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 Retrospective Observational Study To Update 5-Year Survival Of Subjects Who Participated In Axitinib Trial A4061012 (NCT01056263), a registered phase not stated study. The primary outcome is Overall Survival (OS).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01056263 |
| Phase | Phase not stated |
| Condition | Carcinoma, Renal Cell |
| Allocation | Not Stated |
| Design model | Not Stated |
| Masking | Not Stated |
| Enrollment | 52 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Pfizer |
| Results posted | Yes |
2. Clinical Question
Population
People with metastatic renal cancer who had participated in the earlier axitinib study A4061012; the record says some may also have participated in A4061008.
Intervention
Axitinib (AG-013736), received in the earlier study. The current study retrospectively collected survival information and did not assign treatment.
Comparator
No comparator group is specified for this observational study. The record cautions that this is not a randomized comparison and that arms are not a like-for-like control comparison.
Primary question
What is the estimated overall survival, including the median and its 95% confidence interval, among participants who received at least one dose of axitinib?
The objective was to collect current survival data retrospectively for participants originally included in A4061012 and estimate five-year survival. The registry describes the condition as renal cell carcinoma and the study population as people with cytokine-refractory metastatic renal cancer. The primary endpoint is overall survival, defined from the first dose of study medication until death, with follow-up censored at the last contact for participants still alive.
This question concerns the observed survival experience of a previously treated group. It is not a question about whether axitinib produces better outcomes than another treatment, because the record does not specify a concurrent control group or a randomized treatment assignment. The record also does not report the numerical survival estimate, so the endpoint definition and study objective can be described, but the survival result cannot be quantified from the registry record.
3. Trial Design
This was a completed retrospective observational study sponsored by Pfizer. Its stated purpose was to collect current survival information for people who had previously participated in axitinib trial A4061012. The registry says participants may also have participated in A4061008; it does not give further information about that possible participation. The current study lists axitinib as an observational-study drug intervention, rather than describing a newly assigned treatment.
The registry reports enrollment of 52. This is the enrollment figure, not necessarily the number in the primary analysis: the endpoint population is defined as all participants who received at least one dose of axitinib, and the number meeting that definition is not reported in the registry record. The study started in 2010-04, reached primary completion in 2010-12, and is marked completed.
The primary outcome is overall survival, with the median and a 95% confidence interval specified as the summary measures. The stated timeframe is baseline until death or up to Year 5. The endpoint description defines the survival clock as beginning at the first dose of study medication and says that participants alive at last contact are censored then. The registry lists 1 outcome measure and 1 analysis.
This design can describe survival within the identified cohort, subject to how follow-up and censoring were handled. It does not provide a randomized comparison. The registry explicitly cautions that the arms are not a like-for-like control comparison, and no comparator arm is described in the study design information. Details of the original treatment allocation, the protocol for retrospective follow-up, and any other design procedures are not 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
| Stage | Axitinib |
|---|---|
| STARTED | 52 |
| COMPLETED | 0 |
| NOT COMPLETED | 52 |
Reasons for not completing this period:
| Reason | Axitinib |
|---|---|
| Adverse Event | 12 |
| Death | 1 |
| Withdrawal by Subject | 1 |
| Lack of Efficacy | 29 |
| Progressive disease | 2 |
| Neoplasm progression | 1 |
| Objective progression or relapse | 1 |
| Ongoing in study A4061008 (NCT00828919) | 5 |
Analysis population for the primary outcome, as defined in the registry: Full analysis set included all participants who received at least 1 dose of axitinib (AG-013736).
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 | Axitinib |
|---|---|---|
| Participants analysed | 52 | |
| Age Continuous | years | 58.8 (SD 11.3) |
| Sex: Female, Male: Female | Participants | 12 |
| Sex: Female, Male: Male | Participants | 40 |
6. Primary Endpoint
The registry lists the primary outcome as Overall Survival (OS), measured over Baseline until death or up to Year 5.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | 95% Confidence Interval |
| Unit | Days |
| Endpoint classification | Time-to-Event Analysis |
Overall survival (OS) measures the time from the first dose of study medication to death. For participants who were alive, the registry says survival was censored at the last contact. The primary summary measure is the median, with a 95% confidence interval, over the stated timeframe of baseline until death or up to Year 5.
As a general statistical concept, a median time-to-event measure describes the time by which half of the population is estimated to have experienced the event, under the survival analysis approach used. It can be useful when follow-up durations vary and some participants have not experienced the event by their last observation. Censoring allows such participants to contribute follow-up information up to their last known contact without treating that contact as a death.
The confidence interval communicates uncertainty around the estimated median. Its width depends on the amount and distribution of observed follow-up and events, among other features of the analysis. The registry record defines this endpoint and summary measure but does not report the median OS estimate or its 95% confidence interval. It also does not report the number of deaths or the distribution of follow-up times.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies overall survival as the primary outcome and specifies a median with a 95% confidence interval. It defines survival time as running from the first dose of study medication to death, with living participants censored at last contact. These details establish what the intended endpoint represents. They do not establish the numerical survival experience: the median estimate and confidence limits are not reported in the registry record.
The study objective was to estimate five-year survival in people with metastatic renal cancer who had received axitinib in the earlier A4061012 study. The record reports enrollment of 52, but does not state how many participants received at least one dose and therefore belonged to the defined full analysis set. Nor does it report the number of deaths, the number censored, or the follow-up distribution. Without those details and the endpoint estimate, the precision and completeness of the survival summary cannot be assessed from the registry record.
Overall survival is a time-to-event outcome. General statistical interpretation of such an outcome depends on more than the median alone: censoring patterns and the amount of follow-up affect how much information supports the estimate. The 95% confidence interval would help convey uncertainty, but it is not reported. No hazard ratio is reported in the registry record either. A hazard ratio would ordinarily describe a relative event rate between groups over time, but the record does not identify a valid comparator for this observational study.
The record specifically notes that this was not a randomized comparison and that arms are not a like-for-like control comparison. Therefore, the study description supports an estimate of survival in the observed cohort, not a treatment-effect comparison against a concurrent control. It does not provide a basis for attributing observed survival to axitinib rather than to participant characteristics, prior or subsequent care, or other factors. Those considerations are general limitations of observational interpretation; the registry does not report enough detail to evaluate their influence in this cohort.
The record marks the study completed, but completion status does not supply the missing numerical result. The numerical median and confidence interval, and any interpretation of their precision, remain not reported in the registry record. Consequently, no conclusion about the size or certainty of the observed survival estimate can be drawn from the record details available for this analysis.
9. Statistical Methods Explained
The primary analysis is described as an estimate of median overall survival with a 95% confidence interval. The event is death, and the time origin is the first dose of study medication. Participants alive at their last contact are censored at that time. The specified analysis population includes all participants who received at least one dose of axitinib. The registry does not report the numerical median, confidence interval, event count, or actual size of this analysis population.
What does censoring mean?
As a general statistical concept, censoring occurs when the event of interest has not been observed for a participant by the end of their available follow-up. The participant is not treated as though the event occurred at the last contact; instead, the observed time contributes information up to that contact. Survival methods can incorporate these partial follow-up times. Their interpretation relies on assumptions about how censoring relates to the unobserved event time. The registry defines the censoring point as last contact for participants who are alive, but does not report how many participants were censored or describe checks of censoring assumptions.
What does a median and confidence interval convey?
In general, the median survival time is a summary of the estimated time-to-event distribution, not a guarantee about the time any particular person will experience an event. A 95% confidence interval gives an indication of statistical uncertainty in the estimate under the analysis method and its assumptions. A narrower interval generally reflects greater precision than a wider one, while an interval’s interpretation also depends on the method used to construct it. The registry specifies the confidence level but does not identify the calculation method or report the interval itself. Accordingly, precision cannot be evaluated from the registry record.
How does the observational design affect interpretation?
In general, an observational survival estimate describes the cohort as followed; it does not by itself isolate the effect of a treatment. Random allocation can support a direct comparison by balancing factors between groups on average, while a retrospective observational cohort does not have that design feature. The record explicitly says this study is not a randomized comparison and that arms are not a like-for-like control comparison. It does not describe a comparator for the primary endpoint, an adjusted analysis, or methods for controlling confounding. These methods are not reported in the registry record and should not be assumed.
The endpoint’s definition and analysis population are reported, but details of the statistical procedure for estimating the survival curve and median are not reported in the registry record. The record does not state how the confidence interval was constructed, how follow-up was handled beyond the last-contact definition, or whether any sensitivity analyses were conducted. It also does not report a hazard ratio. The registry’s general note says that only sponsor-reported hazard ratios are used for time-to-event interpretations; no such estimate appears in the available record details.
What do the planning assumptions describe?
The record describes sample-size calculations as planning illustrations based on the observed effect, not as the study’s own design. The stated assumptions are a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect to detect expressed as a stated fraction of the observed effect. It also says that time-to-event planning uses a total number of events, while other planning figures are participants per arm. These are planning conventions, not evidence that the observational study used randomized arms or was designed around those assumptions. No numerical planning results are reported in the registry record details used for this interpretation. Planning illustrations must not be read as observed power or as proof that the study can detect a particular effect.
In general, over-dispersion matters when count outcomes vary more than a model’s assumed distribution allows, because standard errors and resulting uncertainty can then be understated. That concept does not define this primary endpoint, which is time-to-event overall survival. The registry does not report a count-outcome analysis or an over-dispersion adjustment for this study.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 1 outcome measure and 1 analysis, with overall survival as the primary outcome. It does not report a multiplicity adjustment, a hierarchy of hypotheses, or a plan for controlling the chance of false-positive findings across multiple analyses. The listed counts alone do not establish whether additional analyses were conducted outside those registered details. A multiplicity plan is not reported in the registry record.
The endpoint population is defined as all participants who received at least one dose of axitinib. Enrollment is reported as 52, but the number who received at least one dose and were included in the full analysis set is not reported in the registry record. The record does not describe exclusions from that population or how participants with incomplete survival information were handled beyond the stated censoring of living participants at last contact.
As a general statistical concept, missing outcome information and censoring are related but not identical. Censoring records that a participant was last known to be alive at a particular contact; missing information may mean that the follow-up status or contact time is unavailable. The record gives a censoring definition but does not report missing-data counts, reasons for loss to follow-up, or analyses examining sensitivity to missingness. It also does not report the method used to obtain or verify retrospective survival information.
These omissions limit assessment of how completely the cohort was followed and how sensitive the estimated survival might be to incomplete information. The record does not report interim analyses, imputation methods, or sensitivity analyses. No such procedures should be inferred from the endpoint definition or the study’s completed status.
11. What the Result Does, and Does Not, Mean
The registry record describes a retrospective observational effort to update survival information for people previously treated with axitinib in A4061012. It identifies overall survival as the primary outcome, defines the time origin and censoring rule, and specifies a median with a 95% confidence interval as the summary. Those details explain the intended question and the general meaning of the endpoint.
The record does not report the median overall survival estimate, its confidence interval, the number of deaths, or the number included in the analysis population. Therefore, the observed survival result and its precision cannot be stated from the registry record. The enrollment figure of 52 is not enough to establish the size of the endpoint population because that population is defined by having received at least one dose, and the count meeting that criterion is not reported.
The study was observational, and the registry states that it was not a randomized comparison and that arms are not a like-for-like control comparison. The described information therefore does not establish how survival would compare with an alternative treatment or what part of the observed survival might be attributable to axitinib. Such a comparison would require an appropriate comparator and methods addressing differences between groups; those details are not reported in the registry record.
In general, an observational survival estimate can provide a description of outcomes in the cohort followed, while its interpretation depends on follow-up, censoring, and cohort composition. The registry record does not provide enough numerical results or analysis details to judge these features. The study’s completion status and stated objective should not be mistaken for a reported survival result or a causal treatment conclusion.
12. Why This Trial Matters Statistically
This study illustrates an important distinction between defining a clinical endpoint and reporting its result. The registry specifies overall survival, the event and time origin, the censoring rule for participants alive at last contact, and the median with a 95% confidence interval as the intended summary. These are essential ingredients for understanding a time-to-event question, but the numerical estimate and interval are not reported in the registry record.
The design also matters. Retrospective collection can extend the observation of a previously treated cohort, but the resulting survival description is not equivalent to a randomized comparison. The registry explicitly cautions that there is no randomized comparison and that arms are not like-for-like controls. This makes it important to distinguish describing survival in the cohort from estimating a comparative treatment effect.
Finally, the analysis population is defined by receiving at least one dose, while the record separately reports enrollment of 52. Because the actual number in the defined population is not reported, the denominator supporting the survival estimate cannot be checked from the record details. Together, these distinctions show why readers need the result, analysis population, and follow-up information—not just a study objective—to assess a survival analysis statistically.
13. 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 main limitation for interpretation is that the registry record does not report the primary numerical result. Although it specifies median overall survival and a 95% confidence interval, neither value is available in the record details. Death counts, censoring counts, and follow-up distribution are also not reported. As a result, neither the magnitude nor precision of the survival estimate can be assessed.
Enrollment is reported as 52, but the endpoint population consists of participants who received at least one dose of axitinib. The size of that population is not reported in the registry record, so enrollment cannot be assumed to equal the analysis denominator. The record also does not report the number of participants with available retrospective survival information or describe how status was ascertained.
The study is observational and the registry cautions against treating arms as a like-for-like control comparison. No comparator, adjustment strategy, or method for addressing confounding is reported. The record does not identify the procedure for calculating the median or confidence interval, nor does it report sensitivity analyses, missing-data methods, or details of follow-up completeness.
These are limitations of what can be interpreted from the registry record; they do not establish that a particular analysis or procedure was absent from the study itself. Such details are not reported in the registry record.
14. Related Tutorials
15. Related Statistical Calculators
16. Sources
- ClinicalTrials.gov: Retrospective Observational Study To Update 5-Year Survival Of Subjects Who Participated In Axitinib Trial A4061012 — NCT01056263.
- Registry record last updated 2012-04-20; status last verified 2012-04.
- Results first posted 2012-03-28.
- 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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17. Record Summary
NCT01056263 is a completed retrospective observational study sponsored by Pfizer. Its objective was to collect current survival data for participants previously included in axitinib study A4061012 and estimate five-year survival in metastatic renal cancer. Participants may also have participated in A4061008.
The registry reports enrollment of 52, a study start of 2010-04, and primary completion in 2010-12. The primary outcome is median overall survival with a 95% confidence interval. Survival is defined from first dose to death, with living participants censored at last contact; the analysis population is all participants who received at least one axitinib dose.
The registry record does not report the median, confidence interval, analysis-population count, death count, or follow-up distribution. It describes no randomized comparator and cautions that arms are not like-for-like controls.