Oslo Randomized Laparoscopic Versus Open Liver Resection for Colorectal Metastases Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Oslo Randomized Laparoscopic Versus Open Liver Resection for Colorectal Metastases Study (NCT01516710), a randomized na study. The primary outcome is 30 Days Perioperative Morbidity.

2. Clinical Question

3. Trial Design

The registry describes a randomized, single-masked, parallel-group study comparing laparoscopic and open liver resection for colorectal metastases. The listed enrollment is 280. The primary outcome population is described as modified intention to treat, but the registry record does not define how that population was formed or explain how participants were handled after randomization if they did not undergo the assigned operation.

The study's stated purpose was to compare outcomes prospectively. Its brief description says it would include all non-anatomic liver resections at the institution. The intervention groups were open liver resection and laparoscopic liver resection. The record lists Oslo University Hospital as sponsor and the trial phase as not applicable. It gives a start date of 2012-01 and a primary completion date of 2016-04. The status is recorded as unknown, so the record does not establish the trial's current status.

Single masking is recorded, but which participants, clinicians or outcome assessors were masked is not reported in the registry record. The record also does not describe the randomization procedure, allocation concealment, stratification factors or whether the operative teams could be masked. Those omissions limit the detail available for evaluating implementation of the randomized design; they do not change the fact that the registry classifies the allocation as randomized.

The registry identifies 16 outcome measures and lists 15 secondary outcomes as posted. Named secondary topics include five-year survival, recurrence pattern, immediate oncologic outcome, postoperative quality of life, surgical trauma and immune-system activation, health economy, postoperative pain severity and molecular biology. These are areas of interest, not evidence that results for each were analyzed or reported. The analysis count is zero, and no inferential analysis results are listed 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

Analysis population for the primary outcome, as defined in the registry: Modified intention to treat

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: A total of 280 patients were enrolled. Only 273 underwent surgery, and only these could reach the primary endpoint of 30 days morbidity. This is why there is a difference between baseline and analyzed for the primary endpoint.

6. Primary Endpoint

The registry lists the primary outcome as 30 Days Perioperative Morbidity, measured over Within 30 days after surgery.

The primary endpoint is labeled 30 days perioperative morbidity. Its timeframe is within 30 days after surgery, and the outcome description defines morbidity as yes or no. The endpoint is intended to capture whether a participant experienced a postoperative or intraoperative complication during the specified period, rather than to measure one continuous quantity such as length of stay or blood loss. The registry's unit wording is “Complications Accordion grade 2 or highe”; the final word is truncated in the record.

The description says events would be classified and analyzed using the Dindo classification, the Accordion system and the Comprehensive Complication Index. It also describes comparisons of operative time, blood loss, transfusion and intraoperative incidents, with incidents classified according to the Satava classification. These details distinguish the primary morbidity outcome from other perioperative measures and indicate that complications were to be characterized in more than one way.

A binary morbidity endpoint is useful for asking whether any qualifying complication occurred, because it gives a direct count of participants with and without the event. General statistical consideration: a yes-or-no outcome does not convey how many events an individual experienced or the severity of every event; classification systems can add information about severity or overall burden. The posted primary result gives counts by arm, but no uncertainty interval or statistical comparison is reported in the registry record. The degree of precision and the strength of evidence for a between-group difference therefore cannot be assessed from those counts alone.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The statistical design begins with the trial's randomized, parallel-group structure. Participants were assigned to one of two surgical approaches, with outcomes intended to be compared between groups. General statistical explanation: randomization aims to make groups comparable at the point of assignment, on average, so that outcome differences can be interpreted as evidence about the assigned strategies. Randomization does not guarantee that every characteristic is balanced in a particular trial, and it does not remove the need to define the analysis population, outcome, follow-up period and statistical comparison. The registry record does not describe the sequence-generation method, concealment procedures or any stratification.

What do the primary outcome counts tell us?

The primary outcome is described as morbidity within 30 days after surgery, recorded as yes or no. A count of participants with the outcome is a natural summary for a binary endpoint. The posted results list 44 among 144 in the open group and 24 among 129 in the laparoscopic group. These are observed counts, not a complete statistical comparison. To assess the uncertainty around a comparison, readers would ordinarily look for an effect estimate and a confidence interval, alongside any test result. None is listed in the registry record. No additional percentage, risk difference or ratio is calculated in this explanation.

General statistical explanation: a confidence interval describes a range of effect estimates compatible with the data under the assumptions of the analysis. Its width conveys precision; a wider interval indicates greater uncertainty than a narrower interval. A p-value, when reported, summarizes how unusual data at least as incompatible with a specified null hypothesis would be under that hypothesis and the model. Neither measure substitutes for judging the clinical meaning of the endpoint or the limitations of the design. Here, neither is available in the posted results.

How should the endpoint definition be read?

The endpoint narrative describes a binary morbidity outcome and says that events would be classified according to Dindo, Accordion and the Comprehensive Complication Index. The registry unit is truncated as “Complications Accordion grade 2 or highe”. The record therefore gives some information about the intended severity classification but does not fully state the unit wording. The description also lists operative time, blood loss, transfusion and intraoperative incidents as perioperative measures, with incidents classified according to Satava. These measures are not interchangeable with the primary yes-or-no morbidity outcome. Their result values and analyses are not reported in the registry record.

The method used to combine multiple complications into a participant-level binary outcome is not described. Nor does the record say whether outcome classification was performed by masked assessors, whether events were independently adjudicated, or how disagreement was handled. General statistical explanation: clear outcome definitions and consistent ascertainment matter because different definitions can classify the same clinical course differently. Masking of outcome assessment can reduce the opportunity for expectations to affect subjective decisions, although the record does not identify who was masked in this single-masked study.

What can be said about the analysis plan?

The registry lists zero analyses. The statistical plan, including the primary comparison method, any adjustment variables, handling of repeated or multiple complications, and approach to missing outcomes, is not reported in the registry record. It is therefore not possible to verify from this record whether the posted counts correspond to a prespecified analysis or whether any additional analyses were conducted. The modified intention-to-treat label identifies the stated analysis population, but its operational definition is not reported.

The record gives a planning illustration assumption: a two-sided significance level of 0.05, equal allocation, a normal approximation and an effect to detect specified as a fraction of the observed effect. It also distinguishes planning illustrations from observed trial results. For this count-other endpoint, the registry's comparison status says values are missing or not estimable for a two-arm comparison. No participants-per-arm planning estimate is available in the record. A planning calculation, when available, is not observed power and does not measure how likely the trial's findings are to be true. The registry does not report its own sample-size justification or whether the listed enrollment was based on a formal calculation.

General statistical explanation: sample-size planning depends on the outcome definition, the effect size chosen as important, variability or event frequency, allocation, and the desired error rates. A planning illustration that uses an effect observed after data collection is not the same as a prospective design justification, and its result should not be interpreted as a measure of the trial's success. No unsupported assumptions about the trial's planning should be inferred from the listed enrollment alone.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 16 outcome measures and 15 secondary outcomes as posted, alongside a designated primary outcome. The named secondary topics include five-year survival, recurrence pattern, immediate oncologic outcome, postoperative quality of life, surgical trauma and immune-system activation, health economy, severity of postoperative pain and molecular biology. Listing these outcomes establishes that they are part of the registry record; it does not show that results or analyses were posted for each.

When many outcomes are tested, the chance of at least one apparently notable result can increase if each is assessed separately. General statistical explanation: multiplicity can be addressed by prespecifying a hierarchy, adjusting the interpretation or using other planned approaches. Whether any multiplicity strategy was specified or used is not reported in the registry record. With no analyses listed, there are no posted inferential results from which to assess multiplicity adjustments or distinguish prespecified from exploratory findings.

The primary population is called modified intention to treat, but the inclusion and exclusion rules for that population are not reported. The record does not say how missing primary-outcome data were handled, whether participants were excluded after randomization, or whether missingness was assessed by group. Imputation methods, sensitivity analyses and reasons for missing outcomes are not reported in the registry record. These details matter because the analyzed population and assumptions about missing data can affect a comparison.

The sample-size field is 280, while the primary-outcome denominators are 144 and 129. The record does not reconcile those figures. It also does not provide an analysis flow or explain the number of participants with unavailable primary-outcome status. Therefore, the extent to which the posted counts represent all randomized participants cannot be determined from the registry record.

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 5% reporting threshold.

Most frequent serious adverse event terms

Serious events with the highest arm-level rate: small bowel perforation (1.5%), fascia dehiscence (1.4%), small bowel obstruction (1.4%), bleeding (0.8%), intraabdominal abcess (0.8%).

The adverse-event record lists serious adverse events for 10 of 147 participants at risk in the open liver resection group and 4 of 133 at risk in the laparoscopic liver resection group. It lists zero other adverse events in each group. Deaths are listed as 1 in the open group and 0 in the laparoscopic group. These are separate safety summaries and should not be substituted for the primary endpoint counts or denominators.

The record also names serious adverse-event terms with percentages: small bowel perforation, 1.5%; fascia dehiscence, 1.4%; small bowel obstruction, 1.4%; bleeding, 0.8%; intraabdominal abcess, 0.8%; and suspected bowel perforation, 0.7%. The registry does not explain in this record how these term percentages were calculated, whether terms can overlap within a participant, or how the terms map to the group-level serious-event counts. They should not be added together or interpreted as an overall event rate.

General statistical explanation: adverse-event counts describe events recorded during a study, but by themselves do not establish that an event was caused by an assigned intervention. The registry record does not give the event-attribution method, event-specific follow-up details or comparative uncertainty estimates. The figures are descriptive safety information, not a substitute for a formal comparative analysis.

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

The posted primary-outcome data show 44 cases among 144 participants in the open liver resection group and 24 among 129 in the laparoscopic liver resection group. These counts describe the registry's 30-day perioperative morbidity outcome for a modified intention-to-treat population. They show a lower recorded count in the laparoscopic arm, but the registry does not provide a confidence interval, p-value or other comparative estimate. The magnitude and precision of a between-group difference cannot therefore be evaluated from the posted results alone.

The findings do not establish that the surgical approaches are equivalent, nor do the counts alone establish that one approach is superior. An absence of an inferential result is not evidence that there is no difference. Conversely, the direction of the raw counts is not sufficient evidence of a reliable effect. A complete interpretation would require the prespecified analysis, clear outcome definition, an effect estimate with uncertainty, and information about missing outcomes and the analyzed population.

The study also included secondary questions about survival, recurrence, oncologic outcomes, quality of life, immune-system measures, health economy, pain and molecular biology. Those questions broaden the intended scope but do not expand what can be concluded from the primary counts. Their results and statistical analyses are not reported in the registry record. The safety summaries likewise describe recorded events without supplying comparative estimates or establishing causation.

General statistical explanation: statistical evidence is most informative when the estimate, its precision, the study methods and the clinical context are considered together. The registry record supplies some design features and outcome counts, but leaves key analytical details unavailable. Consequently, the posted information supports a descriptive account of the recorded data, not a conclusive claim about the comparative effects of laparoscopic and open liver resection.

13. Why This Trial Matters Statistically

This trial is statistically notable because it poses a direct randomized comparison of two surgical approaches and defines a short-term primary morbidity outcome. The parallel-group structure is suited to comparing outcomes between assigned strategies, while the modified intention-to-treat label signals that the posted primary counts refer to a defined analysis population. However, the registry does not explain how that population was defined, so the label alone is not enough to establish how participants were included.

The outcome is clinically interpretable in broad terms as morbidity within 30 days, and the registry describes more than one classification system for complications. At the same time, the truncated unit wording and absent analysis details make it difficult to identify precisely which events qualify for the posted counts and how the categories were used. This illustrates why outcome labels, operational definitions and analysis rules are important complements to summary numbers.

The record also illustrates the distinction between descriptive data and statistical inference. Arm-specific counts can show what was recorded, but they do not communicate the uncertainty around a comparison. Without a reported effect estimate and confidence interval, readers cannot judge precision; without an analysis result, they cannot assess the stated comparison statistically. The registry's lack of posted analyses is therefore central to interpretation, not a minor reporting detail.

Finally, the gap between listed enrollment and primary-outcome denominators, together with the absence of a missing-data account, leaves questions about participant flow unresolved. These limitations are useful reminders that randomized allocation, sample-size fields and outcome counts answer different questions. Each must be interpreted in relation to the stated population and analysis rather than treated as a complete statistical result on its own.

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 registry record leaves several trial-specific details unresolved. It labels the primary population modified intention to treat but does not define eligibility for that analysis. The listed enrollment is 280, whereas the primary-outcome counts use denominators of 144 and 129; no participant flow or reconciliation is reported. The safety summaries use at-risk counts of 147 and 133, and the record does not explain why these denominators differ from those for the primary endpoint.

The endpoint description names Dindo, Accordion and the Comprehensive Complication Index, but the unit wording is truncated and the precise rule used to derive the posted binary result is not stated. The record does not report how events were ascertained, whether adjudication was independent, or which role was masked in the single-masked design. Randomization sequence generation, allocation concealment and any stratification are also not reported.

No analysis results are listed. The primary comparison method, handling of missing data, adjustment strategy, multiplicity approach and sensitivity analyses are not reported in the registry record. The record also does not provide the trial's sample-size justification, so the enrollment figure cannot be interpreted as evidence of a particular planned power or precision. The status is unknown, and secondary outcomes are listed without their results or analyses. Together, these omissions constrain what can be concluded from the posted counts and safety summaries.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Oslo Randomized Laparoscopic Versus Open Liver Resection for Colorectal Metastases Study — NCT01516710.
• Registry record last updated 2024-05-10; status last verified 2023-11.
• Results first posted 2024-05-10.
• 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 describes NCT01516710 as a randomized, single-masked, parallel-group study sponsored by Oslo University Hospital. It compares open liver resection with laparoscopic liver resection for colorectal metastases. Listed enrollment is 280; the start date is 2012-01, primary completion is 2016-04, and status is unknown.

The primary outcome is 30 days perioperative morbidity, with a timeframe of within 30 days after surgery and a modified intention-to-treat population. The posted counts are 44 among 144 in the open group and 24 among 129 in the laparoscopic group. The registry lists 16 outcome measures, 15 posted secondary outcomes and zero analyses. It does not report an inferential comparison, uncertainty interval, missing-data method or detailed definition of the analysis population.