Establishing Pain Thresholds for Functional Recovery After Lung Cancer Surgery: A Mediation Analysis of the Surgery–Pain–Functioning Causal Pathway

Objective Pain is one of the most common and long‐lasting symptoms after lung cancer surgery, potentially impairing physical functioning. This study aims to investigate to what extent pain mediates the association between the different surgical approaches (single‐port VATS versus multiport VATS or thoracotomy) and postoperative functional recovery after lung cancer surgery, with the goal of establishing clinically actionable pain score thresholds. Methods In a prospective cohort study including 1381 patients, pain and functional status (activity limitation and walking difficulty) were assessed daily in hospital with the Perioperative Symptom Assessment for Lung Surgery (PSA‐Lung). The structural equation model (SEM) was used to investigate the mediation effect of pain in the surgery–pain–functioning pathway. The pain thresholds on postoperative day (POD) 1, 2, and 3 for optimal functional recovery were identified, corresponding to the cutoff points of pain categorization that demonstrated the largest indirect effects in the models. Results The surgical approach had a significant indirect effect on activity limitation and walking difficulty through pain severity ( p < 0.001), with a standardized effect value of 0.039 and 0.037, respectively. According to the largest mediation effects of pain categories generated from the each day SEM, the optimal pain score cutoffs are 5 on POD1, 4 on POD2, and 3 on POD3, for both activity limitation and walking difficulty. Conclusion Our study quantified the partial mediating effects of pain between surgical approaches and postoperative functional status in patients with lung cancer surgery. The mediation effect–based pain thresholds support precise strategies for postoperative functional rehabilitation, which is considered the major goal of enhanced recovery after surgery. Trial Registration: Chinese Clinical Trials Registry: ChiCTR2000033016