Physical activity trajectories and associated factors in patients with lung cancer undergoing chemotherapy: A longitudinal study.

Objective: To characterize heterogeneity in physical activity (PA) trajectories among patients with lung cancer during early chemotherapy and examine associated demographic, clinical, and psychosocial factors. Methods: This longitudinal study enrolled 155 patients initiating chemotherapy at the First Affiliated Hospital of Anhui Medical University in Anhui Province, China. PA was assessed using the International Physical Activity Questionnaire-Short Form at baseline and before the second, third, and fourth cycles. Symptom burden, exercise self-efficacy, outcome expectations for exercise, and social support were assessed exclusively at baseline. Latent class growth analysis was utilized to identify PA trajectories. Factors associated with trajectory membership were analyzed using a two-stage strategy combining least absolute shrinkage and selection operator regression and Firth's penalized logistic regression. Results: Among 122 completers, two distinct trajectories were identified. The majority (77.9%) followed a "Moderate-Sustained Decline" trajectory, showing a significant drop at cycle 2 with persistently low activity. Conversely, 22.1% exhibited a "High-Decline-Partial Recovery" trajectory, characterized by a behavioral rebound after the initial decline. Multivariate analysis revealed that higher symptom burden (OR = 1.105, Conclusions: PA patterns are heterogeneous, though a decline prior to the second cycle is universal. Lower symptom burden and stronger cognitive resources may support more favorable physical activity trajectories. Proactive nursing interventions integrating symptom management with cognitive-behavioral empowerment targeting the critical window before the second cycle are recommended to prevent functional decline.