Nilotinib vs Imatinib in Adult Patients With Philadelphia (Ph+) Chronic Myelogenous Leukemia in Chronic Phase (CML-CP): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Nilotinib vs Imatinib in Adult Patients With Philadelphia (Ph+) Chronic Myelogenous Leukemia in Chronic Phase (CML-CP) (NCT00519090), a randomized phase 3 study. The primary outcome is Complete Cytogenetic Response Rate(CCyR) in Patients Who Had a Suboptimal Cytogenetic Response on Imatinib.

2. Clinical Question

In statistical terms, the intended comparison was between the proportions of participants in the two treatment groups who achieved complete cytogenetic response over the stated assessment period. A response rate is a binary outcome: each participant is classified according to whether the specified response occurred. The resulting comparison would describe the observed response proportions and, if an analysis had been reported, the uncertainty around their difference or another prespecified contrast.

The registry does not report a primary outcome estimate, a treatment-effect estimate, or an inferential test. It therefore does not establish whether response rates differed between the groups. It also does not report a separate efficacy analysis for the secondary outcome, durable complete cytogenetic response rate.

3. Trial Design

The registry describes a phase III, randomized, open-label, parallel-group, multicenter study. Its official title identifies nilotinib and imatinib as the treatments under comparison for adults with Ph+ CML-CP who had a suboptimal cytogenetic response on imatinib. The brief summary specifies nilotinib 400 mg twice daily and imatinib 400 mg twice daily.

Random allocation is intended to assign participants to treatment groups by chance rather than by a clinician’s choice. In general, this can reduce systematic differences between groups at the start of a study, although randomization cannot guarantee that groups will be balanced, particularly when the numbers enrolled are limited. The registry specifically states that the patient numbers were too small and imbalanced for the planned primary analysis.

The study was open-label, meaning masking was not used. The registry lists no masking. In general, knowledge of assigned treatment can influence care, reporting, or assessment, depending on the outcome and study procedures. The record does not describe any additional safeguards for outcome assessment.

The registry enrollment is 6. The study start is listed as 2007-10, and primary completion as 2008-10. Its status is terminated. The record does not report a reason for termination beyond the primary outcome description, which says early termination resulted in numbers too small and imbalanced for analysis. The planned primary outcome was complete cytogenetic response rate at 12 months. Durable complete cytogenetic response rate is listed as a secondary outcome, but no analysis of that outcome is reported.

Further details about the randomization procedure, allocation concealment, treatment adherence, visit schedule, and protocol deviations are not reported in the registry record. Those omissions limit what can be assessed about how the planned comparison was conducted.

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 Complete Cytogenetic Response Rate(CCyR) in Patients Who Had a Suboptimal Cytogenetic Response on Imatinib, measured over 12 months.

The primary endpoint was complete cytogenetic response rate among patients who had a suboptimal cytogenetic response on imatinib. It was expressed as a percentage of participants, with a stated timeframe of 12 months. The registry does not provide the operational criteria used to classify a complete cytogenetic response, so the precise assessment rules are not reported in the registry record.

A response rate represents the proportion of participants meeting a defined response criterion within the stated assessment framework. Because the outcome is binary, participants contribute to a response or non-response category under that framework. Such an endpoint can make a treatment comparison clinically interpretable as the frequency of the specified response in each group. The meaning of the rate depends on the outcome definition, the assessment time, and how participants with missing or unevaluable assessments are handled.

The endpoint is relevant to the stated study question because the trial focused on patients whose prior cytogenetic response on imatinib was suboptimal. The registry also lists durable complete cytogenetic response rate as a secondary outcome, which concerns persistence of response, but its definition and analysis are not reported in the registry record.

Most importantly, the primary outcome description says the analysis was not performed because early termination left the patient numbers too small and imbalanced. Therefore, the record supplies the intended endpoint but no observed primary response rate or treatment comparison. The endpoint’s planned use should not be confused with an analyzed result.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies a randomized, parallel-group trial with no masking. These design features describe how the comparison was intended to be organized; they do not, by themselves, supply an outcome analysis. The primary endpoint was a binary response rate at 12 months, but the record explicitly says that analysis was not performed. The statistical concepts below explain how such an analysis would generally be interpreted, not what this trial found.

What does a response rate represent?

For a binary endpoint, each participant is classified according to whether the response criterion is met. A group response rate is the proportion classified as responders under the study’s rules. A treatment comparison can then express how those proportions differ or relate. Which contrast is most informative depends on the analysis plan and clinical question. The registry does not report the planned effect measure or the operational criteria for complete cytogenetic response.

Rates depend on how the analysis population is defined and how participants without an evaluable assessment are treated. For example, an analysis might include all randomized participants or a specified subset, and it might use different rules for missing assessments. These choices can affect the estimate. The registry record does not report an analysis population or a missing-data rule for this endpoint, and the analysis itself was not performed.

What would uncertainty measures add?

An estimate alone does not show how much uncertainty surrounds it. In general, a confidence interval communicates the range of effect values compatible with the observed data under the stated model and assumptions. A wide interval indicates limited precision; a narrow interval indicates greater precision. A hypothesis test can assess how compatible the data are with a specified null hypothesis, but a p-value is not a measure of the size or clinical importance of an effect. No primary effect estimate, confidence interval, or p-value is reported in the registry record.

When group sizes are limited, estimates can be particularly sensitive to the outcomes of individual participants. Imbalance between groups can further complicate interpretation, especially if the groups differ in important characteristics by chance. Randomization is intended to limit systematic allocation bias, but it does not ensure balance in a small study. The registry itself cites small and imbalanced patient numbers as the reason the primary analysis was not performed.

What does randomization contribute?

In general, randomization assigns treatment independently of investigators’ preferences and participant characteristics, helping support a fair comparison. Its value depends on the implementation and the analysis retaining the randomized comparison. The registry says the study was randomized but does not report the sequence-generation method, allocation concealment, stratification factors, or analysis population. Those details are not reported in the registry record, so the conduct of randomization cannot be assessed further.

The study was open-label. Lack of masking can matter if knowledge of treatment influences care, reporting, or assessment. A cytogenetic response endpoint may use laboratory assessment, but the registry does not describe who assessed the endpoint or whether assessment was masked. No additional claims about the likely direction or extent of any bias can be made from the record.

How should planning calculations be read?

Planning illustrations are not observed results. The stated assumptions describe a two-sided significance level of 0.05, equal allocation, and a normal approximation, with effects expressed as fractions of an observed effect. For time-to-event outcomes, such planning tables use total events; other outcomes use participants per arm. These are general design calculations, not evidence that the study achieved a given power or that a treatment effect was established.

In this case, the primary analysis was not performed, so an observed primary treatment effect is not available in the registry record as a basis for interpreting an effect-based planning illustration. A sample-size calculation based on an assumed effect can show how design requirements change under that assumption, but it cannot replace an outcome analysis. It should not be described as observed power. The registry does not report the trial’s own sample-size justification, and it is not reported in the registry record whether the stated planning assumptions were used in the original protocol.

Finally, statistical significance and clinical importance are distinct concepts. A result can be statistically compatible with a nonzero effect yet be small in practical terms, or an important-looking estimate can remain uncertain. Assessing either requires a reported estimate, its uncertainty, and an appropriate context for the endpoint. Those elements are absent for the primary outcome here, so the methods concepts explain how results would ordinarily be read without supplying a result that the registry does not contain.

10. Multiplicity, Missing Data and Analysis Populations

The registry names a primary outcome and lists durable complete cytogenetic response rate as a secondary outcome. It reports 0 analyses. The record does not report a statistical analysis plan describing how multiple outcomes, comparisons, or time points were to be handled. Any multiplicity adjustment, hierarchy, or prespecified testing sequence is not reported in the registry record.

Multiplicity matters in general when several hypotheses are tested: considering more tests can increase the chance of at least one apparently unusual result under a null model. A planned strategy can help interpret a collection of tests, but no such strategy is described in the registry record. In this trial, the primary analysis was not performed, and no secondary outcome analysis is reported, so the record does not present a set of inferential results to interpret collectively.

Missing-data handling and analysis populations are also not reported in the registry record. The primary outcome description attributes the lack of analysis to early termination and patient numbers that were too small and imbalanced; it does not specify whether endpoint assessments were missing, how unevaluable participants would have been classified, or which participants were intended for the analysis. The record does not describe an intention-to-treat analysis or another analysis population.

These omissions should be distinguished from the stated reason the primary analysis was not performed. They do not establish that a particular missing-data problem occurred, or that a particular multiplicity method was omitted from the original protocol. They mean only that these details are not reported in the registry record.

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 0% reporting threshold.

Most frequent non-serious adverse event terms

The registry reports serious and other adverse event fields by treatment group. For nilotinib, the serious adverse event fields list 2 at risk and 0 affected; the other adverse event fields list 2 at risk and 2 affected. For imatinib, the serious fields list 4 at risk and 0 affected; the other fields list 4 at risk and 4 affected.

These are counts in the registry’s safety entries, not a complete description of the nature, timing, duration, or severity of events. No top serious adverse event terms are listed. The registry record does not explain the detailed event definitions, collection period, or whether the other-event category includes all non-serious events. Those details are not reported in the registry record.

Deaths are not reported in the registry record. The safety counts should be read separately from the primary efficacy endpoint: they do not provide a treatment comparison for complete cytogenetic response. With the small and imbalanced patient numbers noted in the primary outcome description, the counts alone do not establish comparative safety.

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

The record establishes that a phase III randomized, open-label, parallel-group study was registered to compare nilotinib and imatinib in adults with Ph+ CML-CP who had a suboptimal cytogenetic response on imatinib. It also identifies the planned primary outcome, complete cytogenetic response rate at 12 months, and gives the reason the analysis was not performed: early termination left patient numbers too small and imbalanced.

What the record does not establish is the comparative response rate. There is no primary endpoint estimate, no reported treatment contrast, and no inferential result. Therefore, the registry does not show that the treatments produced the same response, that one produced a higher response, or that any difference was statistically or clinically meaningful. The lack of a reported analysis is not a null finding.

The same caution applies to the secondary outcome. Durable complete cytogenetic response rate is listed, but no results for it are reported. The safety entries provide event counts, but not event descriptions or a complete comparative safety analysis. They cannot resolve the missing efficacy comparison.

In general, a useful treatment comparison depends on a clearly defined endpoint, an appropriate analysis population, a transparent approach to missing observations, and an estimate reported with its uncertainty. The registry does not provide these analysis details for the primary endpoint. Its status is terminated, and further information about the reason for termination is not reported in the registry record.

The most defensible interpretation is therefore limited: the trial was intended to answer a comparative response question, but the posted registry results do not answer it. No medical decision should be inferred from the absence of an analyzed primary outcome. The record documents a planned comparison and an unperformed analysis, not evidence for or against either treatment.

13. Why This Trial Matters Statistically

This trial illustrates an important distinction between a registered research question and an analyzed result. The registry describes a randomized comparison and a defined primary endpoint, but it also records that the primary analysis was not performed. A study’s design can be informative about what investigators intended to learn, while still providing no estimate of the treatment effect.

The stated reason matters statistically: early termination left the patient numbers too small and imbalanced. Small groups often yield imprecise estimates, and imbalance can make comparisons harder to interpret. In general, reporting an estimate together with its uncertainty helps readers understand those limitations. Here, the registry did not report the primary estimate or its uncertainty because the analysis was not performed.

The record also demonstrates why outcome listings should not be mistaken for outcome findings. Complete cytogenetic response rate is named as the primary endpoint, and durable complete cytogenetic response rate is named as secondary, but neither listing supplies a result. The safety counts are a separate kind of information and do not answer the efficacy question.

For biostatistical interpretation, the central lesson is to distinguish what was planned, what was conducted, and what was reported. The registry gives some design and outcome details, but important analysis information—including the analysis population and missing-data approach—is not reported. Recognizing that boundary prevents unsupported conclusions from being drawn from a trial record that does not contain its planned primary comparison.

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 consequential limitation is that the primary endpoint analysis was not performed. The registry attributes this to early termination and patient numbers that were too small and imbalanced. There is consequently no reported primary response rate by group, no comparative effect estimate, and no measure of uncertainty for the planned treatment contrast.

The registry enrollment is 6, but additional detail on the flow of participants through screening, randomization, treatment, and endpoint assessment is not reported in the registry record. Group-specific primary endpoint denominators and response counts are also not reported. The reason for termination beyond the explanation in the endpoint description is not reported in the registry record.

The record does not provide the operational definition of complete cytogenetic response, the assessment procedures, or the handling of unevaluable participants. Analysis populations, missing-data methods, protocol deviations, adherence, and the statistical analysis plan are not reported in the registry record. These gaps prevent a full assessment of how the intended endpoint would have been analyzed.

The study was open-label, and the registry lists no masking. The record does not describe outcome-assessment safeguards or allocation concealment. The secondary durable response outcome is listed without an analysis. Safety fields contain counts, but event terms and additional details are not reported; deaths are not reported in the registry record.

These limitations restrict interpretation of the registry entry; they do not show that a particular bias occurred or that unreported results had a particular direction. The stated outcome analysis remains unavailable.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Nilotinib vs Imatinib in Adult Patients With Philadelphia (Ph+) Chronic Myelogenous Leukemia in Chronic Phase (CML-CP) — NCT00519090.
• Registry record last updated 2011-11-07; status last verified 2011-11.
• Results first posted 2011-05-10.
• 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

NCT00519090 is a phase III randomized, open-label, multicenter, parallel-group study of nilotinib versus imatinib in adults with Ph+ CML-CP and a suboptimal cytogenetic response on imatinib. The brief summary describes both treatments as 400 mg twice daily. The registry lists enrollment as 6, status as terminated, a study start of 2007-10, and primary completion of 2008-10.

The primary endpoint was complete cytogenetic response rate at 12 months. The registry states that early termination left patient numbers too small and imbalanced, so the analysis was not performed. Durable complete cytogenetic response rate is listed as a secondary outcome, with no analysis reported. Safety entries list serious and other adverse event counts by group, but provide no serious event terms. Further efficacy estimates and analysis details are not reported in the registry record.