Clinical Trial of Consolidation Treatment With Iodine I 131 Tositumomab for Multiple Myeloma: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Clinical Trial of Consolidation Treatment With Iodine I 131 Tositumomab for Multiple Myeloma (NCT00135200), a na phase 2 study. The primary outcome is Percentage of Patients With an Objective Response.

2. Clinical Question

The study aimed to assess whether objective responses occurred after consolidation treatment and also to examine side effects, duration of response, progression-free survival, and time to treatment failure. Those questions describe the scope of the study, not conclusions about the treatment. The registry record does not report the primary endpoint result, so the response percentage and its precision cannot be described from the record. Nor does it provide comparative evidence: without a control group, any reported outcome would describe participants in this study rather than establish how outcomes compare with another approach.

3. Trial Design

The registry identifies this as a phase II, completed, single-group clinical trial of iodine I 131 tositumomab for multiple myeloma. The recorded enrollment is 16. The study began in 2005-08, and primary completion is recorded as 2013-08. Allocation is listed as not applicable, and masking is listed as none. These design features mean the study was not a masked randomized comparison between treatment groups.

The record describes the intended population as patients with newly diagnosed or relapsed multiple myeloma. Its intervention was Bexxar therapeutic treatment. The description says the regimen involved two sets of intravenous infusions given 7-14 days apart, with nonradioactive tositumomab before both the dosimetric and therapeutic infusions. Further details of the treatment description are not reported in the registry record.

The primary outcome was the percentage of patients with an objective response, assessed at 3 months. Secondary outcomes listed are complete response, duration of response, progression-free survival time, and time to treatment failure. Listing an outcome does not establish that its result or analysis was posted. The registry record does not report the primary response estimate, its confidence interval, or results for the listed secondary outcomes. It also does not report a protocol-based statistical analysis plan or an explanation of how the enrollment target was chosen.

Because the study has no control arm, it can describe outcomes within the enrolled group but cannot isolate the effect of treatment from other explanations for those outcomes. Its single-group design is especially important when interpreting a response rate: the percentage is not a randomized treatment contrast, and it does not provide an estimate of what would have happened to comparable participants under a different treatment.

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 Percentage of Patients With an Objective Response, measured over 3 months.

The primary endpoint is the percentage of patients with an objective response at 3 months. It focuses on change in monoclonal protein relative to the pre-Bexxar level. The record defines objective response as a sustained reduction of more than 25%, and gives three response categories: minimal response, partial response, and complete response. Minimal response is a 25-49% reduction in serum monoclonal protein for at least 2 determinations. Partial response is a 50-89% reduction for at least 2 determinations. Complete response is the absence of the original monoclonal protein in serum and urine on at least 2 determinations by immunofixation.

A percentage endpoint is a way to describe how many participants in the study met the response definition, relative to those assessed. It can be useful for describing whether a prespecified response criterion was reached in a single-group study. It does not, by itself, show that treatment caused the response or how the response rate compares with another option. The registry record identifies a 95% confidence interval as the measure of dispersion, but does not report the endpoint estimate or the interval itself. Consequently, the magnitude and precision of the primary result are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The study’s main outcome is a binary response status: a participant either meets the stated objective-response definition or does not. Reporting the percentage with an event expresses that outcome as a proportion of the participants included in the endpoint assessment. This is a general explanation of binary-outcome methods. The registry record specifies the response definition and names a 95% confidence interval as the dispersion measure, but the estimate and interval are not reported in the registry record.

What does a confidence interval convey?

In general, a confidence interval communicates the uncertainty around an estimate under the statistical method used to construct it. A narrower interval indicates greater precision under that method; a wider interval indicates less precision. It is not a guarantee that the true value lies within the interval, nor does it represent the range of individual participant outcomes. For a response percentage, the interval would help readers judge how much uncertainty remains around the estimated proportion. Since the interval is not reported in the registry record, its width and implications cannot be assessed for this study.

With a binary endpoint, the number of participants who meet the definition and the number assessed are both important to interpretation. The percentage alone can obscure how much information supports the estimate. This is a general principle, not a calculation for this study. Although the registry records overall enrollment, it does not report the primary endpoint’s response count, analysis denominator, or handling of participants without an assessment. No response count or analysis denominator can therefore be inferred.

Why does the single-group design matter?

A single-group study can estimate an outcome within its enrolled participants, but it does not produce a randomized comparison between treatment strategies. In a randomized study, allocation is intended to make groups comparable on average, supporting a contrast between outcomes. Here, the registry lists allocation as not applicable and the model as single-group. Any outcome estimate would therefore be descriptive of the study group, rather than a comparative estimate of treatment effect. General statistical adjustment cannot replace an unreported control group or remove all possible alternative explanations.

Masking is listed as none. In general, masking can reduce the influence of expectations on some aspects of treatment delivery, assessment, or reporting. Its relevance depends on the outcome and how it is measured. The registry record does not report additional procedures to reduce assessment bias, so their use cannot be assumed. The primary outcome is defined using laboratory measures of monoclonal protein, but the record does not describe who assessed those results or whether assessment procedures were standardized beyond the stated response definition.

What can be said about planning calculations?

The record describes planning illustrations based on an observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The target effect is described as a stated fraction of the observed effect. Those assumptions characterize planning calculations, not the design of this single-group study. The record explicitly distinguishes the planning illustration from the trial’s own design. Such calculations are not observed power and do not show that a study had a particular probability of detecting an effect after its results were known.

Planning calculations are sensitive to their assumptions. In general, the assumed effect, allocation, significance level, and statistical approximation influence the resulting sample-size illustration. If the assumed effect is optimistic or uncertain, the illustration can be a poor guide to the size needed for a future study. Here, the registry record does not report the original protocol’s sample-size justification, and the planning assumptions do not establish what the investigators planned when conducting the trial. The record does not report the numerical planning outputs in the registry record for this account, so none are restated.

How should multiple outcomes be understood?

The primary response endpoint sits alongside listed secondary outcomes: complete response, duration of response, progression-free survival, and time to treatment failure. In general, testing or interpreting multiple outcomes can raise multiplicity concerns. If many statistical tests are conducted, the chance of at least one apparently notable finding can increase unless the analysis plan addresses that issue. The registry record does not report a multiplicity strategy, which outcomes were formally tested, or the results of any such tests. It is therefore not possible to determine whether or how multiplicity was handled.

For time-to-event outcomes, general methods often account for the timing of events and for participants whose follow-up ends before an event is observed. Their interpretation depends on a clear event definition, follow-up information, and analysis choices. The registry lists duration of response, progression-free survival time, and time to treatment failure, but the relevant event definitions, censoring rules, analysis populations, and estimates are not reported in the registry record. No time-to-event method or result can be attributed to the study on this basis.

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("Bexxar Therapeutic")
n      <- c(16)
events <- c(5)
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  Bexxar Therapeutic  16  5  31.2  11.0  58.7  14.2  55.6  14.2  56.0

11. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary objective-response endpoint and secondary outcomes for complete response, duration of response, progression-free survival time, and time to treatment failure. Considering several outcomes can create multiplicity concerns when statistical tests are performed: the more tests considered, the greater the general possibility of a chance finding among them. Whether that concern applies to a particular analysis depends on the prespecified plan and how results are interpreted. A multiplicity adjustment or other strategy is not reported in the registry record, and the record does not provide analyses that would show how the outcomes were handled.

The registry does not report the analysis population for the primary or secondary outcomes. It also does not report how missing endpoint measurements, incomplete follow-up, withdrawals, or other unavailable data were handled. These details matter because the set of participants included in an analysis and the treatment of missing observations can affect the interpretation of an estimate. The overall enrollment does not establish how many participants contributed data to each outcome.

The response endpoint requires assessment of monoclonal proteins, with repeated determinations specified in the response definitions. The record does not explain whether all participants had the required assessments, what happened when an assessment was absent, or whether response status was assigned under a prespecified missing-data rule. For time-to-event outcomes, censoring and follow-up procedures are also not reported in the registry record. These omissions prevent assessment of the robustness of outcome estimates to missing information and analysis choices.

12. 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: infection with normal neutrophil count (6.2%), infection wtih unknown neutrophil count (6.2%), neuropathy - motor (6.2%).

The registry lists 3 participants affected by serious adverse events among 16 at risk in the Bexxar Therapeutic group. It lists 15 participants affected by other adverse events among 16 at risk. These are separate registry categories; they should not be added together, since the record does not establish that the categories represent different participants. The serious adverse-event count is a participant count, not a count of distinct event types or a rate calculated for this account.

Three serious-event terms are listed: Infection with Normal Neutrophil Count, Infection wtih Unknown Neutrophil Count, and Neuropathy - Motor. Each term is accompanied by 6.2%. The registry does not give corresponding term-specific counts in the record, so those percentages should be read as posted rather than reverse-calculated into counts. Deaths are not reported in the registry record.

These figures describe events recorded in the study group. They do not establish that the intervention caused an event, and the listed percentages do not provide a comparison with another treatment. The registry record does not supply further detail on event timing, duration, management, or attribution. The counts also do not describe events that may have gone unrecorded or provide a complete basis for comparing safety with another population.

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

The study record documents a phase II investigation of iodine I 131 tositumomab as consolidation treatment for multiple myeloma, with objective response as the primary endpoint. It gives a response definition and a 3-month timeframe. However, it does not report the response estimate or its 95% confidence interval. Thus, the primary result’s size and precision are not reported in the registry record.

This absence does not mean that no participants responded, that treatment had no effect, or that the endpoint was not assessed. It means the registry record does not present the result needed to answer those questions numerically. Likewise, the secondary outcomes are listed, but their results are not reported in the registry record. Their inclusion alone is not evidence that an outcome occurred or that a particular statistical finding was obtained.

The design defines the kind of conclusion the study could support. With a single group and no concurrent comparator, any outcome estimate would describe participants in the study, not a randomized contrast between treatments. A difference from an external benchmark, if considered, would not have the same interpretation as a comparison created by random allocation; no such benchmark or analysis is reported in the registry record.

The safety entries add a limited description of adverse events in the treated group. They do not establish causation or allow a comparative assessment. The registry does not report the additional details needed to characterize events fully, and the absence of a reported death count should not be interpreted as a zero count.

Accordingly, the record supports statements about the study’s intended question, design, outcome definitions, and posted safety counts. It does not support a conclusion about the magnitude of objective response, the uncertainty around a response estimate, the secondary outcome results, or comparative benefit and harm. Those conclusions require results and analysis details that are not reported in the registry record.

14. Why This Trial Matters Statistically

This trial illustrates why design and reporting details are essential to statistical interpretation. Its primary endpoint is defined in terms of a specific change in monoclonal proteins, with response categories and a stated assessment timeframe. A clearly described outcome helps readers understand what investigators intended to measure. But a definition cannot substitute for the observed result: the registry record does not report the response percentage or its confidence interval.

The single-group structure is another important statistical feature. An estimate from a single group can describe the participants who received the intervention, but it does not provide the same evidence as a randomized comparison. Readers need to distinguish a within-group response proportion from a treatment contrast. The design and the reported data answer different questions, and the record does not support a comparative estimate.

The record also highlights the role of uncertainty. Percentages are estimates, and confidence intervals can help show their precision. Without the primary estimate and interval, there is no basis for judging whether the result was precise or highly uncertain. Enrollment alone cannot answer that question, because the endpoint analysis denominator and response count are not reported.

Finally, the registry lists multiple secondary outcomes and some safety information, while leaving analysis choices and outcome results unreported. For a statistically useful interpretation, readers need to know which participants contributed to each analysis, how missing observations were handled, and how multiple outcomes were treated. The entries available in the registry are enough to identify these questions, but not to resolve them. This makes careful separation of planned outcomes, posted results, and unsupported conclusions central to reading the study.

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 most direct limitation for interpreting efficacy is that the primary endpoint result is not reported in the registry record. The response percentage, response count, analysis denominator, and 95% confidence interval are unavailable. Without them, neither the magnitude nor precision of the primary result can be evaluated.

The registry also does not report results for the listed secondary outcomes: complete response, duration of response, progression-free survival time, and time to treatment failure. Their detailed definitions and analysis methods are not reported in the registry record. The record does not provide the analysis populations, follow-up details, or missing-data procedures needed to assess these outcomes.

The single-group design, with allocation listed as not applicable and no masking, limits causal interpretation and leaves no concurrent control for comparison. The registry record does not report a statistical analysis plan, multiplicity strategy, interim-analysis approach, or protocol-based sample-size justification. The planning assumptions described in the record are not a substitute for those details and are not the trial’s own design.

Safety interpretation is also constrained. Although participant counts and serious-event terms are posted, details about event timing, attribution, duration, and management are not reported in the registry record. Deaths are not reported, which does not establish that none occurred. More broadly, the record’s description does not provide participant characteristics or enough information to assess how representative the enrolled group may be of other patients with multiple myeloma.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Clinical Trial of Consolidation Treatment With Iodine I 131 Tositumomab for Multiple Myeloma — NCT00135200.
• Registry record last updated 2025-04-30; status last verified 2025-04.
• Results first posted 2014-11-20.
• 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

The registry identifies a completed phase II, single-group study of iodine I 131 tositumomab for multiple myeloma, with recorded enrollment of 16. The intended primary outcome was the percentage of patients with an objective response at 3 months, defined through sustained reductions in monoclonal proteins. Secondary outcomes included complete response, duration of response, progression-free survival, and time to treatment failure.

The record does not report the primary endpoint result or its 95% confidence interval, and it does not report results for the listed secondary outcomes. It does list serious and other adverse-event counts and three serious-event terms. With no concurrent comparator and key results and analysis details unreported, the registry supports a description of the study’s design and posted safety information, but not a numerical assessment of response or a comparative treatment conclusion.