Photodynamic Therapy (PDT) For Recurrent High Grade Gliomas: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Photodynamic Therapy (PDT) For Recurrent High Grade Gliomas (NCT01966809), a na phase 2 study. The primary outcome is Six Month Relapse-free Survival (RFS)..

2. Clinical Question

The study objective was to define the antitumor activity of Photofrin activated by laser light within a Phase II study. The summary also identifies time without new tumor regrowth and overall survival as planned areas of interest, alongside remission rate, progression-free survival, overall survival, and tumor response as secondary outcomes. These stated aims describe what the study intended to assess; they are not evidence that outcomes were measured or that results were recorded.

3. Trial Design

This is a Phase II, single-group study of Photofrin photodynamic therapy in adults with recurrent high grade gliomas. The registry records allocation as NA and masking as none. It lists no separate control arm, and the record should not be read as a randomized or masked comparison. Although the study summary says findings would be compared with typical results, it does not identify a specific external data source, comparison population, or method for making that comparison.

The treatment description combines Photofrin and laser light activation around tumor removal surgery. It specifies a Photofrin dose of 2.5 mg/kg and light at 240 mJ/cm2. The summary describes the drug as given the day before surgery and red laser light as directed into the tumor cavity after the tumor is removed. The registry lists Photofrin photodynamic therapy as the intervention.

The registry lists enrollment as 1 and the status as terminated. The start is recorded as 2015-06, and primary completion as 2017-12-19. A reason for termination is not reported in the registry record. The record does not report whether the listed enrollment represents all participants treated, how many completed follow-up, or whether the primary endpoint was assessed.

There are no posted analyses listed in the registry record. No numerical primary endpoint result, survival estimate, tumor-response result, or comparison with typical results is reported. Consequently, the design and intended outcomes can be described, but the record does not support a treatment-effect estimate or an assessment of how the observed experience compares with another group.

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

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 Six Month Relapse-free Survival (RFS)., measured over Six months from PDT.

The primary endpoint is six-month relapse-free survival from PDT. The registry describes relapse-free survival as the proportion of subjects who have gone six months since PDT without the disease getting worse. In practical terms, this endpoint is intended to capture whether disease progression has occurred by the stated follow-up time. It is a time-specific measure: the question is about remaining relapse-free through six months, not simply whether a participant ever had a relapse during all subsequent follow-up.

General explanation: a fixed-time survival endpoint can provide an interpretable summary of disease control at a clinically specified point. It may also be easier to communicate than a full time-to-event curve. Its interpretation depends on clear definitions of progression, follow-up, and how people without complete observation through the target time are handled. Those details are not reported in the registry record.

The registry lists the unit as participants and the parameter as number, while the endpoint description uses the term proportion. It does not report the endpoint value or explain how that difference between the descriptive wording and the recorded measurement is resolved. There is therefore no posted estimate of the proportion relapse-free at six months, and no uncertainty interval for that estimate. The endpoint’s intended meaning is clear enough to describe, but its observed result and precision cannot be evaluated from the record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What can be concluded from a single-group design?

The registry identifies the study model as single group, allocation as NA, and masking as none. These design features mean the posted record does not describe random assignment between treatment groups or a concurrent control arm. General explanation: randomization can balance measured and unmeasured characteristics on average, while a concurrent control can help distinguish changes associated with treatment from changes that might have occurred over time or under other care. A single-group study can describe what happened among participants who received the intervention, but a causal comparison requires additional assumptions or external evidence.

The summary says results would be compared with typical results. That intention does not establish which external results would be used, whether the populations are comparable, or whether outcome definitions and follow-up are aligned. Those details are not reported in the registry record. Without a named comparator and its results, no comparative effect can be interpreted from this record.

How should the primary endpoint be read?

The registry names six-month relapse-free survival from PDT as the primary endpoint and describes it as the proportion without worsening disease by six months. General explanation: a fixed-time proportion is meaningful only when the denominator and follow-up handling are clear. If some participants are not observed through the target time, an analysis must specify whether those observations are excluded, treated as censored, or handled in another way. The registry record does not report such details or a primary endpoint estimate.

The endpoint is described as a proportion, but the recorded measurement unit is participants and the parameter is number. The registry does not explain how the endpoint was operationalized or reported. This leaves the precise estimand—the quantity the analysis was intended to estimate—unclear beyond the stated clinical description. No estimate or confidence interval is posted to resolve that uncertainty.

What do survival analyses generally address?

General explanation: time-to-event methods use both whether an event occurred and when it occurred. Participants who have not had an event by the end of observed follow-up may contribute information up to that point through censoring, rather than being treated as if they remained event-free indefinitely. A Kaplan–Meier curve is one common way to describe event-free probability over time, while a hazard ratio can compare event rates over follow-up under a specified model. These are general methods, not methods identified as used in this study. The registry record does not report a survival-analysis plan, a curve, a hazard ratio, censoring rules, or an analysis result.

Likewise, the registry does not report the definition or assessment schedule for progression, how relapse was confirmed, or the handling of deaths before the endpoint time. Such decisions can affect interpretation of a time-to-event outcome. Their absence from the record means readers cannot assess whether outcomes were consistently defined or how incomplete observation was handled.

How should planning calculations be understood?

The study record describes a sample-size illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It also says that the effect to detect is a stated fraction of the observed effect. For time-to-event illustrations, the described quantity is total events; for other illustrations, it is participants per arm. These are planning assumptions, not a record of the trial’s original design or a report of observed power. No planning outputs or observed effect value are reported in the registry record.

General explanation: sample-size calculations explore how much information a future study might need under specified assumptions. They do not measure the probability that a completed study has discovered a true effect. When an illustration is based on an observed effect, its conclusions can be especially sensitive to that estimate; a very small or imprecisely estimated observed effect can make planning outputs unstable or uninformative. In this study, no endpoint analysis is posted, so the effect used for the illustration cannot be evaluated from the registry record.

There are no recalculated estimates listed and no sponsor analysis posted in the registry record. No discrepancy between sponsor and recalculated results is reported. In general, a recalculation from summary statistics is an unadjusted check and may not reproduce an analysis that accounts for the original design or covariates; it should not replace a sponsor’s own analysis when the two differ. That distinction does not produce an efficacy result in this case because the registry reports no analyses.

What cannot be inferred?

The registry record does not state a statistical analysis plan, covariate adjustments, interim analyses, stopping boundaries, missing-data procedures, or analysis population. These omissions do not establish that such procedures were absent from the investigators’ work; they mean they are not documented in the registry record. Because no outcome analyses are posted, there is no basis for evaluating model fit, assumptions, multiplicity adjustments, or robustness to alternative analytic choices.

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("Photofrin Photodynamic Therapy.")
n      <- c(1)
events <- c(0)
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  Photofrin Photodynamic Therapy.  1  0  0.0  0.0  97.5  0.0  79.3  1.3  84.2

11. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary endpoint and several secondary outcome descriptions: remission rate, progression-free survival and overall survival, and tumor response. It also reports four outcome measures, but does not post analyses for them. The record does not describe a multiplicity strategy, such as a prespecified hierarchy or adjustment for testing several outcomes. This is not evidence that no such strategy existed; it is not reported in the registry record.

General explanation: when many outcomes or comparisons are tested, the chance of at least one apparently unusual result can increase. A prespecified testing strategy helps readers understand which findings were confirmatory and how uncertainty should be interpreted. With no posted analyses, no multiplicity-adjusted or unadjusted outcome finding can be assessed.

The record also does not report missing-data methods, participant-level follow-up, or the analysis population for the primary endpoint. It does not say whether the listed enrollment contributed to the outcome analysis, whether anyone lacked follow-up at the target time, or how incomplete observation was handled. These omissions matter because a fixed-time relapse-free survival estimate depends on the definition of the analysis set and the treatment of missing outcome information.

General explanation: complete-case analysis, censoring-based methods, and imputation make different assumptions about unobserved outcomes. Their appropriateness depends on why data are missing and on the endpoint structure. The registry record does not identify a method or provide enough information to assess those assumptions. Accordingly, no claim about attrition, missingness, or analysis-population representativeness can be made from the posted record.

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 0% reporting threshold.

Most frequent serious adverse event terms

Serious events with the highest arm-level rate: altered mental status (100.0%).

The registry’s safety listing is grouped under Photofrin Photodynamic Therapy. It records one participant at risk for serious adverse events and one with a serious adverse event. The most frequent serious term is altered mental status, listed at 100.0%. The record also lists one participant at risk for other adverse events and none with other adverse events, and it records no deaths.

These figures are counts in a very limited recorded group and should not be treated as precise estimates of event rates in a wider population. The 100.0% figure describes the listed serious-event term in this registry entry; it does not establish how often the event would occur in other participants or settings. The record does not report timing, duration, severity grading details beyond the serious classification, clinical course, or whether the event was judged related to the intervention.

General explanation: adverse-event counts describe events observed and recorded during a study, while attribution and rate estimation require additional context, including exposure and follow-up. The registry record does not provide that context or a comparative safety group. These data therefore describe the posted safety entries, not a causal assessment of risk.

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

The registry record documents a Phase II study of Photofrin photodynamic therapy for recurrent high grade gliomas, with a stated primary endpoint of six-month relapse-free survival. It records an enrollment of 1, a terminated status, and limited adverse-event counts. Those details describe the study record and its planned clinical question; they do not amount to an efficacy finding.

No primary endpoint result, secondary outcome analysis, survival estimate, tumor-response result, or comparison with typical results is reported in the registry record. It is therefore not possible to determine from the posted information whether the participant met the six-month relapse-free endpoint, what the outcome was over follow-up, or how an observed result compared with another group. A missing result should not be interpreted as a positive or negative result.

The single-group design also limits what a result could establish without an appropriate comparator. General explanation: observing an outcome after an intervention does not by itself show that the intervention caused it. Disease course, participant characteristics, other care, and follow-up can also affect observed outcomes. A comparison with historical or typical results requires a clearly defined benchmark and careful attention to comparability; those details are not reported in the registry record.

The safety entries show a serious adverse event recorded as altered mental status and no deaths in the posted group. Because the record includes a very limited enrollment and no comparator, these entries cannot establish the frequency or cause of adverse events in a broader population. They should be read as descriptive registry data, not as a comprehensive safety analysis.

In short, the record supports a description of the trial’s purpose, intervention, design, endpoint, status, enrollment, and posted safety counts. It does not support a conclusion about treatment benefit, lack of benefit, comparative effectiveness, or the precision of an efficacy estimate.

14. Why This Trial Matters Statistically

This record illustrates why trial design and outcome reporting are as important as the name of a clinical endpoint. Six-month relapse-free survival has a straightforward clinical description, but interpretation also requires an observed value, a defined analysis population, follow-up information, and a method for handling participants whose status is not known at the target time. Those elements are not reported in the registry record.

The single-group structure makes the intended comparison especially important. The summary refers to typical results, but the registry does not identify a benchmark or present its data. General explanation: a historical comparison can be vulnerable to differences in eligibility, disease severity, supportive care, assessment practices, and follow-up. Stating the comparator and analysis method allows readers to judge whether apparent contrasts could plausibly reflect those differences instead of the intervention.

The record also demonstrates the distinction between a study’s objective and its evidence. It outlines a treatment rationale and lists outcomes of interest, but the registry lists no analyses. A planned question does not become an answer unless participant outcomes are reported with enough detail to evaluate the estimate and its uncertainty.

Finally, the posted safety counts show why denominators and context matter. A serious event entry can be reported faithfully while still offering little precision about how commonly an event might occur in a wider population. Enrollment, outcome completion, event definitions, timing, and attribution all help readers understand what the counts can and cannot say.

For biostatistical interpretation, this study is therefore informative as a registry record of a proposed Phase II single-group assessment, but limited as a source of outcome evidence. The distinction between design documentation, observed data, and analyzed results is central to responsible interpretation.

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 limitations constrain interpretation. The registry lists a single-group design, no masking, and allocation marked NA. No concurrent control group is described. Although the summary mentions comparison with typical results, the record does not identify the comparator, its population, or the method of comparison. Consequently, no comparative treatment effect can be evaluated.

The registry lists enrollment as 1, but does not report whether the participant received treatment, completed the planned follow-up, or contributed to an endpoint analysis. The primary endpoint is described as a proportion without worsening disease through six months, while its recorded measurement is number of participants. The record does not clarify how the endpoint was operationalized, and it posts no result or uncertainty interval.

The status is terminated, but a reason for termination is not reported in the registry record. The record also does not explain the timing of termination relative to enrollment or outcome assessment. No protocol details are reported for eligibility, progression assessment, censoring, missing data, analysis population, or statistical analysis methods. The absence of these details from the registry does not establish what investigators did outside the record.

Safety interpretation is limited by the small recorded group and lack of comparative information. The registry does not report event timing, duration, attribution, or follow-up context. It also does not report numerical results for the listed secondary outcomes. These limitations mean the record is insufficient for estimating efficacy, assessing precision, or generalizing observed safety counts to a broader population.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Photodynamic Therapy (PDT) For Recurrent High Grade Gliomas — NCT01966809.
• Registry record last updated 2019-08-20; status last verified 2019-08.
• Results first posted 2019-08-08.
• 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 Phase II, single-group study of Photofrin photodynamic therapy for adults with recurrent high grade gliomas. The intervention description specifies Photofrin at 2.5 mg/kg and light at 240 mJ/cm2. The primary endpoint is six-month relapse-free survival from PDT, described as remaining without disease worsening through that time.

The record lists enrollment as 1, status as terminated, and no posted analyses. It does not report a primary endpoint result or secondary outcome results. The reason for termination, analysis population, missing-data handling, and statistical analysis plan are not reported in the registry record. Safety listings record one serious adverse event, with altered mental status as the listed term, no other adverse events, and no deaths. These entries are descriptive and do not establish comparative efficacy or broader safety rates.