Siltuximab and Spartalizumab in Patients With Metastatic Pancreatic Cancer: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Siltuximab and Spartalizumab in Patients With Metastatic Pancreatic Cancer (NCT04191421), a non-randomized phase 1, phase 2 study. The primary outcome is Maximal Tolerated Dose (MTD) of Siltuximab That Can be Combined With Spartalizumab.

2. Clinical Question

The study asks whether a dose of siltuximab can be identified for use with spartalizumab in people with metastatic pancreatic cancer. Its primary question is about dose and tolerability, not a randomized comparison of the combination against another treatment.

The registry also names overall response rate, response duration, progression-free survival, and overall survival time as secondary outcomes. Those outcomes could address tumor response and time-to-event questions, but the record does not report their results. The available information therefore describes the questions the trial set out to address without establishing an answer about the primary dose endpoint or the secondary outcomes.

3. Trial Design

This was a phase Ib/II, non-randomized, unmasked, sequential trial sponsored by Emory University. The registry records a start date of 2020-01-17, a primary completion date of 2023-04-05, a status of completed, and enrollment of 35. These are record-level design and conduct details; completion status does not itself indicate what the endpoint results were.

The phase I descriptions specify three siltuximab dose levels with spartalizumab: 6 mg/Kg, 11 mg/Kg, and 9 mg/Kg. Each description gives spartalizumab 300 mg intravenously over 30 minutes on day 1 and siltuximab intravenously over 1 hour on day 1. The listed cycles repeat every 3 weeks in the absence of disease progression or unacceptable toxicity. The phase II description uses spartalizumab 300 mg and a siltuximab dose determined in the phase I arms; it does not state the selected dose in the results information.

The sequential structure is relevant to interpretation. Participants were not randomly allocated between arms, and the registry explicitly cautions that the arms are not a like-for-like control comparison. Dose levels can be part of a dose-finding sequence rather than parallel groups intended to estimate treatment differences. No allocation details beyond the non-randomized sequential design, and no explanation of how the sequence was administered, are reported in 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 Maximal Tolerated Dose (MTD) of Siltuximab That Can be Combined With Spartalizumab, measured over Up to 6 weeks from study start.

The primary endpoint is the maximal tolerated dose of siltuximab that can be combined with spartalizumab, expressed in mg/kg. The registry defines this as the dose at which less than one-third of subjects experience a dose-limiting toxicity during the first 6 weeks of treatment. A dose-limiting toxicity is an adverse event or abnormal laboratory value occurring within that period and assessed as definitely at least possibly related to study treatment. The registry says that adverse events are graded using National Cancer Institute Common Terminology Criteria for Adverse Events version 4.03.

In general, a dose-finding endpoint of this kind is used to identify a dose meeting a prespecified tolerability rule for further study. It is not itself a measure of tumor response or survival. Interpretation depends on the number of participants assessed at each dose, the number meeting the dose-limiting toxicity definition, the attribution and grading of events, and the dose-selection rule actually applied. The registry record does not report the MTD value, dose-limiting toxicity counts, or the analysis used to select a dose. Thus the endpoint definition is available, but its result cannot be evaluated from the reported information.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The statistical information in the registry record is limited. It defines the primary dose endpoint and lists trial design features, but does not report the statistical analysis used to determine the MTD, results for that endpoint, or analyses for the secondary outcomes. General statistical context can clarify what would be needed to interpret those results, without implying that a particular method was used in this trial.

How is an MTD defined?

The registry’s rule defines the MTD through the frequency of dose-limiting toxicity in the first 6 weeks. In general, a dose-finding rule uses observed toxicities at dose levels to identify a dose that meets a tolerability criterion. The interpretation depends on which participants are considered evaluable, how missing toxicity observations are handled, how events are judged to be related to treatment, and how the dose-selection algorithm uses the observed data. The record specifies the toxicity window and the threshold definition, but does not report the participant-level evaluability rule, the dose-level toxicity counts, or the selection algorithm. It therefore does not permit reconstruction or evaluation of the selected dose.

What does a confidence interval add?

General statistical explanation: a confidence interval describes uncertainty around an estimated quantity under the assumptions of the method used. For a dose-finding result, interval estimates or other uncertainty summaries can help readers distinguish a stable estimate from one based on sparse observations. For a response proportion, an interval conveys uncertainty around the estimated proportion; for a time-to-event outcome, uncertainty can be described around survival or hazard estimates. No such estimates or intervals for the trial’s endpoints are reported in the registry record. Without them, the precision of any endpoint result cannot be judged.

Why does the design matter?

The record characterizes the trial as non-randomized and sequential. In general, random assignment can balance measured and unmeasured characteristics across comparison groups, while sequential dose-finding assigns groups for a different purpose. Since the registry says the arms are not a like-for-like control comparison, contrasts across them should not be treated as randomized estimates. The record does not report an adjusted comparative analysis, covariate strategy, or model for the secondary outcomes. No such analysis should be inferred from the design description alone.

What do the planning assumptions mean?

The registry includes planning assumptions for an illustration based on an observed effect, rather than a description of the trial’s own design. That illustration specifies a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is described as a stated fraction of the observed effect. For time-to-event illustrations, the assumption concerns the total number of events using the Schoenfeld method; other illustrations refer to participants per arm. These assumptions do not establish that the trial itself used those methods or allocations, and planning sample sizes are not observed power. The effect and resulting planning values are not reported in the registry record. The record also identifies the study as non-randomized and says its arms are not a like-for-like control comparison, so a two-arm illustration should not be mistaken for the trial’s design.

Which analysis details are absent?

The statistical analysis plan, the model or test for each endpoint, any covariate adjustment, the handling of censoring, and the confidence level for reported intervals are not reported in the registry record. The record does not report whether interim analyses occurred, how the sample size was justified, or what analysis populations were used. Those omissions matter because estimates depend not only on an endpoint definition but also on who is included, how incomplete observations are handled, and which analysis is performed. The stated endpoint definition and design details alone do not answer those questions.

In general, sparse event counts can make estimates uncertain, and uneven group sizes can affect the amount of information available from each group. The registry lists 4 participants in one safety group and 31 in the other, but does not provide endpoint-specific analysis denominators. The group counts should not be assumed to represent the population included in every endpoint analysis. No numerical precision estimate can be recovered from those counts alone.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary endpoint, maximal tolerated dose, and secondary outcomes of overall response rate, response duration, progression-free survival, and overall survival time. It does not report how these outcomes were analyzed, whether any formal hypothesis tests were conducted, or whether an approach to multiplicity was specified. When several outcomes are tested, general statistical practice considers how repeated testing affects the chance of false-positive findings. The registry record does not report a multiplicity adjustment or a hierarchy for interpreting secondary outcomes, so no such strategy should be assumed.

Missing-data handling is not reported in the registry record. For response outcomes, interpretation can depend on how participants without an assessable response are treated. For time-to-event outcomes, it depends on event definitions, censoring rules, and follow-up. The record names these outcomes but does not provide those operational details or results. These methods should not be inferred from the outcome names.

Analysis populations are also not reported. The record does not state which participants were included in the primary endpoint analysis or in the secondary outcome analyses, nor does it describe exclusions or evaluability rules. The enrollment figure and the safety-group counts do not establish endpoint-specific denominators.

The registry record reports no analyses. It does not report interim analyses, a statistical analysis plan, or a sample-size justification. These omissions limit assessment of how the listed outcomes were intended to be tested and how the reported safety groups relate to endpoint analyses. They do not establish that the trial did or did not conduct analyses outside what appears in the registry record.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 1% reporting threshold.

Most frequent non-serious adverse event terms

The registry lists serious adverse events for two groups: Treatment Spartalizumab and Siltuximab Phase I Dose Level 1, with 0 of 4 affected, and Experimental: Treatment Spartalizumab and Siltuximab Phase I Level 2, with 0 of 31 affected. It lists other adverse events affecting 2 of 4 and 15 of 31 participants, respectively. These are group counts as recorded, not a randomized comparison. The record does not give a safety observation period for these counts or describe the definitions used for the other-adverse-event category.

Deaths are listed as 4 and 26 in the corresponding groups. The registry information does not state causes of death or whether deaths were attributed to study treatment. These figures should therefore be read as recorded death counts, not as treatment-related death counts. The record also does not provide timing, exposure, or follow-up detail needed to contextualize the counts.

No top serious adverse-event terms are listed. Zero affected participants in the listed serious-event category does not establish that no safety events of any kind occurred: the registry separately reports other adverse events and deaths. Counts alone also do not establish comparative safety or explain differences between groups.

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

The record establishes that a phase Ib/II dose-finding trial of siltuximab with spartalizumab in metastatic pancreatic cancer was completed, with enrollment of 35. It describes the siltuximab dose levels, the combination schedule, and the rule defining the primary MTD endpoint. It also lists several secondary clinical outcomes and safety counts for two groups. These details make the study question and some aspects of its design understandable.

What the record does not establish is the answer to the primary question. The MTD result, dose-limiting toxicity counts, and dose-selection analysis are not reported. Nor are results for overall response rate, response duration, progression-free survival, or overall survival time. Without those outcome results, their magnitude and precision cannot be assessed. The presence of an outcome in the registry is not itself a finding.

The design also limits what can be inferred by comparing groups. The study is non-randomized and sequential, and the registry explicitly says the arms are not a like-for-like control comparison. The listed safety counts therefore do not demonstrate that one dose level is safer or less safe than another. The record does not contain sufficient detail on exposure, follow-up, event attribution, or analysis to support such a comparison.

In general, statistical results are interpreted alongside their uncertainty, analysis methods, and limitations of design. Here, the registry record does not report estimates or confidence intervals for the endpoints. Accordingly, it cannot support conclusions about the strength or precision of efficacy findings, nor can the missing results be interpreted as showing no effect. The scope of interpretation is limited to the trial description and the posted counts, not an unreported endpoint conclusion.

13. Why This Trial Matters Statistically

This trial is statistically notable because its primary question is a dose-selection question rather than a randomized comparison of treatment effects. The MTD definition links the endpoint to dose-limiting toxicities in the first 6 weeks, making the toxicity window and event attribution central to interpretation. A dose-finding result requires more than knowing which dose levels were listed: readers also need the toxicity observations and the rule used to select a dose. The registry record does not report those results.

The sequential design is another important feature. A set of dose groups can reflect progression through a dose-finding process, not parallel arms constructed to estimate comparative effects. The registry specifically cautions against treating the arms as like-for-like controls. That distinction helps prevent group counts from being overread as causal comparisons.

The registry also illustrates why a completed study record and a clinical result are different kinds of information. It reports enrollment, design, endpoint definitions, secondary outcome names, and safety counts, but not the MTD or efficacy analyses. Statistical interpretation depends on the results and their uncertainty, not simply on the presence of a planned outcome or the study’s completion status.

Finally, the record names response and survival outcomes but gives no estimates or analysis details for them. This leaves the trial’s contribution to those questions uncertain from the registry record alone. Clear reporting of endpoint results, denominators, follow-up, analysis methods, and uncertainty would be needed to assess how informative the findings are.

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 principal limitation for interpreting this trial from its registry record is that the primary endpoint result is absent. The registry defines the MTD and dose-limiting toxicity, but does not report the dose selected, toxicity counts by dose, or the analysis used to choose the dose. The named secondary outcomes also lack reported results.

Important statistical details are not reported in the registry record. These include the sample-size justification, any interim analyses, the analysis populations, missing-data methods, and the analysis plan. The record does not provide endpoint-specific denominators or uncertainty estimates. As a result, the precision and robustness of any result cannot be assessed from the posted information.

The study is non-randomized and sequential, and the registry cautions that its arms are not a like-for-like control comparison. This limits interpretation of between-group contrasts. Safety interpretation has additional constraints: the record does not describe the observation period for the listed counts, causes or treatment attribution for deaths, or enough detail to contextualize differences in group exposure and follow-up. These are limitations of the information reported, not evidence that a particular analysis was or was not performed outside the record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Siltuximab and Spartalizumab in Patients With Metastatic Pancreatic Cancer — NCT04191421.
• Registry record last updated 2025-08-22; status last verified 2025-08.
• Results first posted 2025-08-22.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

18. Record Summary

The registry describes a completed, non-randomized, unmasked, sequential phase Ib/II trial sponsored by Emory University, with enrollment of 35. The study evaluates siltuximab with spartalizumab in metastatic pancreatic cancer. Its primary endpoint is the maximal tolerated dose of siltuximab, defined using dose-limiting toxicities during the first 6 weeks. The record lists overall response rate, response duration, progression-free survival, and overall survival time as secondary outcomes.

The registry reports safety counts for two groups but does not report the primary endpoint result, secondary outcome results, analysis methods, or uncertainty estimates. It cautions that the non-randomized arms are not a like-for-like control comparison. The record therefore describes the study design and selected counts, but does not establish the MTD or the clinical outcome findings.