# Decoding Surgical Complexity: Measuring the Impact of Operative Difficulty on Quality Outcomes Following Hepatectomy for Liver Cancer over Two Decades

## TL;DR

This study creates a new score to measure liver surgery difficulty, showing that harder surgeries lead to worse cancer outcomes and recovery.

## Contribution

The paper introduces an objective composite score for operative difficulty in liver surgery, validated against surgical and oncological outcomes.

## Key findings

- Higher operative difficulty scores correlate with lower rates of textbook oncological outcomes and higher futile surgery rates.
- Patients with cholangiocarcinoma and colorectal liver metastases had shorter survival and earlier cancer recurrence with increased operative difficulty.
- Operative difficulty assessment could improve patient counseling and postoperative care planning.

## Abstract

Liver surgery is complex and currently there are significant inconsistencies in determining the difficulty of a procedure. Most existing tools rely on operative time alone, which may not reflect the experience of the operator or unexpected challenges during surgery. This retrospective study aimed to develop an objective operative difficulty score using intraoperative variables (operative time, estimated blood loss, time of hepatic inflow occlusion, and the need for blood transfusion) and stratify patients into low, moderate and high operative difficulty groups. A prospectively collected liver resection database was used, and 699 patients were included in the study. As the operative difficulty score increased, surgical quality and cancer outcomes worsened. Patients in the high operative difficulty group had much lower rates of textbook oncological outcomes and higher rates of futile surgery. Among patients with cholangiocarcinoma and colorectal liver metastases, greater difficulty was also linked to shorter survival and earlier cancer recurrence. Measuring operative difficulty in this way may improve patient counselling, postoperative planning, and quality assessment after liver surgery.

Introduction: Operative time is commonly used as a surrogate marker for operative difficulty in liver resection, but the contribution of other intraoperative factors is less understood. This study aimed to develop an objective, composite score to assess operative difficulty and evaluate its association with postoperative and oncological outcomes in liver surgery. Methods: A retrospective cohort study was conducted on patients who underwent liver resection for malignant disease between 1999 and 2023 at an Australian tertiary hospital, using a prospectively maintained database. Principal component analysis (PCA) was applied to operative time, estimated blood loss, total time of hepatic inflow occlusion and the number of packed red bloods transfused intraoperatively to derive a composite operative difficulty score. Patients were then stratified into low, moderate and high difficult groups using Gaussian mixture models (GMM). Comparison of textbook oncological outcomes (TOO) achievement and futile resection rates were assessed using Chi-squared analysis. Kaplan-Meier analysis was used to assess recurrence-free and overall survival in subgroup analysis. Results: Of 729 patients, 699 met the inclusion criteria. GMM identified three distinct operative difficulty groups: low (n = 540), moderate (n = 143), and high (n = 16). TOO and non-futile resection rates declined with increasing difficulty: 77% and 58% (low), 47% and 52% (moderate), and 6% and 19% (high), respectively (p < 0.001, p = 0.004 respectively). Among patients with cholangiocarcinoma, median overall survival was inversely correlated with operative difficulty (40 months low, 16 months moderate, 7 months high, p = 0.004). In patients with colorectal liver metastases, there was a trend towards worse overall survival and disease-free survival with increasing operative difficulty, however, this did not reach statistical significance. Conclusions: An objective intraoperative difficulty score was developed and demonstrated a significant inverse association with both quality and oncological outcomes. While external validation is required, these findings support the potential of operative difficulty assessment to enhance perioperative decision-making, inform patient counselling, and optimise postoperative care planning.