LEE011 (Ribociclib) in Combination With Docetaxel Plus Prednisone in mCRPC: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for LEE011 (Ribociclib) in Combination With Docetaxel Plus Prednisone in mCRPC (NCT02494921), a non-randomized phase 1, phase 2 study. The primary outcome is Maximally Tolerated Dose (MTD) (Phase 1b).

2. Clinical Question

3. Trial Design

The registry describes a completed, open-label Phase 1b/2 study with non-randomized, parallel groups. The listed enrollment is 43. The study concerned ribociclib, an oral CDK4/6 inhibitor, given with docetaxel and prednisone in mCRPC. Because treatment assignment was not randomized and there was no control arm, the trial was not designed as a like-for-like comparison of the combination against another treatment.

Phase 1b was a dose-finding portion. The brief summary says that up to three cohorts were planned to evaluate DLTs and establish a maximum tolerated dose (MTD). Dose escalation was to follow a standard 3+3 design. The starting regimen described docetaxel at 75 mg/m2 on day 1 of each cycle, prednisone at 5 mg twice a day, and ribociclib at 200 mg orally once daily beginning on day 1 of the 21-day cycle. The summary also describes a possible alternative weekly docetaxel schedule if excess toxicity occurred at the first dose level. These are protocol descriptions; the registry record does not report which schedule was ultimately used for each participant.

Phase 2 is described as a single-arm, two-stage, open-label study at the RP2D, with N = 29 in the brief summary. Its stated purpose was to assess efficacy and further define safety. The treatment description says participants received the recommended Phase 2 dose for docetaxel and ribociclib. The registry lists primary completion on 2021-07-30 and study start on 2015-11-20, with status completed. It does not report the operational details of the stages or any randomized comparison.

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.

Before assignment: The initial dosing schedule was chosen as the most efficacious dosing schedule of docetaxel. If dose level I is not tolerated, then alternative dosing schedules of docetaxel were evaluated, starting with dose level IA. Depending on the safety data observed, alternative dosing schedules and intermediate dose levels of ribociclib was investigated (Cohort / Dose Levels IC - IIIC) per protocol.

Phase 1b, Dose Level I

Reasons for not completing this period:

Phase 1b, Dose Level IA

Reasons for not completing this period:

Phase 1b, Dose Level IIC

Reasons for not completing this period:

Phase 1b, Dose Level IIIC, RP2D

Analysis population for the primary outcome, as defined in the registry: All participants in Phase 1b including those who received the RP2D were included in this analysis

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: Participants assigned to the recommended phase 2 dose (RP2D) during their Phase 1b enrollment, were included in the Phase 1b/2 RP2D group for data analysis

6. Primary Endpoint

The registry lists the primary outcome as Maximally Tolerated Dose (MTD) (Phase 1b), measured over Up to 2 years.

The primary endpoint is the maximally tolerated dose of ribociclib in combination with docetaxel and prednisone in Phase 1b. The registry classifies the endpoint as a number and gives the unit as mg/m^2. It defines the MTD through evaluation of DLTs and adverse events among Phase 1b participants who received treatment. The specific observed MTD value is not reported in the registry record.

Dose-finding endpoints serve a different purpose from endpoints that measure whether a treatment changes disease outcomes. They help identify a dose or schedule for later study by balancing the planned treatment exposure against observed toxicity in the early-phase setting. The registry’s rules specify how DLT counts within a cohort would affect expansion, escalation, or stopping. They also allow investigators to establish an RP2D without reaching the MTD. An RP2D and an MTD are therefore related dose-selection concepts, but they are not necessarily interchangeable.

The registry lists other outcomes, including radiographic progression-free survival, objective response rate, duration of response, PSA response, PSA progression-free survival, treatment-related adverse events, and pharmacokinetic measures. Those outcomes may describe activity, safety, or drug exposure, but they do not replace the stated primary dose-finding question. Their results are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The statistical methods described in the registry are primarily dose-finding rules. They are not a full statistical analysis plan for estimating treatment effects. The record describes a Phase 1b 3+3 dose-escalation design, a single-arm Phase 2 portion, and several planned outcomes. It does not report the final analysis methods, the observed primary endpoint result, or inferential analyses.

How does the Phase 1b dose-finding rule work?

In a 3+3 design, a small cohort is treated at a dose level and assessed for DLTs. According to the registry description, if 1 of 3 participants in a cohort experiences a DLT, the cohort is expanded to treat an additional 3 participants. If only 1 of 6 participants experiences a DLT, the next cohort is treated at the next higher dose level. If 2 or more participants in a cohort experience a DLT, the MTD is considered exceeded and the previous dose level is considered the MTD. The record also specifies a stopping condition at dose level IA if more than 1 of 6 participants experiences a DLT, because de-escalation from that level was not planned.

These rules are decision rules for moving between dose levels. They are not a conventional hypothesis test of whether treatment is effective, and they do not guarantee that the selected dose is the best dose for every patient or setting. A small number of observed DLTs can inform dose selection, but estimates from small cohorts are inherently limited in precision. The registry does not report how the rules played out or what dose was selected.

What is the distinction between MTD and RP2D?

The MTD is defined in this record through DLT and adverse-event evaluation. The RP2D is the dose recommended for the Phase 2 portion. The record explicitly allows investigators to establish an RP2D even if the MTD is not reached. This means that dose selection need not consist solely of identifying the highest dose that meets the stated DLT rule. The criteria used to select the RP2D in this study, beyond the described safety assessments, are not reported in the registry record.

What can the Phase 2 design estimate?

The Phase 2 portion is described as single-arm and two-stage. A single-arm study can describe outcomes among participants receiving the regimen, such as response or time to progression, if those results and analysis details are reported. Without a concurrent randomized control group, it does not directly estimate the difference between treatment and a control treatment. Interpretation of single-arm outcomes may also depend on eligibility, follow-up, outcome definitions, and handling of missing observations. These details are not reported in the registry record.

The listed secondary outcomes span different statistical questions. Response rates are proportions; time-to-event outcomes concern the timing of an event and may require methods that account for censoring; pharmacokinetic outcomes describe drug exposure; and adverse-event outcomes count safety events or affected participants. Each requires a clear analysis population and outcome definition. The registry lists the outcome names but does not report their analysis methods or results.

How should uncertainty be understood?

In general, a confidence interval expresses the range of values compatible with the observed data under the analysis assumptions. It conveys precision as well as the point estimate. A narrow interval indicates greater precision than a wide interval, while neither interval alone resolves bias from study design or measurement. No confidence intervals for the primary endpoint or listed efficacy outcomes are reported in the registry record.

In general, over-dispersion occurs when observed variation in count data exceeds what a simple statistical model expects. If present, ignoring it can make standard errors too small and uncertainty appear less than it is. The registry record does not report a count-model analysis or any assessment of over-dispersion for this study.

The posted safety counts are descriptive. A count of participants affected does not communicate how many events each participant experienced, how long events lasted, or whether events were attributed to treatment. The record does not provide event-level details or uncertainty intervals for these counts. It also lists illustrative sample-size calculations based on the observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. Such calculations are planning illustrations, not observed power and not evidence that the actual trial was designed or powered according to those assumptions. They do not substitute for a reported analysis.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists multiple outcomes beyond the primary Phase 1b dose endpoint. These include radiographic progression-free survival, objective response rate, duration of response, PSA response rate, PSA progression-free survival, treatment-related adverse events, and pharmacokinetic measures. When several outcomes or analyses are examined, the chance of finding an apparently notable result by chance can increase. Statistical approaches to multiplicity can include prespecifying a primary outcome, controlling the overall error rate, or treating other analyses as exploratory. The registry record does not report a multiplicity adjustment or a detailed statistical analysis plan.

The record does not report how missing outcome data were handled, how participants who stopped treatment were included in efficacy analyses, or how censoring was defined for time-to-event outcomes. These are important because incomplete follow-up can affect response summaries and time-to-event estimates. No analysis populations are described beyond the primary endpoint population, which includes all Phase 1b participants who received treatment, including those who received the RP2D.

There are no posted analyses in the registry record. Therefore, the reader cannot assess whether analyses followed the planned endpoint definitions, whether any outcomes were analyzed at interim stages, or how deviations and missing observations were handled. Interim analyses and the rationale for the planned sample size are not reported in the registry record. The listed sample-size calculations are illustrative planning calculations, not evidence of observed power or a substitute for the trial’s own design rationale.

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: febrile neutropenia (40.0%), thromboembolic event (33.3%), headache (25.0%), hyponatremia (25.0%), back pain (20.0%).

The serious adverse event summaries give the number of participants at risk and the number affected in each listed group. The affected counts are 4 of 5 in Phase 1b Non-RP2D Cohort I, 2 of 4 in Cohort IA, 0 of 4 in Cohort IIC, 3 of 6 in Phase 1b RP2D Cohort IIIC, and 5 of 24 in Phase 2 RP2D. These are descriptive group-specific counts. The cohorts differed by phase and dose status, and treatment assignment was non-randomized, so their counts are not a controlled comparison of safety.

The registry lists febrile neutropenia at 40.0%, thromboembolic event at 33.3%, headache at 25.0%, hyponatremia at 25.0%, back pain at 20.0%, and intracranial hemorrhage at 20.0% among the top serious terms. The record does not specify the denominator for these term percentages in the summary, so they should not be interpreted as percentages of all trial participants. Nor do the posted figures alone establish severity beyond the serious-event classification, treatment attribution, timing, or recurrence.

Deaths are reported by group, but the counts do not establish that deaths were treatment-related. The registry record does not report a detailed causal assessment in this summary.

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

The trial is statistically informative about the questions it was designed to address only to the extent that the corresponding results are reported. The registry describes a Phase 1b dose-finding process and a single-arm Phase 2 study, but does not report the observed MTD, RP2D rationale, or results for the listed efficacy outcomes. As a result, the posted record does not provide a quantitative estimate of the regimen’s effect on response or disease progression.

The safety counts describe events among participants in the listed cohorts. They do not establish a causal relationship between the regimen and each event, and they cannot show how the event frequency compares with another treatment. A randomized control group is absent, and the cohorts are not like-for-like groups by design. Differences in their counts may reflect differences in dose, phase, follow-up, or participant characteristics, but those explanations cannot be evaluated from the reported summary.

The Phase 1b dose-escalation rules provide a framework for selecting a dose based on observed toxicity. They do not demonstrate efficacy. Similarly, the Phase 2 single-arm design can describe outcomes in treated participants if results are available, but cannot alone establish the treatment effect relative to an alternative. The record does not report the outcome analyses needed to assess those questions.

Accordingly, the registry record supports understanding the intended study structure, primary endpoint definition, and posted safety summaries. It does not support a conclusion that the regimen does or does not work, nor does it establish comparative safety. The absence of reported endpoint results is a limitation of what can be interpreted from this registry record, not evidence that an outcome was favorable or unfavorable.

13. Why This Trial Matters Statistically

This trial illustrates the distinction between dose-finding and efficacy evaluation. The Phase 1b objective is to identify a tolerable dose of ribociclib with docetaxel and prednisone using prespecified DLT-based escalation rules. That is a different statistical task from estimating whether the regimen improves a clinical outcome. Early-phase dose decisions are driven by safety observations, while the Phase 2 outcomes listed in the registry concern response, progression, adverse events, and pharmacokinetics.

It also illustrates why design determines the scope of inference. The study is open-label and non-randomized, and its Phase 2 portion is single-arm. These features permit description of treated cohorts but do not create a concurrent control comparison. A statistical interpretation must therefore distinguish observed outcomes from causal treatment effects, rather than treating separate dose cohorts as if they were randomized arms.

The record further shows why endpoint reporting matters. Defining the MTD and listing secondary outcomes is not the same as reporting their observed values or uncertainty. Without posted endpoint results and analysis details, readers cannot assess precision, missing-data handling, or whether the study met its stated objectives. The safety summaries provide useful descriptive counts, but their interpretation depends on denominators, event definitions, attribution, and follow-up that are not fully reported in the registry summary.

For biostatisticians and clinical researchers, the central lesson is to align each conclusion with the design and the reported analysis. Dose-finding rules, single-arm outcome descriptions, and randomized comparative estimates answer different questions. Keeping those distinctions clear prevents descriptive evidence from being overstated as comparative evidence.

14. Limitations

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

The primary limitation for interpretation is that the registry record defines the primary endpoint but does not report its observed result. It also does not report results for the listed efficacy outcomes, confidence intervals, or other inferential analyses. The registry lists no analyses, so the precision and statistical basis of any endpoint estimate cannot be assessed from this record.

The study is non-randomized and open-label, with a single-arm Phase 2 portion. There is no concurrent control group for estimating comparative effects. The Phase 1b cohorts represent dose-finding groups rather than randomized alternatives. This limits conclusions about causal effects and makes direct comparisons across cohort counts inappropriate.

The summary includes a planned dose-escalation scheme and treatment descriptions, but does not report the dose ultimately selected, participant-level exposure, actual follow-up, or how closely conduct matched the described plan. Detailed definitions of DLTs, adverse-event attribution, and missing-data handling are not reported in the registry record. The record also does not give analysis populations for the secondary outcomes or describe censoring for time-to-event endpoints.

Safety summaries lack detail needed to interpret event timing, duration, recurrence, and causal attribution. The top serious adverse-event terms are accompanied by percentages, but their denominator is not specified in the summary. Death counts are listed without a reported causal interpretation. These limitations do not change the counts; they constrain what can be concluded from them.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: LEE011 (Ribociclib) in Combination With Docetaxel Plus Prednisone in mCRPC — NCT02494921.
• Registry record last updated 2022-08-31; status last verified 2022-08.
• Results first posted 2022-08-31.
• 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.

18. Record Summary

The registry describes a completed, open-label, non-randomized Phase 1b/2 study of ribociclib with docetaxel and prednisone in metastatic castration-resistant prostate cancer. The listed enrollment is 43. Phase 1b used a DLT-based dose-escalation design to assess MTD, while Phase 2 was described as a single-arm, two-stage study at the RP2D.

The primary endpoint is the Phase 1b MTD, defined through DLT and adverse-event evaluation. Although the record describes the dose-selection rules, the MTD result and analyses are not reported in the registry record. Secondary outcomes include response, progression, adverse-event, and pharmacokinetic measures, with no results reported in the record. Safety counts are posted by group, but they are descriptive and do not provide a randomized comparison. The registry record supports interpretation of the planned design and available safety summaries, but not an estimate of comparative efficacy.