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 Phase 2 Study of S-1 in Advanced or Metastatic Pancreatic Cancer (NCT00651742), a na phase 2 study. The primary outcome is Overall Tumor Response Rate (ORR).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00651742 |
| Phase | Phase 2 |
| Condition | Locally Advanced or Metastatic Pancreatic Cancer |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 28 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Taiho Oncology, Inc. |
| Results posted | Yes |
2. Clinical Question
Population
The study concerned chemotherapy-naïve participants with locally advanced or metastatic pancreatic cancer. The primary efficacy population was described as participants in the safety population who met key eligibility criteria, had measurable disease, and had at least one response assessment after starting treatment.
Intervention
Participants received S-1 at 30 mg/m^2 orally twice daily for 2 weeks, followed by a 1 week recovery period. Treatment was repeated every 3 weeks. The regimen description in the registry record ends before the full treatment-discontinuation criteria are stated.
Comparator
This was a single-group, non-randomized study, with no concurrent control group described. Its findings therefore characterize outcomes among participants receiving S-1; they do not provide a direct randomized comparison with another treatment or with no treatment.
Primary question
The primary endpoint was the overall tumor response rate: the percentage of participants whose best overall response was a complete response or partial response, assessed using RECIST. The primary response estimate and its confidence interval are not reported in the registry record.
3. Trial Design
The registry describes a phase 2, open-label, non-randomized, multicenter, two-stage study. Its model is single-group, and the listed intervention is S-1. The study enrolled 28 participants. The registry status is completed; the recorded start date is 2006-01-09 and the primary completion date is 2008-07-08.
In an open-label study, treatment assignment is not masked from participants or study personnel. In this single-group design, there is no concurrent randomized group against which to compare the observed response or safety outcomes. Consequently, the study can describe results among those treated, but differences from an external treatment or historical experience cannot be interpreted as a randomized treatment effect.
The official title calls the study two-stage, but the stage-specific rules, decision thresholds, and any stage-specific enrollment or stopping details are not reported in the registry record. A two-stage label alone does not establish how the stages affected recruitment or analysis. The record also does not report a statistical design justification or a target enrollment beyond the recorded enrollment.
The listed regimen was S-1 30 mg/m^2 orally twice daily for 2 weeks, followed by a 1 week recovery period; one cycle was described as 21 days, with treatment repeated every 3 weeks. The record’s regimen description ends partway through the stopping conditions, so the complete protocol for treatment continuation or discontinuation is not reported in the registry record.
The primary endpoint was overall tumor response rate. Secondary outcomes listed include disease control rate, duration of response, time to tumor progression, overall survival, progression-free survival, performance-status changes, pain-intensity change, and adverse events. Listing an outcome does not by itself establish that its result or analysis is reported.
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: The enrollment of Stage 2 of the study was not initiated, as sufficient efficacy per protocol was not demonstrated in Stage 1. Overall, 29 participants were screened, of them 28 participants were enrolled and 27 received study treatment in Stage 1.
Overall Study
| Stage | S-1 30 mg/m^2 |
|---|---|
| STARTED | 28 |
| Treated | 27 |
| Efficacy Analysis Per Investigator | 21 |
| Efficacy Analysis Per Independent Reader | 25 |
| COMPLETED | 0 |
| NOT COMPLETED | 28 |
Reasons for not completing this period:
| Reason | S-1 30 mg/m^2 |
|---|---|
| Objective Disease Progression | 22 |
| Toxicity | 3 |
| Investigator Judgment | 1 |
| Withdrawal of Consent | 1 |
| Enrolled but not treated | 1 |
Analysis population for the primary outcome, as defined in the registry: Primary efficacy population included all participants in the safety population who met the key eligibility criteria (1st line therapy in participants with measurable pancreatic locally advanced or metastatic disease) and had at least one response assessment after starting study treatment. Here, 'Number analyzed' signifies number of participants in the specified population.
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.
Population: Safety population included all participants who had received at least one dose of study treatment.
| Characteristic | Unit | S-1 30 mg/m^2 |
|---|---|---|
| Participants analysed | 27 | |
| Age, Continuous | years | 64.3 (SD 10.48) |
| Sex: Female, Male: Female | Participants | 13 |
| Sex: Female, Male: Male | Participants | 14 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 |
| Race (NIH/OMB): Asian | Participants | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 |
| Race (NIH/OMB): Black or African American | Participants | 0 |
| Race (NIH/OMB): White | Participants | 27 |
| Race (NIH/OMB): More than one race | Participants | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 |
6. Primary Endpoint
The registry lists the primary outcome as Overall Tumor Response Rate (ORR), measured over From first dose of study medication until disease progression, permanent discontinuation of study treatment, or death due to any cause, assessed up to 2 years 5 months.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | 95% Confidence Interval |
| Unit | percentage of participants |
| Endpoint classification | Binary Endpoint |
Overall tumor response rate (ORR) measures the percentage of participants whose best overall tumor response was a complete response (CR) or partial response (PR). The registry defines the endpoint using the best response across treatment cycles and states that response was assessed according to RECIST. CR and PR were determined from target and non-target lesion criteria, with specified requirements for lesion change and duration of response.
As a general statistical concept, a response rate is a binary-outcome summary: each participant is classified according to whether the endpoint definition was met, and the rate describes the proportion meeting it in the analyzed population. It offers a direct description of tumor response under the study’s assessment rules. It does not, by itself, show how long a response lasts, whether disease control persists, or how outcomes compare with those under another treatment.
The registry specifies a 95% confidence interval for the endpoint. In general, a confidence interval conveys uncertainty around an estimated response rate; its width depends on the amount of information and the observed response pattern. The numerical ORR estimate and confidence interval are not reported in the registry record, so the response level and its precision cannot be evaluated from the record.
The stated assessment window runs from the first dose until disease progression, permanent discontinuation of study treatment, or death due to any cause, assessed up to 2 years 5 months. The record does not report the numerical response result.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The primary endpoint is clearly defined, but the registry record does not report the numerical overall tumor response rate or its 95% confidence interval. Without those values, the central efficacy result cannot be described, and its precision cannot be judged. The definition alone explains what was to be measured; it does not establish how many participants met the response criteria.
The primary efficacy population was not simply described as everyone enrolled. It included participants in the safety population who met key eligibility criteria, had measurable locally advanced or metastatic pancreatic disease, and had at least one response assessment after starting study treatment. The registry text describing that population is cut off after beginning to clarify the meaning of “Num”; any further definition is not reported in the registry record. The number included in this efficacy analysis is also not reported in the registry record.
The single-group, non-randomized design is important when interpreting outcomes. A response rate among treated participants can be described, but the study does not provide a concurrent randomized control group for estimating a comparative treatment effect. Differences from outcomes reported in other settings could reflect differences in participants, assessment, follow-up, or other factors; the registry record does not provide a basis for resolving those possibilities.
The endpoint uses best response across cycles and RECIST criteria. These choices define what counts as a response, but the registry record does not report details such as the response-assessment schedule, independent review, or the method used to handle participants without an assessable response. Such details can affect how a response rate is interpreted and are not to be inferred from the endpoint definition.
Safety information is reported for a group at risk of 27 participants: 15 were reported with serious adverse events, 25 with other adverse events, and 24 deaths. The registry lists selected serious-event terms with percentages. These figures describe the registry’s safety reporting; they do not establish that S-1 caused each event or death. The event attribution rules and fuller context for the death count are not reported in the registry record.
In general, an estimate and its uncertainty should be considered together. A confidence interval helps readers distinguish a more precisely estimated rate from one with substantial uncertainty, but it cannot remove design limitations or unmeasured sources of bias. Here, because the primary estimate and interval are not reported, a quantitative assessment of response and precision is not possible from this record.
9. Statistical Methods Explained
The primary endpoint is a proportion: the percentage of participants with a best overall response of complete response or partial response. In general, a proportion summarizes a binary classification, in this case whether the response criteria were met. Its interpretation depends on both the response definition and the population in which the proportion is calculated.
What does the confidence interval add?
The registry specifies a 95% confidence interval for ORR, but it does not report the interval’s values or the method used to calculate it. In general, a confidence interval is a range of values compatible with the data under the assumptions of the statistical procedure. It expresses sampling uncertainty, rather than the range of outcomes expected for individual participants. Narrower intervals generally indicate greater precision, while wider intervals indicate greater uncertainty. The interval does not correct for selection, measurement, or design limitations.
Because the numerical response estimate and interval are not reported in the registry record, neither their magnitude nor their precision can be described. It would not be appropriate to reconstruct them without the response count, analysis denominator, and calculation method. The enrollment figure alone is not enough to recover those quantities, particularly because the registry defines a primary efficacy population with eligibility and response-assessment requirements.
How does RECIST shape the endpoint?
The registry states that tumor response was assessed according to RECIST. It defines CR and PR using target and non-target lesion criteria and specifies minimum durations for these classifications. The endpoint uses best overall response across treatment cycles, rather than a response at a single specified visit. This means the endpoint classification relies on the sequence of assessments, as well as the lesion criteria. The record does not report the assessment schedule, whether assessments were reviewed independently, or how missing or unevaluable assessments were handled.
As a general concept, outcome definitions improve consistency by stating which observations count as events. They do not guarantee that assessments were complete or comparable across participants. Interpretation therefore depends on both the stated response rules and the details of how those rules were implemented. Any unreported implementation detail remains unknown from the registry record.
Why does the study design affect interpretation?
This was an open-label, non-randomized, single-group phase 2 study. In general, a single-group estimate describes outcomes observed in the treated group. Without a concurrent randomized control group, it cannot isolate a treatment contrast from differences in prognosis, participant selection, follow-up, or other influences. Open-label conduct can also matter for outcomes involving judgment or reporting, although the record does not establish whether or how this affected response assessment.
The official title identifies a two-stage design. In general, staged designs can use results from an earlier stage to guide continuation, but the registry record does not report the stage rules, decision boundaries, or analysis plan. It is therefore not possible to explain what role staging played in this particular study or whether it affected the reported efficacy analysis.
What do planning calculations represent?
Any sample-size planning illustration associated with the posted results is based on the observed effect, not on the trial’s own design. The stated illustration 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. For time-to-event outcomes, the illustration concerns the total number of events using Schoenfeld; other outcomes are expressed as participants per arm.
In general, such figures describe hypothetical planning under specified assumptions. They are not observed power, do not establish what the original investigators planned, and do not show that the study was designed to detect the illustrated effect. The registry record does not report the trial’s own sample-size justification or the statistical plan that governed any such planning.
What does over-dispersion mean in general?
For outcomes summarized as counts or rates, over-dispersion means that variability exceeds what a simple model assumes. If it is ignored, standard errors and uncertainty intervals may be too small, making results appear more precise than warranted. This is a general statistical issue; the primary endpoint is a response percentage, and the registry record does not report a model-based analysis addressing over-dispersion.
More broadly, the record does not report the ORR calculation method, the confidence-interval procedure, covariate adjustment, or a statistical analysis plan. No adjusted or unadjusted efficacy analysis result is reported in the registry record. General statistical explanations cannot fill these reporting gaps or substitute for the underlying analysis.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists several secondary outcomes in addition to ORR, including disease control, response duration, time to tumor progression, overall survival, progression-free survival, performance-status change, pain-intensity change, and adverse events. Considering multiple outcomes can raise a multiplicity issue: when many hypotheses are tested, the chance of at least one apparently notable finding can increase. As a general statistical approach, investigators may prespecify a hierarchy or adjust inference across outcomes. The registry record does not report whether any multiplicity strategy was specified or used.
The record does not report how missing outcome data were handled, how participants without a response assessment were classified, or whether any sensitivity analyses were conducted. This matters because the primary efficacy population required at least one response assessment after treatment began. The registry does not state how the analysis treated participants who did not meet that assessment condition or explain the number included in the primary analysis.
The record describes the primary efficacy population by eligibility, measurable disease, and assessment requirements, but the population definition is truncated. Further details are not reported in the registry record. The safety group at risk is reported as 27; the record does not provide enough information to equate that group with the efficacy analysis population.
In general, an analysis population should be described clearly because exclusions or missing measurements can affect what an estimate represents. The registry does not report a full analysis-population flow, the handling of protocol deviations, or the approach to missing data. It also does not report the statistical analysis plan or any interim-analysis details. Those methods should not be inferred from the study’s phase or its two-stage title.
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 |
|---|---|---|---|
| S-1 30 mg/m^2 | 15 | 27 | 55.6% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| S-1 30 mg/m^2 | 24 of 27 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| S-1 30 mg/m^2 | 25 of 27 |
Most frequent serious adverse event terms
| Event term | Organ system | S-1 30 mg/m^2 |
|---|---|---|
| Abdominal pain | Gastrointestinal disorders | 4 of 27 |
| Disease progression | General disorders | 4 of 27 |
| Diarrhoea | Gastrointestinal disorders | 2 of 27 |
| Neoplasm progression | Neoplasms benign, malignant and unspecified (incl cysts and polyps) | 2 of 27 |
| Ascites | Gastrointestinal disorders | 1 of 27 |
| Constipation | Gastrointestinal disorders | 1 of 27 |
| Duodenal stenosis | Gastrointestinal disorders | 1 of 27 |
| Vomiting | Gastrointestinal disorders | 1 of 27 |
| Fatigue | General disorders | 1 of 27 |
| General physical health deterioration | General disorders | 1 of 27 |
Most frequent non-serious adverse event terms
| Event term | Organ system | S-1 30 mg/m^2 |
|---|---|---|
| Nausea | Gastrointestinal disorders | 10 of 27 |
| Fatigue | General disorders | 10 of 27 |
| Diarrhoea | Gastrointestinal disorders | 9 of 27 |
| Vomiting | Gastrointestinal disorders | 9 of 27 |
| Weight decreased | Investigations | 9 of 27 |
| Abdominal pain upper | Gastrointestinal disorders | 7 of 27 |
| Lacrimation increased | Eye disorders | 6 of 27 |
| Constipation | Gastrointestinal disorders | 6 of 27 |
| Flatulence | Gastrointestinal disorders | 5 of 27 |
| Anorexia | Metabolism and nutrition disorders | 5 of 27 |
Serious events with the highest arm-level rate: abdominal pain (14.8%), disease progression (14.8%), diarrhoea (7.4%), neoplasm progression (7.4%), ascites (3.7%).
The registry reports safety figures for the S-1 group with 27 participants at risk: 15 participants were reported with serious adverse events, 25 with other adverse events, and 24 deaths. These are separate reported safety counts. They should not be added together, since the record does not indicate that the categories are mutually exclusive, and the counts may describe overlapping participants or different event definitions.
The listed serious-event terms include abdominal pain and disease progression at 14.8% each; diarrhoea and neoplasm progression at 7.4% each; and ascites and constipation at 3.7% each. These are the percentages reported in the registry record. They describe recorded event terms, not a causal assessment of S-1. The registry also does not report the full event-level details, timing, or attribution basis alongside these selected terms.
In general, serious adverse events are a safety category and should not be treated as interchangeable with all adverse events. A listed term may reflect an event occurring during a study without establishing that the study treatment caused it. Likewise, the death count alone does not show cause of death or treatment attribution. Those details are not reported in the registry record.
12. What the Result Does, and Does Not, Mean
The registry record describes a phase 2 study of S-1 in chemotherapy-naïve participants with locally advanced or metastatic pancreatic cancer and identifies ORR as its primary endpoint. It explains that response was based on best overall response across cycles and assessed according to RECIST. These details clarify the intended clinical question and the endpoint’s classification rules.
The numerical ORR and its 95% confidence interval are not reported in the registry record. As a result, the record does not support a statement about the observed response level or how precisely it was estimated. The endpoint definition is not itself an efficacy result.
The design also limits what can be concluded comparatively. Because this was a non-randomized, single-group study, its outcomes do not constitute a randomized comparison with another treatment. A response or safety observation in this group cannot, on its own, establish what would have happened to comparable participants under a different treatment or without treatment.
The safety figures describe reported counts and selected serious-event percentages, but do not establish causation. The reported deaths likewise cannot be attributed to treatment based on the counts alone. Details about event attribution and the relationship between the safety and efficacy populations are not reported in the registry record.
In general, interpreting a clinical trial result requires the estimate, its uncertainty, the population analyzed, and the design context. Here, key efficacy results and several analysis details are not reported in the registry record. The available information therefore supports a description of the study’s design, endpoint, and selected safety reporting, but not a quantitative conclusion about the primary response outcome or a causal comparative effect.
13. Why This Trial Matters Statistically
This study illustrates why an endpoint definition and an endpoint result are not interchangeable. ORR is defined as the percentage of participants whose best overall response was CR or PR under RECIST, and the registry specifies a 95% confidence interval. Yet the numerical estimate and interval are not reported in the registry record. Without them, readers cannot assess either the observed response level or its statistical precision.
It also highlights the importance of identifying the analysis population. The primary efficacy population had stated eligibility and response-assessment conditions, while the safety group at risk is reported separately. The primary efficacy population description is truncated, and the number analyzed for ORR is not reported in the registry record. Enrollment alone does not resolve which participants contributed to a particular endpoint estimate.
The single-group design makes the distinction between description and comparison especially important. Results from a treated group can describe what was recorded among those participants, but there is no concurrent randomized group in this study to support a direct causal comparison. This is a design feature, not a problem that can be resolved by statistical terminology after the fact.
Finally, the record includes a list of secondary outcomes and selected safety information, but does not report a multiplicity approach, missing-data handling, or the complete statistical analysis plan. In general, these details help readers understand how multiple outcomes, incomplete observations, and analysis choices influence interpretation. Their absence underscores why transparent reporting of estimates and methods is essential to statistical assessment.
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 record does not report the ORR estimate or its 95% confidence interval. The numerical result, response count, and ORR analysis denominator are not reported in the registry record. Consequently, the primary efficacy finding cannot be assessed from the information described.
The primary efficacy population description is incomplete: the registry text ends while defining “Num”. It does state that participants needed to be in the safety population, meet key eligibility criteria, have measurable disease, and have at least one response assessment after starting treatment. The remaining population details and the count analyzed are not reported in the registry record.
The study was open-label, non-randomized, and single-group, with no concurrent control group described. This limits comparative interpretation. The official title identifies a two-stage design, but stage-specific rules and their effect on analysis are not reported. The full regimen description is also truncated before its stopping conditions are complete.
Other methods relevant to interpretation are not reported in the registry record, including the ORR calculation and confidence-interval methods, the missing-data approach, multiplicity handling, analysis-plan details, and interim-analysis procedures. The safety counts and selected serious-event terms do not provide event attribution or a complete account of timing. These gaps constrain interpretation and should not be filled by assumptions about typical phase 2 practice.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Phase 2 Study of S-1 in Advanced or Metastatic Pancreatic Cancer — NCT00651742.
- Registry record last updated 2024-09-19; status last verified 2024-08.
- Results first posted 2021-12-10.
- 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
The registry describes a completed, open-label, non-randomized, multicenter, single-group phase 2 study of S-1 in chemotherapy-naïve participants with locally advanced or metastatic pancreatic cancer. Enrollment was 28. The primary endpoint was ORR, defined as the percentage with a best overall response of complete or partial response under RECIST, with a stated 95% confidence interval.
The numerical ORR and confidence interval are not reported in the registry record. The primary efficacy population required specified eligibility and at least one post-treatment response assessment, but its description is truncated and its analysis count is not reported. Safety reporting lists 15 participants with serious adverse events, 25 with other adverse events, and 24 deaths among a group at risk of 27. The record does not establish treatment causation for those events or deaths.