This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Study of PEG-Intron for Plexiform Neurofibromas (NCT00396019), a na phase 2 study. The primary outcome is Number of Participants With Imaging Response in Strata 1 and 2.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00396019 |
| Phase | Phase 2 |
| Condition | Plexiform Neurofibroma |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 86 |
| Arms in the primary outcome | n/a |
| Lead sponsor | University of Pittsburgh |
| Results posted | Yes |
2. Clinical Question
Population
The study concerned people with plexiform neurofibromas, tumors associated in the registry summary with neurofibromatosis type 1. Participants were grouped by symptoms and tumor growth: stratum 1 had no symptoms, with or without tumor growth; stratum 2 had symptoms without tumor growth; and stratum 3 had tumor growth, with or without symptoms. The registry record does not report further eligibility details.
Intervention
Participants received PEG-Intron, a pegylated, long-acting form of interferon alfa-2b. The registry record identifies the intervention but does not report the dosing schedule, treatment duration rules, or treatment adherence.
Comparator
This was a single-group study with no masking and no randomized or parallel control group. The imaging response definition uses baseline tumor volume as a reference, but that is not a separate treatment comparator.
Primary question
The primary outcome asked how many participants in strata 1 and 2 had an imaging response, defined by a reduction in target tumor volume on MRI that was confirmed on a follow-up scan. Imaging response in stratum 3 was listed as a secondary outcome.
The study was registered as a phase II trial of PEG-Intron for plexiform neurofibromas. Its stated clinical context is that these tumors can cause symptoms and functional problems as they grow, while complete surgical removal may not be possible. The registry summary also describes earlier interferon experience, but that background is not a control group for this study and does not establish what happened among the enrolled participants.
The statistical question is narrower than whether treatment improves a person’s health overall. It concerns the frequency of a prespecified imaging response in the primary strata, using MRI tumor-volume measurements. The registry record does not report the number of participants with that primary response, so the magnitude and precision of the observed response cannot be described from the posted results. Nor does a single-group study establish how the same participants would have fared without PEG-Intron.
3. Trial Design
This was a phase II, single-group study sponsored by the University of Pittsburgh. The registry lists an enrollment of 86 and a completed status. The recorded start was 2006-12, and primary completion was 2014-04. Allocation is listed as not applicable, consistent with the single-group model, and masking is listed as none.
Participants were classified into three clinical strata. Stratum 1 was described as no symptoms, with or without tumor growth; stratum 2 as symptoms without tumor growth; and stratum 3 as tumor growth, with or without symptoms. The primary outcome concerned imaging response in strata 1 and 2. Imaging response in stratum 3 was a secondary outcome. The registry record does not report the rationale for assigning participants to strata, or whether those definitions changed during the study.
All participants received the named intervention, PEG-Intron. With no concurrent control group and no masking, the design is not a randomized comparison of treatments. MRI measurements were scheduled at baseline and at months 4, 8, 12, 18, and 24 while on treatment, then every 6 months thereafter until participants were off study. This schedule describes planned assessments; it does not establish how many participants completed each scan or remained under observation at each time.
The registry record does not report the treatment dose, rules for changing or stopping treatment, adherence, or a formal statistical analysis plan. It also does not report the planned sample-size justification. Those details should not be inferred from the phase designation, enrollment, or the posted outcome definitions. In a single-group study, observed changes over time can describe what happened during follow-up, but without a separate control group they cannot isolate treatment effects from other explanations for change.
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
| Stage | Stratum 1 No Symptom With or Withour Tumor Growth | Stratum 2 Symptoms no Tumor Growth | Stratum 3 Tumor Growth With or Without Symptoms |
|---|---|---|---|
| STARTED | 27 | 29 | 30 |
| COMPLETED | 27 | 26 | 29 |
| NOT COMPLETED | 0 | 3 | 1 |
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.
| Characteristic | Unit | Stratum 1 No Symptom With or Withour Tumor Growth | Stratum 2 Symptoms no Tumor Growth | Stratum 3 Tumor Growth With or Without Symptoms | Total |
|---|---|---|---|---|---|
| Participants analysed | 27 | 26 | 29 | 82 | |
| Age, Customized: Less than 5 years | Participants | 3 | 8 | 9 | 20 |
| Age, Customized: 5 to 12 years | Participants | 10 | 9 | 12 | 31 |
| Age, Customized: greater than or equal to 12 years | Participants | 14 | 8 | 8 | 30 |
| Sex: Female, Male: Female | Participants | — | — | — | 0 |
| Sex: Female, Male: Male | Participants | — | — | — | 0 |
| Race and Ethnicity Not Collected | Participants | — | — | — | 0 |
| Region of Enrollment: United States | participants | 27 | 26 | 29 | 82 |
6. Primary Endpoint
The registry lists the primary outcome as Number of Participants With Imaging Response in Strata 1 and 2, measured over MRI scans were performed at baseline and at months 4, 8, 12, 18, and 24 while on treatment and every 6 months thereafter until off study..
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint counted participants in strata 1 and 2 who met the study’s imaging-response definition. A response required at least a 20% reduction in the sum of the volume of the target plexiform neurofibroma within 12 months, with the reduction confirmed by a follow-up MRI after at least 4 weeks. The endpoint is therefore a binary classification for each participant: response or no response under that definition.
MRI assessments were scheduled at baseline and at months 4, 8, 12, 18, and 24 while on treatment, followed by scans every 6 months until off study. Repeated imaging allows tumor-volume change to be assessed over time. Requiring a confirmatory scan is intended to make the response classification depend on more than a single observed measurement. These are general measurement considerations; the registry record does not report how images were read, whether readers were independent, or how measurement variability was handled.
An imaging endpoint gives a defined way to describe tumor-volume change, but it is not the same as a measure of symptoms, function, or overall health. The registry lists imaging response in stratum 3 as a secondary outcome, while the primary endpoint focuses on strata 1 and 2. The actual number meeting the primary response definition is not reported in the registry record, so the endpoint’s observed frequency and statistical precision cannot be assessed from the posted results.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record specifies the primary imaging endpoint and the strata to which it applies, but it does not report the primary response count or an estimated response proportion. As a result, the posted information does not establish how many participants in strata 1 and 2 met the response definition. A numerical description of the primary outcome, its uncertainty, and any comparison with a target response level is not reported in the registry record.
The same limitation applies to the secondary imaging outcome in stratum 3. Although the registry names the outcome, the number of participants with response in that stratum is not reported in the registry record. The listed enrollment of 86 is the study’s enrollment, not necessarily the number with evaluable MRI data for each endpoint. The registry record does not report the analysis population, participant flow, missing scans, or how missing outcome assessments were treated.
In general, an estimate of the proportion meeting a binary endpoint describes the observed frequency in the analyzed group. A confidence interval would communicate how precisely that frequency is estimated, while reflecting sampling uncertainty. Neither the primary response estimate nor its confidence interval is reported in the registry record. The response threshold and confirmation requirement define what counted as an event, but they do not supply the event count.
The design also limits what an observed response could establish. Because the study had a single group and no masking, an observed change would not be a randomized comparison against another treatment or no treatment. Baseline MRI is part of the response definition, but a before-and-after assessment is not equivalent to a concurrent control group. General statistical interpretation therefore distinguishes a description of outcomes during the study from an estimate of a causal treatment effect.
The safety figures show zero participants with serious adverse events among those listed at risk in each stratum, and no deaths are listed in those groups. Other adverse events are recorded for participants in all three strata. These are counts, not comparative estimates, and the record does not identify the event terms or provide a causal attribution. They should be read as registry-recorded counts rather than proof that no other harms occurred.
Overall, the record establishes the design, endpoint definition, imaging schedule, and some safety counts. It does not provide the primary efficacy result or the statistical details needed to quantify uncertainty or account for missing data. Conclusions about response frequency or treatment effects cannot be drawn from these posted results alone.
9. Statistical Methods Explained
The endpoint is a binary participant-level outcome: each participant either meets the stated imaging-response definition or does not. For such an endpoint, a common descriptive summary is the number of participants meeting the definition and the proportion among those assessed. The registry record does not report either primary response count or proportion, so those summaries cannot be interpreted. It also does not report a confidence interval or a hypothesis test for the primary outcome.
What does a confidence interval communicate?
In general, a confidence interval expresses the uncertainty around an estimate arising from sampling variation, under the assumptions of the method used. A narrower interval indicates greater precision, while a wider interval indicates less precision. It does not account automatically for design limitations, measurement error, selective reporting, or missing data. Since the primary response estimate and interval are not reported in the registry record, the precision of the study’s primary result cannot be judged from the posted information.
Why does the single-group design matter?
In general, a single-group study can describe outcomes among participants receiving an intervention, but it lacks a concurrent group to represent what might have happened under another strategy. Comparing follow-up imaging with baseline can define within-person change, as this response endpoint does. Such a comparison does not by itself separate treatment-related change from natural history, measurement variation, or other influences over time. This is a design consideration, not a claim about the direction or size of any change in this study.
The registry identifies the study as single group, with allocation listed as not applicable and masking as none. It does not report a statistical analysis plan, including a planned inferential framework, covariate adjustment, or a method for handling repeated imaging measurements. Those methods should not be assumed from the endpoint definition. In general, an analysis plan is important because it specifies which participants and observations contribute to each estimate and how uncertainty is calculated.
How should the MRI schedule be understood?
The record describes assessments at baseline and at months 4, 8, 12, 18, and 24 while on treatment, with assessments every 6 months thereafter until off study. This specifies the intended observation schedule. It does not show that every participant completed every scan, nor does it report how scans outside the defined response window contributed to analyses. The response definition includes a follow-up scan after at least 4 weeks to confirm a qualifying reduction. In general, repeated assessment and confirmation can help make an endpoint definition more reproducible, while still leaving questions about image reading, missing scans, and measurement consistency.
What do the planning illustrations represent?
The registry record does not report a trial-specific sample-size justification. Any accompanying planning illustration is a hypothetical exercise based on the observed effect, not the original design rationale or evidence of achieved power. Its stated assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect expressed as a fraction of the observed effect. These assumptions describe a planning scenario and do not turn this single-group study into a two-arm trial. Sample-size illustrations are not observed power and do not indicate the probability that the study found a true effect. No specific planning result should be interpreted without the corresponding stated scenario and its limitations.
More generally, a design-based sample-size calculation depends on assumptions about the endpoint, anticipated effect, variability or event frequency, significance threshold, and desired power. Changing assumptions changes the planning result. Since the registry does not report its own justification, the planning illustration cannot be taken as evidence about the investigators’ original target, nor does it establish that the enrolled group was adequate for every endpoint or stratum.
What can the safety counts support?
The listed safety outcomes are counts of participants with events. General interpretation of event counts depends on knowing the event definitions, observation period, severity criteria, and analysis population. The registry record provides counts at risk and affected for serious and other events, but does not report detailed event terms for the serious events or a broader analysis plan. Counts alone do not identify whether an event was caused by treatment, and they do not measure comparative risk in the absence of a control group.
Statistical interpretation should therefore stay close to what is recorded: a defined imaging endpoint, a single-group design, and listed safety counts. The registry record does not report the primary endpoint estimate, confidence intervals, inferential analyses, or the methods needed to assess missing outcomes. General statistical concepts clarify what such information would mean, but cannot substitute for unreported study results.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists a primary imaging outcome for strata 1 and 2 and a secondary imaging outcome for stratum 3. It also records four outcome measures and zero analysis entries. The registry record does not report whether the investigators specified a hierarchy among outcomes, adjusted for multiple testing, or selected a particular analysis as primary after reviewing results. A multiplicity strategy is not reported in the registry record.
In general, testing or estimating multiple outcomes can increase the chance of emphasizing a result that appears notable by chance. Prespecified outcome priorities and appropriate methods can help readers interpret a collection of findings. Here, the endpoint labels identify primary and secondary status, but do not disclose a multiplicity procedure. Because outcome results and analysis entries are not reported, the impact of multiplicity on interpretation cannot be assessed.
Missing-data handling is not reported in the registry record. The scheduled MRI assessments do not establish that all participants had evaluable scans at all visits. The record does not describe incomplete follow-up, reasons for missing imaging, imputation, or sensitivity analyses. The analysis populations are also not reported: it is unclear from the registry record which participants were included in each endpoint analysis or whether inclusion required particular follow-up data.
These omissions matter because response is defined using serial imaging and confirmation. If confirmatory or follow-up scans are unavailable, the way those observations are handled can affect the number classified as responders and the population represented by the estimate. Without response counts, participant flow, and analysis rules, neither the direction nor the size of any potential missing-data influence can be determined.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Stratum 1 No Symptom With or Withour Tumor Growth | 0 | 27 | 0.0% |
| Stratum 2 Symptoms no Tumor Growth | 0 | 26 | 0.0% |
| Stratum 3 Tumor Growth With or Without Symptoms | 0 | 29 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Stratum 1 No Symptom With or Withour Tumor Growth | 0 of 27 |
| Stratum 2 Symptoms no Tumor Growth | 0 of 26 |
| Stratum 3 Tumor Growth With or Without Symptoms | 0 of 29 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Stratum 1 No Symptom With or Withour Tumor Growth | 7 of 27 |
| Stratum 2 Symptoms no Tumor Growth | 8 of 26 |
| Stratum 3 Tumor Growth With or Without Symptoms | 6 of 29 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Stratum 1 No Symptom With or Withour Tumor Growth | Stratum 2 Symptoms no Tumor Growth | Stratum 3 Tumor Growth With or Without Symptoms |
|---|---|---|---|---|
| Fatigue | General disorders | 2 of 27 | 4 of 26 | 2 of 29 |
| Behavior | Psychiatric disorders | 2 of 27 | 3 of 26 | 2 of 29 |
| Depression | Psychiatric disorders | 2 of 27 | 1 of 26 | 0 of 29 |
| Transaminitis | Investigations | 0 of 27 | 0 of 26 | 2 of 29 |
| Allergic Reaction | General disorders | 1 of 27 | 0 of 26 | 0 of 29 |
The safety record lists three strata, with 27 participants at risk in stratum 1, 26 in stratum 2, and 29 in stratum 3. Serious adverse events affected 0 participants in each listed group. The record lists 7 participants with other adverse events in stratum 1, 8 in stratum 2, and 6 in stratum 3. Deaths are listed as 0 in each group.
These are participant counts, not rates or comparisons between treatments. The groups are clinical strata within a single-group study, not randomized intervention arms. The registry record lists no top serious-event terms. It does not report the detailed types of other adverse events, their timing, severity, duration, or whether investigators considered them related to PEG-Intron. The counts therefore describe what is recorded in the registry, but cannot establish causation or provide a complete safety profile.
Zero listed serious adverse events or deaths should not be read as proof that no such events occurred outside the recorded categories, observation periods, or reported groups. The registry record does not report additional details needed to assess completeness of safety ascertainment. Interpretation should remain limited to the counts and group denominators recorded.
12. What the Result Does, and Does Not, Mean
The registry record describes a phase II, single-group evaluation of PEG-Intron for plexiform neurofibromas, including an MRI-based primary endpoint for strata 1 and 2. It defines response as a specified reduction in target tumor volume within 12 months, confirmed by a later MRI. It also lists imaging response in stratum 3 as a secondary outcome and records adverse-event counts by stratum.
These design and endpoint details explain what the study intended to assess, but they are not the primary result. The number of participants with primary imaging response is not reported in the registry record. The secondary response count is also not reported. There is therefore no posted estimate of response frequency, no confidence interval to describe its precision, and no basis in the registry record for assessing whether the response met a prespecified target.
Even if an imaging response result were available, interpretation would need to account for the single-group design. A change from baseline can describe what occurred during follow-up, but it cannot alone show what would have happened without treatment. The design does not provide a randomized or parallel control group, and masking is listed as none. These features limit causal interpretation; they do not determine the direction of any observed outcome.
Imaging response is also a particular type of outcome. It measures change in tumor volume under the registry’s definition and is not interchangeable with symptoms, function, quality of life, or other clinical outcomes. The record does not report results for those domains. The adverse-event counts likewise do not establish whether events were caused by treatment or how they compare with an alternative.
The appropriate reading is therefore limited: the registry documents the trial framework and selected safety counts, while leaving the primary response result and key analytic details unreported. It does not support a conclusion about treatment benefit, lack of benefit, or comparative safety.
13. Why This Trial Matters Statistically
This trial illustrates why endpoint definitions and outcome results must be read separately. The registry gives a specific MRI response threshold, a confirmation requirement, and an assessment schedule. Those details make clear what would qualify as a response, but a clearly defined outcome is not itself evidence that participants met it. Without the primary response count, the endpoint cannot be summarized quantitatively.
The study also illustrates the distinction between longitudinal observation and controlled comparison. Baseline imaging allows change to be evaluated within participants, while the single-group design provides no concurrent group for estimating what might have occurred under another strategy. This distinction is central when interpreting outcomes from nonrandomized designs: a measured change and a causal treatment effect are not the same statistical quantity.
Stratification adds another interpretive layer. The primary outcome focuses on strata 1 and 2, while stratum 3 has a separate secondary imaging outcome. Different strata represent distinct clinical descriptions, and their results should not be combined or compared casually. The registry record does not provide the response counts or analysis methods needed to evaluate these groups statistically.
Finally, the record demonstrates the value of reporting uncertainty, missing-data methods, and analysis populations alongside outcome definitions. None of those details, nor the primary result, is reported in the registry record. A planning illustration under hypothetical two-arm assumptions cannot fill that gap or serve as observed evidence. The statistical importance of the record lies in identifying what the design and definitions can support, and where the available information stops.
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 main limitation for interpreting this trial from the registry record is that the primary response count and estimate are not reported. The secondary imaging response count is also not reported. Without those results, the frequency and precision of response cannot be described. The registry record does not report confidence intervals or inferential analyses for the imaging endpoints.
The single-group design has no concurrent randomized comparator, and masking is listed as none. Consequently, even a reported before-and-after imaging change would not, by itself, isolate the effect of PEG-Intron from other possible influences. This is a design limitation rather than a finding about the outcome.
The record does not report the statistical analysis plan, sample-size justification, analysis populations, missing-data methods, or multiplicity procedures. It also does not report image-reading methods or how measurement variability was handled. These omissions limit assessment of how the endpoint was analyzed and how robust an estimate might be. The MRI schedule does not establish the completeness of follow-up or confirmatory scans.
The enrollment of 86 does not establish the number analyzed for each outcome. Stratum-specific counts at risk are listed for safety outcomes, but the registry does not report corresponding imaging-analysis denominators. Safety information is limited to grouped participant counts; detailed event terms, attribution, timing, and severity are not reported. These limitations are specific to what the registry record documents and do not imply that unreported methods or results were absent from other study materials.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Study of PEG-Intron for Plexiform Neurofibromas — NCT00396019.
- Registry record last updated 2017-11-06; status last verified 2017-10.
- Results first posted 2017-11-06.
- 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.
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18. Record Summary
NCT00396019 is a completed phase II, single-group study of PEG-Intron for plexiform neurofibromas, sponsored by the University of Pittsburgh. The registry lists enrollment of 86, a start of 2006-12, and primary completion in 2014-04. Masking is listed as none.
The primary outcome was the number of participants with imaging response in strata 1 and 2. Response required at least a 20% reduction in target tumor volume within 12 months, confirmed by MRI after at least 4 weeks. MRI assessments were scheduled from baseline through follow-up. Imaging response in stratum 3 was a secondary outcome.
The registry record does not report the primary or secondary response counts, a statistical analysis plan, or methods for missing data and multiplicity. Safety counts list 0 participants with serious adverse events and 0 deaths in each stratum; other adverse events affected 7, 8, and 6 participants, respectively. These counts do not provide a controlled comparison or establish causality.