Pilot Study of Gleevec/Imatinib Mesylate (STI-571, NSC 716051) in Neurofibromatosis (NF1) Patient With Plexiform Neurofibromas: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Pilot Study of Gleevec/Imatinib Mesylate (STI-571, NSC 716051) in Neurofibromatosis (NF1) Patient With Plexiform Neurofibromas (NCT01140360), a na phase 1, phase 2 study. The primary outcome is Disease Response.

2. Clinical Question

This is a question about response assessment in a small, uncontrolled pilot study, rather than a comparative treatment effect. The registry describes the study as using new response assessment modalities and lists secondary goals of assessing toxicity and characterizing markers of response. However, the posted primary outcome information is limited: it identifies the endpoint, its definitions, and the number of participants who reached or withdrew before the 1 year evaluation time-point, but gives no observed count for stable disease, partial response, complete response, or progressive disease. Consequently, the record does not establish how many participants met the disease control definition, nor how precisely such a rate was estimated.

3. Trial Design

The registry describes a completed pilot study in neurofibromatosis and neurofibromas. It lists phase 1 and phase 2, a single-group model, allocation as NA, and no masking. Enrollment was 21. The record gives a start date of 2012-02 and primary completion of 2016-08. The sponsor is listed as Kent Robertson. These design details describe the registry entry; they do not by themselves provide an account of how participants were selected, how treatment decisions were made, or how the study was conducted at each site.

All participants were assigned to the Gleevec group in the registry description; no separate control arm is listed. The intervention is oral Gleevec/imatinib mesylate. The dose description varies by BSA: participants with BSA above 1.8 m2 had a starting dose of 100 mg twice daily, while participants with BSA below 1.8 m2 had a starting dose of 55 mg/m2 twice daily. The dose was to increase every two weeks as tolerated, with maximum doses described for each BSA category. Treatment was planned for 6 months, with an option to continue for 24 months if the participant was deriving clinical benefit.

The primary outcome is titled Disease Response and is measured in participants at 1 year. The registry states that 13 participants reached that evaluation time-point and 6 withdrew before it. These statements do not give outcome classifications for those evaluated, and the record does not explain the evaluation status of participants not covered by those statements. No statistical analysis is listed in the registry record. The description of allocation, masking, and study model means there is no randomized concurrent comparison from which to estimate a treatment contrast. Findings from the study must therefore be read as descriptive observations within a single group, with the limits that entails for causal interpretation.

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

Analysis population for the primary outcome, as defined in the registry: 13 participants reached the 1 year evaluation time-point. 6 participants withdrew prior to the 1 year evaluation time-point.

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 Disease Response, measured over 1 year.

The primary endpoint is disease response at 1 year, reported as a count of participants. The stated objective is to estimate the disease control rate, with disease control defined as stable disease (SD), partial response (PR), or complete response (CR). The registry bases disease measurement on the sum of the longest diameter (LD) for all target lesions.

The response definitions distinguish degrees and directions of change. CR is disappearance of target lesions. PR requires at least a 30% decrease in the disease measurement relative to the measurement used to confirm measurable disease at study entry. PD requires at least a 20% increase, using the smallest disease measurement recorded since treatment began as the reference. SD means that neither the criteria for PR nor those for PD are met, using the stated reference for SD.

These categories provide a structured way to describe lesion measurements over time. Combining SD, PR, and CR into a disease control rate captures participants who meet any of those categories, rather than reporting only tumor shrinkage. It is important, though, that the endpoint definition is not itself an observed result. The registry does not report the count in each response category or the number meeting the combined disease control definition. Nor does it report uncertainty around an estimated rate. Thus, the endpoint is described, but its observed value and precision cannot be evaluated from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a single-group design tell us?

In a single-group study, outcomes are observed among participants who receive the study intervention, without a concurrent control group. This can describe what happened to participants under the study conditions. It cannot, on its own, show what would have happened to comparable participants under a different intervention or no intervention. A randomized comparison helps balance measured and unmeasured differences between groups on average; this registry record lists no such comparison. The study model is single group, allocation is NA, and masking is none. These features constrain causal interpretation, regardless of how precisely an outcome might be measured.

Because this study uses response categories tied to lesion measurements, careful and consistent assessment is important. The registry defines changes relative to specified reference measurements. In general, a clear reference rule helps make classifications reproducible. The record says the study used new response assessment modalities, but does not give enough information to evaluate the assessment procedures, assessor training, or consistency across assessments. Those details are not reported in the registry record.

How should a disease control rate be understood?

A rate for a binary outcome summarizes the proportion of participants meeting a stated condition, such as disease control versus not meeting that definition. The registry defines disease control as SD, PR, or CR. To interpret such a rate, readers need to know the numerator—the participants who met the definition—and the denominator—the participants included in the analysis. The registry identifies the primary outcome as a participant count and reports how many reached the 1 year time-point, but it does not report response counts or the denominator used for a disease control calculation. No rate can be reconstructed without inventing information, which would be inappropriate.

For a binary endpoint, uncertainty is commonly expressed with a confidence interval. General explanation: a confidence interval describes the range of values compatible with the observed data under the method used; it conveys precision, rather than proving that the true value lies within a particular range. When the number of observed events is limited, estimates can be imprecise, and the interval can be wide. No confidence interval or inferential analysis for disease response is reported in this registry record, so neither the point estimate nor its precision can be assessed.

What do response thresholds contribute?

The response rules use changes in the sum of the longest diameters of target lesions. The registry sets a decrease threshold for PR and an increase threshold for PD, each with its own reference measurement. SD covers neither sufficient shrinkage for PR nor sufficient increase for PD, using the stated reference since treatment started. These definitions make the endpoint operational: they specify how measurements are translated into categories. They do not tell readers how many participants fell into those categories. Classification depends on the measurements and on applying the criteria; the posted description supplies the rules but not the outcome values.

Combining SD, PR, and CR into disease control gives a broader endpoint than response based only on shrinkage. Such a combined endpoint can be useful when the research question includes disease stabilization. It also combines distinct clinical and measurement states, so the individual categories remain informative. The registry does not report those category-specific counts. As a result, it is not possible to determine whether any disease control result, had it been reported, was driven by SD, PR, or CR.

What is the role of planning illustrations?

Sample-size calculations are planning tools, not evidence that a study achieved a particular level of statistical power. The stated assumptions for the planning illustrations are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. They use fractions of an observed effect as planning targets. Those assumptions describe an illustrative two-arm calculation, whereas this study is registered as single group and has no like-for-like control comparison. The illustrations should therefore not be read as the study's original design justification or as observed power. The registry record does not report the trial's own sample-size justification or statistical plan. The actual numerical planning outputs are not described in the registry entries used for this explanation.

More generally, planning calculations depend on assumptions about the target effect, variability or event frequency, significance level, power, and design. Changing an assumed target effect changes the required sample size. In time-to-event settings, calculations can be based on a total number of events; for other outcomes, they may be expressed as participants per arm. These are planning concepts, not measurements from participants. No numerical planning estimate should be interpreted as the number enrolled, the number analyzed, or an observed treatment effect.

Why are missing outcome data important?

The record states that 13 participants reached the 1 year evaluation time-point and 6 withdrew before that time-point. A withdrawal before assessment means the primary outcome at that time may not be observed for that participant, but the registry does not state how those cases were treated analytically. In general, excluding participants with missing outcomes can bias a result if missingness is related to their likely outcomes. Imputation methods can address missing values under assumptions, but the method and assumptions need to be reported. Neither an imputation method nor an analysis population is reported.

The record also does not describe interim analyses, covariate adjustment, a statistical model, or multiplicity procedures. With no analysis listed, there is no basis for inferring how any of these issues were handled. The endpoint definitions and design information are enough to describe the intended question, but not enough to reproduce or assess a statistical analysis.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary outcome measure, Disease Response, with a 1 year timeframe. It does not list an analysis for that outcome. The record does not report a statistical plan, inferential tests, or procedures for handling multiple outcomes or comparisons. Although the study description includes secondary goals of assessing toxicity and characterizing markers of response, the registry information in this record does not provide a multiplicity strategy. It would therefore be inappropriate to assume that any particular adjustment, testing hierarchy, or interpretation of multiple results was used.

The primary outcome information notes that 13 participants reached the 1 year evaluation time-point and 6 withdrew before it. It does not state why participants withdrew, whether they had an earlier response assessment, or how they were included in the primary analysis. The record does not report an analysis population, a missing-data method, or an assumption about outcomes among participants without the 1 year assessment. The evaluation status and outcome information for participants not accounted for by those statements are not reported in the registry record.

These omissions limit interpretation because a disease control rate depends on both the response classifications and the denominator used. If participants without an assessment were excluded, the result would describe those assessed; if they were handled by another method, the result would depend on that method and its assumptions. The registry does not report which approach was used. It is therefore not possible to assess whether missing outcome data could have affected the endpoint estimate or to reproduce an analysis from the posted information.

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: pseudoaneurysm of carotid artery (4.8%), dehydration (4.8%), hepatic failure (4.8%).

The registry lists 21 participants at risk for serious adverse events in the Gleevec group and 3 affected. It gives pseudoaneurysm of carotid artery, dehydration, and hepatic failure as the top serious terms, each with a listed percentage of 4.8%. These are registry safety entries. The percentages should be read as reported, not as a basis for calculating a new count or a rate for the entire safety profile. The record does not provide further event-level detail in the registry record.

The same group entry lists 21 participants at risk for other adverse events and 21 affected. Serious and other adverse-event reporting are separate entries; they should not be added together to create a total because participants or events may overlap. The registry does not report whether the listed serious events were judged related to Gleevec, how severity was classified beyond the serious-event designation, or whether events were ongoing or resolved. Those details are not reported in the registry record.

The deaths field is null, so deaths are not reported in the registry record. This should not be treated as evidence that no deaths occurred. The safety counts describe what was recorded and do not establish causality. In a single-group study, there is no concurrent control group for comparing event frequencies under the same study conditions.

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

The result that can be interpreted from the registry is primarily a description of what was planned and what follow-up information was recorded. The study set out to estimate disease control at 1 year, using prespecified categories based on lesion measurements. It also reports the number of participants who reached the assessment time-point and the number who withdrew before it. These details clarify the endpoint and the follow-up context, but they do not reveal the observed disease response.

The record does not report how many participants had stable disease, partial response, complete response, or progressive disease. It also does not report a disease control rate, confidence interval, or statistical test. Consequently, the posted information cannot establish the size or precision of an observed response estimate. It cannot establish that the intervention did or did not change disease outcomes. Avoiding such claims is important: an endpoint definition is not an outcome, and a follow-up count is not a response result.

The single-group design also means there is no concurrent control comparison. Even if response counts were available, they would describe outcomes in the treated group and would not, by themselves, distinguish an intervention effect from other explanations for observed change. The record does not provide a randomized comparison or an adjusted estimate of a treatment contrast.

Safety entries provide a separate descriptive account. They report serious and other adverse-event counts and list serious-event terms, but the record does not establish whether those events were caused by the intervention. Missing details on attribution, withdrawal reasons, and analysis handling further limit interpretation. The appropriate conclusion is bounded: the registry documents a completed single-group pilot study, its intended response measure, follow-up status, and some safety reporting, while leaving the primary response result and its uncertainty unreported.

13. Why This Trial Matters Statistically

This study is statistically notable for the gap between a clearly defined primary endpoint and the absence of reported response counts. The registry gives operational definitions for CR, PR, PD, and SD, including measurement thresholds and reference points. Such definitions are essential for interpreting a response outcome, but they are only one part of a complete statistical report. Readers also need the observed classifications, the analysis denominator, and an estimate of uncertainty. Those elements are not reported for disease response.

The single-group structure is another central feature. A pilot study can describe outcomes and may help characterize assessment procedures or generate questions for further research. Without a concurrent comparator, however, it cannot provide a randomized estimate of the difference between treatment strategies. Statistical precision and causal strength are separate issues: more precise descriptive results would not, by themselves, remove the limitations of an uncontrolled design.

Follow-up completeness also matters. The registry reports participants who reached the 1 year assessment and participants who withdrew before it, but does not explain the reasons for withdrawal or how missing primary outcomes were handled. Reporting those details alongside a transparent analysis would help readers assess the possibility of selection or missing-data bias. The posted record leaves these questions open.

Finally, planning calculations should not be confused with observed evidence. The listed planning assumptions describe illustrative two-arm calculations, whereas the registered study is single group. They do not supply an observed effect, an observed power value, or the study's own design rationale. Taken together, these features make the record useful for understanding the intended statistical question and its constraints, while also making clear that the primary outcome cannot be quantitatively interpreted from the posted results.

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 interpreting efficacy is that the registry does not report the disease response counts or disease control rate. It gives response definitions and follow-up status, but not the observed classifications, denominator, or uncertainty estimate. Without those elements, the primary endpoint cannot be quantified or independently checked.

The study is registered as single group, with allocation listed as NA and masking as none. It has no concurrent comparator, so any descriptive outcomes would not provide a randomized estimate of treatment effect. The registry does not describe a statistical analysis, adjustment strategy, or analysis population. It also does not report how missing outcome data were handled or why participants withdrew before the 1 year evaluation.

Further limitations are that the registry does not explain the assessment procedures underlying the new response assessment modalities, or provide details on the timing and completeness of lesion measurements. The record does not report whether outcome assessors were independent, how response classifications were verified, or whether the protocol changed. These details are not reported in the registry record.

Safety interpretation is also limited. The record lists serious and other adverse-event counts and selected serious-event terms, but does not report attribution to treatment or further event-level context. A null deaths field does not establish that no deaths occurred. The planning assumptions are illustrative and do not supply the trial's own sample-size justification. These limitations mean the available record supports a careful account of design and reporting, but not a full assessment of response efficacy, safety causality, or statistical robustness.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Pilot Study of Gleevec/Imatinib Mesylate (STI-571, NSC 716051) in Neurofibromatosis (NF1) Patient With Plexiform Neurofibromas — NCT01140360.
• Registry record last updated 2017-07-02; status last verified 2017-06.
• Results first posted 2017-07-02.
• 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 phase 1/phase 2, single-group pilot study of oral Gleevec/imatinib mesylate in people with NF1 and plexiform neurofibromas. Enrollment was 21, and the primary outcome was disease response at 1 year, with disease control defined as SD, PR, or CR using lesion measurements. The record states that 13 participants reached the 1 year assessment and 6 withdrew before it.

It does not report response-category counts, the disease control rate, a confidence interval, or a statistical analysis. Safety reporting lists 3 participants affected by serious adverse events among 21 at risk and names three serious-event terms, each with a listed percentage of 4.8%. With no concurrent comparator and key outcome details unreported, the registry supports a description of the study design and reporting, but not a quantitative conclusion about the primary response outcome or a causal treatment effect.