Sorafenib in Treating Patients With Malignant Gastrointestinal Stromal Tumor That Progressed During or After Previous Treatment With Imatinib Mesylate and Sunitinib Malate: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Sorafenib in Treating Patients With Malignant Gastrointestinal Stromal Tumor That Progressed During or After Previous Treatment With Imatinib Mesylate and Sunitinib Malate (NCT00265798), a na phase 2 study. The primary outcome is Objective Response Rate.

2. Clinical Question

The clinical context is treatment-resistant gastrointestinal stromal tumor, as defined in the study title and summary. The summary states that sorafenib may inhibit enzymes needed for tumor-cell growth and may block blood flow to a tumor. These are proposed mechanisms in the trial description, not evidence of a clinical response. The design addresses whether objective responses were observed in this selected setting; without a control group, it cannot establish how outcomes compare with another treatment or with no study treatment. Progression-free survival and overall survival are listed as secondary outcomes, but their results are not reported in the registry record.

3. Trial Design

The registry identifies NCT00265798 as a phase 2 study of sorafenib for imatinib- and sunitinib-resistant gastrointestinal stromal tumor. The sponsor is the National Cancer Institute (NCI). The study started on 2005-09-14, and the primary completion date is 2010-02-11. Its status is active, not recruiting. The record lists enrollment of 38 and one treatment group, described as sorafenib tosylate.

This is a single-group, nonrandomized design: allocation is NA, and masking is NONE. Participants received oral sorafenib twice daily on days 1-28; courses repeated every 28 days in the absence of disease progression or unacceptable toxicity. Since there is no concurrent comparator, the design can describe outcomes observed under the study regimen but cannot isolate a treatment effect from the natural course of disease, participant selection, or other influences. It is not a like-for-like comparison of treatment arms.

The primary outcome is objective response rate, assessed using RECIST. The record defines objective response as complete response plus partial response. Disease reassessment by CT was scheduled before therapy and every 8 weeks. Following initial documentation of objective response, confirmatory scans were to be obtained 4 weeks later. The primary outcome timeframe is up to 5 years. Progression-free survival and overall survival are listed as secondary outcomes.

The enrollment figure is not itself an outcome result. It does not reveal how many participants had an evaluable response assessment, how many responded, or how long participants remained on treatment. Those details are not reported in the registry record. The record also does not report a detailed statistical analysis plan, eligibility criteria beyond the disease and treatment-resistance description, or the handling of treatment discontinuation. Because no endpoint estimates or analyses are reported, the clinical question and measurement schedule can be described, but the size and precision of any observed response cannot be assessed from the registry record.

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 Objective Response Rate, measured over Up to 5 years.

Objective response rate captures the proportion of participants whose tumors meet the study's criteria for complete or partial response. Under the registry's RECIST description, complete response means disappearance of all target lesions. Partial response requires at least a 30% decrease in the sum of the longest diameters of target lesions, using the baseline sum as the reference. The endpoint combines these response categories rather than measuring a change in symptoms, duration of response, or survival.

Response is used as an indicator of measurable tumor shrinkage. It offers a defined way to summarize imaging findings, but does not by itself describe how long a response lasts or whether a participant's disease remains controlled. Those are different questions; progression-free survival and overall survival are listed as secondary outcomes in this study.

CT reassessment was scheduled before therapy and every 8 weeks, with a confirmatory scan 4 weeks after an initial objective response was documented. Confirmation is intended to check that an apparent response is supported on a subsequent assessment. The endpoint timeframe is up to 5 years. The registry record does not report the number of complete or partial responses, the response percentage, or its 95% confidence interval, so the endpoint's observed value and precision cannot be described.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical methods determine how an outcome is summarized and how much uncertainty surrounds that summary. In this study, the primary outcome is objective response rate, defined as complete response plus partial response under RECIST. A response rate is a proportion: it relates the number meeting the response definition to an appropriate set of assessed participants. The registry record does not report the response count, denominator, estimate, or 95% confidence interval. It is therefore not possible to explain a numerical response estimate or verify which analysis population was used.

What does the confidence interval represent?

A confidence interval expresses uncertainty around an estimated quantity. For a response proportion, it would show a range of values compatible with the observed data under the method's assumptions. A narrower interval generally indicates greater precision; a wider interval indicates more uncertainty. The registry lists 95% Confidence Interval as the primary outcome's dispersion measure, but the actual interval is not reported in the registry record. Without the estimate, interval limits, and analysis denominator, precision cannot be assessed.

Confidence intervals do not remove design limitations. In a single-group trial, an interval around a response rate would quantify sampling uncertainty for the treated group under the chosen method. It would not create a comparison group, control confounding, or show what would have happened to the same participants under another treatment. The allocation is listed as NA, masking as NONE, and the model as SINGLE GROUP. The record therefore describes no randomized contrast to which a treatment-difference interval could apply.

How does response assessment affect the endpoint?

RECIST provides operational criteria for classifying imaging changes. In this record, complete response is disappearance of all target lesions, and partial response requires at least a 30% decrease in the sum of the longest diameters relative to baseline. CT assessments were scheduled before therapy and every 8 weeks. A confirmatory scan was scheduled 4 weeks after initial documentation of objective response. Such rules help make the endpoint more consistent, but actual assessment can still depend on scan availability, timing, and whether participants remain under observation. Assessment completion and missing-scan handling are not reported in the registry record.

The response endpoint is different from time-to-event outcomes. Progression-free survival and overall survival are listed as secondary outcomes, but the registry does not provide their definitions, event counts, follow-up summaries, or estimates. Methods for censoring, handling incomplete follow-up, and estimating survival are not reported in the registry record. Those methods should not be inferred from the outcome names alone.

What can planning calculations show?

Planning illustrations are not observed results and are not observed power. The stated illustration assumptions use a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect defined as a stated fraction of the observed effect. For time-to-event outcomes, the planning approach uses a total number of events; for other outcomes, it gives participants per arm. These are planning conventions, not the design of this study: the registry identifies this trial as single-group, with no randomized two-arm comparison. The actual planning values and the observed effect used for such illustrations are not reported in the registry record. They should not be read as evidence that the study achieved a particular power or as a description of its actual enrollment allocation.

In general, over-dispersion means that observed variability exceeds what a simpler statistical model assumes. If a model ignores that extra variability, uncertainty can be understated and intervals can be too narrow. No over-dispersion model or related adjustment is reported for this study, and the primary endpoint is not reported with an analysis method beyond the stated response definition and confidence-interval measure. Accordingly, no claim about model adequacy or adjusted inference is possible.

Why does the analysis population matter?

An analysis population defines which participants contribute to a result. Possible choices in clinical research can include all enrolled participants or only those with adequate outcome assessments, but the choice and its consequences depend on the protocol and analysis plan. The registry record does not report the primary analysis population, how participants without evaluable scans were handled, or whether analyses followed treatment assignment or treatment received. In a single-group study, that missing information still matters: exclusions or incomplete assessments can affect the denominator and the interpretation of a response proportion.

There are no reported outcome analyses in the record. The number of analyses is listed as 0. No p-value, adjusted estimate, prespecified hypothesis-testing procedure, or interim-analysis plan is reported in the registry record. General statistical concepts can explain what such methods would mean, but they cannot supply missing trial-specific results. The most defensible reading is therefore descriptive: the registry specifies a response endpoint and assessment schedule, while the numerical outcome and the methods used to analyze it remain unreported.

10. Multiplicity, Missing Data and Analysis Populations

Multiplicity arises when researchers evaluate several outcomes, time points, subgroups, or statistical tests. When many questions are tested, the chance of at least one apparently notable result can increase unless the analysis plan accounts for that multiplicity. This is a general statistical concern, not a claim that the study performed a particular set of tests. The registry lists objective response rate as the primary outcome and progression-free survival and overall survival as secondary outcomes. A full testing hierarchy, adjustment strategy, and interim-analysis plan are not reported in the registry record.

The registry record lists 0 analyses, so it does not provide outcome estimates or tests from which to assess multiplicity in practice. It also does not report subgroup analyses or repeated testing procedures. These details should not be guessed from the phase or the endpoint list.

Missing data can affect an outcome when participants do not have an assessment, leave follow-up, or lack the information needed for classification. For a response proportion, the denominator and rules for unassessable participants can influence the estimate. The record does not report how missing scans, unevaluable responses, treatment discontinuation, or incomplete follow-up were handled. It does not state which participants were included in the primary analysis population.

These omissions limit interpretation of both the size and reliability of an outcome estimate. They do not establish that data were missing or that a particular analysis was used; they mean the relevant methods are not reported in the registry record. Similarly, no details are reported about imputation or sensitivity analyses. With no primary result or analysis population reported, readers cannot determine how missingness or multiple outcome testing may have affected the findings.

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: gastrointestinal hemorrhage (5.3%), thrombosis (2.6%), rash (2.6%), diarrhea (2.6%), dehydration (2.6%).

The registry record reports a serious-adverse-event group titled Sorafenib, with 38 participants at risk and 5 affected. It separately reports 38 at risk and 23 affected for other adverse events. These are event summaries, not a randomized comparison. The record does not state whether participants could contribute to more than one event term, so the figures should not be added or treated as mutually exclusive categories.

The serious-event terms listed include gastrointestinal hemorrhage at 5.3%, and thrombosis, rash, diarrhea, dehydration, and hypertension at 2.6% each. These percentages describe the registry's listed event terms; they do not establish that the treatment caused an event. The record does not provide event-level timing, duration, severity grading details, or participant-level overlap in the information. Deaths are not reported in the registry record.

At-risk counts indicate the group considered for the adverse-event summary; they do not tell readers how long each participant was observed. The record does not provide exposure duration or a comparison group, so these figures should be read as descriptive safety reporting rather than a rate comparison or a causal estimate. They also do not replace the missing primary efficacy result.

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

The study addresses a defined clinical setting: gastrointestinal stromal tumor that progressed during or after imatinib mesylate and sunitinib malate. It describes a phase 2, single-group regimen of oral sorafenib and identifies objective response under RECIST as the primary endpoint. That design can be used to describe response observations among treated participants if results are reported. In this registry record, the numerical response result is not reported.

Without a response estimate and its confidence interval, the record does not show the frequency of complete or partial response or the precision of an estimated response rate. It is not possible to conclude from the absence of those results that there were no responses. The registry gives the endpoint definition and assessment schedule, not the outcome value.

Even if a response rate were available, a single-group study would not establish a randomized treatment difference. There is no concurrent control arm, and allocation is listed as NA. The study can describe outcomes in its enrolled group, but it cannot directly distinguish the effect of sorafenib from other influences or establish how outcomes would compare under another treatment.

The record lists progression-free survival and overall survival as secondary outcomes but does not report their results or analysis methods. It also does not report the primary analysis population, missing-data handling, or the details needed to evaluate follow-up completeness. The serious and other adverse-event summaries provide descriptive safety information, but they do not establish causality or comparative risk.

The registry summary describes proposed ways sorafenib may affect tumor growth. A proposed biological rationale is not an observed clinical outcome. The record therefore supports a clear account of what was studied and how response was intended to be measured, but not a conclusion about the size, precision, or comparative meaning of an efficacy result.

13. Why This Trial Matters Statistically

This trial is statistically informative as an example of the distinction between a research question, a study design, and a reported result. The registry identifies a specific population with disease progression during or after prior imatinib and sunitinib, a single-group sorafenib regimen, and an imaging-based primary endpoint. It also supplies operational response criteria and a schedule for CT reassessment. Those details define what an outcome would mean if its estimate were reported.

The single-group design is central to interpretation. It can describe outcomes observed in the treatment group, but it does not estimate a randomized contrast with a concurrent comparator. Recognizing this prevents an observed proportion, if reported, from being mistaken for proof of a treatment effect or a comparative advantage. In this record, even the response proportion itself is not reported, making restraint especially important.

The record also illustrates why precision and analysis details matter. A response estimate would need its denominator and confidence interval for readers to judge uncertainty. The population included in the analysis, handling of missing assessments, and follow-up methods would further shape interpretation. Those details and the endpoint result are not reported in the registry record. Enrollment alone cannot substitute for them.

Finally, the safety summaries and proposed mechanism answer different questions from objective response. Adverse-event counts describe reported events, while biological rationale explains why the treatment was studied; neither supplies the missing response estimate. Keeping these evidence types separate helps readers avoid turning a study rationale or descriptive safety report into a claim about efficacy.

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 of the registry record for interpreting this study is that it does not report the primary outcome estimate. The number of complete or partial responses, response percentage, and 95% confidence interval are not reported in the registry record. The listed enrollment of 38 does not establish how many participants had evaluable imaging or contributed to an outcome analysis.

The single-group design has no concurrent comparator. Therefore, the study design cannot provide a randomized comparison with another treatment or separate treatment effects from other influences. Allocation is listed as NA and masking as NONE. The registry record does not describe a detailed statistical analysis plan or explain whether the outcome analysis used any adjustment.

Several factors needed to assess the endpoint are also not reported: the primary analysis population, handling of participants without evaluable scans, missing-data methods, and follow-up completeness. Although CT assessment was scheduled before therapy and every 8 weeks, with confirmation 4 weeks after an initial response, the record does not report how many assessments occurred or how deviations from that schedule were handled.

Progression-free survival and overall survival are listed as secondary outcomes, but their results and analysis details are not reported in the registry record. The registry also does not report an interim-analysis plan, multiplicity procedure, or subgroup analyses. These absences do not demonstrate that such procedures or data were absent from the conduct of the study; they limit what can be established from the registry record.

Safety summaries are descriptive and lack a concurrent comparison. The record does not report deaths, event timing, exposure duration, or participant-level overlap among event terms. Consequently, the available information cannot support causal attribution or comparative safety conclusions.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Sorafenib in Treating Patients With Malignant Gastrointestinal Stromal Tumor That Progressed During or After Previous Treatment With Imatinib Mesylate and Sunitinib Malate — NCT00265798.
• Registry record last updated 2026-09-09; status last verified 2026-08.
• Results first posted 2014-01-21.
• 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

NCT00265798 is a phase 2, single-group study sponsored by the National Cancer Institute (NCI). It evaluates sorafenib tosylate in gastrointestinal stromal tumor that progressed during or after imatinib mesylate and sunitinib malate. The record lists enrollment of 38, status active, not recruiting, and primary completion on 2010-02-11.

The primary endpoint is objective response rate by RECIST, with a timeframe up to 5 years. CT assessment was scheduled before therapy and every 8 weeks, with confirmation 4 weeks after an initial objective response. Progression-free survival and overall survival are listed as secondary outcomes.

The registry record does not report the primary response estimate, its confidence interval, or the secondary outcome results. It provides descriptive adverse-event figures but no concurrent comparator. Analysis-population and missing-data methods are not reported in the registry record.