Chemotherapy Response Monitoring With 18F-choline PET/CT in Hormone Refractory Prostate Cancer: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Chemotherapy Response Monitoring With 18F-choline PET/CT in Hormone Refractory Prostate Cancer (NCT00928252), a na phase 1, phase 2 study. The primary outcome is Metabolically Active Tumor Volume (MATV) Response.

2. Clinical Question

Statistically, the study is framed as an assessment of an imaging-defined change within a single group, rather than an estimate of the difference between two assigned treatments. The study purpose describes imaging as potentially informative for later treatment decisions; it does not make the imaging endpoint itself a comparison of subsequent clinical outcomes. Without a reported endpoint result or analysis, the record does not establish how often the specified reduction occurred or how precisely that frequency was estimated.

3. Trial Design

The registry describes a completed, single-group study with phase 1 and phase 2 listed. Its title is “Chemotherapy Response Monitoring With 18F-choline PET/CT in Hormone Refractory Prostate Cancer.” Queen's Medical Center is listed as sponsor. The recorded enrollment is 25. The study start is listed as 2009-06 and primary completion as 2016-06.

The intervention is intravenous fluorine-18 labeled methylcholine before PET/CT. The arm description says participants received 18F-fluorocholine PET/CT. The record lists no masking and allocation as not applicable. In practical statistical terms, this is not a randomized, masked, controlled comparison; there is one registered arm. A single-group design can describe the outcome observed in that group, but does not by itself distinguish an intervention effect from other explanations for change over time.

The primary endpoint is a participant count: the number achieving a 30% or greater reduction in MATV on 18F-fluorocholine PET/CT. The stated timeframe is 21 to 98 days. Three outcome measures are listed in total, but descriptions of the other measures are not reported in the registry record. The record lists no analyses.

The study status is completed, but completion status does not establish that every planned measure has a posted result. In particular, the observed primary endpoint count and its analysis are not reported in the registry record. A protocol, detailed eligibility criteria, visit schedule, dose information, or explanation of the phase labels is also not reported in the registry record. These omissions limit the extent to which the design, conduct, and analysis can be reconstructed from the registry information alone.

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:

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 Metabolically Active Tumor Volume (MATV) Response, measured over 21 to 98 days.

The primary endpoint counts participants who meet a specified imaging-response threshold: a 30% or greater reduction in metabolically active tumor volume (MATV) measured on 18F-fluorocholine PET/CT. Its timeframe is 21 to 98 days. A threshold-based endpoint turns a change measured on imaging into a yes-or-no classification for each participant, then expresses the result as a count of participants meeting that criterion.

Such an endpoint can provide a defined way to describe imaging changes after study procedures or treatment, and the study purpose presents PET/CT information as potentially useful for guiding subsequent investigational or clinical treatments. That purpose is not evidence that the imaging measure predicts a later outcome or improves a treatment decision. The registry record does not report validation of MATV as a surrogate for another clinical outcome, nor does it report how the threshold was selected.

The count is interpretable only alongside the number of participants assessed and the rules used to handle missing or unevaluable scans. Those details, as well as the observed count meeting the threshold, are not reported in the registry record. Therefore, the endpoint definition is available, but its frequency and precision cannot be evaluated from the registered result information.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies the primary measure as a count of participants meeting a binary criterion: a 30% or greater reduction in MATV on 18F-fluorocholine PET/CT. Each assessed participant would be classified as meeting or not meeting that threshold, assuming the endpoint can be evaluated. A count is a descriptive summary; to understand the frequency, it must be read with the number assessed. That denominator and the observed count are not reported in the registry record.

What does a binary endpoint describe?

In general, a binary endpoint reduces a potentially continuous measurement to two categories, such as meeting or not meeting a prespecified cutoff. This can make a result easier to communicate, but it discards information about the size of changes on either side of the cutoff. Participants with changes just below and just above a threshold may be categorized differently even when their measurements are close. The record specifies the cutoff but does not report its rationale, the underlying individual measurements, or whether a separate continuous MATV analysis was conducted.

A count can be used to estimate the fraction of assessed participants meeting the criterion, but that estimate depends on the analysis population and handling of missing measurements. General statistical practice is to define in advance who is included and what happens when an assessment is unavailable or cannot be interpreted. Those rules and the primary analysis population are not reported in the registry record. No response fraction or uncertainty interval is reported either.

What can a single-group design estimate?

With one registered group, the endpoint can describe the observed response status within that group if the data are reported. It does not provide a concurrent comparison group. A comparison of outcomes between randomized groups can help separate treatment-group differences from changes that could also arise over time or from other influences. Because allocation is listed as not applicable and the model is single group, this record does not describe such a comparison. The design should not be interpreted as a randomized efficacy test.

Masking is listed as none. In general, masking is used to limit the influence of knowledge about an assigned intervention on measurement, treatment, or assessment. Imaging assessments can involve technical and interpretive choices, so the procedures for image reading and any safeguards against assessment bias can matter. Reader procedures, reproducibility methods, and image adjudication are not reported in the registry record. Their absence from the record does not establish that no such procedures occurred; it means they cannot be assessed from the registry information.

What do significance tests and confidence intervals add?

In general, a significance test evaluates how compatible observed data are with a specified statistical hypothesis under stated assumptions. A p-value is not a measure of the probability that a treatment works, nor does it convey the magnitude or importance of an effect. A confidence interval focuses on estimation and precision. For a binary outcome, the interval would depend on the count, denominator, and method used. The registry record reports no primary endpoint analysis, p-value, or confidence interval, so there is no inferential result to interpret. No test or interval method is reported in the registry record.

When event counts are sparse, estimates can be imprecise and standard approximations may be less reliable. Exact or alternative methods may be considered in general, depending on the data and analysis objective. The record does not provide the primary endpoint count, so the suitability of any particular method cannot be judged. There is also no reported adjustment or model for covariates.

How should planning calculations be understood?

The record describes a sample-size illustration as using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It further says the effect to detect is a stated fraction of the observed effect, and that the illustration is based on the observed effect rather than the trial's own design. For non-time-to-event outcomes, such illustrations are expressed as participants per arm for 80% or 90% power, as applicable to the calculation. No numerical planning values or observed effect are reported in the registry record.

In general, a planning calculation asks what sample size might be needed under specified assumptions. It is not a description of the actual enrolled group, does not establish that the trial had a particular power, and does not demonstrate that an effect exists. The registry's illustration assumptions refer to two arms, while the registered study model is single group. Since the observed effect and numerical illustration are not reported in the registry record, those calculations cannot be evaluated or treated as the study's original design plan.

Power is a design property under an assumed effect and analysis method; it is not a retrospective measure of whether a result is true. A calculation based on an observed effect can be particularly dependent on the estimate used. The registry record does not report a sample-size justification or original design assumptions, so the adequacy of enrollment for the primary question cannot be assessed from the available 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("Received 18F-fluorocholine PET/CT")
n      <- c(42)
events <- c(20)
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  Received 18F-fluorocholine PET/CT  42  20  47.6  32.0  63.6  33.4  62.3  33.3  62.3

11. Multiplicity, Missing Data and Analysis Populations

The registry lists three outcome measures, but the primary endpoint is the only one described in the available record. The other outcome definitions, their status as primary or secondary, and their results are not reported in the registry record. The record lists zero analyses. It does not describe a statistical analysis plan, a hierarchy of endpoints, or a plan for controlling multiplicity.

In general, testing multiple outcomes or multiple versions of an outcome can increase the chance of a misleading positive finding if each is interpreted without considering the full set of analyses. A prespecified hierarchy, adjustment method, or clear distinction between confirmatory and exploratory analyses can help readers understand how multiple results were handled. No such approach is reported in the registry record. Since no analysis results are reported, there are no posted p-values to assess for multiplicity.

The record also does not report the number included in the primary endpoint analysis, the analysis population definition, missing scan counts, or rules for handling missing or unevaluable imaging. Missingness can affect a binary response count if participants without an assessment are excluded, counted as not meeting the threshold, or handled by another method. These choices can produce different interpretations, so they need to be stated rather than assumed.

There is no reported description of interim analyses, stopping rules, or missing-data sensitivity analyses. Their absence from the registry record does not show whether they were or were not conducted. It means that the effect of missing outcome data and any repeated review of results cannot be evaluated from the available registry information.

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

Serious events with the highest arm-level rate: severe back pain (2.2%), cellulitis (2.2%), myocardial ischemia, diagnosis (2.2%), severe influenza (2.2%), obstructive uropathy (2.2%).

The registry safety group is labeled “Single Arm.” It reports 45 at risk for serious adverse events and 5 affected by serious adverse events. For other adverse events, it reports 45 at risk and 0 affected. The listed serious terms are Severe Back Pain, Cellulitis, Myocardial Ischemia, Diagnosis, Severe Influenza, and Obstructive Uropathy; each is reported as 2.2%.

These are safety summaries, not a randomized comparison. The percentages describe the registry's listed event terms and should not be interpreted as evidence that the intervention caused them. The record does not provide an attribution assessment, event timing, severity details beyond the serious-event classification, or a comparison group.

The safety group denominator of 45 does not match the recorded enrollment of 25. The reason for this difference is not reported in the registry record, so the figures should not be reconciled by assumption. The registry also does not clarify the relationship between the affected-participant count and the term-specific percentages. A term may be reported as an event category, and the listed percentages should not be summed or treated as independent person-level risks. The safety information is therefore best read as the figures recorded for the safety group, with the denominator and reporting details left unresolved.

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

The result that can be interpreted from the registry record is the definition of the intended primary measure: a count of participants achieving a 30% or greater reduction in MATV on 18F-fluorocholine PET/CT during 21 to 98 days. The record does not report the observed count or an analysis. It therefore does not show how frequently participants met the endpoint or how precisely that frequency was estimated.

The study's stated purpose was to determine whether imaging could provide information that may help guide subsequent investigational or clinical treatments for patients with advanced, hormone-refractory metastatic prostate cancer. This is a research question, not a reported conclusion. The record does not establish that the imaging changed treatment decisions, improved outcomes, or predicted response to a subsequent treatment.

Even with a reported within-group imaging response, the single-group design would describe observed outcomes without a concurrent control for comparison. It could not, by itself, establish that the imaging procedure or another intervention caused a change. No randomized comparison is registered, and no inferential analysis is reported.

The endpoint is a thresholded imaging measure, not a reported patient-centered outcome. The registry does not report whether MATV change was associated with symptoms, survival, or another clinical measure, and no such relationship should be inferred. Nor does the endpoint definition alone validate the cutoff as a surrogate for clinical benefit.

The safety figures describe serious-event reporting in a group with 45 at risk, while recorded enrollment is 25; the registry does not explain the discrepancy. Thus, neither the primary outcome nor the safety summary supports a broad conclusion about the balance of clinical benefits and harms. The appropriate statistical reading is limited: the registry records a study design and endpoint definition, but does not report the primary outcome result needed to quantify the imaging response.

14. Why This Trial Matters Statistically

This study raises a useful statistical distinction between measuring a biological or imaging change and demonstrating that the change answers a clinical question. MATV is operationalized through an imaging threshold, making the endpoint countable. But a defined measurement is only one part of the evidence: readers also need the result, an analysis population, uncertainty, and a clear account of how measurements were obtained and handled.

The single-group structure is especially relevant. A descriptive response frequency could characterize participants in the study, but without a comparator it cannot establish how the observed pattern differs from what would have occurred otherwise. This distinction matters when imaging is proposed as information for later treatment decisions. The registry states that purpose, while the available results do not show whether the information changed decisions or was linked to later outcomes.

The record also illustrates why registration details and posted results must be read together. A completed status and an endpoint definition do not supply the observed endpoint estimate. The record lists three outcome measures but describes only the primary endpoint in the available information, and lists zero analyses. This leaves key questions about estimation, missing assessments, multiplicity, and analysis populations unanswered.

Finally, the safety denominator differs from recorded enrollment, without an explanation in the registry record. Identifying such a discrepancy is not a reason to select one figure over the other; it is a signal that the data context needs clarification. Statistically, transparent denominators and explicit analysis rules are essential for interpreting both efficacy-related measures and adverse events.

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 central limitation of the registry information is that it does not report the observed primary endpoint count, the number assessed, or an estimate of uncertainty. The intended measure and timeframe are specified, but the endpoint result cannot be quantified or assessed for precision. The record lists three outcome measures and zero analyses; descriptions and results for the other measures are not reported in the registry record.

The design is single group, with allocation not applicable and no masking. There is no registered randomized control group for comparative interpretation. The record does not report image-reading procedures, reproducibility information, a statistical analysis plan, or the justification for the response threshold. It also does not report the analysis population, missing-data rules, or whether scans were unevaluable.

Additional limitations include the absence of reported information about interim analyses, multiplicity handling, covariate adjustment, or sample-size justification. The record gives assumptions for planning illustrations, but no numerical illustration or observed effect is reported. Those assumptions are not described as the trial's original design plan.

The recorded enrollment is 25, whereas the safety group reports 45 at risk. The reason for this discrepancy is not reported in the registry record. The record does not provide details that would allow the relationship between these figures, the safety counts, and the primary endpoint population to be determined. These gaps prevent a fuller assessment of outcome completeness, safety denominators, and statistical reliability.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Chemotherapy Response Monitoring With 18F-choline PET/CT in Hormone Refractory Prostate Cancer — NCT00928252.
• Registry record last updated 2017-08-14; status last verified 2017-07.
• Results first posted 2017-08-14.
• 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, single-group phase 1 and phase 2 study sponsored by Queen's Medical Center, with recorded enrollment of 25. The study evaluates intravenous fluorine-18 labeled methylcholine before PET/CT in the context of chemotherapy response monitoring for hormone-refractory prostate cancer. Allocation is listed as not applicable and masking as none.

The primary measure counts participants achieving a 30% or greater reduction in MATV on 18F-fluorocholine PET/CT over 21 to 98 days. The registry record does not report the observed endpoint count, its denominator, or an analysis. Three outcome measures are listed, and zero analyses are recorded.

The safety summary reports 5 participants with serious adverse events among 45 at risk, with five listed serious-event terms each reported as 2.2%. The safety denominator differs from the recorded enrollment, and the registry record does not explain why. The primary result and the context needed for a complete statistical interpretation are therefore not available in the registry record.