Image-guided Cryoablation of Head, Neck and Spine Tumors: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Image-guided Cryoablation of Head, Neck and Spine Tumors (NCT02085941), a non-randomized na study. The primary outcome is Number of Participants Undergoing Image-guided Cryoablation of a Head, Neck, or Spine Tumor With Adverse Events.

2. Clinical Question

In statistical terms, the central question is descriptive: what adverse-event counts were recorded among participants in the two procedure groups during the stated follow-up window? The record gives group-level counts for serious events, other events, and deaths. It does not report a randomized estimate of the effect of cryoablation, nor does it establish that any observed event was caused by the procedure.

The groups differ in size and were not formed through random allocation. Comparisons between them may reflect differences in who received each imaging approach, the tumors treated, clinical circumstances, or other factors not described in the record. The primary outcome therefore does not answer whether one guidance method is safer or more effective than the other.

3. Trial Design

This completed study, NCT02085941, evaluated image-guided cryoablation for head, neck, and spine tumors. The registry lists Dana-Farber Cancer Institute as the sponsor, an enrollment of 30, a start in 2015-02, and primary completion in 2021-07. The phase is listed as NA. These registry entries describe the study record; they do not establish that every planned outcome or analysis was reported.

The design is listed as single group and non-randomized, with no masking. The arm descriptions distinguish MRI-guided cryoablation from PET-CT-guided cryoablation. Both descriptions specify an intraoperative imaging approach and use of a 17G Galil cryoprobe. They also describe concurrent biopsy with an 18G Temno core biopsy needle if biopsy had not previously been performed. Biopsy is therefore described as conditional rather than as an intervention necessarily received by every participant.

Although the registry presents two guidance groups, this is not a randomized head-to-head trial. Assignment procedures, reasons for choosing an imaging approach, and other details needed to assess how comparable the groups were are not reported in the registry record. The group counts are useful as descriptions of the posted safety record, but they do not support an unconfounded comparison of the guidance approaches.

The primary outcome timeframe is one month, described as the period from the procedure to one month post-procedure. The registry lists progression rates and pain assessment as secondary outcomes. Their assessment methods, timeframes, and results are not reported in the registry record. The record lists three outcome measures and zero analyses. It does not report a statistical analysis plan, planned interim analyses, or a sample-size justification.

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 Number of Participants Undergoing Image-guided Cryoablation of a Head, Neck, or Spine Tumor With Adverse Events, measured over One month.

The primary endpoint is described as the number of participants undergoing image-guided cryoablation of a head, neck, or spine tumor with adverse events. Its timeframe is one month, from the procedure through one month post-procedure. This is a count-based safety outcome: it is intended to describe how many participants experienced an event during the stated period, rather than to measure tumor response or compare time until an event.

Safety outcomes are used to characterize events occurring around a procedure and to make their frequency and type visible in the study record. A participant count can communicate how many people were affected, while separate event counts may communicate how many events occurred. Those are not interchangeable measures. The endpoint description refers to the number of adverse events, while the outcome is also described in terms of participants with an event. The registry’s adverse-event fields distinguish participants at risk from participants affected, but the record does not give further operational definitions for the primary endpoint.

The posted group information separates serious adverse events, other adverse events, and deaths. This is useful descriptive context, but it does not by itself identify event causes, severity criteria, duration, recurrence, or relationship to cryoablation. Those details are not reported in the registry record. A one-month window also describes only the stated follow-up period; it should not be treated as a complete account of events outside that window.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a count-based endpoint describe?

In general, a count-based safety endpoint describes how many participants experienced an event, or how many events were recorded, during a defined observation period. These are related but distinct quantities. One participant may experience more than one event, so a total event count need not equal the number of participants affected. The record uses participant counts in its adverse-event fields, but its primary outcome description also refers to the number of adverse events. Without a fuller endpoint definition, it is important not to treat those measures as interchangeable.

The outcome timeframe is one month from the procedure to one month post-procedure. A fixed follow-up window makes the period of interest explicit, but it does not tell readers whether every participant was observed for the full period or how events outside that window were handled. Follow-up completeness and rules for counting recurring events are not reported in the registry record.

What do the group counts mean?

The adverse-event fields show, for each group, participants at risk and participants affected. The at-risk count supplies context for the affected count: the affected count is not a standalone estimate of how often events occurred. The registry lists serious and other adverse-event categories separately, and deaths in a separate field. Without definitions for these categories, event terms, or rules for assigning events, the categories should be reported as the registry labels them rather than reinterpreted.

In general, a confidence interval expresses uncertainty around an estimate, with a method that reflects the data and assumptions used. It can help distinguish a small observed count from a precise estimate of the underlying frequency. No confidence intervals for the adverse-event counts are reported in the registry record. The posted counts therefore have no accompanying numerical uncertainty range in the record.

Why does non-random allocation matter?

In general, random allocation helps balance measured and unmeasured participant characteristics between comparison groups, on average. This study is listed as non-randomized and single group, while its adverse-event record distinguishes two imaging approaches. The groups should not be read as randomized treatment arms. The reason a participant received MRI guidance or PET-CT guidance may relate to clinical features or other factors, but those reasons are not reported in the registry record.

Consequently, a difference in group counts would not isolate an effect of imaging approach. Even if an adjusted analysis were available, interpretation would depend on which characteristics were measured and how the analysis was specified. No adjusted comparison is reported. The posted counts are best read as descriptions of the participants in each recorded group, not as causal estimates.

What can planning calculations tell readers?

Sample-size calculations are planning tools: they explore how much information a future study might need under stated assumptions. The record’s planning illustration is described as based on the observed effect, with two-sided significance level 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is described as a stated fraction of the observed effect. Such illustrations do not describe the number of participants actually observed, and they are not observed power. They also do not replace the trial’s original design rationale. That rationale and a sample-size justification are not reported in the registry record.

For non-time-to-event outcomes, planning calculations may be expressed as participants per arm; time-to-event calculations may instead refer to total events. These are general distinctions about what a planning output represents. A planning result depends on assumptions about the target effect, variability, allocation, and analysis method. If those assumptions do not match a future study, the calculation may not be informative for that study. The registry record does not report a full protocol or statistical plan to show how such assumptions relate to the original study design.

How should the statistical record be read?

The registry lists three outcome measures and zero analyses. It does not report inferential results for the primary safety outcome, such as a hypothesis test or an adjusted estimate. A count can still be informative as descriptive evidence, but the absence of an inferential analysis means readers should not infer statistical significance, equivalence, or a quantified comparison from the count fields.

In general, over-dispersion matters when count data vary more than a chosen statistical model expects. A model that underestimates that variation can make uncertainty appear too small. The registry does not report a count model or any analysis of over-dispersion, so there is no basis for saying that either issue was assessed in this study. Likewise, no statistical model, covariate adjustment, or method for handling repeated events is reported. These concepts describe general considerations, not methods attributed to the trial.

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("MRI Guided Cryoablation", "PET-CT Guided Cryoablation")
n      <- c(25, 5)
events <- c(3, 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  MRI Guided Cryoablation  25  3  12.0  2.5  31.2  4.2  30.0  4.4  30.2
ARM  PET-CT Guided Cryoablation  5  0  0.0  0.0  52.2  0.0  43.4  0.4  45.9

11. Multiplicity, Missing Data and Analysis Populations

The record lists progression rates and pain assessment as secondary outcomes in addition to the primary adverse-event outcome. It reports three outcome measures overall, but detailed definitions, timeframes, and results for those secondary outcomes are not reported in the registry record. The record lists zero analyses and does not describe a prespecified statistical analysis plan.

In general, when a study examines multiple outcomes or performs multiple statistical tests, the chance of a false-positive finding can increase if the analyses are treated as independent opportunities to declare a result. Methods for addressing multiplicity may include prioritizing outcomes or adjusting inference, but no such approach is reported in the registry record. Because no inferential results are reported, there is no stated multiplicity adjustment to interpret.

The record does not describe missing outcome data, loss to follow-up, or the rules used to determine which participants were included in each outcome analysis. It also does not report an analysis population, such as a defined set of participants used for the primary endpoint. These details matter because a count based on incomplete follow-up can differ in meaning from a count based on complete observation. No assumptions about missing outcomes or exclusions should be inferred from the posted group counts.

The event fields include counts at risk, but the registry does not explain how those denominators were established or whether they represent all participants who could have contributed to each outcome. The one-month timeframe is reported, but completeness of follow-up within that timeframe is not. These reporting gaps limit assessment of endpoint completeness and the risk of selective outcome reporting.

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

For serious adverse events, the registry lists 25 participants at risk and 0 affected in the MRI-guided group, and 5 at risk and 0 affected in the PET-CT-guided group. For other adverse events, it lists 25 at risk and 3 affected in the MRI-guided group, and 5 at risk and 0 affected in the PET-CT-guided group. The record lists 6 deaths for MRI-guided cryoablation and 1 for PET-CT-guided cryoablation.

These fields should be kept distinct. Serious and other adverse events are separate categories in the record, while deaths are reported separately. The registry does not describe the deaths’ causes, timing, or attribution to the procedure, so they cannot be assumed to be procedure-related or to fall within the primary outcome’s one-month timeframe. The record also does not give descriptions of the other adverse events, and its serious-event terms list is empty.

Counts do not establish comparative safety. The groups were not randomized, their sizes differ, and the record does not report uncertainty estimates or complete follow-up information. The counts describe what is recorded, not a causal conclusion about either imaging approach.

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

The posted results provide a descriptive account of adverse-event fields for participants undergoing MRI-guided or PET-CT-guided cryoablation. They show no serious adverse events recorded in either group, three participants affected in the MRI-guided group for other adverse events, and none recorded in that field for the PET-CT-guided group. Death counts are also listed separately. These statements describe the registry entries and do not determine why events occurred.

The study does not establish that cryoablation caused or prevented any event. A safety count is not a causal estimate, particularly when the study is non-randomized and does not include a like-for-like control group. Nor can the two guidance groups be compared as though assignment had been randomized. Differences in patient characteristics, tumor locations, or clinical decisions could affect who was treated with each approach, and those factors are not detailed in the registry record.

The results also do not establish that the two imaging approaches are equivalent, or that no additional safety concerns exist. Zero events recorded in a category is not the same as evidence that the true event rate is zero. The record supplies no confidence intervals for these counts, and it does not describe how complete follow-up was or how missing information was handled. The one-month outcome window cannot answer questions about events beyond that interval.

Progression rates and pain assessment are named as secondary outcomes, but their methods and results are not reported in the registry record. Accordingly, the posted safety counts cannot be used to draw conclusions about tumor control, pain, or comparative effectiveness. They are a limited descriptive record, with interpretation constrained by missing endpoint details, lack of a randomized comparison, and absence of reported inferential analyses.

14. Why This Trial Matters Statistically

This trial is statistically notable because it illustrates the difference between recording safety counts and estimating a treatment effect. The registry includes adverse-event information for two image-guidance groups, but the study is listed as non-randomized and single group. The presence of two groups does not by itself create a valid controlled comparison. Study design determines what a statistical contrast can support.

It also highlights why outcome labels and definitions matter. The primary outcome description refers to participants with adverse events, while the record also separates serious and other adverse events and reports deaths separately. Without fuller definitions and event descriptions, readers need to preserve those distinctions and avoid combining or reclassifying the fields. Counts can be easy to read but still leave important questions about what was counted and over what period.

The one-month window makes the intended period of safety assessment explicit, yet the record does not state how complete follow-up was or explain event attribution. Those omissions affect the strength of any interpretation, even when the counts themselves are clear. Reporting uncertainty estimates and analysis details would help readers assess the precision and meaning of the observed counts.

Finally, the record names secondary outcomes without reporting their detailed results, and it lists zero analyses. This illustrates that a completed study record and a complete statistical account are not necessarily the same thing. For biostatisticians and clinical researchers, the key lesson is to distinguish registry-level descriptive findings from protocol-defined analyses and causal conclusions. In this case, only a cautious description of recorded events is warranted.

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 registry record does not report the eligibility criteria, baseline characteristics, tumor features, or reasons participants received MRI guidance rather than PET-CT guidance. These omissions make it difficult to assess how the groups differed before treatment or whether their observed safety counts are comparable. Non-random allocation further limits interpretation of any between-group contrast.

Event definitions and details are limited. The record does not describe how serious and other adverse events were defined, how recurrent events were counted, or what the three other adverse events in the MRI-guided group involved. The serious-event terms list is empty. The separate death counts are not accompanied by causes, timing, or attribution information. It is therefore not possible to determine from these fields whether deaths were related to treatment or occurred within the primary outcome window.

The stated one-month timeframe does not establish that every participant completed follow-up. Follow-up completeness, missing data, exclusions, and analysis-population definitions are not reported in the registry record. There are no reported confidence intervals, hypothesis tests, or adjusted estimates for the safety counts. The record also does not supply the statistical analysis plan or sample-size justification.

Progression rates and pain assessment are listed as secondary outcomes, but their measurement methods, timeframes, and results are not reported. This limits any broader interpretation of the study beyond the posted safety fields. These limitations do not negate the value of the recorded counts; they define what can and cannot be concluded from them.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Image-guided Cryoablation of Head, Neck and Spine Tumors — NCT02085941.
• Registry record last updated 2022-08-15; status last verified 2022-07.
• Results first posted 2022-08-15.
• 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

NCT02085941 is a completed, non-randomized, single-group study of image-guided cryoablation for head, neck, and spine tumors. The registry lists an enrollment of 30, Dana-Farber Cancer Institute as sponsor, a start in 2015-02, and primary completion in 2021-07. The phase is listed as NA, and masking is listed as none.

The procedure groups are MRI-guided cryoablation and PET-CT-guided cryoablation, with biopsy described when it had not previously been performed. The primary outcome concerns adverse events through one month after the procedure. Progression rates and pain assessment are listed as secondary outcomes.

Adverse-event fields report serious and other event counts by group and list deaths separately. The record lists three outcome measures and zero analyses. Detailed event definitions, follow-up completeness, secondary-outcome results, and an inferential analysis plan are not reported in the registry record. The counts therefore support descriptive reading, not a randomized or causal comparison.