Coated VICRYL* Plus Suture Compared to Chinese Silk in Scheduled Breast Cancer Surgery: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Coated VICRYL* Plus Suture Compared to Chinese Silk in Scheduled Breast Cancer Surgery (NCT00768222), a randomized phase 4 study. The primary outcome is Mean Score on Cosmetic Outcome Visual Analog Scale (VAS).

2. Clinical Question

3. Trial Design

This was a randomized, parallel-group study comparing two closure approaches in scheduled breast cancer surgery. The registry lists the study as Phase 4, completed, and enrolling 101 participants. Its brief description characterizes it as a 90-day study involving approximately 100 patients at 6 centers in China who underwent scheduled modified radical mastectomy.

The two arms differed in both suture and closure technique. Chinese silk was described as natural, non-absorbable silk used in a simple interrupted transdermal pattern. VICRYL* Plus was described as a synthetic absorbable suture containing triclosan antibacterial, used in a subcuticular closure technique. Therefore, the comparison is between these treatment approaches as implemented, rather than a comparison that changes only the suture material while holding technique constant.

Allocation was randomized. The registry lists masking as none, while also describing the primary outcome photographs as assessed by an independent blinded central assessor. These descriptions refer to different aspects of trial conduct: the record does not characterize the trial as masked overall, but does state that the central assessor was blinded for the primary assessment.

The primary outcome was assessed at 30 days (+/- 5) post-operative. The registry also lists a 90-day study duration and secondary measures at 12 days and Day 3. Further details about the randomization procedure, site-specific enrollment, follow-up completion, and the trial's original statistical plan are 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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Intention to treat (ITT)

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 Mean Score on Cosmetic Outcome Visual Analog Scale (VAS), measured over 30 days (+/- 5) post-operative.

The primary endpoint was the mean score on a cosmetic outcome visual analog scale at 30 days (+/- 5) post-operative. An independent blinded central assessor evaluated surgical-site photographs using a validated 100 mm scale. The scale ran from 0, representing the worst possible scar, to 100, representing the best possible scar. Thus, a higher score corresponds to a more favorable assessment of the scar on this measure.

A continuous score retains gradations in cosmetic assessment rather than reducing the outcome to a simple yes-or-no category. Reporting the mean and standard deviation describes both the average score in each group and the variability of individual scores around that average. The difference between group means then expresses the contrast in average scores on the scale's original units.

Photographic assessment by a central assessor provides a common rating process across participants and centers. The assessor's blinding is relevant because judgments of scar appearance involve assessment rather than a purely mechanical measurement. The registry does not report the rating instructions beyond the scale anchors, nor does it describe how photographs were selected or how missing assessments were handled.

The endpoint represents cosmetic appearance at the specified follow-up assessment. It does not by itself measure infection, other complications, patient satisfaction, or longer-term appearance. Those are distinct questions, and the registry lists surgical site infection scores among the secondary outcomes.

7. Results Posted in the Registry

• VICRYL* Plus Suture: mean 67.20 versus 45.40 on control; difference 21.80 (95% CI 15.80 to 27.80), standardized effect d = 1.41; z-test p = <0.001.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Mean Cosmetic Outcome Score on Modified Hollander Scale

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • VICRYL* Plus Suture: mean 5.70 versus 5.20 on control; difference 0.50 (95% CI 0.10 to 0.90), standardized effect d = 0.49; z-test p = 0.014.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically higher for VICRYL* Plus Suture than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Mean Surgical Site Infection Score on Modified ASEPSIS Scale

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • VICRYL* Plus Suture: mean 1.20 versus 1.60 on control; difference -0.40 (95% CI -0.91 to 0.11), standardized effect d = -0.31; z-test p = 0.122.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between VICRYL* Plus Suture and the control. The interval gives the range of effects that remain compatible with the data.

The posted secondary results add context across two different types of assessment and follow-up times: cosmetic appearance on the Modified Hollander Scale at 12 days, and surgical site infection scores on the Modified ASEPSIS Scale at Day 3. They do not measure the same construct as the primary visual analog scale at 30 days (+/- 5), and their numerical scales should not be directly compared with its score.

The direction of the early cosmetic-score comparison is consistent with the direction of the primary cosmetic result: the VICRYL* Plus group had the higher reported mean on the Modified Hollander Scale. The infection-score comparison has a negative mean difference for VICRYL* Plus relative to Chinese Silk, while its reported interval includes zero. This pattern does not establish that one closure approach has a consistent advantage across all outcomes. Different outcomes, assessment times, and scales capture different aspects of the postoperative course.

The registry lists additional secondary outcome measures, including repeated assessments of cosmetic outcome and surgical site infection scores, but does not report analyses for those measures in the record. The detailed timing and results for those unreported measures are not reported in the registry record.

The secondary p-values are unadjusted. In general, examining multiple outcomes or time points creates more opportunities for apparently unusual results to occur by chance. If no adjustment or prespecified hierarchy is used, individual p-values can overstate the strength of evidence when interpreted as if they were the only analysis. The registry record does not report a multiplicity strategy or identify a hierarchy that would give particular secondary outcomes confirmatory status.

For that reason, secondary findings are best treated as supporting or exploratory context rather than as independent confirmation of the primary result. Their interpretation also depends on completeness of assessments and the analysis population, details that are not reported for the secondary outcomes.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Mean Cosmetic Outcome Score on Modified Hollander Scale
• Mean Cosmetic Outcome Score on Modified Hollander Scale
• Mean Surgical Site Infection Score on Modified ASEPSIS Scale
• Mean Surgical Site Infection Score on Modified ASEPSIS Scale
• Mean Surgical Site Infection Score on Modified ASEPSIS Scale
• Mean Surgical Site Infection Score on Modified ASEPSIS Scale
• Mean Surgical Site Infection Score on Modified ASEPSIS Scale
• Mean Surgical Site Infection Score on Modified ASEPSIS Scale

9. Statistical Interpretation

10. Statistical Methods Explained

The primary measure is continuous: it is a score on a 100 mm visual analog scale, summarized by a mean and standard deviation. In general, a mean gives the arithmetic average of the observed scores, while a standard deviation describes how dispersed those scores are around the average. These summaries help distinguish the average group result from the variability among participants. The registry identifies the primary analysis population as intention to treat, but does not describe the detailed analysis procedure used to produce the comparison.

What does the mean difference represent?

The reported mean difference compares the VICRYL* Plus Suture mean with the Chinese Silk Suture mean. For the primary endpoint, the reported estimate is 21.8 score points. Since the scale's direction runs from 0 for the worst possible scar to 100 for the best possible scar, a positive contrast is in the direction of a higher average score in the VICRYL* Plus group. This is a difference in group averages on the scale, not a percentage change and not an estimate of how much any individual participant's score changed.

The comparison is unadjusted in the sense that the posted p-value is identified as unadjusted. No covariate-adjustment details are reported in the registry record. The record also does not describe whether the comparison used a particular parametric model, how assumptions were checked, or how center effects were handled. Those details should not be inferred from the summary statistics alone.

How should the p-value be read?

In general, a p-value describes how incompatible the observed data, or more extreme data, would be with a specified null hypothesis under the assumptions of the statistical procedure. It is not the probability that the null hypothesis is true, and it does not measure the size or practical importance of a difference. The primary unadjusted p-value is <0.001. Its interpretation depends on the analysis assumptions and on whether the comparison was selected and interpreted within a wider set of outcomes. The registry record does not report a multiplicity plan.

A small p-value does not replace consideration of the estimated difference, its interval, the measurement scale, or the trial's design. Similarly, a p-value that is not small does not prove that the groups are identical. The posted Day 3 infection-score comparison has an unadjusted p-value of 0.122 and an interval that includes zero; this is not evidence that the underlying group means are exactly equal.

Why does variability matter?

In general, more variability in scores makes a group mean less precise when sample size is held constant. The primary standard deviations are 12.0 in the Chinese Silk group and 18.2 in the VICRYL* Plus group. The comparison's pooled standard deviation is 15.45. A pooled standard deviation is a combined measure of variability used in some standardized comparisons; it is not the scale's range and does not replace the reported group-specific standard deviations.

Standard errors describe the estimated sampling variability of a statistic, rather than the spread of individual observations. The reported primary standard errors are 1.697 for the Chinese Silk mean and 2.549 for the VICRYL* Plus mean. They help characterize precision of the separate means, while the interval around the mean difference addresses uncertainty in the contrast. The registry record does not state the exact method or confidence level used to form that interval.

What is the role of standardized effect size?

In general, a standardized effect size expresses a mean difference relative to a measure of score variability, making it less tied to the original scale's units. The listed standardized effect for the primary comparison is 1.411. It is a derived summary for comparison and planning, not an additional outcome measured in participants. Standardized effect sizes can aid planning, but their interpretation depends on the measure, variability, and context; they do not determine clinical importance on their own.

The sample-size illustrations use the observed effect and a stated normal approximation. They are planning calculations, not estimates of the probability that the completed study detected an effect. The original trial's sample-size justification and design assumptions are not reported in the registry record.

Why can over-dispersion matter in other settings?

In general, over-dispersion means observed variation is greater than a statistical model expects. If a model underestimates variability, standard errors may be too small and intervals too narrow. This is a general consideration for statistical analyses, not a claim that over-dispersion was present in this trial. The registry record does not report a model-based assessment of over-dispersion.

11. Confidence Intervals and Precision

The reported primary mean difference is 21.8 score points, with an interval from 15.8 to 27.8. The interval is centered around the estimated contrast and communicates uncertainty about the group-level difference under the analysis assumptions. Its endpoints are both above zero, consistent with the positive point estimate. The registry record does not state the interval's confidence level or the exact calculation method, so those details should not be assumed.

An interval for a mean difference is not a range expected to contain most individual participants' scores. Individual scores vary within each group, as reflected by the standard deviations of 12.0 and 18.2. The interval instead concerns uncertainty in the estimated contrast between group means. It is useful to consider the interval's width together with the point estimate and the scale's 0-to-100 anchors.

The primary comparison's unadjusted p-value is <0.001. A p-value and an interval answer related but different questions: the p-value summarizes compatibility with a null hypothesis under a specified procedure, while the interval conveys a range of estimates compatible with the analysis. Neither alone describes clinical importance or resolves potential bias, incomplete outcome assessment, or the effect of comparing different closure techniques.

For the posted secondary comparisons, the 12-day Modified Hollander Scale interval is from 0.102 to 0.898, while the Day 3 Modified ASEPSIS Scale interval is from -0.907 to 0.107. These intervals address separate outcomes at separate times and should not be read as precision estimates for the primary visual analog score. Unadjusted secondary comparisons also require caution because the registry does not report how the wider set of outcome assessments was accounted for statistically.

12. 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 sample-size illustrations are planning calculations based on the observed effect, not the original design justification for the trial. For this continuous-outcome study, the figures are participants per arm, rather than total events. The assumptions stated for the illustrations are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is expressed as a stated fraction of the observed effect.

The 80% power column gives the planned number of participants per arm for a calculation intended to have an 80% chance of detecting the specified effect under the stated assumptions, if that effect and the assumptions were correct. The 90% power column expresses the corresponding planning target for a 90% chance. Power is a property of a proposed design under assumptions; these figures are not observed power for the completed study.

Rows that plan for 100% of the observed effect use the full observed contrast as the target; rows planning for 75% or 50% use progressively smaller target effects. Smaller effects are harder to distinguish from sampling variability, so they require more participants under otherwise unchanged assumptions. The same general relationship applies when a higher target power is desired: the design generally needs more information.

These illustrations are sensitive to the observed effect used as their starting point. An effect estimated in a modest-sized trial can be uncertain, and the assumptions may not reflect the trial's actual design or analysis. The trial's original sample-size justification and design assumptions are not reported in the registry record. The illustrations should therefore be read as hypothetical planning aids, not evidence that the completed study was designed to detect a particular effect.

13. 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, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 21.800; pooled standard deviation σ = 15.446.
2. n = 2 × (1.96 + 0.842)² × 15.446² / 21.800² = 7.9, rounded up to 8 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
delta <- 21.8                      # observed difference in means
sigma <- 15.445570775004                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^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 (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(768222)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 8 (80% power), 11 (90% power)
 75% of observed effect: n per arm = 15 (80% power), 19 (90% power)
 50% of observed effect: n per arm = 32 (80% power), 43 (90% power)
power.t.test: 9 
Simulated power at n = 8 per arm: 0.746 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-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.

14. Multiplicity, Missing Data and Analysis Populations

The primary outcome is clearly identified in the registry, and the registry labels its analysis population as intention to treat. However, the record does not report a detailed statistical analysis plan, a hierarchy of hypotheses, or a method for controlling multiplicity across outcome measures and assessment times. The listed secondary outcomes include multiple cosmetic and surgical site infection assessments, while only some secondary analyses have posted results. Without a reported plan, it is not possible to determine whether the analyses were confirmatory, exploratory, or selected after examining the data.

Multiplicity matters because repeated testing can increase the chance of at least one apparently notable result arising by chance. In general, methods such as a prespecified hierarchy or an adjustment to the testing procedure can address this issue, but no such approach is reported in the registry record. The secondary p-values are unadjusted and should be interpreted in that context. The primary p-value is also identified as unadjusted; whether it was the sole primary hypothesis in the original analysis plan is not reported.

The registry identifies the primary population as intention to treat, but the record does not explain how that population was implemented. The reported endpoint group sizes are 50 for Chinese Silk Suture and 51 for VICRYL* Plus Suture. The handling of participants with missing photographs, incomplete follow-up, protocol deviations, or unavailable endpoint measurements is not reported in the registry record. The record also does not say whether any imputation, sensitivity analysis, or alternative analysis population was used.

Missing outcome data can affect interpretation if the likelihood of an assessment being unavailable is related to the outcome or differs between groups. In general, intention-to-treat principles aim to preserve the randomized comparison, but the label alone does not show how incomplete observations were handled. The trial's original sample-size rationale, interim-analysis plans, and detailed missing-data procedures are not reported in the registry record.

15. 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 3% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: deep incisional ssi (2.0%), allergic shock (2.0%), skin lymphangitis (2.0%), bone marrow suppression (2.0%).

The registry reports serious adverse events affecting 3 participants at risk in the Chinese Silk Suture group and 1 participant at risk in the VICRYL* Plus Suture group. It also reports other adverse events affecting 14 participants at risk in the Chinese Silk group and 7 in the VICRYL* Plus group. These are descriptive counts from the registry record; they do not by themselves establish that the suture caused an event or that the groups differ reliably in safety.

The record lists Deep incisional SSI, Allergic shock, Skin lymphangitis, and Bone marrow suppression among the top serious terms, each reported as 2.0%. The record does not provide enough detail to determine the timing, duration, severity beyond the serious classification, or relationship of each event to the intervention. Deaths are not reported in the registry record.

Serious adverse event counts and other adverse event counts are separate summaries and should not be treated as measures of overall benefit or harm without further context. The registry record does not report a formal statistical comparison of adverse events, detailed event narratives, or an attribution assessment. Small group sizes and the absence of those details limit conclusions from these counts.

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

The posted primary data show a higher average cosmetic visual analog score in the VICRYL* Plus Suture group than in the Chinese Silk Suture group at 30 days (+/- 5) post-operative. The estimated mean difference is 21.8 points on a scale where higher scores represent a better possible scar. Its reported interval, from 15.8 to 27.8, describes uncertainty around the group-level contrast under the analysis assumptions. The unadjusted p-value is <0.001.

This result is specific to the study population, outcome measure, and follow-up assessment described in the registry. It is not a prediction of an individual patient's scar score. Nor does it establish that the difference is clinically important: the registry record does not report a threshold for a meaningful difference on this scale. The result also cannot separate the contribution of suture material from the contribution of closure technique, because the two arms used different materials and different closure patterns.

The secondary outcomes address early cosmetic ratings and surgical site infection scores. They provide additional observations but do not turn the primary comparison into a comprehensive account of every outcome relevant to surgery. Some listed secondary measures do not have reported analyses in the registry record, and the multiplicity plan is not reported.

The trial record does not establish how missing assessments were handled, whether the primary result was adjusted for other factors, or how outcomes varied across centers. The absence of those details limits the extent to which the summary can support broader conclusions. The posted data describe the observed group scores and reported comparisons; they should not be used alone to make medical decisions or to claim that a treatment works or does not work.

17. Why This Trial Matters Statistically

This trial illustrates why a clinical comparison must be read in relation to its outcome scale and design. The primary endpoint is a continuous photographic rating with defined anchors, so the mean difference can be interpreted in score points and the standard deviations show the spread of scores around the group averages. The reported interval adds an indication of precision that a point estimate alone cannot convey.

It also demonstrates the distinction between a treatment package and a single component. Chinese silk and VICRYL* Plus were paired with different closure techniques. The randomized comparison therefore evaluates the approaches as described, but cannot attribute the observed difference solely to material, antibacterial content, absorbability, or closure pattern.

The record also provides a useful example of why statistical significance and clinical importance are not interchangeable. The primary comparison has an unadjusted p-value of <0.001, but the record does not state a threshold for a meaningful change on the visual analog scale. Interpretation still requires attention to the size and precision of the estimate, the scale's meaning, and the limits of the design.

Finally, the posted secondary results and planning illustrations show why transparency about analysis plans matters. Unadjusted secondary comparisons across outcomes and times need cautious interpretation, while planning calculations based on an observed effect should not be mistaken for the trial's original sample-size rationale or for observed power. These issues are central to reading clinical results responsibly, regardless of the specific intervention.

18. 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 describes a randomized comparison, but its masking field is none. The primary photographs were assessed by an independent blinded central assessor, which is a specific safeguard for that outcome; it does not mean participants, clinicians, or other personnel were masked. The record does not provide further detail about who knew the assigned group during care or data collection.

The arms differ in both suture and closure technique: Chinese silk was used in a simple interrupted transdermal pattern, while VICRYL* Plus was used for subcuticular closure. This limits attribution of the observed cosmetic contrast to any single feature of the intervention. The record does not report a design intended to separate those components.

The study involved 101 participants across 6 centers in China, according to the registry description. The record does not provide center-specific results, details about participant characteristics, or information needed to assess how closely the enrolled population represents other settings. The trial duration is described as 90 days, and the primary endpoint is an assessment at 30 days (+/- 5); longer-term cosmetic results are not reported in the registry record.

Detailed methods for the primary comparison, missing-data handling, multiplicity, and sample-size justification are not reported. Some listed secondary measures also lack posted analyses. The available results therefore do not permit a complete assessment of the prespecified analysis plan, completeness of outcome follow-up, or consistency across all registered outcomes.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Coated VICRYL* Plus Suture Compared to Chinese Silk in Scheduled Breast Cancer Surgery — NCT00768222.
• Registry record last updated 2011-08-31; status last verified 2011-08.
• Results first posted 2011-08-25.
• 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.

22. Record Summary

NCT00768222 is a completed randomized, parallel-group Phase 4 study of VICRYL* Plus Suture compared with Chinese Silk Suture in scheduled breast cancer surgery. The registry describes approximately 100 patients undergoing modified radical mastectomy at 6 centers in China; enrollment was 101.

The primary outcome was mean cosmetic outcome score on a 100 mm visual analog scale at 30 days (+/- 5) post-operative, assessed from photographs by an independent blinded central assessor. The primary mean difference was 21.8 points, with a reported interval from 15.8 to 27.8 and an unadjusted p-value of <0.001.

The arms used different suture materials and closure techniques. The registry record does not report the original sample-size justification, detailed statistical analysis plan, multiplicity strategy, or missing-data procedures.