Topical Tazarotene in Treating Patients With Basal Cell Skin Cancer and Basal Cell Nevus Syndrome on the Face: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Topical Tazarotene in Treating Patients With Basal Cell Skin Cancer and Basal Cell Nevus Syndrome on the Face (NCT00489086), a na phase 2 study. The primary outcome is Complete Response Rate.

2. Clinical Question

3. Trial Design

This was a phase II, single-arm, open-label trial of topical tazarotene cream. The stated study population was people with basal cell skin cancer and basal cell nevus syndrome on the face. The registry lists an enrollment of 36, identifies the sponsor as UCSF Benioff Children's Hospital Oakland, and records the study status as completed. The listed start is 2004-07 and the primary completion is 2012-06.

A single-group design means the intervention was assessed without a concurrent control arm. The record lists allocation as not applicable and masking as none. There is therefore no randomized treatment comparison in this trial, and differences from an external population or another study would not constitute a randomized estimate of treatment effect.

The primary endpoint was a participant-level complete-response rate, with a stated timeframe of 36 months. Its definition incorporates an application period of 18 months and a subsequent 18-month period in which the lesion must not recur. Surgical removal of a target lesion was classified as failure. The record describes an intention-to-treat approach for participants who completed baseline evaluation and applied at least one dose; drop-outs were counted as non-responders. It also identifies N=2 exclusions from analysis, for reasons related to revised diagnosis and inability to confirm at least one dose.

The registry lists secondary outcomes concerning time to lesion clearance, time to progression, estimated duration of complete response, and overall response at treated lesions. Their numerical results and detailed analysis procedures are not reported in the registry record. A protocol-level account of the rationale for enrollment, planned analyses, and any interim monitoring is also 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: N=2 participants excluded from analysis: N=1 due to revised BCNS diagnosis and N=1 because unable to confirm administration of at least one dose of tazarotene.

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 Complete Response Rate, measured over 36 months.

The primary endpoint was the complete-response rate, measured as a count of participants meeting the trial's complete-response definition. A target lesion had to disappear visibly during the 18 months of tazarotene application and remain absent, without recurrence, during the ensuing 18 months. Surgical removal of a target lesion counted as treatment failure. Drop-outs were also considered non-responders under the stated analysis approach.

This endpoint was intended to capture more than an initial visible change: it required a response to persist through the specified follow-up period. In general, a sustained-response endpoint can distinguish an initial clearance from a response that remains present over time. That interpretation depends on consistent assessment and complete follow-up, details that are not fully reported in the registry record.

The registry gives a 36 months timeframe and states the prespecified decision thresholds: a complete-response rate of at least 50% was defined as treatment success, while a rate of 25% or less was defined as treatment failure. These are decision criteria, not observed results. The posted information does not include the number of participants with complete response, the observed rate, or an uncertainty interval. Whether the trial met either threshold is therefore not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a single-group design estimate?

This trial assigned participants to a single intervention group and had no concurrent control arm. In general, a single-group study can describe outcomes observed after an intervention, but it cannot provide the same controlled comparison as a randomized trial. A change or response may reflect the intervention, the natural course of the condition, measurement practices, participant selection, or other influences. Without a concurrent comparator, these explanations are not separated by random allocation.

The registry identifies the study as open label and lists masking as none. In general, masking is used to limit the influence of knowledge about treatment on care, participant reporting, or outcome assessment. The record does not report additional procedures that would show how outcome judgments were protected from such influence. This matters because the primary endpoint involves visible lesion disappearance and recurrence.

How should the response endpoint be understood?

The endpoint was a count of participants meeting a sustained complete-response definition. It required visible disappearance of a target lesion during the application period and no recurrence during the subsequent follow-up period. Surgical removal was a failure, as were drop-outs under the stated analysis description. These rules determine how outcomes were classified; they do not tell the reader how many participants met the criteria.

In general, a binary endpoint records whether each participant meets a defined condition, such as complete response, or does not. A response rate summarizes the fraction meeting that condition in the analysis population. Interpreting a rate requires a clear numerator and denominator, consistent outcome assessment, and information about how missing observations were handled. The registry gives the classification rules but not the response numerator, reported rate, or analysis denominator.

What do uncertainty measures add?

A point estimate alone gives an estimated response level, while an uncertainty interval conveys how much statistical uncertainty surrounds that estimate. In general, intervals tend to be wider when information is limited or outcomes are variable, and narrower when the data provide greater precision. A significance test addresses a different question and does not by itself describe the range of plausible effect values. The registry record does not report a primary response estimate, confidence interval, or test result, so these features cannot be assessed for this trial.

The record's prespecified success threshold of at least 50% and failure threshold of 25% or less are decision criteria. They are not estimates and do not quantify uncertainty. A result near a threshold can be difficult to interpret without precision information; even a result on one side of a threshold would need to be read in light of its uncertainty and the design's limitations. The observed value needed for that assessment is not reported in the registry record.

What do the planning illustrations mean?

In general, sample-size calculations describe how much information a future study might need under stated assumptions about the target effect, significance level, allocation, and statistical model. Such calculations are planning illustrations, not outcomes observed in the trial and not evidence that the trial had a particular probability of detecting an effect. The registry record does not report the trial's own sample-size justification or statistical plan. It also does not report an observed primary effect from which a trial-specific planning illustration could be interpreted as a result.

For a binary outcome, planning depends on the assumed response rates in the groups being compared and on the chosen comparison. This trial had no concurrent comparator group, so a two-group planning scenario would be hypothetical rather than a description of its design. A sample-size illustration based on an observed effect would also require a reported observed effect; the primary result is not reported in the registry record. No planning illustration should therefore be read as observed power or as evidence of efficacy.

What can be inferred from the safety counts?

The registry lists participants with serious adverse events and participants with other adverse events, alongside the number at risk. These are descriptive safety summaries. In general, counts can indicate how many participants experienced at least one event in a category, but they do not establish why an event occurred. A causal comparison requires a suitable reference group and comparable observation and reporting procedures. Neither is available as a randomized comparison in this single-group record.

Event counts also need careful interpretation because a participant may experience more than one event, and the record's summaries should not be treated as a full event-level account unless the reporting specifies that. The posted serious-event terms and percentages offer limited detail about the events; the registry does not report fuller context, timing, duration, severity grading, or causal attribution for these terms. These omissions constrain interpretation of safety, just as the missing response estimate constrains interpretation of efficacy.

Overall, the statistical framework can be described from the endpoint definition, group structure, and event summaries. The numerical primary result and a detailed statistical analysis plan are not reported in the registry record, so neither an effect estimate nor its statistical precision can be explained from the posted information.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Tazarotene Cream")
n      <- c(34)
events <- c(2)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Tazarotene Cream  34  2  5.9  0.7  19.7  1.6  19.1  1.8  19.2

11. Multiplicity, Missing Data and Analysis Populations

The registry lists the primary complete-response endpoint and secondary outcomes concerning time to lesion clearance, time to progression, estimated duration of complete response, and overall response at treated lesions. It reports five outcome measures and zero analyses. The numerical results for the secondary outcomes, and the analytic details for them, are not reported in the registry record.

When a study evaluates several outcomes or performs several statistical tests, the chance of at least one apparently notable result can increase. In general, multiplicity procedures may adjust interpretation or testing to account for a collection of planned comparisons. The registry record does not report whether any such procedure was planned or used. It also does not report an analysis hierarchy beyond identifying the complete-response rate as the primary endpoint. Without those details and the outcome results, the handling of multiplicity cannot be evaluated.

The primary analysis description specifies an intention-to-treat approach for participants with baseline evaluation and at least one dose, considers drop-outs non-responders, and identifies N=2 exclusions. One exclusion followed a revised diagnosis; the other reflected inability to confirm at least one dose. The analysis denominator and outcome counts are not reported in the registry record. The record does not further describe missing outcome assessments, their timing, or any sensitivity analyses examining alternative assumptions.

In general, missing-data methods can affect estimates when outcome status is unavailable, especially if the likelihood of missingness is related to response. Counting drop-outs as non-responders is a stated rule, but it does not resolve every question about missing measurements or explain how the exclusions were incorporated. The registry record does not report a detailed analysis population definition beyond the information above, or whether the reported safety summaries used the same population as the primary endpoint.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 3% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: prostate cancer diagnosis (2.8%), cellulitis and maxillary sinusitis (2.8%).

The registry lists 2 serious adverse events among 36 participants at risk, 31 participants with other adverse events among 36 at risk, and 0 deaths in the Tazarotene Cream group. The serious-event terms are prostate cancer diagnosis and cellulitis and maxillary sinusitis, each reported as 2.8%. These are descriptive counts and terms, not evidence that the intervention caused the events.

In general, an adverse-event summary records events observed after treatment exposure; an event's presence does not by itself establish a causal relationship. The registry does not provide a randomized comparator group, so these counts cannot be interpreted as a comparative risk estimate. The available information also does not give the timing, duration, severity grading, or attribution for the listed serious events. The percentages are reported as event-term figures, and the record does not provide further context for interpreting their calculation.

Serious and other adverse-event categories should be read separately as recorded. The other-adverse-event count does not indicate which specific events occurred, while the serious-event terms do not provide a comprehensive account of all safety outcomes. These summaries do not establish overall safety or quantify a causal treatment effect.

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

The registry record describes a phase II, open-label, single-group evaluation of topical tazarotene cream for facial basal cell lesions in people with basal cell nevus syndrome. It defines a complete response as visible disappearance of a target lesion during the 18 months of application, with no recurrence during the ensuing 18 months. It also specifies that surgical removal counted as failure and that drop-outs were treated as non-responders.

Those details show what the trial intended to measure and how it intended to classify response. They do not show how many participants achieved complete response. The primary response count, rate, and uncertainty interval are not reported in the registry record. The stated thresholds of at least 50% for success and 25% or less for failure cannot be applied without the observed result.

The design also limits what a result could establish. Because there was no concurrent control group and masking was absent, an observed response would describe the experience in the treated group, not a randomized estimate of the difference attributable to tazarotene. The registry record does not provide sufficient information to assess other potential influences on lesion assessment or follow-up.

The safety summaries report serious and other adverse-event counts and list serious-event terms, but do not establish causation or comparative safety. They should be interpreted as recorded events in the study group, not as proof that treatment caused or prevented any event.

In general, clinical interpretation combines the endpoint estimate, its precision, the study design, and the completeness of reporting. Here, the design and endpoint rules are available, but the primary result and key analytic details are not. The posted information therefore supports a description of the study question and its reporting limits, not a conclusion about the size, reliability, or clinical importance of a treatment effect.

14. Why This Trial Matters Statistically

This trial illustrates why endpoint definitions and result reporting need to be read together. The registry gives a detailed complete-response rule: visible disappearance during treatment, no recurrence during the stated follow-up, and classification of surgical removal or drop-out as failure. Such rules make clear what the investigators intended to count. Without the observed response count and rate, however, the endpoint definition alone cannot answer the clinical question.

The record also highlights the interpretive limits of a single-group design. A response observed among treated participants is not a randomized comparison, and the open-label designation indicates that masking was absent. These design features are important when an endpoint depends on visible assessment and when the outcome is intended to describe treatment efficacy.

For biostatistical interpretation, the missing primary estimate is consequential. A complete-response rate without its denominator and uncertainty measure cannot be assessed for precision, and the prespecified decision thresholds cannot be evaluated. The record identifies exclusions and a rule for drop-outs, but does not report the final analysis denominator or additional missing-data analyses.

The safety counts provide some descriptive information, yet they do not supply a comparator or causal attribution. Taken together, the record shows that statistical interpretation relies not only on the planned endpoint but also on complete numerical reporting, transparent analysis populations, and an appropriate design for the intended comparison. Those elements distinguish a clearly specified question from an answer that can be quantitatively assessed.

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 principal limitation for interpreting the primary endpoint is that its observed result is not reported in the registry record. The complete-response count, rate, analysis denominator, and uncertainty interval are absent. As a result, the prespecified success and failure criteria cannot be evaluated against an observed response.

The single-group, open-label design has no concurrent randomized comparator. It therefore cannot isolate an intervention effect from other explanations for outcomes, and masking was not used. The registry record does not describe additional safeguards or detailed procedures for lesion assessment, recurrence evaluation, or follow-up completeness.

The analysis description identifies N=2 exclusions and states that drop-outs were considered non-responders, but does not report the resulting analysis population or explain whether other outcome data were missing. The record does not report sensitivity analyses for missing data or additional detail on how exclusions and participants with incomplete follow-up were handled.

Although secondary outcomes are listed, their results and analysis details are not reported in the registry record. The statistical plan, sample-size justification, and any interim analyses are also not reported in the registry record. Safety reporting is limited to the listed counts and serious-event terms; timing, severity grading, attribution, and a comparative safety assessment are not reported in the registry record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Topical Tazarotene in Treating Patients With Basal Cell Skin Cancer and Basal Cell Nevus Syndrome on the Face — NCT00489086.
• Registry record last updated 2020-10-29; status last verified 2020-10.
• Results first posted 2016-02-11.
• 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 phase II, open-label, single-group trial of topical tazarotene cream for facial basal cell skin cancer in people with basal cell nevus syndrome. Enrollment was 36. The primary endpoint was a participant-level complete-response rate, defined by visible lesion disappearance during 18 months of application and no recurrence during the ensuing 18 months. Surgical removal and drop-outs counted as failures under the stated rules.

The record identifies N=2 exclusions from the primary analysis description and gives a priori thresholds of at least 50% for success and 25% or less for failure. It does not report the observed primary response result, analysis denominator, or uncertainty interval. Safety reporting lists 2 serious adverse events, 31 participants with other adverse events, and 0 deaths; causal attribution is not established. Secondary outcome results and detailed statistical methods are not reported in the registry record.