Impact of Robot-assisted Radical Prostatectomy Technique on Short-term Continence Recovery: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Impact of Robot-assisted Radical Prostatectomy Technique on Short-term Continence Recovery (NCT02352103), a randomized phase 3 study. The primary outcome is Urinary Continence Recovery.

2. Clinical Question

The trial’s brief summary frames the question as a comparison of short-term post-operative continence recovery in two cohorts of men undergoing RARP. The randomized allocation makes the assigned surgical approach the central contrast. The registry also lists continence recovery within 3 months as a secondary outcome, alongside complications, potency, biochemical recurrence, and urinary function-related quality of life. Those outcomes address different aspects of recovery and follow-up; they do not replace the specified primary endpoint, which is a pad-weight measure at a particular post-catheter-removal time point.

3. Trial Design

This was a randomized, parallel-group, phase 3 trial with single masking. The registry lists enrollment of 120 participants and identifies Henry Ford Health System as the sponsor. The study started in 2015-01, reached primary completion in 2016-04, and is marked completed. The registry record does not report further details about who was masked or how masking was implemented.

The two assigned procedures were Retzius-sparing radical prostatectomy and Vattikuti Urology Institute radical prostatectomy, both using the da Vinci Surgical System. The control arm is described as the Vattikuti technique and the treatment arm as the Retzius-sparing technique. Since this is a comparison of surgical approaches, the contrast concerns the assigned procedure rather than a drug treatment.

The primary outcome summaries list 60 participants in the control arm and 59 in the treatment arm. The registry does not explain the difference in the arm counts or specify the population used for the primary endpoint. It also does not report the randomization ratio, concealment procedures, eligibility criteria, or a detailed analysis population. These details should not be inferred from the randomized, parallel design label alone.

The record lists eight outcome measures and five posted secondary outcomes. It contains no reported analyses for those secondary outcomes and lists zero reported analyses overall. The primary outcome is summarized by medians and inter-quartile ranges rather than a reported model-based comparison. Additional information about the protocol, deviations from the protocol, interim analyses, or sample-size justification is not reported in the registry record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Urinary Continence Recovery, measured over One week after the removal of the suprapubic urinary catheter.

The primary endpoint is urinary continence recovery measured through 24-hour pad weights, in grams, one week after removal of the suprapubic urinary catheter. A lower pad weight indicates less urine collected on the pad during the measurement period. The registry summarizes this endpoint using a median and inter-quartile range for each arm.

Pad weight provides a quantitative measure of urine loss over a defined period. It can therefore represent continence status without reducing the measurement to a yes-or-no classification. The timing is important: the endpoint describes a short-term period tied to catheter removal, not continence at every later point in recovery.

The posted control-arm median is 25.0 grams, with an inter-quartile range from 3.0 to 133.0 grams. The treatment-arm median is 5.0 grams, with an inter-quartile range from 0.0 to 25.0 grams. These are separate arm summaries. A numerical difference between the medians, a confidence interval for a contrast, and a formal primary-outcome test are not reported in the registry record. The available summaries therefore describe the observed distributions but do not by themselves quantify the uncertainty in a between-group effect.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a median summarize?

General statistical explanation: A median is the midpoint of an ordered set of observations: half the observations fall at or below it and half at or above it, allowing for ties. It is less sensitive to extreme observations than a mean. That can be useful when measurements are skewed, as pad weights may be, though the distribution shape is not reported in the registry record.

The inter-quartile range gives the span from the lower quartile to the upper quartile, covering the middle half of observations. It describes spread around the median but is not an interval estimate for a treatment effect. The primary outcome record reports an inter-quartile range for each arm, but not a formal comparison of those distributions. Consequently, the medians and ranges should be read as descriptive arm-level summaries.

What does an unadjusted risk difference mean?

General statistical explanation: A risk difference compares the observed proportions with an outcome in two groups by subtracting one group’s proportion from the other’s. Its sign depends on the order of the comparison. Here, the reported secondary comparison is treatment versus control. A negative estimate means the observed outcome proportion was lower in the treatment arm, while a positive estimate means it was higher. The estimate is expressed as a proportion, not as a count of participants.

The interval accompanying a risk difference describes uncertainty in the estimated contrast. If it includes zero, the data are compatible with no difference as well as effects on either side of zero. An interval that excludes zero can indicate that the unadjusted contrast is not centered on zero under the method used, but does not establish clinical importance or resolve bias, missing-data concerns, or multiplicity. The confidence level and specific interval method are not reported in the registry record. P-values measure how unusual data at least as discrepant as those observed would be under a specified null model and its assumptions; they are not the probability that the null hypothesis is true.

Why treat the secondary comparisons cautiously?

The registry lists no reported analyses, while the binary contrasts and p-values are recalculated from posted summary counts. They are unadjusted comparisons. When several outcomes are examined, the chance of at least one apparently noteworthy result can increase if each is considered separately. This is the general multiplicity concern; whether or how the trial addressed it is not reported in the registry record. The secondary result with an unadjusted p-value of 0.032 should therefore not be interpreted as definitive evidence, particularly in the absence of a reported analysis plan or multiplicity procedure.

Other secondary comparisons have interval estimates that include zero. This means their estimates are imprecise enough to remain compatible with more than one direction of association. A non-small p-value does not demonstrate equivalence or prove that the groups are the same. Establishing equivalence or non-inferiority generally requires a prespecified margin and an analysis designed for that purpose; neither is reported in the registry record.

How should planning illustrations be read?

The sample-size illustrations use the observed effect as a starting point and show planning scenarios for detecting a stated fraction of that effect. The registry states that the calculations use a two-sided significance level of 0.05, equal allocation, and a normal approximation. For binary outcomes, the figures are participants per arm. These calculations are illustrative and depend on assumptions about the effect to detect. They are not the trial’s original sample-size justification, which is not reported in the registry record, and they are not observed power. Planning from an observed effect can also be unstable because an estimated effect from a trial can be imprecise.

For the primary pad-weight endpoint, the posted summaries do not include a two-arm comparison suitable for the recalculated binary-outcome planning approach. The registry record states that values are missing or not estimable for a two-arm comparison for another endpoint. No primary sample-size calculation or alternative analysis is reported. Thus, the planning illustrations should not be treated as a retrospective demonstration that the study could or could not detect a particular primary-outcome effect.

What does the absence of a reported analysis leave unresolved?

Without a reported primary contrast, readers cannot assess an adjusted estimate, its precision, or the inferential method used for pad weights. The registry record does not specify the handling of missing outcomes, deviations from assigned treatment, or the population included in the primary analysis. It also does not report interim analyses or the statistical plan. Such omissions limit what can be concluded from the posted summaries; they do not establish that particular methods were or were not used outside the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists five secondary outcomes and eight outcome measures overall, but reports zero analyses. For the posted secondary binary outcomes, the comparisons are unadjusted recalculations from the arm counts. No multiplicity adjustment, hierarchy among outcomes, prespecified testing sequence, or confirmatory status for secondary outcomes is reported in the registry record. Because several outcomes are examined, an isolated unadjusted p-value should be interpreted cautiously; the record does not establish whether the trial’s protocol addressed this issue.

Missing-data methods are not reported in the registry record. The primary outcome summaries include 60 participants in the control arm and 59 in the treatment arm, while the secondary binary comparisons list 60 per arm. The record does not explain the different arm counts, describe whether any outcome measurements were unavailable, or state how missing observations were handled. The primary-outcome population field is blank, and the analysis population is not reported. It is therefore not possible to determine from these summaries whether the results represent all randomized participants, participants with available measurements, or another defined group.

The registry record also does not report the primary statistical analysis plan, any adjustment variables, interim analyses, or an original sample-size justification. These items should be regarded as unreported rather than assumed absent from trial conduct. The lack of a posted primary comparison particularly limits interpretation: the record gives arm-level medians and inter-quartile ranges, but no inferential estimate or precision for the primary contrast.

11. 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

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: lymphocele (10.0%), pelvic hematoma (1.7%), umbilical hernia (1.7%).

The registry lists serious adverse event figures for both arms. The control arm has 5 participants affected among 60 at risk, and the treatment arm has 7 among 60 at risk. The record lists zero deaths in each arm. It also reports other adverse events affecting 2 participants in the control arm and 4 in the treatment arm, each with 60 at risk. These counts describe the posted safety summaries; they do not establish that the groups have equivalent safety profiles.

The serious-event terms listed include lymphocele at 10.0%, pelvic hematoma at 1.7%, and umbilical hernia at 1.7%. The registry’s summary does not clarify how these term-level percentages relate to individual arms or whether participants could contribute more than one event. The figures should therefore be read as registry-reported event information, not as a complete account of event severity, timing, causality, or comparative risk. Those details are not reported in the registry record.

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

The posted primary summaries describe short-term pad weights after catheter removal. They show that the treatment arm had a lower observed median than the control arm, but the registry does not report a formal primary comparison or an interval estimate for the difference. As a result, the magnitude and precision of the primary between-group effect cannot be assessed from the registry record. The descriptive pattern is not, on its own, proof of a causal advantage or disadvantage.

The randomized design is relevant because random assignment is intended to support a fair comparison of the assigned surgical approaches. However, the registry summary does not provide enough information to evaluate the primary analysis population, missing-data handling, or departures from assigned treatment. The secondary analyses are unadjusted recalculations, and their interpretation is further limited by the absence of a reported multiplicity strategy. These limitations affect how strongly the results can be interpreted; they do not erase the descriptive information that is posted.

The secondary outcomes address additional aspects of recovery and complications, but their estimates are imprecise and their role in the statistical plan is not reported. A result that does not meet a conventional significance threshold would not establish that the approaches are equivalent. Likewise, an unadjusted result with a p-value below a conventional threshold does not by itself establish clinical importance or settle the primary question.

Overall, the registry record supports a description of the observed arm summaries and the reported secondary counts. It does not provide enough reported primary analysis detail to draw a precise inferential conclusion about the trial’s main endpoint. These results should be understood as evidence from one completed randomized study record, with important analysis details not reported.

13. Why This Trial Matters Statistically

This trial is statistically notable because its primary outcome is continuous and is reported using medians and inter-quartile ranges, while its posted secondary outcomes include binary participant counts. Those outcome types call for different summaries and analyses. The primary summaries provide useful information about the observed pad-weight distributions, but the absence of a reported primary contrast leaves the main randomized comparison without an estimate of effect precision.

The distinction between descriptive arm summaries and an inferential treatment comparison is central. A median in each arm does not show how certain the difference between arms is, nor does it account for the trial’s analysis population or missing measurements. This matters especially when readers might otherwise treat visually separated arm summaries as a completed test of the main question.

The record also illustrates why secondary findings need context. Several outcomes are listed, and the available binary comparisons are unadjusted. Without a reported analysis plan or multiplicity strategy, an individual p-value is less persuasive than a prespecified primary result. Planning illustrations based on observed effects can help show how effect size assumptions influence future study planning, but they are not observed power and do not reconstruct the trial’s original design rationale.

For biostatisticians and clinical researchers, the key lesson is to distinguish what is directly reported from what requires an analysis that the registry does not post. The primary arm summaries, secondary counts, and safety figures each answer different descriptive questions. Their limitations should be considered alongside the randomized design rather than overlooked or replaced with assumptions about unreported methods.

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.

A central limitation is that the registry record does not report a primary between-group analysis for the pad-weight endpoint. It presents arm-level medians and inter-quartile ranges but no primary effect estimate, interval, or p-value. The primary outcome population field is blank, and the record does not explain the difference between the primary arm counts of 60 and 59. This leaves uncertainty about the analysis population and the interpretation of the descriptive summaries.

Important statistical details are not reported in the registry record, including the original sample-size justification, the primary analysis method, missing-data handling, interim analyses, and any multiplicity procedure. The record also does not clarify who was masked or provide enough information to evaluate implementation of masking. These missing details should not be replaced by assumptions.

The posted secondary comparisons are unadjusted recalculations and should be considered exploratory in the absence of reported sponsor analyses and a stated testing strategy. Several listed outcomes do not have a posted two-arm comparison suitable for interpretation. The registry’s serious adverse event summary provides counts and selected event terms but does not report enough detail to characterize timing, severity, relatedness, or arm-specific term frequencies.

Finally, the primary endpoint is measured at a specific short-term time after catheter removal. It does not by itself describe continence at other times or capture all dimensions of recovery. Secondary measures extend the follow-up perspective, but their posted analyses are limited. These features constrain what can be concluded from the registry record without negating the randomized comparison that was conducted.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Impact of Robot-assisted Radical Prostatectomy Technique on Short-term Continence Recovery — NCT02352103.
• Registry record last updated 2022-02-25; status last verified 2022-02.
• Results first posted 2019-09-18.
• 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

NCT02352103 is a completed randomized, parallel-group, phase 3 trial sponsored by Henry Ford Health System. It enrolled 120 participants and compared Retzius-sparing with Vattikuti Urology Institute robot-assisted radical prostatectomy using the da Vinci Surgical System. The primary outcome was urinary continence recovery measured as 24-hour pad weight one week after removal of the suprapubic urinary catheter.

The registry reports arm-level primary medians and inter-quartile ranges but no primary between-group analysis. It lists secondary outcomes concerning continence recovery, complications, potency, biochemical recurrence, and urinary function-related quality of life. Three secondary binary comparisons have unadjusted recalculated estimates; no sponsor analyses are listed. Statistical planning details, missing-data methods, analysis populations, and multiplicity procedures are not reported in the registry record.