Xisomab 3G3 for the Prevention of Catheter-Associated Thrombosis in Patients With Cancer Receiving Chemotherapy: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Xisomab 3G3 for the Prevention of Catheter-Associated Thrombosis in Patients With Cancer Receiving Chemotherapy (NCT04465760), a na phase 2 study. The primary outcome is Incidence of Catheter-associated Thrombosis (CAT).

2. Clinical Question

The study asked whether catheter-associated thrombosis could be assessed after patients with cancer received xisomab 3G3 around the time of catheter placement and chemotherapy. Its primary question concerned the incidence of overall CAT, including both symptomatic and asymptomatic events, through the end-of-treatment visit on day 18. The registry record describes ultrasound screening for possible CAT at approximately 2 weeks.

The study description places xisomab 3G3 before standard-of-care chemotherapy, which was to begin 2 days later. It describes the goal as preventing catheter-associated blood clots in patients receiving chemotherapy. However, the registry record does not report the observed primary endpoint count or its confidence interval. The clinical question can therefore be described from the registered design, but the posted results do not establish what incidence was observed.

3. Trial Design

This is a phase II, single-group study of xisomab 3G3. The registry lists allocation as not applicable and masking as none; it does not describe a randomized allocation or a blinded comparison. The record lists enrollment as 9 and the study status as terminated. The recorded start date is 2021-02-25, and the primary completion date is 2021-10-05. A reason for termination is not reported in the registry record.

The intervention description says participants received xisomab 3G3 intravenously or via catheter within 48 hours after catheter placement. Standard-of-care chemotherapy was scheduled 2 days later. After approximately 2 weeks, participants were to undergo standard-of-care ultrasound for possible CAT. The primary endpoint timeframe extended through the end-of-treatment visit on day 18. The record lists supportive care with xisomab 3G3 as the study group; it does not describe an untreated or active-comparator arm.

The registered conditions are lymphoma, malignant solid neoplasm, and plasma cell myeloma. The study rationale identifies catheter-associated clots as a concern for patients with cancer receiving chemotherapy and notes that blood thinners can increase bleeding risk. Xisomab 3G3 is described as a monoclonal antibody intended to prevent activation of FXI by FXIIa.

Design details beyond those stated are not reported in the registry record. In particular, a detailed protocol, recruitment flow, eligibility criteria, dose, and explanation for termination are not reported in the registry record. The design supports descriptive assessment in the treated group, but does not by itself furnish a concurrent estimate of what would have happened under another treatment or under no xisomab 3G3.

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

Analysis population for the primary outcome, as defined in the registry: Eight of nine participants underwent screening ultrasound for catheter thrombosis. One patient had their catheter removed prior to screening ultrasound.

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 Incidence of Catheter-associated Thrombosis (CAT), measured over Up to end of treatment visit (day 18).

The primary endpoint is the incidence of catheter-associated thrombosis, reported as a count of participants. It includes both symptomatic and asymptomatic CAT, and its timeframe is through the end-of-treatment visit on day 18. The registry description says the incidence would be reported with a 95% confidence interval. Eight of the 9 participants underwent screening ultrasound for catheter thrombosis; one participant had the catheter removed before screening ultrasound.

Including asymptomatic events means the endpoint is not limited to clots that caused symptoms. Ultrasound screening was part of the registered assessment, making detection of events that might otherwise go unnoticed relevant to the endpoint definition. In general, a confidence interval expresses the statistical uncertainty around an estimated quantity; it does not remove uncertainty or establish that the estimate applies beyond the people studied.

The registry record does not report the observed CAT count, an estimated incidence, or the stated confidence interval. It also does not say which participants were included in the endpoint analysis or how the participant whose catheter was removed was handled analytically. The screening information describes ascertainment, but is not itself a reported endpoint result.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary endpoint is a binary participant-level outcome: a participant either has a catheter-associated thrombosis during the defined period or does not. The registry identifies the outcome measure as a count of participants and says the overall CAT incidence would be accompanied by a 95% confidence interval. In general, for a binary endpoint, an incidence estimate describes the proportion of an analyzed group with the event. The confidence interval communicates how imprecisely that estimate is determined by the observed data and the method used.

What does the confidence interval represent?

In general, a confidence interval is a range of values compatible with the data under a specified statistical procedure. A narrower interval indicates greater precision under that procedure; a wider interval indicates more uncertainty. It is not a guarantee that the true value lies within the interval, and it does not address bias from incomplete follow-up, outcome misclassification, or the absence of a comparator. Here, the registry says a 95% confidence interval was planned for the CAT incidence, but does not report the interval or the estimate it would accompany.

For an event-count endpoint, the denominator is essential to interpretation. The record reports enrollment of 9 and screening ultrasound for 8 participants; one participant had a catheter removed before screening. It does not identify the primary endpoint analysis denominator or explain the handling of the participant without screening. The numerator and denominator needed to interpret incidence are therefore not reported in the registry record. Neither can be reconstructed from the screening information alone.

What can the single-group design estimate?

A single-group study can describe events observed among participants who received the study intervention, provided the outcome results and analysis population are available. In general, it cannot estimate a randomized treatment contrast because it has no concurrent comparison group. An observed event frequency may also reflect participant characteristics, clinical care, timing, and outcome ascertainment, in addition to any effect of the intervention. This limitation remains even if the event count is precise.

The study is not recorded as randomized or masked. The absence of masking can matter in general when decisions or assessments involve judgment, although the registry record does not describe whether any particular CAT assessments were vulnerable to such influence. Ultrasound screening is specified, but details about image interpretation, adjudication, or blinding of assessors are not reported in the registry record.

How should planning calculations be read?

The record describes planning illustrations based on a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It says the effect to detect is a stated fraction of the observed effect. These assumptions describe hypothetical planning calculations, not the registered trial design: the study itself is single-group, with no randomized comparator. Such illustrations are not observed power and do not show that the trial achieved a particular probability of detecting an effect.

The record also distinguishes participant-per-arm calculations from total-event calculations for time-to-event settings. The primary endpoint in this study is a count of participants, rather than a time-to-event outcome. The registry entries do not include the observed effect or any numerical planning estimate, so those calculations cannot be interpreted numerically. More generally, planning estimates depend on their assumptions; a calculation based on an observed effect can be especially uncertain when that effect comes from a small or incomplete dataset.

Over-dispersion is a general statistical issue when the variation in event counts exceeds what a chosen model assumes. It can make standard errors too small and confidence intervals too narrow if the model does not account for it. The registry record does not report a model for over-dispersion, and the primary endpoint result is not available to assess its relevance. It would be inappropriate to infer that a particular count model was used.

The record lists zero analyses and does not report inferential results for the primary endpoint. No p-value, confidence interval, or adjusted estimate is reported. Recalculation from posted summary statistics is not possible without the primary endpoint count and denominator. Accordingly, statistical interpretation is limited to explaining the endpoint definition, the planned confidence interval, the design constraints, and the missing result rather than estimating an effect.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Supportive Care (Xisomab 3G3)")
n      <- c(8)
events <- c(1)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Supportive Care (Xisomab 3G3)  8  1  12.5  0.3  52.7  2.2  47.1  2.8  48.2

11. Multiplicity, Missing Data and Analysis Populations

The registry record does not report a multiplicity strategy. Multiplicity is a general concern when several outcomes, timepoints, subgroups, or statistical tests are examined: without a plan, the chance of at least one apparently unusual finding can increase. The record lists 10 outcome measures and two secondary safety outcomes, but does not explain how they would be prioritized or whether any adjustment for multiple testing was planned. No analysis results are listed, so there is no reported set of tests from which to assess actual multiplicity handling.

Missing-data methods are also not reported in the registry record. The available screening information says 8 of 9 participants underwent ultrasound and that one participant’s catheter was removed before screening. It does not say whether that participant was considered to have missing outcome data, excluded from an analysis, or handled by another rule. The primary endpoint denominator, analysis population, and any imputation or sensitivity analysis are not reported in the registry record.

In general, missing outcomes can affect an estimate if the likelihood of being observed is related to the likelihood of the event. Even when the reason for a missing assessment is known, the outcome itself cannot be assumed from that reason alone. The catheter removal is a documented circumstance, not evidence about whether CAT occurred.

The analysis populations are not reported in the registry record. It is therefore unclear whether results, if available, would have been based on all enrolled participants, participants who received xisomab 3G3, participants with evaluable ultrasound, or another defined group. The registry lists zero analyses, and it does not report a statistical analysis plan or interim-analysis procedures. No assumptions about these procedures can be made from the registered endpoint description.

12. 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 5% reporting threshold.

Most frequent non-serious adverse event terms

The registry safety summary lists 9 participants at risk for serious adverse events and 0 participants affected. It lists 9 participants at risk for other adverse events and 9 affected. The death count is 0. These are descriptive counts for the supportive-care group with xisomab 3G3.

The counts do not provide event-level descriptions or explain the severity, timing, duration, or outcome of the other adverse events. The registry lists incidence of major and clinically relevant bleeding and incidence of xisomab 3G3-associated adverse events among secondary outcomes, but results for those outcomes are not reported in the registry record. The safety summary therefore cannot be used to infer a specific bleeding rate or determine whether an event was caused by xisomab 3G3.

In general, observing no serious adverse events in a small study does not rule out serious events that could occur in a larger population or with different follow-up. Likewise, a count of participants with other adverse events does not describe the clinical importance of those events without event-specific information. These registry counts should be interpreted as the safety information recorded for this study, not as a complete safety profile.

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

The record establishes that a phase II, single-group study of xisomab 3G3 was registered to assess catheter-associated thrombosis in patients with cancer receiving chemotherapy. It defines overall CAT to include symptomatic and asymptomatic events and sets the primary endpoint timeframe through the end-of-treatment visit on day 18. It also records that 8 of 9 participants underwent screening ultrasound, with one catheter removed before screening.

Those design and assessment details do not answer the primary clinical question. The number of participants with CAT, the incidence estimate, and its planned 95% confidence interval are not reported in the registry record. Without those results, it is not possible to describe the observed primary outcome or how precise its estimate was. The screening count is not a substitute for an endpoint result.

Even a reported event frequency from this design would be descriptive. Because there is no comparator group, the study cannot provide a randomized estimate of the difference between xisomab 3G3 and another strategy. The registry information also does not establish why the study was terminated; a reason is not reported in the registry record.

The recorded safety counts show 0 participants affected by serious adverse events among 9 at risk, 9 affected by other adverse events among 9 at risk, and 0 deaths. They do not provide detailed descriptions of the other events or results for the registered bleeding outcomes. General statistical interpretation requires attention to the limited sample, missing primary endpoint results, and the lack of a concurrent comparison.

Accordingly, the record supports a description of what the study planned and a narrow account of its posted safety counts. It does not support a conclusion about the primary endpoint’s observed incidence, the intervention’s effect relative to an alternative, or the full balance of benefits and harms.

14. Why This Trial Matters Statistically

This study illustrates why a clearly defined endpoint and a reported result are both necessary for statistical interpretation. The registry specifies overall CAT, includes symptomatic and asymptomatic events, identifies ultrasound screening, and states a follow-up endpoint through day 18. Those details help clarify what the study intended to measure. But because the observed event count, incidence, and confidence interval are not reported, the primary result cannot be assessed.

The record also shows why denominators and analysis populations matter. Enrollment is listed as 9, whereas 8 participants underwent screening ultrasound and one had a catheter removed before screening. These registry entries do not establish the denominator for the endpoint analysis. A result without a clearly reported analysis population would be difficult to interpret, and the population is not reported in the registry record.

Statistically, the single-group design separates description from comparison. A count among treated participants may describe what was observed in that group, but it cannot isolate the intervention’s contribution from other influences. Planning illustrations based on a hypothetical equal-allocation, two-arm comparison do not change the actual single-group design, and they are not evidence of observed power.

The study is also a reminder that safety summaries require context. The recorded serious-event and other-event counts answer only limited questions without event descriptions, timing, or attribution. For clinical researchers and biostatisticians, the key lesson is to distinguish protocol definitions, observed data, and inferential claims. In this record, the endpoint and design are documented, but the primary outcome analysis needed to connect them is not reported.

15. 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 is the absence of the primary CAT result. The registry record does not report the event count, incidence estimate, or planned 95% confidence interval. It therefore does not permit assessment of the endpoint’s magnitude or precision. The record also does not identify the analysis denominator, despite reporting that one participant did not undergo screening ultrasound after catheter removal.

The design is single-group, with no comparator. This limits causal interpretation and prevents a randomized comparison with standard care or another intervention. Allocation is listed as not applicable and masking as none. Whether outcome assessors were blinded or whether CAT events were independently adjudicated is not reported in the registry record.

The study lists enrollment as 9 and is marked terminated. The reason for termination, participant flow beyond the screening information, and the number who completed all planned assessments are not reported in the registry record. The endpoint runs through day 18, but the details of follow-up completeness are not reported.

The registry record does not report the dose, detailed eligibility criteria, statistical analysis plan, analysis populations, missing-data handling, multiplicity strategy, or interim analyses. It lists two safety outcomes, but results for major and clinically relevant bleeding and xisomab 3G3-associated adverse events are not reported. The broad safety counts lack event descriptions and causal assessment.

Finally, planning assumptions describe a two-arm calculation, whereas the registered study is single-group. Numerical planning results and the observed effect on which those illustrations depend are not reported in the registry record. These limitations mean the registered question can be described, but neither the primary outcome nor comparative efficacy can be evaluated from the available record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Xisomab 3G3 for the Prevention of Catheter-Associated Thrombosis in Patients With Cancer Receiving Chemotherapy — NCT04465760.
• Registry record last updated 2024-01-24; status last verified 2024-01.
• Results first posted 2024-01-02.
• 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.

19. Record Summary

NCT04465760 is a phase II, single-group study of xisomab 3G3 for prevention of catheter-associated thrombosis in patients with cancer receiving chemotherapy. The registry lists lymphoma, malignant solid neoplasm, and plasma cell myeloma as conditions, enrollment of 9, and study status as terminated. The recorded study start date is 2021-02-25, and the primary completion date is 2021-10-05.

The primary endpoint is overall CAT, including symptomatic and asymptomatic events, through the end-of-treatment visit on day 18, with a 95% confidence interval planned. Eight participants underwent screening ultrasound; one had a catheter removed beforehand. The primary endpoint result and analysis population are not reported in the registry record.

The safety summary lists 0 participants with serious adverse events, 9 with other adverse events, and 0 deaths. The reason for termination and detailed safety results are not reported in the registry record.