Group-based trajectory analysis of postoperative pain and outcomes after liver cancer surgery

Background: Although previous studies have shown connections between pain and worse cancer outcomes, few clinical studies have evaluated their direct association, and the current study aimed to investigate the potential association between acute pain trajectories and postoperative outcomes after liver cancer surgery. Methods: This retrospective study was conducted in a single medical center and included patients who received liver cancer surgery between January 2010 and December 2016. Maximal pain intensity was recorded daily using a numerical rating scale during the first postoperative week. Group-based trajectory analysis was performed to classify the variations in pain scores over time. Cox and linear regression analyses were used to assess the effect of pain trajectories on recurrence-free survival, overall survival, and length of hospital stay (LOS) after surgery and to explore predictors of these outcomes. Results: A total of 804 patients with 5396 pain score observations were analyzed within the present study. Group-based trajectory analysis categorized the changes in postoperative pain into three groups: group 1 had constantly mild pain (76.6%), group 2 had moderate/severe pain dropping to mild (10.1%), and group 3 had mild pain rebounding to moderate (13.3%). Multivariable analysis demonstrated that on average, group 3 had a 7% increase in LOS compared with the group 1 (p = 0.02) and no significant difference in the LOS was noted between pain trajectory groups 2 and 1 (p = 0.93). Pain trajectories were not associated with recurrence-free survival or overall survival after liver cancer surgery. Conclusion: Acute pain trajectories were associated with LOS but not cancer recurrence and survival after liver cancer surgery. Group-based trajectory analysis provided a promising approach for investigating the complex relationships between variations in postoperative pain over time and clinical outcomes.