Imaging Brain Tumors With FACBC and Methionine: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Imaging Brain Tumors With FACBC and Methionine (NCT00597246), a na na study. The primary outcome is Maximum Standardized Uptake Value of 3-[18F]-FACBC.

2. Clinical Question

The study concerns PET imaging in people with brain tumors. Its stated aim is to make pictures of tumors using 18F-FACBC, a new PET tracer, and compare those pictures with the standard 11C-methionine PET scan. The registry summary also describes collecting information about radioactivity exposure in the tumor, brain, and other organs.

Statistically, the question that can be addressed from the registry record is limited: what primary measure was planned, and what information about its result was posted? Without the outcome values and a reported analysis, the record does not show how the two imaging approaches compared or how precisely any difference was estimated.

3. Trial Design

The registry identifies this as a completed, single-group study with enrollment of 30. Allocation is listed as NA and masking as none. These entries do not describe a randomized comparison. Although the study summary says 18F-FACBC PET would be compared with the standard 11C-methionine PET, the registered design does not identify separate randomized arms or a like-for-like control group.

The listed interventions are FACBC and methionine, and PET Scan. The arm description is blank. Consequently, the registry record does not explain how scans were assigned, whether every participant received both scans, or how any within-person comparison would be made. Such details are not reported in the registry record.

The primary outcome is maximum standardized uptake value of 3-[18F]-FACBC, recorded as a mean with standard deviation. Its timeframe is the duration of the scan, described as an average of 1 hour. The outcome description says its purpose is to determine clearance of the tracer in different tissues and organs. A secondary outcome is the rate of 18F-Fluciclovine transport (k1) into tumors. The record lists 2 outcome measures but no analyses.

The record states a planned enrollment of 30 and status completed. It also states that 3 participants did not receive 18F-Fluciclovine PET studies. These statements describe enrollment and a limitation in receipt of the primary imaging procedure; they do not establish the number included in any analysis. The analysis population and handling of participants without the scan are not reported in the registry record.

The stated study purpose includes generating information for an investigational new drug application to the FDA. The registry lists Memorial Sloan Kettering Cancer Center as sponsor. It does not report a protocol-level statistical plan, a sample-size justification, or details of any interim monitoring.

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: 3 participants did not receive 18F-Fluciclovine PET studies

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 Maximum Standardized Uptake Value of 3-[18F]-FACBC, measured over Duration of scan, an average of 1 hour.

The primary endpoint is maximum standardized uptake value of 3-[18F]-FACBC, abbreviated SUVmax. The registry describes it as a continuous measure summarized by a mean and standard deviation. It is assessed over the duration of the scan, described as an average of 1 hour. The stated objective is to determine clearance of the tracer across different tissues and organs.

In general, a maximum uptake measure is used to describe the highest recorded tracer signal within the area being assessed. A standardized uptake value expresses uptake on a common scale, which can support description across measured tissues. These are general explanations of the measure; the registry does not give its calculation details, image-reading rules, or criteria for choosing the measured tumor region.

A mean describes the average value in the analyzed observations. A standard deviation describes how much individual observations vary around that average. Together, these summaries can characterize the level and spread of a continuous imaging measure. They do not, by themselves, establish a difference between tracers, diagnostic accuracy, or clinical benefit.

The registry does not report the primary endpoint's mean or standard deviation. It also does not state how many observations contributed to those summaries, how missing scans were handled, or whether a tumor-specific value was selected for each participant. Accordingly, the endpoint's intended meaning can be described, but its observed level and precision cannot be assessed from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry's methods information is sparse. It identifies a continuous primary endpoint summarized as a mean and standard deviation, a single-group model, no masking, and allocation recorded as NA. It lists no analyses. The following concepts explain how such methods are generally interpreted; they do not imply that an unreported procedure was used in this study.

What do mean and standard deviation describe?

For a continuous outcome, the mean gives the average observed value in the analysis set. The standard deviation describes the spread of individual observations around that mean. A mean can provide a concise description of uptake, while the standard deviation indicates whether observed measurements cluster closely or vary more widely. These summaries answer descriptive questions. They do not show whether two tracers differ, and the standard deviation is not the same as the uncertainty in the estimated mean.

In general, the standard error describes uncertainty in an estimated mean and is used in constructing a confidence interval. A confidence interval gives a range of values compatible with the data and the statistical model, expressing estimation precision rather than certainty that the true value lies within that particular interval. No confidence interval or standard error is reported for the primary endpoint. With no posted mean or standard deviation, the actual level and variability of SUVmax cannot be evaluated.

What would a comparison require?

A comparison requires a defined contrast between measurements. In general, if the same participants receive both imaging procedures, the analysis may need to account for the pairing of their observations. If separate groups are compared, the analysis needs to account for the group structure and the design. These approaches answer different questions and rely on different assumptions. The registry calls the trial single-group and names methionine PET in its summary, but does not state whether the data are paired, how scans were scheduled, or what comparison method was used. No such method is reported in the registry record.

Masking refers to whether participants, investigators, or outcome assessors are kept unaware of assigned treatment or assessment information. The registry records masking as none. That designation alone does not establish how image interpretation was conducted or whether readers knew which tracer produced an image. Details of image-reader procedures are not reported in the registry record.

How should the planning assumptions be understood?

General sample-size illustrations use assumptions to explore how many participants per arm might be needed to detect a specified effect under a chosen statistical model. The assumptions recorded for planning illustrations include a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The target effect is described as a stated fraction of the observed effect. For time-to-event outcomes, the stated convention is a total number of events; for other outcomes, it is participants per arm.

These assumptions are planning illustrations based on an observed effect, not evidence of the trial's original design or its achieved power. They do not show that the study used equal allocation, had two arms, or was planned around the observed result. The registry does not report a protocol sample-size justification, and the design is registered as single-group. No numerical planning results are reported in the registry record, so no sample-size value can be interpreted from it.

Why can variability affect inference?

General statistical principle: greater variability makes an estimate less precise when other design features are held constant. Imaging measurements can vary across participants and tissues, so the distribution and spread matter for interpreting an average. When data show more variability than a simple model assumes, over-dispersion can make conventional uncertainty estimates too small. A model that accounts for the observed variation may be needed. The registry does not report a distributional assessment, an over-dispersion check, or a model for the primary outcome.

Likewise, an analysis plan would ordinarily specify the estimand, inclusion criteria, handling of missing observations, and any adjustment for multiple outcomes. The registry lists 2 outcomes but does not list analyses or explain these choices. The absence of those details means the statistical analysis cannot be reconstructed from the record. It is not appropriate to infer that a particular model, adjustment, or missing-data procedure was used.

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("Participants With Brain Tumors")
n   <- c(27)
m   <- c(4.5)
sp  <- c(2.3)
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  Participants With Brain Tumors  27  4.500  2.300  3.590  5.410

11. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary endpoint, maximum standardized uptake value of 3-[18F]-FACBC, and a secondary outcome, the rate of 18F-Fluciclovine transport (k1) into tumors. It records 2 outcome measures, but no analyses are listed. The record does not explain whether these outcomes were tested, which was considered confirmatory, or whether any adjustment for multiple comparisons was planned or used. Multiplicity handling is not reported in the registry record.

In general, testing multiple outcomes can increase the chance that at least one result appears statistically notable by chance. A prespecified hierarchy or an adjustment method can address that concern, depending on the scientific aims. No such plan is described, and no inferential results are posted. Therefore, statistical significance cannot be evaluated, and no claim about adjustment should be made.

The primary-outcome description says 3 participants did not receive 18F-Fluciclovine PET studies. The registry does not state why, whether their data were otherwise usable, or how their nonreceipt affected the primary endpoint analysis. The number of participants contributing to the SUVmax mean and standard deviation is not reported. Nor does the record identify an intention-to-treat, per-protocol, or other analysis population.

In general, missing-data methods depend on why measurements are absent and on the analysis question. Excluding participants with no scan, imputing values, or analyzing available observations can have different implications. The registry does not report which approach, if any, was used. It also does not describe missingness for the secondary outcome. These omissions limit assessment of possible selection effects and reproducibility.

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 non-serious adverse event terms

The registry reports 0 serious adverse events among 30 participants at risk. It separately lists 2 participants with other adverse events among 30 at risk, and 29 deaths. The record lists no top serious adverse-event terms. These are registry counts, not estimates of comparative risk between imaging procedures.

Serious and other adverse events are distinct categories in the record. The counts should not be combined. The death entry is reported separately and should not be assumed to describe an adverse event, a death caused by the imaging procedure, or a death during a particular follow-up interval. The registry does not report the timing, causes, or attribution of deaths, nor does it explain the relationship between deaths and the adverse-event counts.

These figures also do not establish that an event was caused by FACBC, methionine, or PET imaging. A single-group record without a defined control comparison cannot establish comparative safety from these counts. The registry does not provide event descriptions, follow-up duration for safety, or an attribution assessment. The appropriate reading is limited to what is recorded: the listed counts and risk-group sizes, with causal interpretation not reported in the registry record.

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

The study addresses an imaging question: characterization of brain tumors using 18F-FACBC PET, with 11C-methionine PET named as a standard comparison in the summary. The registered primary measure is SUVmax, intended to describe tracer clearance across tissues and organs. The study also lists tumor transport rate as a secondary outcome and describes an interest in radioactivity exposure.

What the registry does not provide is the observed SUVmax mean or standard deviation, the secondary outcome result, or an inferential comparison. It therefore cannot show the size or direction of a difference between imaging approaches, the uncertainty around any such difference, or whether a statistical test supported one. The stated goal of comparing images is not itself a reported comparison result.

The design label matters for interpretation. The record identifies a single-group study, allocation NA, and no masking. It does not describe a randomized control group or explain how methionine imaging was incorporated into the analysis. Without that information, readers cannot determine whether a paired comparison was possible or how any systematic differences between scans were addressed.

Similarly, enrollment and scan receipt are not interchangeable. The record lists enrollment of 30 and says 3 participants did not receive 18F-Fluciclovine PET studies. The number included in the primary analysis and the handling of missing scans are not reported. Thus the registry does not permit a full assessment of how complete the endpoint data were.

The posted safety counts are descriptive and do not establish causation or comparative safety. The death count has no reported timing or cause, and the adverse-event terms are not listed. Taken together, the record establishes the study's imaging focus, design labels, endpoint definition, and some event counts. It does not establish diagnostic accuracy, a treatment effect, clinical benefit, or comparative performance between tracers. Those conclusions would require results and methods not reported in the registry record.

14. Why This Trial Matters Statistically

This study illustrates why an endpoint definition and a numerical result are both needed for statistical interpretation. SUVmax is identified as a continuous primary measure, and the registry specifies a mean and standard deviation. Those labels explain the intended summary, but without the observed values there is no basis for judging uptake level, variability, or precision.

It also highlights the distinction between a stated comparison and a comparative design. The summary describes comparing FACBC with standard methionine PET, while the registered model is single-group and allocation is NA. The record does not explain whether both scans were obtained in each participant or how their values would be compared. Statistical interpretation depends on that design detail, not only on naming a comparator.

Missing measurements are another important consideration. The endpoint description notes that 3 participants did not receive the FACBC PET study, but the analysis population and missing-data handling are not stated. The effect of missing endpoint observations depends on their number, reasons, and handling; a registry statement about scan nonreceipt alone cannot resolve those questions.

Finally, the record separates scientific aims from posted evidence. It describes tracer imaging, organ exposure measurements, and a secondary transport outcome, yet lists no analyses and no numerical endpoint results. The safety counts are also descriptive, with no reported timing or causal attribution. For biostatistical reading, this is a useful reminder that a completed status and a defined outcome do not substitute for results, uncertainty estimates, or a transparent analysis plan.

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 statistical interpretation is that the registry does not report numerical results for the primary endpoint. Although the endpoint is described as a mean with standard deviation, neither value is posted. No confidence interval, p-value, test statistic, or estimate of a comparison is given. The record lists no analyses.

The design information does not resolve how the intended FACBC-versus-methionine comparison was conducted. The study is registered as single-group, with allocation NA and no masking, while the summary describes methionine PET as a standard comparison. Whether participants received both scans, and how scan order or paired observations were handled, is not reported in the registry record.

The endpoint description reports that 3 participants did not receive 18F-Fluciclovine PET studies. The reasons, analysis consequences, and number of evaluable primary observations are not reported. The registry also does not specify the analysis population, missing-data method, image-reading procedures, or statistical model.

Although 2 outcome measures are listed, the record does not report how multiplicity was handled or whether a hierarchy was prespecified. It does not give a protocol sample-size justification or describe interim analyses. Planning assumptions for sample-size illustrations are not evidence of the trial's original design or achieved power.

Safety interpretation is limited by the absence of event terms, timing, attribution, and death causes. The registry's counts alone cannot establish whether events were related to imaging. More broadly, the record does not provide sufficient outcome and analysis detail to assess precision, bias, or reproducibility of the primary comparison.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Imaging Brain Tumors With FACBC and Methionine — NCT00597246.
• Registry record last updated 2020-12-17; status last verified 2019-06.
• Results first posted 2020-12-17.
• 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

NCT00597246 is a completed, single-group imaging study sponsored by Memorial Sloan Kettering Cancer Center. It lists enrollment of 30 and conditions of Brain Cancer and CNS Cancer. Masking is recorded as none and allocation as NA.

The summary describes 18F-FACBC PET imaging and comparison with standard 11C-methionine PET. The primary outcome is maximum standardized uptake value of 3-[18F]-FACBC, summarized as a mean and standard deviation over the scan duration, described as an average of 1 hour. A secondary outcome is 18F-Fluciclovine transport rate (k1) into tumors. The record lists 2 outcome measures and no analyses.

The primary-outcome description states that 3 participants did not receive 18F-Fluciclovine PET studies. Numerical primary and secondary results, analysis populations, missing-data methods, and a formal comparison are not reported in the registry record. Safety entries list 0 serious adverse events, 2 other adverse events, and 29 deaths, without event terms or causal detail.