Gene Expression in Renal Transplant Patients With Field Actinic Keratosis Undergoing Metvix® Photodynamic Therapy (PDT): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Gene Expression in Renal Transplant Patients With Field Actinic Keratosis Undergoing Metvix® Photodynamic Therapy (PDT) (NCT01000636), a na phase 4 study. The primary outcome is Percent Change From Baseline in Lesion Count at Week 18.

2. Clinical Question

3. Trial Design

This was a Phase 4, completed, single-group clinical study sponsored by Galderma R&D. The registry record lists an enrollment of 9 and identifies Metvix photodynamic therapy as the intervention. It gives the study start as 2009-10 and primary completion as 2011-10. The condition listed is actinic keratosis, and the study population is described as renal transplant recipients with field actinic keratosis.

The registry identifies no allocation scheme and no masking. Its design is therefore not a randomized comparison between treatment arms. Although the primary outcome compares lesion counts at baseline and Week 18, those repeated measurements are observations within the same study group, not evidence from a concurrent untreated or alternative-treatment group. Changes over time may be described, but the design alone cannot identify what would have happened to comparable participants without the intervention.

The stated purpose was exploratory: to determine possible molecular changes on large-scale gene-expression profiling after treatment of actinic keratoses and the cancerised field. The listed primary endpoint, however, is percent change in lesion count at Week 18. A secondary outcome concerns global percent change from baseline in target-field lesion count, including new and recurrent lesions, at Month 15. The registry lists 2 outcome measures and 0 analyses.

The primary endpoint description says the analysis used an intent-to-treat population consisting of the entire population enrolled and randomized, and clarifies assignment as receiving a treatment number. That wording should be read alongside the registry design, which specifies a single group and allocation marked NA; it does not establish a randomized comparison. The number actually analyzed for the primary endpoint is 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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: This trial was of exploratory nature, no statistical rationale for sample size exists. Analysis was performed on Intent to treat (ITT) population that consisted of the entire population enrolled and randomized (i.e., assigned a treatment number). Here, "Overall Number of Participants Analyzed" = participants with available data at specified time point.

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.

Population: Only 9 subjects out of 10 planned ones by the protocol have been included

6. Primary Endpoint

The registry lists the primary outcome as Percent Change From Baseline in Lesion Count at Week 18, measured over Baseline and Week 18..

The primary endpoint is percent change from baseline in lesion count at Week 18. It describes the relative change in the number of counted lesions in the target field between the baseline assessment and the Week 18 assessment. The registry defines the calculation as the Week 18 count minus the baseline count, divided by the baseline count, and multiplied by 100. A negative value would indicate a lower count at Week 18 than at baseline, while a positive value would indicate a higher count; this explains the direction of the measure and is not a claim about the study’s observed result.

Lesion count is a continuous outcome when expressed as percent change, and the registry identifies the summary parameter as the mean with standard deviation as the measure of dispersion. In general, a mean gives the average change across participants, while a standard deviation describes how dispersed individual changes are around that average. Reporting both can help readers distinguish the average pattern from the variability among participants.

A percent-change endpoint puts change in relation to each participant’s baseline count, which can make changes easier to interpret across participants starting with different counts. It also has limitations: its meaning depends on the baseline value, and a group mean does not show the full distribution of individual responses. The registry record does not report the mean, standard deviation, analyzed count, or other numerical primary-endpoint result. The endpoint’s observed size and precision therefore cannot be described from the posted results.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry classifies the primary outcome as a continuous measure summarized by a mean and standard deviation. The explanatory points below describe those methods generally; they do not supply unreported analyses or results for this trial.

What does a mean describe?

For a continuous outcome, the mean is the arithmetic average of the measured values in the analysis population. In this study, the intended values are participant-level percent changes in lesion count from baseline to Week 18. The mean can convey the average direction and size of change, but it does not show whether most participants had similar changes or whether the average is influenced by a small number of unusually large values. Individual observations and a distribution summary can add context to a mean.

The registry record does not report the mean percent change. It also does not provide participant-level observations. Consequently, it is not possible to examine the shape of the outcome distribution, identify outliers, or determine whether a mean is a representative description of the enrolled group. These are general interpretation considerations, not claims about the study’s data.

What does the standard deviation describe?

The standard deviation describes the spread of values around the mean in the analyzed group. A smaller standard deviation indicates values are more clustered around the mean; a larger one indicates greater dispersion. It is not itself a measure of uncertainty in the estimated mean. Uncertainty about the mean is commonly expressed using a confidence interval, which describes a range of estimates compatible with the data under the method’s assumptions.

No standard deviation or confidence interval for the primary endpoint is reported in the registry record. Therefore, neither the variability of participant-level changes nor the precision of the mean can be assessed. General explanations of these statistics should not be mistaken for estimates from this trial.

How should percent change be read?

The endpoint is defined using the follow-up count relative to baseline: Week 18 count minus baseline count, divided by baseline count, multiplied by 100. This puts the change on a percentage scale relative to baseline. Its sign indicates the direction of change: a negative value means the follow-up count is lower than baseline, and a positive value means it is higher. The endpoint is not an absolute count difference. The registry does not report the baseline counts or the calculated participant-level or group-level percent changes, so no numerical interpretation is possible.

As a general matter, ratio-based measures such as percent change can be affected by the baseline value because the baseline appears in the denominator. When baseline values vary, participants with similar absolute changes may have different percentage changes. The registry record does not provide enough detail to evaluate how that feature affected this study’s outcome.

What do the design labels imply?

A single-group design means the registry identifies one intervention group rather than distinct groups allocated to different treatments. Allocation is listed as NA and masking as none. Thus, this is not a blinded randomized comparison. The baseline and Week 18 observations can be compared descriptively within the group, but the design has no concurrent control outcome to represent the course of the condition in the absence of the intervention.

In general, an uncontrolled before-and-after comparison is vulnerable to influences other than the intervention. The timing and measurement of outcomes, changes in other care, and natural changes over time can contribute to the observed difference. This does not establish that any such influence occurred in this trial; it explains why a within-group change does not have the same causal interpretation as a randomized between-group contrast.

What is the role of planning assumptions?

The registry states that no statistical rationale for the sample size exists because the trial was exploratory. The listed planning assumptions describe illustrations based on an observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. Those assumptions describe a planning calculation, not the actual single-group trial design. The trial record does not identify a two-arm randomized sample-size plan, and the planning illustration should not be read as an observed trial result or as observed power.

In general, sample-size planning asks how many participants would be needed under specified assumptions to detect a defined effect with a chosen statistical procedure. Such an illustration depends on the assumed effect and model. It does not show that a study actually had that probability of finding an effect, and it cannot establish precision without an observed estimate and its uncertainty. No numerical planning results are reported in the registry record.

Why does over-dispersion matter in general?

Over-dispersion is a general issue for count data when the variability is greater than a chosen statistical model expects. A model that understates variability can produce uncertainty estimates that are too narrow and statistical evidence that appears stronger than warranted. Appropriate handling depends on the analysis model and the data. The registry does not report an analysis model for the lesion-count endpoint, and no over-dispersion assessment is reported in the registry record. It would therefore be inappropriate to infer whether over-dispersion was present or how it was handled.

The registry lists 0 analyses. That listing does not provide an inferential procedure, adjustment method, or uncertainty estimate for the primary endpoint. Without a reported analysis and numerical result, statistical significance, precision, and model adequacy cannot be evaluated.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Metvix® Photodynamic Therapy (PDT)")
n   <- c(8)
m   <- c(95.5)
sp  <- c(9.1)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Metvix® Photodynamic Therapy (PDT)  8  95.500  9.100  87.892  103.108

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 2 outcome measures: the primary percent change in lesion count at Week 18 and a secondary global percent change in target-field lesion count, including new and recurrent lesions, at Month 15. It does not report an analysis plan explaining whether or how testing across outcomes or time points was handled. Multiplicity refers generally to the increased chance of a chance-positive finding when multiple statistical questions are tested. Whether an adjustment was planned or used is not reported in the registry record.

The registry lists 0 analyses and gives no primary-endpoint test result, confidence interval, or other inferential output. There is therefore no reported multiplicity procedure to assess and no basis for judging which outcome was treated as confirmatory in statistical testing beyond the registry’s designation of the Week 18 measure as primary. The exploratory purpose is stated, but details of a prespecified statistical analysis plan are not reported in the registry record.

The primary outcome description says the analysis used an intent-to-treat population consisting of the entire population enrolled and randomized, with assignment explained as receiving a treatment number. The trial design is listed as single-group and allocation as NA. Those entries do not establish random allocation between treatment arms. The record does not report the number of participants with an observed Week 18 outcome, the number included in each analysis, or how missing outcome data were handled. It also does not report whether any participants discontinued or whether imputation or another missing-data method was used.

In general, missing outcome data can affect an estimate if the availability of measurements is related to participant outcomes. The extent and direction of such effects depend on why measurements are missing and on the analysis assumptions. Since participant flow and missing-data methods are not reported in the registry record, the potential impact cannot be evaluated. Enrollment of 9 is not, by itself, confirmation that all 9 contributed to the primary endpoint analysis.

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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: urinary track infection (11.1%).

The registry lists 9 participants at risk for serious adverse events in the Metvix PDT group and 1 participant affected. For other adverse events, it lists 9 participants at risk and 9 affected. These are separate registry categories and should not be combined or treated as counts of distinct events: the figures refer to participants, and the record does not provide event-level detail for all reported categories.

The top serious adverse event term is Urinary Track Infection, listed as 11.1%. The registry record does not give further detail about timing, severity beyond the serious-event classification, relatedness to the intervention, or outcomes for this term. Deaths are not reported in the registry record. A blank death entry should not be interpreted as evidence about the cause or circumstances of death beyond what the record states.

These safety figures are descriptive. In a single-group study with 9 participants and no comparator, they cannot determine whether an event occurred more often than it would have without treatment or establish that the intervention caused an event. The registry record also does not report a statistical comparison of adverse events. The listed counts should therefore be read as the recorded participant figures for this study, not as comparative estimates of risk.

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

The record establishes that an exploratory, single-group study enrolled 9 renal transplant recipients with field actinic keratosis and evaluated Metvix PDT. Its primary endpoint was percent change in lesion count from baseline to Week 18, and a secondary outcome concerned target-field lesion count at Month 15, including new and recurrent lesions. These details describe the question the study set out to address.

The registry does not report the numerical primary or secondary outcome results. It therefore does not support a statement about the direction or size of lesion-count change, how variable participants’ changes were, or how precise an estimate might be. No conclusion about statistical significance can be drawn from the posted information. The study’s stated molecular objective also should not be confused with a reported gene-expression result: such a result is not reported in the registry record.

Even if a within-group change were available, it would describe change among participants in this study, not establish what caused that change. There was no separate comparator group, and the registry lists no allocation scheme and no masking. In general, an uncontrolled comparison of measurements over time cannot rule out other explanations for change. It can offer descriptive information, but it does not provide the same causal evidence as a suitable controlled comparison.

The enrollment of 9 and the exploratory designation are important context for interpretation. The registry explicitly states that no statistical rationale for sample size exists. This does not tell readers what the study would have found with a different enrollment, and it does not mean that an unreported effect is either present or absent. Planning illustrations, when based on an observed effect, are hypothetical calculations and not observed power.

Accordingly, the record supports a careful account of the design, endpoint definitions, and listed adverse-event figures. It does not support claims that Metvix PDT did or did not change lesion counts, that it caused a molecular change, or that its effects differ from another approach. Those questions require reported outcome estimates and, for causal comparison, an appropriate comparative design.

14. Why This Trial Matters Statistically

This trial is statistically informative as an example of the distinction between a study question and evidence that can answer it. The stated objective concerns possible large-scale gene-expression changes after PDT, while the registered primary endpoint is percent change in lesion count at Week 18. Those are not interchangeable outcomes. A registry entry can specify what was intended to be measured without reporting the resulting estimate.

The single-group design also makes the interpretation of any before-and-after comparison especially important. A change from baseline can be summarized as an observation within the treated group, but there is no concurrent group to provide a direct contrast. In general, causal questions require comparison with an appropriate counterfactual, meaning an estimate of what would have happened to similar participants without the intervention or under an alternative. This registry record does not include such a comparator.

The record’s explicit statement that the study was exploratory and had no statistical rationale for sample size helps separate exploratory work from a confirmatory design with a documented target effect and precision. It also cautions against treating a planning calculation based on an observed effect as evidence that the study was adequately powered. Planning illustrations are conditional on assumptions and are not a substitute for reporting observed results with uncertainty.

Finally, the gap between enrollment and a reported analysis is consequential. The record lists enrollment of 9 and 0 analyses, but does not report an analyzed count or missing-data handling for the primary outcome. Without those details and the endpoint estimate, readers cannot assess data completeness, variability, or precision. This case therefore highlights why complete outcome reporting and clear analysis-population descriptions matter alongside the choice of endpoint and design.

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 main limitation for interpretation is that the registry record does not report numerical results for the primary or secondary outcome. No Week 18 mean percent change, standard deviation, confidence interval, or test result is available in the record. The Month 15 secondary result is also not reported. This prevents assessment of the outcomes’ direction, magnitude, variability, or precision.

The study is listed as single-group, with allocation marked NA and masking listed as none. There is no separate comparator group for interpreting changes over time. The design can describe observations within participants who received the procedure, but cannot isolate the intervention’s contribution from other possible influences. No causal comparison with no treatment or another treatment is available in the registry record.

The registry states that the study was exploratory and that no statistical rationale for sample size exists. Enrollment was 9. The number analyzed for the primary endpoint, participant flow, missing outcome data, and methods for addressing missingness are not reported in the registry record. The description of the intent-to-treat population refers to the entire population enrolled and randomized, with assignment defined as receiving a treatment number; that language does not resolve the actual analyzed count or change the registry’s single-group design.

Further details about eligibility criteria, treatment delivery, endpoint assessment procedures, the analysis model, and any prespecified statistical plan are not reported in the registry record. The registry lists 2 outcomes and 0 analyses, and does not explain how multiplicity was handled. These omissions limit assessment of reproducibility, completeness, and the robustness of any inferential claims. The listed adverse-event figures are descriptive and do not establish comparative safety or causation.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Gene Expression in Renal Transplant Patients With Field Actinic Keratosis Undergoing Metvix® Photodynamic Therapy (PDT) — NCT01000636.
• Registry record last updated 2021-05-26; status last verified 2021-05.
• Results first posted 2021-05-26.
• 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 NCT01000636 as a completed Phase 4, single-group study sponsored by Galderma R&D, with enrollment of 9. The study concerned Metvix photodynamic therapy for renal transplant recipients with field actinic keratosis. The listed study dates are 2009-10 for start and 2011-10 for primary completion.

The primary endpoint was percent change from baseline in lesion count at Week 18, summarized as a mean with standard deviation. A secondary outcome concerned global percent change in target-field lesion count, including new and recurrent lesions, at Month 15. The registry lists 2 outcome measures and 0 analyses. Numerical results for these outcomes are not reported in the registry record.

The study is marked as having no masking and no allocation scheme, and is identified as single-group. The registry describes the trial as exploratory and states that no statistical rationale for sample size exists. Safety listings include 1 participant affected by a serious adverse event among 9 at risk and a top serious-event term of Urinary Track Infection at 11.1%. These entries are descriptive and do not provide a controlled comparison.