unique to this trial, but they are especially consequential when the design has no comparator and the main endpoint result is absent from 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 most direct limitation for interpreting this trial record is that the primary response result is not reported. The endpoint is described, but there is no count, response rate, or uncertainty interval. The registry also does not state how many participants were included in the endpoint analysis, so the enrollment of 60 cannot be assumed to be the analysis denominator.

The single-group design provides no concurrent treatment comparison. Allocation is recorded as NA, and the model is single group. Consequently, the record does not support a direct estimate of how outcomes differ between MLN8237 and another treatment or control. Masking is recorded as none; the registry does not clarify whether imaging assessments were independently reviewed or whether any other safeguards against assessment bias were used.

Some aspects of the endpoint are difficult to evaluate from the recorded description. The partial-response criterion is worded as a 30% 56 or greater reduction, which is unclear as written. The record does not specify how missing scans, unevaluable disease, or participants who withdrew were handled in the primary analysis. Assessment timing within the one-year timeframe is not detailed.

The registry names secondary outcomes but does not report their results or a statistical analysis plan. It does not describe multiplicity procedures, analysis populations, interim analyses, sample-size justification, or methods for handling missing data. These omissions limit evaluation of how the study’s analyses were planned and carried out.

For safety, the record reports affected counts and selected serious adverse event terms, as well as deaths, but does not state the relevant follow-up duration, event timing, treatment attribution, or how repeat events were counted. The counts therefore cannot be interpreted as causal or comparative estimates. These limitations describe what the registry record does not report; they do not establish what the underlying protocol or other study documents may have contained.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: A Phase II Trial of MLN8237 in Patients With Metastatic Castrate Resistant and Neuroendocrine Prostate Cancer — NCT01799278.
• Registry record last updated 2018-01-23; status last verified 2017-12.
• Results first posted 2017-11-29.
• 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

The registry record describes a completed Phase II, single-group study of MLN8237 in patients with metastatic castrate resistant and neuroendocrine prostate cancer. Enrollment is listed as 60. The treatment description specifies 50 mg twice daily for 7 days, repeated every 21 days, until disease progression, unacceptable toxicity, or withdrawal of consent. Masking is recorded as none.

The primary endpoint was a response count assessed by CT/MRI and bone scan over one year, with response criteria referencing RECIST 1.1 and PCWG2. The primary response result is not reported in the registry record. Named secondary outcomes include progression-free survival, overall survival, PSA response, and circulating tumor cell response; their results are not reported.

Safety entries report 23 affected among 60 at risk for serious adverse events, 60 affected among 60 at risk for other adverse events, and 48 deaths. The registry does not report the timing or treatment attribution of deaths, the primary analysis population, missing-data procedures, or a detailed statistical analysis plan. The single-group design does not provide a concurrent comparator for treatment-effect estimation.