Evaluation of the Impact of Adjuvants Accompanying Peptide Immunization in High-Risk Melanoma: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Evaluation of the Impact of Adjuvants Accompanying Peptide Immunization in High-Risk Melanoma (NCT00273910), a randomized phase 2 study. The primary outcome is Immunologic Response Rate.

2. Clinical Question

3. Trial Design

This was a randomized, phase 2, parallel-group study with no masking. The registry lists an enrollment of 104 and a completed status. The brief summary described enrollment of up to 132 participants; the registry does not explain the distinction between that planned figure and the recorded enrollment.

The study compared six preparations of gp100:209-217 (210M). Montanide-containing regimens used subcutaneous injection; saline-containing regimens used intradermal injection. Imiquimod was applied to the skin at the injection site in some regimens. The arm descriptions specify injection on day one every three weeks, for twelve cycles over 33 weeks. Where included, imiquimod was applied daily for 5 days following injection. The registry lists vortex and two-syringe versions of some Montanide regimens.

The primary outcome timeframe is 48 months. The stated endpoint is the number of participants meeting an immunologic response threshold, not a time-to-event measure. The posted arm counts are 14 participants with 2 responses for the vortex Montanide comparator; 10 with 0 for vortex Montanide plus imiquimod; 12 with 0 for saline; 15 with 3 for saline plus imiquimod; 5 with 1 for the two-syringe Montanide preparation; and 5 with 0 for the two-syringe Montanide preparation plus imiquimod.

The sponsor is the National Cancer Institute (NCI). The registry records a start of 2006-01 and primary completion in 2010-05. Further details about randomization procedures, allocation concealment, or protocol amendments 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

Analysis population for the primary outcome, as defined in the registry: The number of participants analyzed and results are correct. We do not have the immunologic response rate data for all patients.

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.

Only the first 6 of 7 groups are shown.

6. Primary Endpoint

The registry lists the primary outcome as Immunologic Response Rate, measured over 48 months.

The primary endpoint is the number of participants with an immunologic response to the assigned gp100 preparation. The registry defines evidence of immunization as at least 10 Elispots/100,000 cells above background. An injection site reaction is specifically excluded from the definition, so a local reaction alone does not satisfy the endpoint.

This endpoint is used to compare whether the different vaccine preparations prompt a measurable immune response. The registry states that the preparation with the greater number of immunologic responses would be the one most likely to be selected for future study on the basis of immunization alone. That makes the outcome an immune-response measure, rather than a direct measure of melanoma recurrence, survival, or clinical benefit.

The outcome timeframe is 48 months. Arm-level counts are posted, but the registry also says immunologic response-rate data are not available for all patients. The endpoint description says the number analyzed and results are correct; eligibility for analysis, the handling of unavailable results, and the timing of response assessments are not reported in the registry record.

7. Results Posted in the Registry

• Adj-3 A2 gp209(2M) in IFA SQ + Imiquimod (Vortex): 0.0% (0/10) versus 14.3% (2/14) on control; risk difference -14.3 percentage points (95% CI -32.6 to 4.0); unadjusted two-proportion z-test p = 0.212.
• Adj-3 A2 gp209(2M) in Saline ID: 0.0% (0/12) versus 14.3% (2/14) on control; risk difference -14.3 percentage points (95% CI -32.6 to 4.0); unadjusted two-proportion z-test p = 0.173.
• Adj-3 A2 gp209(2M) in Saline ID + Imiquimod: 20.0% (3/15) versus 14.3% (2/14) on control; risk difference 5.7 percentage points (95% CI -21.6 to 33.0), risk ratio 1.40 (0.27–7.18); unadjusted two-proportion z-test p = 0.684.

8. Statistical Interpretation

9. Statistical Methods Explained

What does a risk difference describe?

General statistical explanation: A risk difference compares the proportion with an event in one arm with the proportion in a reference arm. A value below zero indicates fewer observed events in the comparison arm; a value above zero indicates more. In this study, the event is meeting the immunologic response definition. Risk differences are reported for three comparisons with the vortex Montanide preparation. Their estimates are -0.143, -0.143, and 0.057. These are unadjusted comparisons based on the posted arm summaries, not evidence that the treatment preparations are interchangeable.

How should confidence intervals be read?

General statistical explanation: A confidence interval represents uncertainty around an estimate under the statistical method used. A wide interval means the estimate is not precise; an interval spanning the no-difference value leaves a range of possibilities that includes no difference. Here, all three risk-difference intervals include zero. The intervals are wide relative to their point estimates, consistent with limited precision in these small arm-level samples. The registry does not report the method used to construct the comparative confidence intervals.

What do the p-values add?

General statistical explanation: A p-value measures how incompatible the observed data are with a specified null model, under assumptions of the analysis. It is not the probability that the null hypothesis is true, and it does not measure the size or clinical importance of a difference. The unadjusted p-values are 0.212, 0.173, and 0.684. The analysis plan, test used, and any prespecified threshold for interpreting these comparisons are not reported in the registry record. The 0.05 significance level appears in the planning illustration, not as a reported analysis-plan threshold.

What do the relative measures mean?

General statistical explanation: A risk ratio compares event proportions as a ratio; an odds ratio compares the odds of the event. These measures express the contrast differently from an absolute risk difference and can be especially unstable when event counts are sparse. For saline plus imiquimod versus the reference arm, the posted risk ratio is 1.4, with an interval from 0.273 to 7.176; the odds ratio is 1.5, with an interval from 0.211 to 10.65. Their breadth reflects substantial uncertainty. No relative estimates are posted for the other comparisons.

How do the planning figures differ from trial results?

The planning illustration applies assumptions to the observed effect for the saline-plus-imiquimod comparison. It specifies a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. For planning at 100% of the observed effect, it gives 682 participants per arm for 80% power and 913 participants per arm for 90% power. At 75% of the observed effect, the corresponding figures are 1,173 and 1,569 participants per arm. At 50% of the observed effect, they are 2,546 and 3,408 participants per arm. These are planning illustrations, not observed power, trial enrollment targets, or observed outcomes. They are not a reconstruction of the trial's original design; the registry does not report the original sample-size justification.

In general, over-dispersion means that outcome variability exceeds what a chosen statistical model expects. Accounting for it can affect uncertainty estimates and required sample sizes. The registry record does not identify an over-dispersion model or report an analysis method that would require interpreting one. More broadly, the statistical test, confidence-interval construction, covariate adjustment, and analysis population definitions are not reported in the registry record, so the comparative findings should be read as posted summaries rather than as a fully documented statistical analysis.

10. Confidence Intervals and Precision

The response counts are low in each arm, and the analyzed arm sizes range from 5 to 15. A small number of outcomes makes each estimate sensitive to individual observations and leaves substantial uncertainty about the underlying response patterns. The point estimates alone should therefore not be read as stable rankings of the preparations.

For the three comparisons with the vortex Montanide reference, the risk-difference intervals are -0.326 to 0.040, -0.326 to 0.040, and -0.216 to 0.330. Each contains zero and also spans values on both sides of zero. The results do not precisely distinguish a lower response proportion from a higher one. The exact confidence level and construction method are not reported in the registry record.

The relative estimates for saline plus imiquimod are also imprecise: the risk ratio is 1.4 with an interval from 0.273 to 7.176, while the odds ratio is 1.5 with an interval from 0.211 to 10.65. Both intervals cover a wide range of possible relative associations, including values in either direction around no relative difference.

There are no comparative confidence intervals posted for the two-syringe preparations. In addition, the registry states that response data are unavailable for all patients. Without details on the amount, pattern, and handling of missing response information, precision based on analyzed participants may not capture all uncertainty relevant to the full study population. Overall, the results support only a cautious description of observed counts; they do not provide a precise ordering of all preparations.

11. Multiplicity, Missing Data and Analysis Populations

The study compares six preparations, creating the possibility of multiple pairwise questions. The registry posts comparative estimates for three preparations versus the vortex Montanide reference. Estimates for the two-syringe preparations are not reported. The registry record does not report whether other comparisons were planned, whether the posted comparisons were prespecified, or whether any adjustment for multiple testing was used. The p-values are explicitly unadjusted, so they should not be treated as accounting for the full set of possible comparisons.

The registry identifies the number analyzed and results as correct, but also states that immunologic response-rate data are not available for all patients. This means the posted outcome data do not cover every patient for whom response information would be relevant. The number with unavailable outcome data by arm, the reasons for missingness, the method used to handle missing data, and any sensitivity analyses are not reported in the registry record.

Enrollment in the registry is listed as 104, while the brief summary describes enrollment of up to 132 participants. The record does not explain the relationship between these figures. The arm-level analysis counts are smaller than the planned maximum described in the summary, but the record does not say whether that reflects recruitment, eligibility, follow-up, outcome availability, or other analysis-population criteria.

The registry does not report whether analyses followed intention-to-treat principles, whether participants were excluded after randomization, or how protocol deviations were handled. It also does not describe an interim-analysis plan. These omissions do not alter the posted counts, but they limit assessment of how representative the analyzed participants are and how the comparative findings relate to the original randomized groups.

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.

Most frequent non-serious adverse event terms

The serious-adverse-event figures list 0 affected participants in each of the six arms. The numbers at risk differ by arm: 19, 19, 18, 19, 15, and 14, respectively. These are the registry's reported serious-event counts and denominators; they are not the primary immunologic-response analysis counts.

The registry also lists other adverse events as affecting all participants at risk in each arm: 19 of 19, 19 of 19, 18 of 18, 19 of 19, 15 of 15, and 14 of 14. The record does not provide further detail about the nature, severity, duration, or attribution of these other events in the information. The serious adverse event terms are not reported in the registry record. Death counts are also not reported in the registry record.

These figures should be read as descriptive counts within the reported safety groups. They do not establish comparative safety, and the absence of reported serious events in these groups does not show that serious events are impossible. The registry does not report a statistical comparison or additional information needed to assess differences in safety between preparations.

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

The posted data describe immunologic response counts for six gp100 preparations and provide unadjusted estimates for three comparisons with the vortex Montanide reference. The response counts are 2 in the reference arm, 0 for vortex Montanide plus imiquimod, 0 for saline, 3 for saline plus imiquimod, 1 for the two-syringe Montanide preparation, and 0 for the two-syringe Montanide preparation plus imiquimod. The comparative estimates are uncertain, and their confidence intervals include no difference.

These findings do not establish that any preparation is superior, equivalent, or inferior. Nor do the counts demonstrate that an added component caused a difference: the posted results are small, imprecise comparisons, and the analysis details are limited. The unadjusted p-values do not resolve those uncertainties, and the record does not report adjustment for multiple comparisons.

The endpoint measures an immune response by an Elispot threshold. It is not a direct measure of melanoma recurrence or another clinical outcome. The registry's stated rationale was to identify a preparation for possible future study based on immunization alone; the results cannot establish whether any preparation changes recurrence risk or other patient outcomes.

The registry says response data are not available for all patients, and the handling of unavailable results is not reported. Safety listings show no serious adverse events among those listed at risk, while other adverse events are recorded for all participants at risk in each arm. These safety counts are descriptive and do not support a definitive comparative safety conclusion. Taken together, the record provides exploratory information about observed immunologic responses, with substantial limits on precision and completeness.

14. Why This Trial Matters Statistically

This trial is statistically informative as an example of how a randomized comparison can still yield limited precision when event counts and analyzed arm sizes are small. The arms recorded between 0 and 3 immunologic responses, and the posted confidence intervals are broad. A point estimate may look favorable in one direction, but the interval shows that the estimate is compatible with a much wider range of underlying differences.

The comparison also involves more than one preparation. When many arms can be contrasted, multiplicity becomes relevant: selective attention to a single observed contrast can overstate how compelling it is. The registry reports three unadjusted comparisons against one reference arm but does not report a multiplicity strategy or the status of other planned contrasts. This makes it important to distinguish descriptive patterns from confirmatory evidence.

The outcome is an immunologic response, an intermediate measure intended to inform future research on vaccine preparation. Such an endpoint can answer a focused biological question without answering whether recurrence or other clinical outcomes change. Keeping that distinction clear prevents an immune-response count from being interpreted as direct evidence about a clinical endpoint.

Finally, missing response information and incomplete reporting of analysis methods affect interpretation even when the posted arm counts are considered accurate. The record's acknowledgment that response data are unavailable for all patients makes completeness a central issue, not a technical footnote. The trial illustrates why effect estimates, uncertainty, outcome meaning, analysis transparency, and multiplicity need to be considered together.

15. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The primary limitation is incomplete outcome availability: the registry says immunologic response-rate data are not available for all patients. It does not report the number with missing responses by arm, why results were unavailable, or how missing observations were handled. As a result, the posted analyzed counts cannot be assumed to describe all randomized participants equally well.

Arm sizes are small, and response counts are sparse. The reported confidence intervals are broad, and there are no comparative estimates for the two-syringe preparations. Although the study lists six preparations, the registry's comparative results cover only three contrasts against the vortex Montanide reference. It does not report how the other comparisons were analyzed or whether the reported contrasts were selected in advance.

Statistical reporting is limited. The analysis test, confidence-interval method, analysis population, allocation procedures, and multiplicity approach are not reported in the registry record. The planning illustration is based on the observed effect and specified assumptions; it is not the trial's own design justification. The record does not report the original sample-size rationale or an interim-analysis plan.

The primary endpoint is immunologic and does not directly measure recurrence. The registry's stated 48 months timeframe does not by itself clarify when immune responses were assessed or how repeated observations were summarized. The relationship between the listed enrollment of 104 and the brief summary's planned enrollment of up to 132 is also not explained. Safety information is limited to event counts; event terms and death counts are not reported in the registry record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Evaluation of the Impact of Adjuvants Accompanying Peptide Immunization in High-Risk Melanoma — NCT00273910.
• Registry record last updated 2012-10-19; status last verified 2012-10.
• Results first posted 2012-08-14.
• 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 describes a completed randomized phase 2 parallel-group study with no masking, sponsored by the National Cancer Institute (NCI). It compared six gp100:209-217 (210M) preparations involving Montanide or saline, different injection routes, and imiquimod use. The primary endpoint was the number of participants meeting an immunologic response threshold, with a stated timeframe of 48 months.

Arm-level response counts are posted, along with three unadjusted comparisons against the vortex Montanide preparation. The estimates are imprecise, and response data are not available for all patients. The registry does not report comparative results for the two-syringe preparations or several details of the statistical analysis. Safety listings report 0 serious adverse events in each arm and other adverse events among all participants at risk. The findings describe immune-response counts, not melanoma recurrence outcomes.