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 A Study Called EPI VITRAKVI to Compare Treatment Results in Patients With Infantile Fibrosarcoma (IFS), a Type of Connective Soft Tissue Cancer, Who Received a Treatment Called Larotrectinib From a Study Called SCOUT With Patient Data From an External Database (NCT05236257), a registered phase not stated study. The primary outcome is Time to Medical Treatment Failure.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT05236257 |
| Phase | Phase not stated |
| Condition | Locally Advanced or Metastatic Infantile Fibrosarcoma Harboring an NTRK Gene Fusion, Infantile Fibrosarcoma |
| Allocation | Not Stated |
| Design model | Not Stated |
| Masking | Not Stated |
| Enrollment | 93 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Bayer |
| Results posted | Yes |
2. Clinical Question
Population
Pediatric patients with infantile fibrosarcoma (IFS) harboring an NTRK gene fusion. The larotrectinib group comprises patients enrolled in the SCOUT study; the external-control group comprises patients in eligible external cohort(s).
Intervention
Larotrectinib, also called Vitrakvi or BAY2757556, is the treatment received by patients in SCOUT. The registry describes the study as observational and uses past patient data.
Comparator
External historical control cohort(s) of pediatric patients with IFS harboring an NTRK gene fusion, described as receiving standard care. The allocation process is not stated, and the groups are not a like-for-like randomized comparison.
Primary question
How does time to medical treatment failure compare between the SCOUT larotrectinib group and the external historical cohort(s)? Failure is defined as the earliest of subsequent systemic treatment, radiation therapy, mutilating surgery, or death from any cause. The primary endpoint estimate is not reported in the registry record.
The question is about a time-to-event outcome, rather than simply whether a listed event occurred. The endpoint starts at treatment initiation and ends at the earliest qualifying event. Its composite definition combines several kinds of subsequent treatment or intervention with death. The registry describes follow-up as up to 5.5 years for SCOUT participants and 22.5 years for participants in the external historical control. Those different maximum follow-up windows matter when interpreting the comparison: opportunities to observe events may differ between cohorts, and the record does not provide further detail about follow-up distributions or the analysis population.
3. Trial Design
This is an observational study of past data, not a randomized treatment trial. It compares pediatric patients with NTRK gene fusion-positive IFS who received larotrectinib in the phase I/II SCOUT study with patients in eligible external historical cohort(s). The record describes the comparator as standard care. Allocation to the groups is not stated, and the arms are not a like-for-like control comparison.
The listed enrollment is 93. That figure does not, by itself, establish how many patients contributed to each endpoint analysis, how many were included in each cohort, or how many had complete outcome information. Analysis-specific participant counts are not reported in the registry record. The study is marked completed; its start date is 2022-03-10 and its primary completion date is 2022-09-13.
The primary outcome is time to medical treatment failure, measured in months. The registry defines failure as the time from treatment start to the earliest of subsequent systemic treatment, radiation therapy, mutilating surgery, or death from any cause. The registry gives different maximum follow-up windows: up to 5.5 years for SCOUT participants and 22.5 years for external historical controls. It also lists secondary outcomes concerning subsequent systemic treatment, mutilating surgery, radiation therapy, complete surgical resection, overall survival, and treatment discontinuation due to treatment-emergent adverse events.
Because the comparator is historical and the groups were not randomized, differences between groups cannot automatically be attributed to treatment. Eligibility, patient characteristics, care settings, outcome recording, and follow-up could differ. Details about cohort construction, adjustment for differences between groups, and the statistical analysis plan are not reported in the registry record. The record identifies Bayer as the sponsor.
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: In total, 93 patients were included in this study (IFS population). The larotrectinib arm of the study included 51 patients from the SCOUT study. The single comparator arm of patients that received conventional chemotherapy included in total 42 external control patients, pooled from the Institut Curie database (N=18) and the CWS database (N=24).
Overall Study
| Stage | Larotrectinib | External Controls |
|---|---|---|
| STARTED | 51 | 42 |
| COMPLETED | 0 | 0 |
| NOT COMPLETED | 51 | 42 |
Reasons for not completing this period:
| Reason | Larotrectinib | External Controls |
|---|---|---|
| Ongoing with study treatment | 29 | 1 |
| Discontinued study treatment | 22 | 41 |
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 | Larotrectinib | External Controls | Total |
|---|---|---|---|---|
| Participants analysed | 51 | 42 | 93 | |
| Age, Continuous | years | 2.01 (SD 3.49) | 0.73 (SD 1.81) | 1.43 (SD 2.91) |
| Sex: Female, Male: Female | Participants | 21 | 15 | 36 |
| Sex: Female, Male: Male | Participants | 30 | 27 | 57 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Asian | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Black or African American | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): White | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): More than one race | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 51 | 42 | 93 |
6. Primary Endpoint
The registry lists the primary outcome as Time to Medical Treatment Failure, measured over up to 5.5 years for participants in SCOUT study and 22.5 years for participants in external historical control.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | 95% Confidence Interval |
| Unit | months |
| Endpoint classification | Time-to-Event Analysis |
Time to medical treatment failure measures the interval from the start of treatment until the earliest qualifying event: subsequent systemic treatment, radiation therapy, mutilating surgery, or death due to any cause. The registry reports the endpoint in months and specifies the median with a 95% confidence interval as the summary measure. The estimate itself and its confidence interval are not reported in the registry record.
In general, a time-to-event endpoint retains information about when an event occurs, rather than reducing the outcome to a simple event/no-event count. This can be useful when participants have different lengths of follow-up. Participants without a recorded event by the end of their observed follow-up may be censored: their event time is known only to exceed the observed period. How censoring was handled, and whether the assumptions required for the analysis were assessed, are not reported in the registry record.
The endpoint is composite: any one of the listed events can define failure. A composite can capture several clinically consequential changes in management or outcome, but it does not show which component accounts for a group difference. Component-specific results would be needed to understand the pattern across subsequent treatment, radiation, surgery, and death. The registry lists related outcomes separately, but their estimates are not reported in the registry record.
The median is the time by which half of the event-time distribution has experienced the event, when that quantity can be estimated. Its confidence interval describes uncertainty around the estimated median under the analysis method; it is not a range containing individual participants’ event times. The registry does not report the median values or interval limits for this endpoint.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies the primary comparison and defines its endpoint, but it does not report the primary median time to medical treatment failure, its 95% confidence interval, or a treatment-effect estimate. It therefore does not provide enough numerical result information to describe the direction or magnitude of the primary comparison, or its precision. The record also does not report a p-value for the primary endpoint.
The endpoint is a composite of subsequent systemic treatment, radiation therapy, mutilating surgery, and death. Even if a composite estimate were available, it would not by itself reveal whether any difference arose mainly from one component or was consistent across components. The component-specific endpoint estimates are not reported in the registry record.
This is an observational comparison with external historical controls, not a randomized comparison. In general, historical cohorts can differ from a treatment cohort in patient characteristics, eligibility, clinical practice, outcome ascertainment, and duration of observation. Such differences may influence estimated outcomes independently of treatment. The registry explicitly indicates that the arms are not a like-for-like control comparison; details of any adjustment for confounding are not reported in the registry record. Consequently, the design does not support treating an observed group contrast as an unbiased causal effect without additional assumptions and methods.
The follow-up windows also differ: up to 5.5 years for SCOUT participants and 22.5 years for participants in the external historical control. These are maximum windows, not descriptions of the actual follow-up experienced by every participant. The record does not report follow-up distributions, numbers at risk over time, or censoring patterns. Those details would help assess how much information supports estimates at different times.
The registry indicates that sponsor-reported hazard ratios are the basis for hazard-ratio interpretation, but no hazard-ratio value or confidence interval is reported in the registry record. A hazard ratio, in general, compares instantaneous event rates among participants still at risk under the model; it is not the same as a ratio of median times or a direct measure of the probability of an event. The assumptions and adjustment details for any such estimate are not reported.
In short, the registry record describes what was intended to be compared, but the numerical primary result needed to interpret that comparison is not reported. No conclusion about the size, direction, or statistical precision of the primary result can be drawn from the information available in the record.
9. Statistical Methods Explained
Time-to-event methods are designed for outcomes recorded as the time from a defined starting point to an event. Here, the starting point is treatment initiation, and the event is the earliest of subsequent systemic treatment, radiation therapy, mutilating surgery, or death due to any cause. The registry describes the primary summary as the median time, with a 95% confidence interval. The median and interval values are not reported in the registry record.
What does a median time represent?
In general, the median event time is the point at which half of the event-time distribution has experienced the event, provided it can be estimated from the available follow-up. It is a summary of the event-time distribution, not an average and not a statement that every participant experiences the event at that time. When follow-up is incomplete, estimation methods account for participants whose event has not been observed by their last recorded follow-up. The specific method used for the median is not reported in the registry record.
How should a confidence interval be read?
In general, a confidence interval communicates uncertainty in an estimated quantity under a specified statistical procedure and its assumptions. A narrower interval indicates greater precision than a wider interval, while an interval’s limits show a range of values compatible with the data and method. A confidence interval does not show the range of individual outcomes, and it does not remove bias from differences between cohorts. The registry names a 95% confidence interval for the primary median but does not report its limits.
What does a hazard ratio describe?
In general, a hazard ratio compares event rates at a given time among participants who have not yet experienced the event, as represented by a statistical model. It is not a direct comparison of median times, cumulative event probabilities, or individual outcomes. Interpretation depends on the model and its assumptions, including how the relative event rates behave over time. The registry indicates that sponsor-reported hazard ratios are the basis for interpretation, but their values, confidence intervals, model details, and assumption checks are not reported in the registry record.
Why does censoring matter?
In general, censoring occurs when a participant’s event is not observed before the end of the available follow-up. The participant contributes information up to the last known event-free time, but the eventual event time is unknown. Valid time-to-event estimation requires appropriate handling of censoring and assumptions about how censoring relates to event risk. The record does not report censoring counts, reasons for censoring, or the methods used to address it.
Why does the historical comparison need caution?
In general, randomization helps balance measured and unmeasured characteristics between treatment groups. External historical controls do not obtain that protection through random assignment. Differences in who entered each cohort, when and where care occurred, how outcomes were recorded, or how long participants were followed may affect the observed comparison. Statistical adjustment can address some measured differences, but it cannot guarantee control of unmeasured differences. Whether and how the analysis adjusted for cohort characteristics is not reported in the registry record.
The comparison also has unequal maximum follow-up windows: up to 5.5 years in SCOUT and 22.5 years in the external historical control. These maxima do not establish that every participant was observed for the full period. In general, unequal follow-up can affect the amount and timing of information available, making follow-up summaries and numbers at risk useful for interpretation. These details are not reported in the registry record.
What does a planning calculation mean?
In general, a sample-size calculation estimates how much information a future study might need under specified assumptions. The registry describes a planning illustration based on the observed effect, a two-sided significance level of 0.05, equal allocation, and a normal approximation; the effect to detect is described as a stated fraction of the observed effect. For time-to-event outcomes, the described totals concern events, while other planning quantities concern participants per arm. These are planning illustrations, not observed power and not evidence that the study was designed to achieve a particular power. The actual planning values are not reported in the registry record, and the calculation is not identified as the trial’s own design justification.
Overall, the record gives the endpoint definition and indicates the intended use of a median and confidence interval, with sponsor-reported hazard ratios used for interpretation. It does not report the estimates or enough methodological detail to independently assess their calculation. Statistical concepts above are general explanations, not claims that a particular unreported method was used.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 7 outcome measures and 10 analyses. It names secondary outcomes concerning time to subsequent systemic treatment, time to mutilating surgery including limb amputation, time to first radiation therapy, time to complete surgical resection, overall survival, and treatment discontinuation due to treatment-emergent adverse events. The registry record does not report how the analyses were organized across outcomes, cohorts, or subgroups.
When several outcomes or analyses are examined, the chance of obtaining at least one apparently unusual result can increase. In general, prespecified testing procedures or adjustments can help control this multiplicity, while clearly labeling exploratory analyses helps readers distinguish them from confirmatory tests. Whether a multiplicity adjustment, testing hierarchy, or other prespecified strategy was used is not reported in the registry record. The primary endpoint is identified, but the record does not describe how secondary analyses relate to it statistically.
The registry does not report missing-data amounts, reasons for missingness, or methods for handling missing endpoint or covariate information. In general, missing information can affect an estimate if its occurrence is related to participant characteristics or outcomes. The impact depends on what is missing and on the assumptions and methods used; these cannot be assessed from the registry information available.
Analysis populations are also not described in sufficient detail. The listed enrollment is 93, but the registry record does not report endpoint-specific analysis counts, exclusions, or the handling of participants without adequate follow-up. It does not report whether analyses used all eligible cohort members or a defined subset. These omissions limit assessment of how the analyzed populations relate to the intended cohorts and how complete the outcome information was.
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 |
|---|---|---|---|
| Larotrectinib | 1 | 51 | 2.0% |
| External Controls | 3 | 42 | 7.1% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Larotrectinib | 1 of 51 |
| External Controls | 3 of 42 |
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 |
|---|---|
| Larotrectinib | 0 of 51 |
| External Controls | 0 of 42 |
Most frequent serious adverse event terms
| Event term | Organ system | Larotrectinib | External Controls |
|---|---|---|---|
| Death | General disorders | 1 of 51 | 3 of 42 |
Serious events with the highest arm-level rate: death (7.1%).
The registry’s adverse-event information lists serious events and other affected participants separately for the larotrectinib and external-control groups. For larotrectinib, the serious-event fields report 1 affected participant among 51 at risk; the other-event fields report 0 affected among 51 at risk, and the death count is 1. For external controls, the serious-event fields report 3 affected among 42 at risk; the other-event fields report 0 affected among 42 at risk, and the death count is 3. The registry also lists Death as the top serious term, with 7.1%.
These are descriptive registry figures. The record does not provide enough detail to determine from these figures alone the timing, cause, relationship to treatment, or clinical circumstances of each death. The death counts should not be interpreted as establishing that treatment caused or prevented deaths. The groups are observational and are not a like-for-like randomized comparison.
In general, adverse-event counts depend on how events were defined, collected, and attributed, as well as on the amount of follow-up. The registry record does not report further event-level detail or an adjusted safety comparison. The figures therefore describe the recorded counts, not a causal estimate of comparative safety.
12. What the Result Does, and Does Not, Mean
The registry record sets out an observational comparison of larotrectinib-treated SCOUT participants with external historical controls and defines time to medical treatment failure as the primary endpoint. It also describes the endpoint’s component events and the different maximum follow-up windows. However, the primary median, its 95% confidence interval, and a hazard-ratio estimate are not reported in the registry record. The magnitude, direction, and precision of the primary comparison therefore cannot be interpreted from the record.
Even when numerical estimates are available, a historical comparison requires caution. In general, cohort differences can influence observed outcomes, and adjustment for measured characteristics cannot necessarily address unmeasured differences. The registry notes that the arms are not a like-for-like control comparison and does not report analysis details sufficient to assess confounding control. A difference between groups would not, on its own, establish that treatment caused the difference.
The composite endpoint also has limits as a summary. It combines subsequent systemic treatment, radiation therapy, mutilating surgery, and death. A single time-to-event estimate would not identify which component contributed most to an observed pattern. The registry lists related secondary outcomes, but their numerical results are not reported in the registry record.
The adverse-event counts are descriptive, not a randomized safety comparison. The registry record does not supply event-level context or an adjusted comparison. Likewise, the listed enrollment does not reveal how many participants contributed to each specific outcome analysis.
The record’s planning illustration should be read as a hypothetical design aid based on stated assumptions, not as observed power or proof that a study had a particular probability of detecting an effect. Overall, the registry supports describing the study question, design, endpoint, and some safety counts. It does not support a numerical conclusion about comparative effectiveness or a causal conclusion about treatment.
13. Why This Trial Matters Statistically
This study addresses a comparison that is difficult to evaluate using a conventional randomized design within the information available in the registry record: it places data from a larotrectinib study alongside an external historical cohort for a rare pediatric cancer. Statistically, the central challenge is not only estimating an outcome but judging whether the cohorts are sufficiently comparable for the contrast to be informative.
The primary endpoint is time to medical treatment failure, a time-to-event measure with a composite definition. Such endpoints can retain information about when events occur and can accommodate participants with different follow-up, provided the analysis handles censoring appropriately. The record does not report the primary estimate or enough analysis detail to assess that handling, so the statistical question is clearly defined but its numerical answer is unavailable in the registry record.
The comparison also illustrates why study design and statistical adjustment cannot be separated. Historical controls may differ from the treatment cohort in ways that matter for the outcome. Adjustment can help with measured differences, but the adequacy of any adjustment depends on the data collected and the assumptions made. The registry does not report those details. The unequal maximum follow-up windows further make transparent reporting of follow-up and numbers at risk important.
Finally, the endpoint combines several events, and the registry lists multiple secondary outcomes and analyses. Clear reporting of component results, analysis populations, missing data, and multiplicity procedures would help readers understand how robustly the evidence addresses the question. These are general statistical considerations; the relevant details are not reported in the registry record. The example therefore highlights both the potential role of external comparisons and the limits on inference when key estimates and methods are unavailable.
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 does not report the primary median time to medical treatment failure, its confidence interval, or a hazard-ratio estimate. Without these values, the direction, size, and precision of the primary comparison cannot be assessed. The record also does not report component-specific results for the events included in the composite endpoint.
The comparison uses external historical controls and is observational. The record states that the arms are not a like-for-like control comparison, and allocation is not stated. Cohort eligibility and construction, baseline characteristics, adjustment methods, and checks for remaining differences are not reported in the registry record. These omissions prevent assessment of how comparable the cohorts were or how far confounding may affect an estimate.
The maximum follow-up windows differ: up to 5.5 years for SCOUT participants and 22.5 years for external historical controls. The registry does not report actual follow-up distributions, censoring information, or numbers at risk over time. It also does not report endpoint-specific analysis populations, exclusions, or missing-data methods. Thus, the listed enrollment does not indicate how much information supports each endpoint analysis.
The record identifies multiple outcomes and analyses but does not report a multiplicity strategy, analysis hierarchy, or which analyses were prespecified. The statistical analysis plan and detailed modeling assumptions are not reported. These limitations constrain assessment of both the reliability of any comparison and the degree to which secondary findings should be viewed as confirmatory. The safety figures are also descriptive and lack event-level context in the registry record.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: A Study Called EPI VITRAKVI to Compare Treatment Results in Patients With Infantile Fibrosarcoma (IFS), a Type of Connective Soft Tissue Cancer, Who Received a Treatment Called Larotrectinib From a Study Called SCOUT With Patient Data From an External Database — NCT05236257.
- Registry record last updated 2024-12-10; status last verified 2024-12.
- Results first posted 2024-12-10.
- 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.
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18. Record Summary
This completed observational study compares pediatric patients with NTRK gene fusion-positive infantile fibrosarcoma who received larotrectinib in the SCOUT study with patients in eligible external historical cohort(s) described as standard care. The listed enrollment is 93, and Bayer is the sponsor. The study began on 2022-03-10 and has a primary completion date of 2022-09-13.
The primary endpoint is median time to medical treatment failure, defined from treatment start to the earliest of subsequent systemic treatment, radiation therapy, mutilating surgery, or death from any cause. The registry specifies a 95% confidence interval and different maximum follow-up windows for the cohorts. It does not report the primary estimate, interval limits, or hazard-ratio value. Cohort comparability, analysis populations, missing-data handling, and multiplicity methods are also not reported in the registry record.
The registry includes descriptive serious-event figures and identifies several secondary outcomes. These details do not establish a causal treatment effect. The study design and available result information support describing the intended comparison, but not drawing a numerical conclusion about comparative outcomes.