An investigation of the relationships between postoperative pain trajectories and outcomes after surgery for colorectal cancer

Background: Although animal studies have shown that pain can suppress host immunity and promote tumor metastasis, few clinical studies have evaluated the association between acute pain and long-term outcomes after cancer surgery. Methods: Patients undergoing colorectal cancer resection at a medical center between November 2010 and December 2014 were collected. Pain intensity was recorded using a numeric rating scale at 12, 24, 36, 48, 72, 96, and 120 hours postoperatively. Group-based modeling of longitudinal pain scores was used to categorize pain trajectories. Recurrence-free survival and overall survival were analyzed using Cox proportional hazards models. Results: A total of 2401 patients with 13931 pain score observations were analyzed. The trajectory model identified three groupings of inpatient postsurgical pain, including 70.3% with mild pain dropping to low (group 1), 20.0% with moderate/severe pain dropping to mild (group 2), and 9.7% with moderate pain rebounding to severe (group 3). Univariate models showed that pain trajectories were significantly associated with recurrence-free survival (group 2 vs 1: hazard ratio [HR], 1.23; 95% CI, 1.02-1.47 and group 3 vs 1: HR, 1.63; 95% CI, 1.30-2.04) and overall survival (group 2 vs 1: HR, 1.36; 95% CI, 1.05-1.77 and group 3 vs 1: HR, 1.81; 95% CI, 1.31-2.51). However, the associations disappeared after adjusting for other significant risk factors. Conclusion: Abnormal pain resolution identified by pain trajectory analysis and resulting from complex interactions among disease progression, surgery, and analgesia may be considered as an indicator of an inferior prognosis following colorectal cancer resection.