TXA Study in Major Oncologic Surgery: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for TXA Study in Major Oncologic Surgery (NCT01980355), a randomized na study. The primary outcome is Number of Participants Who Required Transfusion.

2. Clinical Question

This question concerns a count of participants with a transfusion event, rather than the number of transfusion units or the volume of blood lost. It is relevant to the trial's stated focus on blood loss and transfusion rates in major oncologic surgery, while remaining a distinct endpoint: a transfusion is not a direct measurement of blood loss. The posted comparison describes observed transfusion counts in the two assigned arms. It does not, by itself, explain why an individual participant did or did not receive a transfusion. The criteria used to make transfusion decisions are not reported in the registry record.

3. Trial Design

The registry record identifies this as a randomized, parallel-group trial with quadruple masking. Participants were assigned to tranexamic acid or placebo. The study summary describes assignment by chance and says the chance of receiving either intervention was equal. The total enrollment was 76. The posted arm counts are 39 for tranexamic acid and 37 for placebo.

The intervention was a single intravenous administration of 1000mg tranexamic acid over 15 minutes prior to surgery. The placebo was also given intravenously over 15 minutes once prior to surgery. The study summary describes the placebo as resembling tranexamic acid without an active ingredient. The registry record labels masking as quadruple, but does not identify the specific groups of people who were masked or describe how masking was maintained.

The registry record lists the study as completed. The recorded start date is 2012-06-12, and the primary completion date is 2017-12-01. The condition entries are tranexamic acid, cancer, and major surgery. The sponsor is Corewell Health West. The record lists the phase as NA.

The primary outcome was the number of participants who required transfusion, assessed from surgery to 90 days post hospital discharge. Estimated blood loss is listed as a secondary outcome. A detailed protocol, eligibility criteria, allocation concealment procedures, and the rationale for the enrollment target are not reported in the registry record. The original statistical analysis plan and its planned handling of outcomes are also not reported in the registry record. Those omissions limit how fully the posted outcome comparison can be evaluated against the study's original design.

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 Number of Participants Who Required Transfusion, measured over From time of surgery to 90 days post hospital discharge.

The primary endpoint is the number of participants who required transfusion. It is a binary event outcome at the participant level: each participant either required a transfusion during the stated follow-up timeframe or did not. The outcome is reported as counts in the two arms, with arm enrollment giving the context for those counts. The timeframe runs from surgery to 90 days post hospital discharge.

Transfusion is used as a clinically relevant endpoint in a study focused on blood loss and transfusion rates. It captures whether a participant crossed the threshold for receiving a transfusion, rather than measuring blood loss continuously. Because transfusion decisions can depend on clinical circumstances and practice, a count of transfused participants does not directly quantify blood loss or explain the decision for any particular participant. The registry record does not report transfusion criteria.

The record's primary outcome description also refers to determining the impact of perioperative tranexamic acid on blood loss and transfusion rates. However, the posted primary measure is the count of participants requiring transfusion. Estimated blood loss is separately listed as a secondary outcome, and its numerical findings are not reported in the registry record. As a result, the posted primary comparison addresses transfusion occurrence; it does not provide a complete numerical account of blood loss.

7. Results Posted in the Registry

• Tranexamic Acid: 20.5% (8/39) versus 13.5% (5/37) on control; risk difference 7.0 percentage points (95% CI -9.8 to 23.8), risk ratio 1.52 (0.55–4.22); unadjusted two-proportion z-test p = 0.418.

8. Statistical Interpretation

9. Statistical Methods Explained

The main statistical comparison concerns the proportion of participants requiring transfusion in each randomized arm. A participant-level event count is a binary outcome: the event is either recorded or not recorded for each person. The arm counts provide the number of recorded events, while the arm sizes provide the denominator for interpreting how common those events were in each group. The registry record reports 8 events among 39 participants assigned to tranexamic acid and 5 among 37 assigned to placebo.

What does a risk difference express?

A risk difference subtracts the event proportion in one arm from the event proportion in the other. It stays on an absolute scale, so it describes the separation between the observed event proportions rather than comparing them as a multiple. The posted risk difference is 0.07, with the comparison oriented as tranexamic acid relative to placebo. A positive estimate in that orientation means the observed event proportion was higher in the tranexamic acid arm. It does not identify the cause of that difference.

An absolute measure is often useful because it keeps the comparison tied to the observed frequency of the event. It is also sensitive to the event frequency in the study population. The same relative contrast can correspond to different absolute differences in settings where baseline event frequency differs. The registry record does not establish how results would compare in populations with different characteristics or clinical practice.

How do relative measures differ?

A risk ratio compares the event proportions by division, whereas an odds ratio compares the odds of an event. Both are relative measures, but odds and risks are not interchangeable. In this trial, the reported risk ratio is 1.518 and the reported odds ratio is 1.652. These estimates use the same posted event counts and are not independent replications. Their confidence intervals are broad, reflecting substantial uncertainty about the relative association. In particular, point estimates alone do not show how much the data can support values on either side of no difference.

What does the p-value say?

The reported unadjusted p-value is 0.418. A p-value describes how unusual results at least as discrepant as those observed would be under a specified null model and its assumptions. It is not the probability that the null hypothesis is true, and it is not the probability that the observed difference arose by chance. The registry record does not detail the full test specification. A p-value also does not measure the size or clinical importance of an effect. Interpretation should consider the estimate and its uncertainty alongside the p-value.

The term unadjusted indicates that the posted comparison is not presented as adjusted for covariates. The registry record does not report a covariate-adjusted model, so there is no adjusted estimate to compare with the arm-level contrast. Randomization supports comparison of assigned groups in expectation, but does not remove uncertainty in a trial of this size or document the success of every aspect of trial conduct.

Why does the confidence interval matter?

A confidence interval describes a range of effect estimates reasonably compatible with the data and the method used to calculate it. It is not a guarantee that the true effect lies within the reported limits, nor is it a range of individual participant outcomes. The risk-difference interval crosses the no-difference value, extending toward both a lower and a higher event proportion with tranexamic acid. That makes the direction uncertain. The intervals for the risk ratio and odds ratio also include their respective no-difference values. Their breadth indicates limited precision.

For a binary outcome, the amount of information depends in part on how many events are observed, not only on the total enrollment. The posted counts are modest, so the estimates have limited ability to pin down the size of an underlying effect. This is one reason a result without a small p-value should not be read as evidence of equivalence. Equivalence or non-inferiority conclusions require a prespecified margin and an analysis designed for that purpose; such a margin and analysis are not reported in the registry record.

The registry record lists estimated blood loss as a secondary outcome, but does not report its numerical result. It reports no additional analyses. The statistical interpretation is therefore constrained to the posted primary event comparison and the associated unadjusted effect measures. Missing details on the protocol, analysis population, missing data, and multiplicity mean the broader analysis strategy cannot be reconstructed from the registry record.

10. Confidence Intervals and Precision

The posted risk-difference estimate is 0.07. Its confidence interval extends from a possible lower event proportion in the tranexamic acid arm to a possible higher event proportion. Thus, the interval includes no difference as well as effects in both directions. The interval is broad relative to the point estimate, so the direction and size of the underlying difference are not determined precisely by these data.

The risk ratio estimate is 1.518, and the odds ratio estimate is 1.652. Their reported confidence intervals are also broad and include the respective no-difference values. The relative measures do not resolve the uncertainty apparent in the absolute measure. Because there were 8 transfusion events in the tranexamic acid arm and 5 in the placebo arm, the estimates are based on a limited number of observed events. The uncertainty is therefore an important part of the result, not a technical qualification to set aside.

A confidence interval is a range of estimates compatible with the observed data under the calculation method. It does not show where individual outcomes lie, and it does not assign a probability to a particular treatment effect. A wide interval means that the data do not sharply distinguish among multiple plausible effect sizes. A confidence interval crossing no difference does not prove that there is no effect; it indicates that the data do not exclude that value at the interval's confidence level.

The registry record does not report the confidence level in the narrative outcome description, so the interpretation should not assign a level beyond what the posted analysis specifies. The posted comparison includes interval estimates, but the result remains imprecise in practical terms. A single point estimate should not be used to imply a stable or definitive effect when the interval allows materially different directions and magnitudes.

11. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning estimates are participants per arm, not total events. They are illustrations based on the observed effect, rather than the trial's original enrollment rationale. The registry record does not report the original sample-size justification or the assumptions used to plan the actual trial.

The planning calculation assumes a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. It considers the stated fractions of the observed effect: 100% of the observed effect, 75% of the observed effect, and 50% of the observed effect. For each target effect, the 80% power column means the number of participants per arm in a hypothetical study designed to have an 80% chance of detecting an effect of that size under those assumptions. The 90% power column has the same interpretation, but targets a 90% chance.

For planning at 100% of the observed effect, the estimates are 452 participants per arm for 80% power and 604 participants per arm for 90% power. For planning at 75% of the observed effect, they are 770 and 1,031 participants per arm, respectively. For planning at 50% of the observed effect, they are 1,657 and 2,218 participants per arm, respectively. These are planning illustrations, not observed power. They do not change the results of the completed trial.

The pattern reflects a general feature of study planning: smaller target effects are harder to distinguish from random variation, so detecting them with the same power generally requires more participants. The illustration also depends on the assumptions and on using the observed effect as its starting point. The observed estimate is uncertain, particularly with the posted event counts, so these figures should not be treated as a definitive enrollment recommendation for another study.

12. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, p₀ and p₁ are the control and treatment proportions, and p̄ is their average.

Worked calculation for this trial

1. Control proportion p₀ = 0.135; treatment proportion p₁ = 0.205; average p̄ = 0.170.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.5314 = 1.0415.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.5291 = 0.4453.
4. n = (1.0415 + 0.4453)² / (0.0700)² = 451.2, rounded up to 452 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
p0 <- 0.135135135135135                          # control proportion
p1 <- 0.205128205128205                          # treatment proportion
n_per_arm <- function(power, frac = 1) {
  q1 <- p0 + (p1 - p0) * frac               # smaller effect = fraction of the observed difference
  pbar <- (p0 + q1) / 2
  z_b <- qnorm(power)
  ceiling(round((z_a * sqrt(2 * pbar * (1 - pbar)) + z_b * sqrt(p0 * (1 - p0) + q1 * (1 - q1)))^2 / (q1 - p0)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (unrounded n per arm)
cat("power.prop.test:", round(power.prop.test(p1 = p0, p2 = p1, power = 0.80)$n, 1), "\n")

# Simulation: how often does the z-test reject at the 80%-power sample size?
set.seed(1980355)
n    <- n_per_arm(0.80)
reps <- 20000
x0 <- rbinom(reps, n, p0); x1 <- rbinom(reps, n, p1)
ph <- (x0 + x1) / (2 * n)
z  <- ((x1 - x0) / n) / sqrt(ph * (1 - ph) * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE), reps))

Output from running the code

100% of observed effect: n per arm = 452 (80% power), 604 (90% power)
 75% of observed effect: n per arm = 770 (80% power), 1,031 (90% power)
 50% of observed effect: n per arm = 1,657 (80% power), 2,218 (90% power)
power.prop.test: 451.2 
Simulated power at n = 452 per arm: 0.801 (20000 replicates)

The simulation draws many pairs of event counts at the planned sample size and counts how often the two-proportion z-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

13. Multiplicity, Missing Data and Analysis Populations

The registry record lists one primary outcome and estimated blood loss as a secondary outcome. A numerical result for estimated blood loss is not reported in the registry record. No analysis results are posted for that secondary outcome, and the record reports no additional analyses. The registry record does not explain whether other outcomes were collected or analyzed but not posted.

Multiplicity arises when several outcomes, time points, subgroups, or statistical comparisons are tested. As the number of tests grows, the chance of obtaining a seemingly notable result by chance can also grow. A prespecified analysis plan may address this through a testing hierarchy or another adjustment. The registry record does not report whether a multiplicity strategy was planned or applied. The posted p-value is described as unadjusted; no adjusted p-value or family-wide inference is reported.

Missing-data handling is not reported in the registry record. The posted arm counts and participant numbers do not explain whether all randomized participants had outcome data, whether any outcome values were missing, or how missing values were treated. No imputation method, complete-case definition, or sensitivity analysis is reported. Without this information, the impact of missing primary outcome data cannot be assessed from the registry record.

The analysis population is also not reported in the registry record. In particular, the record does not say whether the primary comparison included all randomized participants according to their assigned arm, or whether it used another population definition. This matters because exclusions after randomization can affect comparability between arms. The posted result should therefore be read as the registry's arm-level comparison without assuming a particular intention-to-treat, per-protocol, or safety population.

The record does not report a statistical analysis plan, model details, covariate adjustment, subgroup analyses, or interim analyses. Those items should not be inferred from the randomization or masking labels. Their absence limits assessment of prespecification and the relationship between the posted analysis and the intended study analysis.

14. 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 serious adverse event terms

Serious events with the highest arm-level rate: surgical morbidity (35.1%).

The registry record reports serious adverse events in 11 participants in the tranexamic acid arm, where 39 were at risk, and in 13 participants in the placebo arm, where 37 were at risk. It reports 2 deaths in the tranexamic acid arm and 0 in the placebo arm. Other adverse events are reported as 0 in each arm. These are descriptive safety counts; the record does not provide an adjusted comparison or a statistical test for them.

The serious adverse event counts should not be read as proof that an event was caused by the assigned intervention. The registry record does not report event-level narratives, timing, severity definitions, or an assessment of relatedness for these totals. It lists Surgical Morbidity as the top serious term, with 35.1%; the denominator and context for that percentage are not reported in the registry record.

These figures describe what the record reports for the trial arms, but their interpretation is limited by the modest enrollment and the absence of further detail. They do not establish a comparative safety profile or explain the circumstances of the reported deaths. No causal conclusion follows from the counts alone.

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

The central posted result is a comparison of participants who required transfusion: 8 in the tranexamic acid arm and 5 in the placebo arm. The reported risk difference is 0.07, oriented toward a higher observed event proportion in the tranexamic acid arm. The unadjusted p-value is 0.418. The confidence intervals are broad and include no difference, as well as effects in either direction. Taken together, the posted data do not identify a precise effect on transfusion occurrence.

This result does not establish that tranexamic acid increased transfusion, nor does it establish that the interventions had equivalent effects. A result that does not provide strong evidence against a no-difference model can still be compatible with a range of underlying effects, especially when precision is limited. A claim of equivalence would require an appropriate design and a prespecified margin; that is not reported in the registry record.

The primary endpoint concerns whether participants required transfusion during the stated timeframe. It is not a direct measure of blood loss, transfusion volume, or the reason a transfusion decision was made. Although estimated blood loss is listed as a secondary outcome, its numerical result is not reported in the registry record. The primary finding therefore cannot stand in for a missing blood-loss result.

The trial enrolled 76 participants and reports 39 in the tranexamic acid arm and 37 in the placebo arm. The event counts are limited, and the record does not report details of missing data, the analysis population, or adjustment for other factors. These limitations make it important to describe the result as uncertain rather than to overstate its direction or reach.

The posted numbers are evidence about the observed randomized comparison in this study. They do not determine outcomes for every patient or establish what would occur in other surgical settings. The registry record does not provide enough information to assess all aspects of the planned analysis, and it does not report a numerical secondary outcome result. The defensible conclusion is therefore bounded: the primary outcome comparison is imprecise, and its direction remains uncertain.

16. Why This Trial Matters Statistically

This trial illustrates why an event count and its uncertainty should be interpreted together. The observed counts differ between arms, and the risk-difference estimate points toward a higher event proportion in the tranexamic acid arm. But the confidence interval spans possible effects in both directions, while the unadjusted p-value is 0.418. Looking only at the point estimate would understate the uncertainty; looking only at the p-value could wrongly suggest that the arms are known to be alike.

It also illustrates the distinction between a clinically relevant event and a direct measurement of the biological process motivating the study. Transfusion is a meaningful outcome for the study question, but it is not itself a measurement of blood loss. Estimated blood loss is listed as secondary, yet its result is not reported in the registry record. Statistical interpretation must stay aligned with the outcome actually reported rather than treating a related endpoint as interchangeable.

The planning illustrations make another statistical point: sample-size requirements depend on the effect a future study aims to detect. Smaller effects require larger participant numbers for the same target power under the stated assumptions. Since these illustrations use the observed effect, which is uncertain, they are useful for understanding the relationship between effect size and planning but should not be mistaken for the trial's original design rationale.

Finally, the record's omissions matter. Details about missing outcomes, analysis populations, multiplicity, and the original statistical plan are not reported. Statistical literacy includes recognizing these limits rather than filling them with assumptions. The result is best understood as an uncertain comparison of observed transfusion events, with important aspects of analysis and secondary outcomes undocumented in the registry record.

17. 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 result is based on 8 transfusion events in the tranexamic acid arm and 5 in the placebo arm, with 39 and 37 participants in those arms. The associated effect estimates have broad confidence intervals. This limits precision and means that plausible effects in either direction remain compatible with the posted comparison.

The registry record does not report eligibility criteria in detail, the criteria for transfusion, or the clinical factors that informed transfusion decisions. Those details would help readers understand how the event was defined and whether practice could vary across participants or circumstances. The record also does not report details of missing outcome data, the analysis population, or any adjusted analysis. The extent to which these issues affected the posted comparison cannot be assessed.

Estimated blood loss is listed as a secondary outcome, but its numerical result is not reported in the registry record. No secondary outcome analysis is posted, and no additional analyses are reported. The record also does not report a multiplicity plan, original sample-size justification, or statistical analysis plan. These gaps prevent assessment of whether the posted analysis matches a prespecified plan and how unreported outcomes should be interpreted.

For safety, the record gives serious adverse event and death counts, but does not provide event-level detail or a full account of attribution and timing. The reported Surgical Morbidity percentage has no stated denominator in the record. Consequently, these figures are descriptive and do not support a detailed causal or comparative safety assessment.

The study is marked completed, but the registry record alone does not provide all information needed to evaluate conduct, follow-up completeness, or generalizability beyond the enrolled participants. These are limitations of what can be concluded from the posted record, not evidence that a particular unreported problem occurred.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: TXA Study in Major Oncologic Surgery — NCT01980355.
• Registry record last updated 2023-08-07; status last verified 2023-08.
• Results first posted 2022-05-05.
• 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.

21. Record Summary

The registry record describes a completed randomized, quadruple-masked, parallel-group comparison of tranexamic acid and placebo in major oncologic surgery. Enrollment was 76, with 39 participants assigned to tranexamic acid and 37 to placebo. The primary endpoint was the number of participants requiring transfusion from surgery to 90 days post hospital discharge.

The posted counts were 8 in the tranexamic acid arm and 5 in the placebo arm. The risk-difference estimate was 0.07, and the unadjusted p-value was 0.418. The confidence interval spans possible effects in both directions, leaving the result imprecise. Estimated blood loss is listed as a secondary outcome, but its numerical result is not reported in the registry record.

The record does not report the original sample-size justification, analysis population, missing-data handling, or multiplicity plan. The posted findings should therefore be read as an uncertain arm-level comparison, not as proof of a treatment effect or of equivalent outcomes.