Trilogy Stereotactic Body Radiotherapy for Pancreatic Cancer: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Trilogy Stereotactic Body Radiotherapy for Pancreatic Cancer (NCT00350142), a na phase 2 study. The primary outcome is Rate of Local Control.

2. Clinical Question

In statistical terms, the study question is descriptive: how often was local control recorded among participants receiving the study regimen during the stated follow-up period? It is not a comparison of the regimen against a control treatment. Although the registry lists median overall survival time as a secondary outcome, it does not report a median or other numerical survival result. The registry record also does not describe whether the primary endpoint was assessed in all enrolled participants or a narrower analysis population. Those omissions matter because an endpoint proportion depends on both the number meeting the definition and the denominator used.

3. Trial Design

This is a phase 2, single-group study of stereotactic body radiotherapy for pancreatic cancer. The registry record lists an enrollment of 20 and marks the study as completed. Allocation is listed as not applicable, masking as none, and the study model as single group. These design features mean the record does not describe random assignment or a masked comparison between groups.

The intervention list includes stereotactic body radiotherapy, gemcitabine, a 4D pancreatic protocol CT scan, and an FDG PET scan. The arm is titled SBRT With Gem. Its description states that the CT and PET scans were used for planning, and that an SBRT plan was developed based on tumor geometry and location. Participants were to receive a single fraction of 25 Gy using a Trilogy Linear Accelerator. The registry record does not state the gemcitabine dose, schedule, or timing relative to radiation.

The study start is recorded as 2006-04, and primary completion as 2008-10. The sponsor is Albert Koong. The stated study purpose is to assess treatment of locally advanced pancreatic cancer using SBRT with Trilogy and gemcitabine. The primary endpoint is the rate of local control up to 3 years, while median overall survival time is listed as a secondary outcome.

A single-group design can describe outcomes observed in participants who receive the regimen, but it does not isolate the contribution of one component from another or establish what would have happened under a different treatment. The registry record does not report a protocol rationale for choosing this design, a sample-size justification, an interim analysis plan, or a detailed statistical analysis plan. Details of eligibility, follow-up completeness, and endpoint assessment procedures beyond the stated definitions are 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

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 Rate of Local Control, measured over up to 3 years.

The primary endpoint is the rate of local control, measured as the proportion of participants with no recurrence or disease progression in the primary disease site, with a timeframe of up to 3 years. This is a binary outcome at the participant level: each assessed participant either meets the local-control definition or does not. The registry describes disease progression using RECIST or PET criteria. Under RECIST, progression is defined as more than 25% tumor increase by volume and/or the presence of a new lesion. Under PET criteria, progression is defined as increased PET activity compared with the scan used for treatment planning; any subsequent increase in SUVmax is defined as local progression.

In general, a local-control endpoint focuses on whether disease recurs or progresses at the treated primary site. It differs from an overall survival endpoint, which concerns time to death from any cause. The endpoint can therefore describe local disease status without, by itself, describing survival or disease activity elsewhere.

The registry record does not report the observed number of participants with local control, the proportion, a confidence interval, or the number included in the endpoint analysis. It also does not state how participants without sufficient follow-up or an assessable scan were handled. Consequently, the endpoint definition is available, but the observed local-control result and its precision are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What kind of outcome is local control?

General: A participant-level binary outcome classifies each assessed participant into one of two categories, such as meeting or not meeting a defined endpoint. A local-control rate is ordinarily expressed as the number meeting the endpoint relative to the analysis denominator. The registry record identifies this outcome type and defines local control, but does not report the count, denominator, or resulting rate. Enrollment alone should not be treated as the analysis denominator unless the record says that all enrolled participants were analyzed.

How does the endpoint definition affect interpretation?

The record defines local control as no recurrence or disease progression in the primary disease site. It permits progression assessment using RECIST or PET criteria. RECIST progression is described as more than 25% tumor increase by volume and/or a new lesion. PET progression is an increase in PET activity compared with the planning scan, with any subsequent increase in SUVmax defined as local progression. These criteria determine which observations count as progression and therefore affect the binary classification. The record does not explain how the criteria were selected for individual participants, how conflicting assessments were handled, or whether assessments were reviewed independently.

What would uncertainty mean?

General: A confidence interval communicates statistical uncertainty around an estimated quantity. For a binary proportion, its width depends in part on the observed event count and the denominator, as well as the method used to construct it. A narrow interval generally indicates greater precision than a wide interval, but neither one removes limitations in the design or measurement. No local-control estimate or confidence interval is reported in the registry record, so precision cannot be evaluated from this record.

General: A p-value addresses how compatible data are with a specified statistical model or null hypothesis. It does not measure the probability that a treatment works, and it does not describe the size or clinical importance of an effect. The registry record does not report a p-value for the primary endpoint, nor does it specify a null value or hypothesis test for that endpoint. It would therefore be inappropriate to infer a test result from the study label or enrollment count.

Why does the single-group design matter?

The study is recorded as single group, with no masking and allocation listed as not applicable. A single-group outcome can be described as an observed proportion, provided the denominator and follow-up are clear. It cannot produce a randomized between-group estimate because there is no separate control arm. General: comparison with an external benchmark may sometimes be considered in research, but such a comparison depends on assumptions about comparability and is not equivalent to randomization. The registry record does not identify a benchmark or report such an analysis.

The intervention includes SBRT and gemcitabine. Thus, even if an outcome estimate were reported, this design would not separate the effects of radiation from those of the drug or other aspects of care. Nor does the record report how concomitant or subsequent treatments were accounted for.

How should the planning illustration be understood?

The registry record describes a planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is expressed as a stated fraction of the observed effect. This is a planning framework, not a description of the trial design. The trial itself is recorded as single group. No numerical planning estimates are reported in the registry record, and such illustrations are not observed power or evidence that the study had a particular probability of detecting an effect.

General: Power calculations depend on the assumed effect, variability, significance level, allocation, and analysis method. When an assumed effect is derived from an observed estimate, it may not represent a stable or reproducible effect. Planning outputs are conditional on their assumptions and do not establish what the study actually observed. The record does not report the trial's own sample-size justification, so the enrollment of 20 should not be interpreted as evidence that a particular precision or power target was achieved.

What is not available about analysis?

The registry record lists two outcome measures and one analysis, but does not give a detailed statistical plan, analysis population, missing-data method, censoring method for survival, or multiplicity procedure. General: Over-dispersion matters when count data vary more than a simple model expects, because a model that understates variability can produce overly narrow uncertainty intervals. That concept is not directly enough to determine an appropriate analysis here, and the record does not report a model or over-dispersion assessment. For the binary primary endpoint, the key information needed for interpretation includes the endpoint count, denominator, follow-up handling, and uncertainty estimate; these are not reported.

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("Stereotactic Radiosurgery")
n      <- c(20)
events <- c(15)
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  Stereotactic Radiosurgery  20  15  75.0  50.9  91.3  53.1  88.8  52.8  88.7

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists two outcome measures: local-control rate as the primary endpoint and median overall survival time as a secondary outcome. It lists one analysis, but does not describe which outcomes or time points that analysis covered. No multiplicity adjustment or prespecified testing hierarchy is reported in the registry record.

General: When several outcomes or analyses are tested, the chance of at least one apparently notable result can increase if each is interpreted without regard to the others. A multiplicity strategy can define which outcome is primary, how secondary outcomes are interpreted, and whether statistical error rates are adjusted. The record identifies a primary and secondary outcome, but does not report a procedure for handling multiple inferences. Since numerical outcome results are not reported, the impact of multiplicity on any claimed finding cannot be assessed.

Missing-data handling and analysis populations are also not reported in the registry record. It is not stated how many participants had endpoint assessments, whether follow-up was complete, how missing scans or other unavailable assessments were classified, or whether the primary analysis included every enrolled participant. These choices can affect a binary proportion because the endpoint count and denominator depend on how unassessed participants are treated.

The secondary outcome, median overall survival time, would generally require information about follow-up and censoring to interpret its estimate. The registry record does not report a median, an analysis population, a time origin, a censoring approach, or a confidence interval. No specific missing-data or survival-analysis procedure should be inferred from the fact that the outcome is listed.

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: perforation (5.0%).

The safety record lists one group, titled SBRT With Gem, with 20 participants at risk for serious adverse events and 1 affected participant. It separately lists 20 participants at risk for other adverse events and 6 affected participants. Perforation is listed among the top serious terms at 5.0%. These are the registry figures and should be read as counts and a reported term frequency, not as a comparison between treatment groups.

The record does not define the observation period for these safety counts, provide event-level descriptions, or state whether participants could contribute more than one event. It also does not explain how the listed serious term relates to the affected-participant count. The figures therefore do not establish timing, severity details beyond the serious-event classification, causality, or the overall safety profile. The study has no separate control group, so the registry record does not support a comparative estimate of adverse-event risk.

General: Adverse-event counts describe events recorded under a study's collection and classification procedures. The number of participants affected is not necessarily the same as the number of events, since a participant may experience more than one event. The record does not report event totals or further detail needed to distinguish those quantities. These safety entries should be interpreted narrowly as the reported counts and term frequency.

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

The record establishes that a completed phase 2, single-group study enrolled 20 participants and evaluated SBRT using Trilogy alongside gemcitabine. It describes the primary endpoint as local control up to 3 years and gives the criteria used to define progression. It also lists median overall survival time as a secondary outcome and provides limited adverse-event counts. These details clarify what the study set out to examine and how the registry characterized some outcomes.

The record does not report the observed local-control result or a numerical overall-survival result. It therefore cannot show what proportion of participants had local control, how precise that estimate was, or what median survival was observed. No claim about the magnitude or direction of the primary endpoint can be drawn from the endpoint definition, the enrollment figure, or the study's completed status.

Even if numerical outcomes were available, the single-group design would limit causal interpretation. Without a concurrent comparator, observed outcomes cannot be attributed solely to the intervention by comparing them with what would have occurred under another treatment. Because SBRT and gemcitabine are both part of the regimen, the study design also cannot isolate the effect of either component. The registry record does not report details that would allow adjustment for other influences or comparison with an external group.

General: A clinical study result is best interpreted by considering the estimate, its uncertainty, the outcome definition, follow-up, and design together. A numerical estimate would describe the study participants and analysis used; it would not automatically establish broader applicability. In this record, the missing outcome estimates and analysis details make even a descriptive assessment of endpoint frequency unavailable. The posted safety figures are also limited counts without a comparator or detailed event context.

The appropriate conclusion is therefore about the registry information, not treatment efficacy: the study question and endpoint are described, but the numerical primary outcome and survival findings are not reported in the registry record. The available information is insufficient to determine the observed local-control rate or its statistical precision.

14. Why This Trial Matters Statistically

This study is statistically useful to examine because it illustrates the distinction between a clearly named endpoint and a reportable endpoint result. The registry defines local control and specifies progression criteria, which makes the intended outcome more interpretable than an endpoint label alone. But without the number of participants meeting the definition, the analysis denominator, and an uncertainty estimate, readers cannot assess the observed rate or its precision.

The single-group design is another important feature. It can support description of outcomes among participants receiving the regimen, but it does not create a randomized contrast. The record lists both SBRT and gemcitabine, so attribution to either component is also not possible from this design. These distinctions matter when translating an observed clinical outcome into a statistical claim: description and causal comparison answer different questions.

The safety entries show why counts need context. The registry reports affected-participant counts and a serious-term frequency, but does not provide event narratives, follow-up duration, or a comparison group. Those numbers can be stated accurately, while conclusions about relative risk or causation cannot be drawn from them.

More broadly, the record demonstrates the role of reporting details in reproducible interpretation. The analysis population, missing-data approach, follow-up completeness, and statistical plan are not reported. Those items are not administrative extras: for a binary endpoint, the denominator and handling of unassessed participants directly affect what an estimated proportion represents. For survival, follow-up and censoring details are essential to understanding an estimate. Their absence limits statistical interpretation even when the study question and endpoint definitions are available.

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 limitations are specific to the information recorded for this study. First, the primary endpoint result is not reported: the record gives no local-control count, proportion, confidence interval, or analysis denominator. The endpoint timeframe is up to 3 years, but the record does not report actual follow-up completeness or the number of participants assessed during that period.

Second, although the study is described as SBRT with gemcitabine, the registry does not report the gemcitabine dose or schedule. The treatment description does specify a single fraction of 25 Gy using a Trilogy Linear Accelerator. Further treatment-delivery details and adherence information are not reported in the registry record.

Third, the study is single group, with no masking and allocation listed as not applicable. There is no concurrent control group for interpreting outcomes comparatively, and the combined regimen prevents separation of the contributions of SBRT and gemcitabine. The registry record does not report a protocol rationale or a trial-specific sample-size justification.

Fourth, the endpoint allows progression to be defined using RECIST or PET criteria, but the record does not explain how the criteria were applied or reconciled. It also does not report endpoint assessment schedules, review procedures, missing-assessment handling, or the analysis population. For the secondary median overall survival outcome, no estimate or analysis details are reported.

Finally, the safety information is limited to participant counts and a listed serious term. The observation period, event-level detail, and relationship of the term listing to the affected-participant count are not reported. These omissions limit conclusions about both endpoint interpretation and safety context.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Trilogy Stereotactic Body Radiotherapy for Pancreatic Cancer — NCT00350142.
• Registry record last updated 2017-02-14; status last verified 2016-12.
• Results first posted 2014-08-22.
• 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 record describes a completed phase 2, single-group study of Trilogy stereotactic body radiotherapy and gemcitabine for pancreatic cancer. Enrollment was 20. The primary endpoint was local-control rate up to 3 years, defined as no recurrence or progression at the primary disease site using RECIST or PET criteria. Median overall survival time was listed as a secondary outcome.

The arm description specifies planning with a 4D pancreatic protocol CT and FDG PET scan, followed by a single fraction of 25 Gy SBRT using a Trilogy Linear Accelerator. The registry lists 1 participant with a serious adverse event among 20 at risk, 6 with other adverse events among 20 at risk, and perforation at 5.0% among the top serious terms.

The numerical local-control and survival results, analysis denominator, missing-data procedures, and detailed statistical plan are not reported in the registry record. The single-group design does not provide a randomized comparison.