Safety Study of Avastin Used as Adjunctive Therapy in Pterygium Surgery: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Safety Study of Avastin Used as Adjunctive Therapy in Pterygium Surgery (NCT01115517), a randomized phase 2 study. The primary outcome is Number of Participants Who Had Recurrence of Pterygia up to 1 Year.

2. Clinical Question

The study was framed as an assessment of both safety and efficacy. Its rationale was that recurrence can follow surgical removal, and that medications applied during surgery might affect recurrence. The registry summary distinguishes the mechanisms of action of bevacizumab and mitomycin C, but does not provide mechanistic measurements as trial outcomes. The direct clinical question in the primary result is narrower: how many participants in each group had recurrence by the one-year timeframe.

3. Trial Design

The registry identifies this as a phase 2, randomized, triple-masked, parallel-group trial. The listed enrollment is 51, and the study status is completed. The record gives a start date of 2010-10 and a primary completion date of 2015-07. The sponsor was The University of Texas Health Science Center, Houston. These registry entries describe the trial’s recorded design and conduct period; they do not establish how participants were recruited or how the masking was implemented.

The two named groups were bevacizumab and mitomycin C. The comparison was intended to evaluate adjunctive intraoperative use of these medications in pterygium surgery. The official title refers to topical application to bare sclera, while the brief summary describes a direct comparison of the safety and efficacy of adjunctive intraoperative use. Arm descriptions are not reported in the registry record, so the precise treatment procedures, doses, and any accompanying surgical details cannot be specified from the record.

Random allocation means that assignment is intended to use a chance-based process, which can help balance measured and unmeasured characteristics across groups. The registry record does not report the sequence-generation method, allocation concealment, or the details of the randomization process. Triple masking indicates that the record classifies the trial as masked at three levels, but the identities of the masked parties and procedures used to maintain masking are not reported in the registry record.

The primary endpoint was the number of participants who had recurrence of pterygia up to 1 year. The posted group results include 14 participants in the bevacizumab group and 16 in the mitomycin C group. These outcome denominators do not match the listed enrollment of 51; the registry record does not explain the difference or report how many enrolled participants were included in this endpoint analysis. The planned sample-size justification and the target number for the primary analysis 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.

Before assignment: 51 participants were consented and screened for this study, however only 39 of the 51 met eligibility criteria and were randomized.

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 Number of Participants Who Had Recurrence of Pterygia up to 1 Year, measured over 1 year.

The primary endpoint counts participants who had recurrence of pterygia up to 1 year. It is a binary outcome at the participant level: a participant is counted as having the event if recurrence is recorded during the stated period. The registry identifies the unit as participants and the timeframe as 1 year. It does not report an operational definition of recurrence, such as clinical criteria, assessment procedures, or how borderline findings were classified.

Recurrence is relevant to the study question because the registry summary describes regrowth after surgical removal as a concern and identifies prevention of recurrence as the intended purpose of adjunctive medication. Counting participants with recurrence gives a direct, clinically interpretable measure of how often the event was recorded in each group during follow-up. It does not capture the timing of recurrence within the follow-up period, the severity of recurrence, or additional clinical features unless these are separately reported.

The posted count was 0 of 14 participants for bevacizumab and 3 of 16 participants for mitomycin C. These are the reported endpoint observations, not estimates of what would necessarily occur in another group of patients or in a different setting. The registry record does not report the method used to ascertain recurrence, the completeness of follow-up, or whether all participants had the full opportunity for assessment through 1 year. Those details would help clarify how the endpoint was measured and how missing or incomplete observations were handled.

7. Results Posted in the Registry

• Mitomycin C: 18.8% (3/16) versus 0.0% (0/14) on control; risk difference 18.8 percentage points (95% CI -0.4 to 37.9); unadjusted two-proportion z-test p = 0.088.

8. Statistical Interpretation

9. Statistical Methods Explained

What does a participant count represent?

The primary endpoint is a count of participants with recurrence, rather than a count of every recurrence event. If one participant had more than one relevant observation, the endpoint still concerns whether that participant was recorded as having recurrence. This makes the outcome a participant-level binary measure: each participant contributes an event status for the specified endpoint. The registry record does not explain the detailed rules used to assign that status.

For binary outcomes, a group’s event count is interpreted relative to the number of participants contributing to that group’s endpoint result. The record reports 0 events among 14 participants for bevacizumab and 3 among 16 participants for mitomycin C. The comparison is expressed as a risk difference. In general, a risk difference subtracts one group’s event proportion from the other group’s event proportion, following a stated direction. Here, the posted direction is mitomycin C relative to bevacizumab. The listed estimate is 0.188. This is an absolute contrast in event proportions, not a relative risk or an odds ratio.

How should the confidence interval be read?

A confidence interval gives a range of values compatible with the observed data under the method used to construct it. Its endpoints reflect sampling uncertainty and the assumptions of that method. For this risk difference, the reported 95% confidence interval runs from -0.004 to 0.379. The interval crosses the no-difference value, so the data are compatible with a comparison near no difference as well as with a positive risk difference. The interval does not tell the reader the probability that the true value lies within those particular endpoints, nor does it incorporate every possible source of uncertainty, such as incomplete follow-up or outcome misclassification.

What does the p-value add?

The unadjusted p-value is 0.088. As a general statistical concept, a p-value summarizes how unusual data at least as incompatible with a null hypothesis would be if that null model and the test assumptions were correct. It does not state the probability that a treatment is effective or ineffective. It also does not convey the magnitude or precision of the estimated contrast, which are better considered using the estimate and its confidence interval. The registry record does not identify the test or report whether the p-value was prespecified, adjusted, or selected from multiple analyses.

What can be inferred from the trial design?

The record describes randomized allocation and a parallel design. In general, randomization aims to make treatment groups comparable at assignment, reducing the risk that systematic differences in participant characteristics explain an outcome contrast. It does not guarantee that groups are identical, particularly in a small trial. The record does not report the allocation sequence, concealment procedures, stratification factors, or baseline characteristics. Triple masking is recorded, but the record does not identify who was masked or how masking was maintained. These omissions limit assessment of how the design was implemented.

Parallel-group trials compare separate groups assigned to different interventions over the study period. Here, the named groups are bevacizumab and mitomycin C. The record identifies a phase 2 trial and a listed enrollment of 51. It does not report the sample-size rationale, whether enrollment met a target, or the planned statistical method. The result denominators are 14 and 16, and the record does not explain how those analysis counts relate to enrollment.

What do planning calculations mean?

In general, power calculations estimate how much information a study would need to detect a specified effect under chosen assumptions. A calculation based on an effect observed in the same trial is illustrative rather than evidence that the trial had a particular observed power. Planning illustrations are not trial outcomes, and they do not replace the actual event counts, estimate, or confidence interval. The registry record does not report the trial’s own sample-size justification, so the assumptions used in any design planning cannot be confirmed from the record. No planning calculation should be read as a claim about the probability that the observed result is correct.

The record states that planning illustrations use a two-sided significance level of 0.05, equal allocation, a normal approximation, and an effect defined as a stated fraction of the observed effect. Those are calculation assumptions, not a description of the trial’s original protocol. The record does not provide the trial’s planned target effect or establish that these assumptions were used in the original design. A sample-size illustration can show how requirements change when the effect to detect changes, but it cannot recover unreported design decisions or remedy uncertainty in the observed endpoint estimate.

What analysis details remain unknown?

The registry lists no posted analyses. That means inferential analysis entries are not reported in the registry record; it does not establish that investigators conducted no analyses. The record does not report a statistical analysis plan, covariate adjustment, handling of missing outcomes, analysis population, or sensitivity analyses. These details matter because analysis choices can affect estimates and uncertainty. The reported unadjusted comparison is therefore best interpreted as the posted result with its analysis details left unspecified.

The registry lists three outcome measures, including the primary recurrence endpoint and two secondary safety-related outcomes. The record does not report a multiplicity procedure or identify a hierarchy for interpreting multiple outcomes. In general, examining multiple outcomes can increase the chance that at least one result appears notable by chance, depending on the analysis strategy. Without a stated plan, the p-value should be treated as an unadjusted result rather than as evidence that accounts for all possible outcome testing.

10. Confidence Intervals and Precision

The estimated risk difference for mitomycin C relative to bevacizumab is 0.188. Its 95% confidence interval extends from -0.004 to 0.379. The interval is wide relative to the point estimate and includes values close to no difference, while also extending to substantially larger positive differences. This indicates that the observed data do not pin down the size of the group contrast precisely.

Precision depends on the amount of information in the data, including the number of participants and, for an event outcome, how many events occurred. The posted primary outcome includes 0 events in the bevacizumab group and 3 in the mitomycin C group. With so few observed events, the estimate can remain uncertain even when the point estimate appears to favor one direction. The reported confidence interval makes that uncertainty visible; focusing only on the point estimate or the raw counts would conceal it.

In general, a 95% confidence interval describes the range produced by a method that, under repeated use and its assumptions, would cover the target value at the stated rate. It is not a guarantee that the interval contains the true value in this particular study. It also does not account automatically for unreported design or data issues. The registry record does not provide enough detail to assess the method used to calculate this interval or whether it accounts for any features beyond the posted group counts.

The p-value is 0.088, and it is reported as unadjusted. It should be read with the estimate and interval rather than as a stand-alone verdict. The interval’s breadth is a central feature of the result: the data are compatible with a range of possible group differences. The listed enrollment of 51 does not by itself establish the precision of this endpoint estimate, because the reported outcome denominators are 14 and 16 and the relationship between these numbers is not explained in the registry record.

11. Multiplicity, Missing Data and Analysis Populations

The registry lists three outcome measures: the primary recurrence measure and two secondary outcomes concerning complications and related serious adverse events. It reports no analysis entries. A count of posted analyses is not evidence that no analyses were performed; it indicates that inferential analysis details are not reported in the registry record. The record does not identify a prespecified statistical analysis plan, a hierarchy among outcomes, or a multiplicity adjustment.

In general, multiplicity arises when several outcomes, comparisons, or analyses are considered. Without a clear prespecified strategy, the chance of a seemingly notable result can be difficult to interpret across all the analyses undertaken. The primary endpoint is identified, but the registry record does not explain whether it was the sole primary analysis or how secondary outcomes were to be interpreted. The unadjusted p-value of 0.088 should therefore be understood as an unadjusted result, not as a result that is known to account for all possible testing.

The listed enrollment is 51, while the primary endpoint counts use 14 participants in the bevacizumab group and 16 in the mitomycin C group. The record does not explain the difference, report a participant flow, or state whether the endpoint denominators represent everyone assigned, everyone treated, or another analysis population. It also does not report the number or reasons for missing outcome observations, how missing data were handled, or whether participants were analyzed according to assigned group.

These omissions matter because missingness and analysis-population choices can affect the interpretation of an estimated group contrast. In general, analyses based on participants with observed outcomes rely on assumptions about why other outcomes are missing; different assumptions can lead to different conclusions. The posted result does not allow those assumptions to be evaluated. The registry record also does not report a sensitivity analysis addressing incomplete follow-up or missing endpoint data.

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 0% reporting threshold.

The posted safety figures record 0 related serious adverse events among 14 participants at risk in the bevacizumab group and 0 among 16 participants at risk in the mitomycin C group. The registry also records 0 in the other related adverse-event count for each group, with the same group counts at risk. These figures describe the events recorded in the registry; they do not establish that no adverse events of any kind occurred or that the treatments have equivalent safety.

The secondary outcomes include the number of participants with complications from treatment to recurrence and the number with related serious adverse events from treatment to 1 year. The registry record does not provide posted results for these outcome measures as separate endpoint analyses. The safety summary does not report event-level details or describe how events were assessed for relatedness. Death counts are not reported in the registry record.

In general, a zero count means that no event in the specified category was recorded among the participants included in that safety summary. It does not establish that the underlying risk is zero. The group sizes and event counts are limited, and the record does not provide enough information to assess completeness of adverse-event collection, follow-up duration for every participant, or the criteria used to classify seriousness and relatedness. These safety figures should be read as descriptive registry counts, not as a definitive comparison of overall safety.

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

The posted primary result is a comparison of observed recurrence counts through 1 year: 0 of 14 participants in the bevacizumab group and 3 of 16 in the mitomycin C group. The reported risk difference, in the direction of mitomycin C relative to bevacizumab, is 0.188, with a 95% confidence interval from -0.004 to 0.379. The unadjusted p-value is 0.088. Together, these statistics describe the outcome in the trial and show substantial uncertainty around the size of the comparison.

The result does not prove that one treatment is better, worse, or equivalent to the other. A point estimate is not a guarantee of the underlying difference, and the confidence interval includes a range of possibilities. The posted counts are also based on fewer participants than the registry’s listed enrollment of 51, with no explanation of the difference. That limits conclusions about how completely the endpoint results represent everyone enrolled.

The trial’s primary endpoint addresses recurrence, not every aspect of safety or surgical outcome. The registry summary describes safety as part of the study purpose, but the available safety figures are limited to the recorded adverse-event categories and do not supply detailed event descriptions. Likewise, the endpoint does not report timing, severity, or clinical course of recurrence. Those matters cannot be inferred from a participant count alone.

The findings apply to the trial as recorded: a phase 2 randomized, triple-masked, parallel study comparing bevacizumab and mitomycin C as adjunctive treatments in pterygium surgery. The registry record does not report participant characteristics, operational outcome definitions, the exact procedures, or the analysis plan. Without those details, the result cannot establish how well it generalizes to other populations, clinical settings, or treatment procedures. It is one estimate with limited event information, not a complete answer about comparative effects.

In general, clinical interpretation should distinguish the direction of an observed estimate from the certainty around it. The estimate is positive in the stated comparison direction, while the interval indicates that the true difference remains uncertain. The result should not be converted into a treatment recommendation. It provides a statistical description of the posted data and leaves important questions about design implementation, missing observations, and outcome assessment unresolved.

14. Why This Trial Matters Statistically

This trial raises a useful statistical question: how should a small event count be interpreted when the estimated contrast is accompanied by substantial uncertainty? The recurrence counts are 0 of 14 for bevacizumab and 3 of 16 for mitomycin C. A comparison based on these observations yields a risk difference of 0.188, but its 95% confidence interval ranges from -0.004 to 0.379. The interval illustrates why the estimated direction and the precision of the estimate must be considered together.

The registry also makes clear that enrollment and endpoint denominators are different quantities. Enrollment is listed as 51, while the primary outcome results include 14 and 16 participants in the respective groups. Without participant flow or an account of the analysis population, readers cannot determine how the endpoint counts relate to everyone enrolled. This is a practical reminder that denominator information is essential when interpreting clinical trial results.

The study is identified as a pilot phase 2 trial and compares two adjunctive medications in a surgical setting. Such a setting can raise distinct questions about outcome definition, follow-up, and safety monitoring. The registry specifies recurrence up to 1 year and names secondary outcomes for complications and related serious adverse events, but detailed assessment procedures and separate secondary results are not reported. Statistical interpretation depends on these design and measurement details as well as on the numerical estimate.

Finally, the posted unadjusted p-value of 0.088 does not replace consideration of the effect estimate, interval, event counts, and missing analysis details. The record does not report a statistical analysis plan or multiplicity strategy. This trial therefore illustrates a broader principle: a single inferential statistic cannot carry the whole interpretation. Transparent reporting of denominators, outcome definitions, analysis populations, and uncertainty is needed to assess what a clinical comparison can support.

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.

Several trial-specific details needed to evaluate the primary result are not reported in the registry record. The operational definition of recurrence, method of clinical assessment, and procedures for resolving uncertain classifications are not specified. The recurrence timeframe is listed as up to 1 year, but completeness of follow-up and the timing of assessments are not described. Without these details, the consistency and completeness of outcome ascertainment cannot be evaluated.

The registry lists enrollment of 51, but the primary outcome is reported for 14 participants in the bevacizumab group and 16 in the mitomycin C group. Participant flow, reasons for any exclusions or missing outcomes, and the analysis population are not reported. The record does not state whether the result includes all randomized participants or how participants with incomplete follow-up were handled. This is a material limitation for interpreting the scope of the posted comparison.

The record also omits arm-specific treatment procedures, dose and application details, baseline characteristics, and details of randomization and masking. Although the trial is classified as randomized and triple-masked, the methods used to implement these features are not reported. The statistical analysis plan, sample-size justification, analysis test, and any sensitivity analyses are also not reported in the registry record. Consequently, it is not possible to assess whether the displayed inferential analysis followed a prespecified plan.

The safety information is limited: the registry records no related serious adverse events in either group, but does not provide detailed event descriptions or explain event ascertainment. Separate posted results for the secondary outcome measures are not available in the record. These limitations do not negate the reported counts; they define the boundaries of what those counts can establish.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Safety Study of Avastin Used as Adjunctive Therapy in Pterygium Surgery — NCT01115517.
• Registry record last updated 2016-10-21; status last verified 2016-09.
• Results first posted 2016-09-02.
• 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

The registry record describes a completed phase 2 randomized, triple-masked, parallel trial sponsored by The University of Texas Health Science Center, Houston. Listed enrollment was 51. The study compared bevacizumab with mitomycin C as adjunctive therapy during pterygium surgery. Its primary endpoint was the number of participants with recurrence up to 1 year.

The posted primary counts were 0 of 14 participants for bevacizumab and 3 of 16 for mitomycin C. The risk difference for mitomycin C relative to bevacizumab was 0.188, with a 95% confidence interval from -0.004 to 0.379 and an unadjusted p-value of 0.088. The registry also recorded 0 related serious adverse events in each group. Participant flow, analysis populations, missing-data handling, outcome definitions, and the statistical analysis plan are not reported in the registry record.