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 Zevalin (Ibritumomab Tiuxetan) for Early Stage Indolent Lymphomas (NCT00493467), a na phase 2 study. The primary outcome is Overall Response Rate (ORR).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00493467 |
| Phase | Phase 2 |
| Condition | Lymphoma |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 31 |
| Arms in the primary outcome | n/a |
| Lead sponsor | M.D. Anderson Cancer Center |
| Results posted | Yes |
2. Clinical Question
Population
The study concerns people with early-stage indolent lymphoma, as indicated by its title. The registry’s condition entry is lymphoma, and its brief summary describes the disease as low-grade lymphoma. More detailed eligibility criteria and participant characteristics are not reported in the registry record.
Intervention
The study treatment combined rituximab with ibritumomab tiuxetan (Zevalin). The brief summary describes the ibritumomab tiuxetan as 90Y Zevalin. Regimen details such as dose and schedule are not reported in the registry record.
Comparator
There was no separate control group. The record describes a single-group study, with the combination listed as the study arm. A randomized or like-for-like treatment comparison is therefore not available in this trial record.
Primary question
The primary endpoint was overall response rate (ORR): the percentage of participants whose disease met the record’s criteria for complete response, complete response unconfirmed, or partial response. Response was evaluated after three months using radiographic and clinical parameters. The registry record does not report the observed ORR, the number of participants in each response category, or an uncertainty estimate.
In practical statistical terms, the study set out to describe response after the treatment combination in the enrolled group. It also listed progression-free survival rate at 3 years as a secondary outcome and stated that safety would be studied. Because there is no concurrent comparator group, the study’s design does not estimate a randomized treatment contrast. Its primary question is about the observed response in this group, not how response compares with another treatment or with no treatment.
3. Trial Design
The registry identifies NCT00493467 as a phase II study titled “Zevalin (Ibritumomab Tiuxetan) for Early Stage Indolent Lymphomas.” It lists M.D. Anderson Cancer Center as the sponsor, an enrollment of 31, and a completed status. The recorded start was 2006-06 and primary completion was 2015-04.
The design is listed as single group, with allocation recorded as NA and masking as none. The only listed arm received ibritumomab tiuxetan (Zevalin) plus rituximab. This is not a randomized comparison, and the record does not describe a concurrent control arm. The terms phase II and single group identify the broad design, but do not supply details about the protocol’s statistical planning or conduct.
The primary outcome was overall response rate. The record defines response using International Working Group revised response criteria for malignant lymphoma and describes evaluation after three months using radiographic and clinical parameters. It gives an overall assessment timeframe of up to 5 years, with evaluations at 3-month intervals during Year 1 and then every 6 months to Year 4. It also notes a median follow-up of 56 months for censored observations. A secondary outcome was progression-free survival rate at 3 years.
The registry record does not report the eligibility criteria, treatment doses or schedule, the number of participants assessed for each outcome, or the statistical analysis plan. It also does not report details of recruitment, protocol deviations, or how the study’s completion status relates to the availability of outcome analyses. Those omissions limit how fully the conduct and analysis can be reconstructed from the 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
| Stage | Zevalin |
|---|---|
| STARTED | 31 |
| COMPLETED | 30 |
| NOT COMPLETED | 1 |
Reasons for not completing this period:
| Reason | Zevalin |
|---|---|
| Death | 1 |
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.
| Characteristic | Unit | Zevalin |
|---|---|---|
| Participants analysed | 31 | |
| Age, Continuous | years | 60 (29 to 87) |
| Sex: Female, Male: Female | Participants | 19 |
| Sex: Female, Male: Male | Participants | 12 |
| Region of Enrollment: United States | participants | 31 |
6. Primary Endpoint
The registry lists the primary outcome as Overall Response Rate (ORR), measured over Up to 5 years; Evaluation at 3-month intervals during Year 1, then every 6 months to Year 4. The median follow-up was 56 months for censored observations..
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | Percentage of Participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint, overall response rate (ORR), is a percentage based on participants whose disease met at least one of three response categories: complete response (CR), complete response unconfirmed (CRu), or partial response (PR). It is intended to describe the proportion of the assessed group meeting the record’s response criteria, rather than the duration of response or a comparison between treatment groups.
The registry defines CR as disappearance of all detectable clinical and radiographic evidence of disease and disease-related symptoms. CRu allows a residual lymph node mass greater than 1.5 cm that has regressed by more than 75% in the sum of the products of the greatest diameters, with the stated additional conditions for previously confluent nodes and indeterminate bone marrow. PR requires at least a 50% decrease in the sum of the products of the diameters of the six largest dominant nodes or nodal masses, without the specified increase elsewhere or new disease sites.
Using an established response definition makes the endpoint interpretable as a structured assessment rather than an informal judgment. The registry states that ORR was evaluated after three months using radiographic and clinical parameters. However, it does not report the observed percentage, response counts, denominator used in the analysis, or a confidence interval. The endpoint’s definition is available; its result is not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies ORR as the primary outcome, but it does not report the observed response percentage, the number of complete or partial responses, or an estimate of uncertainty. It is therefore not possible to describe the size or precision of the primary result from this record. The enrolled total of 31 does not establish how many participants contributed to the ORR analysis; that analysis denominator is not reported in the registry record.
The study is described as single group, with one arm receiving the combination of ibritumomab tiuxetan and rituximab. Its response data, if available elsewhere, would describe outcomes in the treated group. Without a concurrent randomized comparator, they would not by themselves quantify a treatment difference against another intervention. This distinction is important: an observed response proportion and a comparative treatment effect answer different statistical questions.
The secondary outcome listed is progression-free survival rate at 3 years. The record does not include its estimate, an event count, a confidence interval, or an analysis description. The follow-up description notes evaluation over up to 5 years and a median follow-up of 56 months for censored observations, but it does not provide a distribution of follow-up or explain how censoring was handled in an analysis. The listed follow-up information alone cannot establish the secondary outcome result.
No p-value, confidence interval, or other inferential result for either outcome is reported in the registry record. A confidence interval, as a general statistical concept, communicates the uncertainty around an estimate under specified methods and assumptions. Without an estimate and its interval, readers cannot assess statistical precision from the record. Nor can an absent estimate be treated as evidence of no response, no progression-free survival, or no treatment effect.
The safety entries are also descriptive rather than comparative. For the Zevalin group, the registry lists 31 participants at risk for serious adverse events and 1 affected, and 31 at risk for other adverse events and 29 affected. These group-level figures do not establish whether an event was caused by treatment, and the record does not give a comparison group. Specific serious-event terms and their recorded percentages should be read as registry entries, not as a complete account of clinical safety.
Overall, the registry supplies design and endpoint definitions but not the analyses needed to judge outcome magnitude or precision. Any conclusion about response or progression-free survival would require outcome results that are not reported in the registry record. The posted information supports a description of what the study intended to assess, not a claim about the treatment’s efficacy.
9. Statistical Methods Explained
What kind of endpoint is ORR?
As a general statistical concept, an endpoint recorded as a percentage of participants with an event is a binary outcome: each participant is classified according to whether the defined event occurred or did not occur. For ORR, the event is meeting one or more of the stated response categories. A percentage then summarizes the number meeting that definition relative to the participants included in the analysis. The registry record describes ORR as a percentage but does not report either the response count or the analysis denominator, so the result cannot be reconstructed from the enrollment total.
Why does the response definition matter?
A response percentage depends on the criteria used to classify participants. The record specifies CR, CRu, and PR using clinical and radiographic findings and measurements of lymph nodes or masses. The criteria determine which observations count as a response; they are not interchangeable with a general impression of improvement. The registry says the response evaluation was performed after three months using radiographic and clinical parameters. The details of who assessed response, whether assessment was blinded, and how missing or indeterminate assessments were handled are not reported in the registry record.
How should precision be assessed?
In general, a confidence interval gives a range of values compatible with an estimate under the statistical method and its assumptions. For a percentage, its width depends in part on the number of observations and the observed proportion. A small study can yield an imprecise estimate even when its point estimate is available. In this record, no ORR estimate or confidence interval is reported, so readers cannot quantify its precision. The enrolled total of 31 is not a substitute for the analyzed denominator, since the record does not specify how many participants were evaluable for the primary endpoint.
What can a single-group design estimate?
As a general design principle, a single-group study can describe outcomes among participants receiving the listed intervention. A randomized comparison is designed to estimate a contrast between assigned groups; this record lists no second arm and identifies the design as single group. Therefore, a result from this study would not be a randomized estimate of how the combination compares with another treatment. Differences between a single-group result and results from other settings can reflect factors beyond treatment, and this record does not provide a comparative analysis.
How does follow-up relate to the outcomes?
The registry states that response evaluation continued up to 5 years, with assessments at 3-month intervals during Year 1 and then every 6 months to Year 4. It also reports a median follow-up of 56 months for censored observations. These details describe the planned or recorded assessment timeframe, but do not supply a response estimate or explain the analysis. The secondary endpoint, progression-free survival rate at 3 years, is a time-to-event outcome in concept: participants may have different follow-up times, and some observations may be censored rather than having a recorded event by the end of observation. As a general matter, survival analysis methods account for follow-up time and censoring. The method used for this study is not reported in the registry record.
What do the planning illustrations represent?
Planning illustrations are not trial results. The record’s stated assumptions for sample-size illustrations include a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is specified as a fraction of the observed effect. These assumptions describe hypothetical planning calculations, not the design of the listed single-group study and not its observed power. They should not be read as evidence that the trial enrolled enough participants to achieve a particular power. The protocol’s own sample-size justification is not reported in the registry record.
The record also states that time-to-event sample-size illustrations use the total number of events, while other illustrations use participants per arm. This is a general distinction in planning: time-to-event calculations are often driven by event information, whereas other designs may be expressed in participants. Neither kind of planning output supplies the missing ORR or progression-free survival result. No recalculated result or sponsor analysis is reported in the registry record.
What is not available for evaluating the analysis?
The registry lists 2 outcome measures and 0 analyses. It does not report the analysis population, the statistical method for the primary endpoint, a missing-data strategy, an interim-analysis plan, or a multiplicity procedure. Those items matter because they specify how observations become an estimate and how uncertainty or multiple outcome assessments are addressed. Without them, readers should avoid assuming that a particular method, population, or adjustment was used. The endpoint definitions and follow-up description help explain what was intended to be measured, but do not replace an analysis report.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 2 outcome measures: ORR as the primary outcome and progression-free survival rate at 3 years as a secondary outcome. It reports 0 analyses. No multiplicity procedure is reported in the registry record. As a general statistical issue, evaluating more than one outcome can raise questions about how to interpret multiple statistical tests or confidence intervals. The record does not indicate whether formal testing was planned, whether outcomes were ranked in a testing hierarchy, or whether any adjustment was intended.
Missing-data handling is also not reported in the registry record. The primary endpoint requires a participant-level response classification, but the record does not say how missing assessments, unevaluable participants, or incomplete imaging would be handled. The enrollment of 31 does not show how many participants had evaluable primary outcome data. For the secondary time-to-event outcome, the record mentions censored observations and a median follow-up of 56 months, but does not describe the censoring rules or analysis method.
The analysis population is not reported in the registry record. It is therefore unclear whether the intended analysis included all enrolled participants, only those who received treatment, or a defined evaluable group. Interim analyses and any stopping rules are also not reported. These omissions prevent a full assessment of analysis decisions and how they might influence the interpretation of estimates. They should not be filled in by assumption.
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 |
|---|---|---|---|
| Zevalin | 1 | 31 | 3.2% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 3% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Zevalin | 29 of 31 |
Most frequent serious adverse event terms
| Event term | Organ system | Zevalin |
|---|---|---|
| PERFORATION, GI | Gastrointestinal disorders | 1 of 31 |
| DEATH | General disorders | 1 of 31 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Zevalin |
|---|---|---|
| NEUTROPHILS CHANGE (Absolute neutrophil count (ANC)) | Investigations | 21 of 31 |
| PLATELETS, DECREASE | Investigations | 21 of 31 |
| FATIGUE | General disorders | 19 of 31 |
| LEUKOCYTOSIS | Blood and lymphatic system disorders | 19 of 31 |
| HEMOGLOBIN INCREASE | Investigations | 12 of 31 |
| NAUSEA | Gastrointestinal disorders | 8 of 31 |
| NEUROPATHY: SENSOR | Nervous system disorders | 8 of 31 |
| BLURRED VISION | Eye disorders | 4 of 31 |
| CONSTIPATION | Gastrointestinal disorders | 4 of 31 |
| DIARRHEA | Gastrointestinal disorders | 4 of 31 |
Serious events with the highest arm-level rate: perforation, gi (3.2%), death (3.2%).
The safety record lists the Zevalin group with 31 participants at risk for serious adverse events and 1 participant affected. For other adverse events, it lists 31 at risk and 29 affected. These are separate registry categories; whether the participants overlap between categories is not reported in the registry record. The figures describe counts in this group and do not provide a comparison with an untreated or alternative-treatment group.
The record identifies PERFORATION, GI and DEATH among the top serious adverse-event terms, each listed as 3.2%. These entries are term-level percentages; the record does not provide enough detail to determine whether participants could appear under multiple terms or how each term was counted. Although DEATH appears as a serious-event term, a separate death count is not reported in the registry record.
Adverse-event entries alone do not establish that the treatment caused an event. The record does not describe event ascertainment, severity grading, exposure duration, or attribution procedures. The figures should therefore be read as registry safety summaries, not as proof of causation or a complete comparative safety assessment.
12. What the Result Does, and Does Not, Mean
The registry record establishes that a completed phase II, single-group study assessed a combination of rituximab and ibritumomab tiuxetan in early-stage indolent lymphomas. It defines ORR as the primary endpoint and describes the response categories and evaluation schedule. It also lists progression-free survival rate at 3 years as a secondary outcome and provides group-level adverse-event entries.
What the record does not establish is the observed ORR or progression-free survival result. It reports no response count, percentage, confidence interval, or analysis estimate. Accordingly, it is not possible to tell from this record how large the response proportion was or how precisely it was estimated. The absence of an analysis result should not be interpreted as a zero result or as evidence for or against a treatment effect.
Even if an outcome estimate were available, the single-group design would describe outcomes in the group that received the combination. It would not provide a randomized comparison with another treatment or a control. A descriptive response proportion does not by itself establish what would have happened to comparable participants under another treatment strategy. The design also cannot separate the contribution of the two drugs to any observed outcome.
The record’s safety counts and event terms likewise describe recorded events, not causation. Without a comparator and fuller information about ascertainment and analysis, the entries cannot establish comparative risk. Missing information about the analysis population, missing assessments, statistical methods, and multiplicity further limits interpretation.
Thus, the registry record is informative about the study question, the broad design, the endpoint definition, and selected safety entries. It does not provide the outcome analyses needed to judge effect magnitude, precision, or comparative benefit and risk. Any efficacy conclusion would go beyond what is reported in the registry record.
13. Why This Trial Matters Statistically
This trial is statistically instructive because the registry record pairs a clear response endpoint with a design that does not include a concurrent control group. That distinction helps separate the question of how many participants met response criteria from the question of whether a treatment changes outcomes relative to an alternative. They are different estimands and require different designs for interpretation.
The endpoint definition also illustrates why operational criteria matter. ORR combines CR, CRu, and PR, each defined through clinical and radiographic findings. A response estimate is meaningful only in relation to those rules and to a clearly described analysis population. The record gives the criteria and assessment schedule, but does not report the response count, analysis denominator, or estimate.
The safety entries offer another useful statistical reading lesson: counts and percentages are descriptive, and do not automatically establish causation. Without a comparison group and more information about event collection and attribution, the entries should not be treated as comparative risk estimates.
Finally, the absence of reported analyses illustrates why registration details and outcome analyses serve different purposes. Study status, enrollment, endpoints, and follow-up give context, but do not replace effect estimates and measures of uncertainty. Readers can identify what the study intended to measure while recognizing that its outcome magnitude and precision are not reported in the registry record.
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.
Several limitations are specific to the information recorded for this trial. The study is single group, with allocation listed as NA and masking as none. There is no concurrent control arm in the registry record, so it does not provide a randomized treatment comparison. The listed arm combines ibritumomab tiuxetan and rituximab; the design cannot distinguish the contribution of one drug from the other.
The enrollment is 31, but the registry does not report the number analyzed for ORR or the outcome result itself. The reported assessment schedule and median follow-up of 56 months for censored observations do not disclose how complete the outcome data were. Eligibility criteria, participant characteristics, treatment details, and analysis population are not reported in the registry record, limiting assessment of who was studied and how closely the endpoint denominator corresponds to enrollment.
The record lists a secondary progression-free survival outcome but does not provide its estimate or analysis method. It does not report the statistical analysis plan, confidence intervals, missing-data methods, multiplicity handling, or interim analyses. The safety entries are not comparative and lack details about event ascertainment and attribution. These limitations apply to the registry information; they do not establish that the omitted methods or results were absent from other study documents.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Zevalin (Ibritumomab Tiuxetan) for Early Stage Indolent Lymphomas — NCT00493467.
- Registry record last updated 2022-09-15; status last verified 2022-08.
- Results first posted 2020-09-01.
- 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
NCT00493467 is a completed phase II, single-group study sponsored by M.D. Anderson Cancer Center. It enrolled 31 participants and lists ibritumomab tiuxetan (Zevalin) plus rituximab as the intervention. The registry records a start of 2006-06 and primary completion of 2015-04.
ORR, defined using CR, CRu, and PR criteria, was the primary outcome. Progression-free survival rate at 3 years was listed as a secondary outcome. The record gives an assessment timeframe for response and reports a median follow-up of 56 months for censored observations. It also includes safety counts and selected serious-event terms.
The registry record does not report an ORR estimate, a progression-free survival estimate, or outcome analyses. It also does not report the analysis population, statistical methods, or missing-data approach. The study design has no concurrent control group, so the record does not provide a randomized comparison.