Evaluate the Use of Paravertebral Block in Reconstructive Breast Surgery: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Evaluate the Use of Paravertebral Block in Reconstructive Breast Surgery (NCT00542542), a randomized phase 3 study. The primary outcome is Proportion of Participants With No Pain Immediately After Surgery.

2. Clinical Question

The registry frames the main question as whether adding a paravertebral block is associated with less immediate postoperative pain than general anesthesia alone. Pain was assessed with a verbal numeric rating scale, with scores from 0 to 10, where 0 means no pain and 10 means the worst pain. The stated primary outcome is the proportion of participants with no pain immediately after surgery.

The registry also describes secondary questions about postoperative pain in the first 24 hours, postoperative nausea and vomiting in the first 24 hours, and length of hospital stay. These are stated objectives, not results. Because the registry says analysis of the primary outcome was not possible due to reporting inconsistencies, it does not establish a comparative answer to the primary question. Comparative results for the secondary objectives are not reported in the registry record.

3. Trial Design

This was a Phase 3, randomized, parallel-group trial listed as completed. Masking is recorded as none. The registry lists M.D. Anderson Cancer Center as the sponsor and 89 as the enrollment. That enrollment figure does not, by itself, establish how many participants were assigned to or analyzed in each group.

The experimental group was assigned to paravertebral block plus general anesthesia; the block is described as using ropivacaine. The comparator group received general anesthesia alone, described as involving propofol, midazolam, and fentanyl. The registry lists paravertebral block as a procedure and also lists propofol, fentanyl, ropivacaine, and midazolam as interventions. The record does not provide additional detail about how these interventions were administered.

The recorded start is 2007-09 and primary completion is 2014-03. The status is completed. These registry dates describe the trial record, but they do not fill in details about recruitment progress, follow-up completeness, or when individual outcomes were collected beyond the stated assessment schedule.

Random assignment is intended to make the groups comparable on average, while a parallel design assigns participants to a group rather than switching each participant between treatments. In an unmasked trial, participants and study personnel are not recorded as blinded. That can matter for outcomes involving subjective assessment, including self-reported pain. The registry record does not report further safeguards or procedures for outcome assessment.

Although the design and comparison are identified, the registry does not provide a usable primary outcome analysis. The stated reason is reporting inconsistencies in the collected data. Therefore, the design describes the question the investigators intended to study, not a demonstrated estimate of the difference between groups.

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.

Before assignment: Of the 89 participants enrolled, one participant was excluded prior to group assignment.

Overall Study

Analysis population for the primary outcome, as defined in the registry: Analysis was not possible from data collected due to reporting inconsistencies.

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.

Population: One participant was removed prior to study randomization.

6. Primary Endpoint

The registry lists the primary outcome as Proportion of Participants With No Pain Immediately After Surgery, measured over Starting immediately after surgery, every 2 hours till the 6th hour following surgery.

The listed primary endpoint is the proportion of participants with no pain immediately after surgery. Pain was assessed using a verbal numeric rating scale scored with integers from 0 to 10. The record defines 0 as no pain and 10 as the worst pain. A proportion with no pain would summarize how many assessed participants met the no-pain criterion, rather than describe the distribution of all pain scores.

The registry gives an assessment schedule beginning immediately after surgery and continuing every 2 hours till the 6th hour following surgery. Its description also mentions evaluation within the first hour, between 1 - 3 hours, and between 3 - 6 hours post-operatively. It says additional reporting was planned for the following morning, 18 - 24 hours post-operatively. The endpoint title emphasizes pain immediately after surgery, while the description covers several assessment periods. The record does not clarify which time point or summary defines the primary comparison.

A binary no-pain endpoint can make a result easier to interpret as the share of participants meeting a specified pain state. It also discards information about participants' scores above 0, so it does not convey the full range or severity of reported pain. These are general properties of this kind of endpoint, not findings from this trial.

Most importantly, the registry states that analysis was not possible from the collected data due to reporting inconsistencies. It therefore provides no analyzable primary endpoint estimate in the record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical methods determine how observations are converted into a comparison and how uncertainty is represented. For this trial, the registry record supplies the randomized parallel-group design, the intended primary outcome, the assessment description, and the reason an analysis could not be performed. It does not report a statistical analysis plan or an outcome-effect estimate. The explanations below describe general concepts and should not be read as claims about methods actually used in this trial.

What does randomization contribute?

In general, random assignment aims to prevent systematic selection into treatment groups. If implemented and preserved, it can support a fair comparison because measured and unmeasured participant characteristics are less likely to be deliberately concentrated in one group. Randomization does not guarantee that groups will be identical, and it does not correct errors in data collection or reporting. Here, the registry records the study as randomized, but does not report the allocation procedure, concealment details, or a comparison of baseline characteristics.

What would the primary comparison estimate?

The endpoint is expressed as a proportion: participants classified as having no pain immediately after surgery relative to the participants assessed in a group. A comparison would need to define the relevant time point, specify which participants were included, and state how the group proportions were contrasted. Common measures for binary outcomes include a difference in proportions or a ratio of proportions. These are general options only; the registry does not report which effect measure, if any, was used for this trial. No new contrast can be calculated from the record because the primary outcome group results are not available.

Why does the assessment schedule matter?

The listed primary outcome refers to no pain immediately after surgery, while the description includes repeated assessment from immediately after surgery through the 6th hour and mentions planned reporting the following morning, 18 - 24 hours post-operatively. When an outcome is measured at multiple times, the analysis needs to distinguish the prespecified primary time point from other measurements. Repeated assessments from the same participant are related rather than independent; treating them as unrelated observations can misstate uncertainty. The registry does not explain how the time points were intended to be combined or which one was to drive the primary test.

This distinction matters even when all measurements use the same scale. A proportion meeting a no-pain threshold at one time point answers a different question from a summary across repeated times or a comparison of the full score distribution. The record does not report such a repeated-measures model or a rule for selecting among assessments, and none should be inferred.

What does a confidence interval communicate?

In general, a confidence interval communicates the uncertainty around an estimated effect under a specified statistical model and sampling process. A narrow interval indicates greater precision than a wide interval, while an interval that includes values on both sides of a null contrast may be consistent with several possible effects. Its interpretation depends on the endpoint, effect measure, and assumptions. No confidence interval is reported for the primary outcome in this registry record, so precision cannot be assessed.

A p-value, in general, summarizes how incompatible the observed data are with a specified null model, under assumptions. It does not measure the probability that the null hypothesis is true, and it does not describe the size or clinical importance of an effect. The registry does not report a primary outcome p-value. It would be inappropriate to infer one from the safety counts or the enrollment figure.

How should planning illustrations be distinguished from trial findings?

Sample-size calculations can illustrate how many participants per arm might be needed under stated assumptions about the effect to detect, variability, allocation, and significance level. The registry describes a planning illustration based on the observed effect, with the effect to detect expressed as a fraction of that effect, a two-sided significance level of 0.05, equal allocation, and a normal approximation. Such calculations are conditional planning exercises, not results observed in the trial. They are not observed power.

The record also states that time-to-event planning tables give the total number of events, while other planning illustrations give participants per arm. These are different quantities. A target number of events is not interchangeable with a number of participants, because the number of observed events depends on event occurrence and follow-up. No time-to-event primary endpoint is identified in the trial information. The registry does not report the trial's own sample-size justification or establish that the planning illustration was used to design the study.

Why can over-dispersion matter?

In general, over-dispersion occurs when observed variation is greater than a statistical model expects. A model that assumes too little variation can produce uncertainty estimates that are too small, making results appear more precise than they are. Methods that account for over-dispersion may be appropriate for some count or clustered data, but their relevance depends on the outcome structure and design. The registry does not report an over-dispersion assessment or a statistical model for the primary endpoint, so no such method can be attributed to this trial.

Because analysis of the primary outcome was not possible due to reporting inconsistencies, the central statistical limitation is not a choice among competing estimators; it is the absence of a usable reported comparison. The registry record does not provide sufficient detail to reconstruct the intended analysis or independently check its assumptions.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary objective focused on immediate postoperative pain and secondary objectives concerning pain during the first 24 hours, nausea and vomiting during the first 24 hours, and length of hospital stay. Testing several outcomes or time points can raise a multiplicity issue: when many hypotheses are examined, the chance of at least one apparently unusual finding can increase. In general, a prespecified hierarchy, adjustment procedure, or clear distinction between confirmatory and exploratory analyses can help readers interpret multiple comparisons.

The registry record does not report a multiplicity strategy, a hierarchy among secondary outcomes, or how repeated pain assessments were to be handled in statistical testing. It does not report comparative results for the secondary objectives. The listed objectives therefore cannot be treated as completed analyses, and no adjustment or unadjusted interpretation can be inferred.

Missing-data methods and analysis populations are also not reported in the registry record. The primary outcome entry says analysis was not possible from data collected due to reporting inconsistencies. That statement identifies a problem affecting analysis, but does not specify which records or measurements were inconsistent, whether any observations were missing, or how participants were to be included in an analysis. No imputation procedure, exclusion rule, or intention-to-treat or per-protocol population is described.

In general, missing observations can reduce precision and can bias a comparison if the reasons for missingness differ across groups or relate to outcome values. The extent and direction of any such problem cannot be assessed from the information recorded. The inability to analyze the primary outcome should therefore remain a central limitation rather than being treated as a neutral or favorable result.

11. 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.

The registry records 44 participants at risk for serious adverse events and 0 affected in the paravertebral block plus general anesthesia group. For general anesthesia alone, it records 44 at risk and 0 affected. It also records 44 at risk for other adverse events and 0 affected in each group. No serious adverse event terms are listed.

Deaths are recorded as null for both groups. Null does not provide a numeric death count, so deaths should not be described as zero or as absent. The registry record does not report additional details about how adverse events were defined, collected, or followed up.

In general, a count of zero recorded events means no affected participants appear in that specific registry category during the recorded assessment, not that the possibility of an event has been ruled out. The at-risk counts indicate the denominators recorded for the safety entries; they do not establish the analysis population for the pain endpoint. These safety figures should not be combined with the missing primary outcome analysis to infer an overall benefit or harm comparison.

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

The record establishes what the investigators intended to compare: paravertebral block with general anesthesia against general anesthesia alone for reconstructive breast surgery in patients with breast cancer. It also identifies the primary outcome as the proportion with no pain immediately after surgery and describes a numeric pain scale and assessment schedule.

It does not establish a comparative result for that outcome. The registry explicitly states that analysis was not possible because of reporting inconsistencies. Without group-specific primary outcome data and a reported analysis, the direction, magnitude, and precision of any difference are unknown from the registry record. The missing estimate is not evidence that the groups were the same, nor is it evidence that either approach produced a better pain outcome.

The registry's safety entries show zero affected participants in the listed serious and other adverse-event categories for each group, with 44 at risk recorded in each group for each category. Deaths are not given as a numeric count. These entries describe what was recorded in those categories; they do not establish that all possible harms were assessed or that there was no risk.

The stated secondary objectives also do not supply answers. Objectives about pain over the first 24 hours, nausea and vomiting, and hospital stay are questions the trial intended to examine. Comparative results for them are not reported in the registry record.

Accordingly, the trial record is informative about the design and the intended outcome, and it documents a reporting problem that prevented the primary analysis. It does not support a conclusion that paravertebral block does or does not change postoperative pain, or that the two approaches are equivalent. A conclusion about treatment effects would require interpretable outcome results and an analysis that addresses the relevant uncertainty.

13. Why This Trial Matters Statistically

This trial illustrates a key distinction in clinical research: a clearly stated question and randomized design do not guarantee that the collected data can be converted into an interpretable result. The registry identifies a comparison and a patient-relevant endpoint, but it also records that reporting inconsistencies made primary outcome analysis impossible. Statistical interpretation depends on usable outcome data as well as on the design.

The endpoint description also highlights why precise outcome definitions matter. The title names no pain immediately after surgery, while the assessment description covers repeated measurements through the 6th hour and refers to planned reporting the following morning, 18 - 24 hours after surgery. Readers need to know which time point is primary and how repeated assessments enter the analysis. Without that clarity, even complete measurements may not yield a single unambiguous primary comparison.

There is also an important distinction between efficacy questions and safety counts. The registry records no affected participants in its listed adverse-event categories, but those counts do not answer the pain question. Meanwhile, the missing pain analysis cannot be replaced by the trial's enrollment figure, study status, or randomized design. Each part of a trial record answers a different question.

Finally, planning calculations and observed results serve different purposes. Planning illustrations can show how assumptions about an effect and statistical method relate to a target sample size, but they do not demonstrate what happened in the completed trial. This case underscores the need for transparent reporting of endpoint definitions, analysis populations, handling of data inconsistencies, and comparative estimates with measures of uncertainty. Those details allow readers to distinguish an unanswered question from evidence of no difference.

14. 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 primary limitation is stated directly in the registry: analysis was not possible from the collected data because of reporting inconsistencies. The record does not describe the inconsistencies or say whether they affected all assessments, particular time points, or particular participants. Consequently, readers cannot judge the extent of the problem or determine whether a valid subset analysis was possible.

The primary endpoint description leaves uncertainty about the target time point. The outcome title specifies no pain immediately after surgery, while the description includes assessment periods within the first hour, between 1 - 3 hours, and between 3 - 6 hours, with additional reporting planned for 18 - 24 hours. The registry does not explain which assessment defines the primary endpoint or how the repeated measurements relate to that endpoint.

The record does not report group-specific primary outcome data, an effect estimate, a confidence interval, a p-value, or an analysis population. It also does not report how missing observations or inconsistent records were handled. Without these details, the comparative result and its precision cannot be assessed or reproduced.

Masking is recorded as none. Since pain is a participant-reported outcome, lack of masking may be relevant to reporting or assessment in general, but the registry does not describe how this issue was addressed. Further limitations include the absence of reported multiplicity handling for the listed secondary objectives and the lack of comparative results for those objectives.

The safety entries are limited to counts in the listed categories, and deaths are recorded as null. The registry does not provide event descriptions or further safety-collection detail. These limitations are specific to what the record reports and should not be taken as proof that unreported outcomes or methods were not collected elsewhere.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Evaluate the Use of Paravertebral Block in Reconstructive Breast Surgery — NCT00542542.
• Registry record last updated 2015-04-13; status last verified 2015-03.
• Results first posted 2015-04-13.
• 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.

18. Record Summary

The registry record describes a completed Phase 3 randomized parallel-group trial with no masking, sponsored by M.D. Anderson Cancer Center. Enrollment is listed as 89. The comparison was paravertebral block plus general anesthesia versus general anesthesia alone in reconstructive breast surgery for breast cancer.

The primary outcome was the proportion of participants with no pain immediately after surgery, assessed using a verbal numeric rating scale from 0 to 10. The registry states that analysis was not possible due to reporting inconsistencies. Comparative results for the primary and secondary objectives are not reported in the registry record.

For each group, the registry records 44 at risk and 0 affected for serious adverse events, and 44 at risk and 0 affected for other adverse events. Deaths are recorded as null. The record therefore identifies the intended question and some safety counts, but does not provide an interpretable primary pain comparison.