ObjectiveTo explore the dynamic evolution trajectory of symptom clusters and the influencing factors among lung cancer patients during their first chemotherapy cycle, so as to provide evidence for precise and stratified symptom management. MethodsA convenience sampling method was adopted. Incident lung cancer patients were recruited from the Cancer Hospital, Chinese Academy of Medical Sciences between December 2025 and April 2026. Longitudinal surveys were conducted at 1 day before the first chemotherapy, and on days 1, 3, 5 and 7 after chemotherapy using the general information questionnaire, the Chinese version of the M. D. Anderson Symptom Inventory-Lung Cancer Module (MDASI-LC), and the Charlson Comorbidity Index (CCI). Exploratory factor analysis was used to identify the composition of symptom clusters at different time points. Latent class mixed models (LCMM) were applied to fit the developmental trajectories of symptom clusters. The least absolute shrinkage and selection operator (LASSO) regression was used for variable screening, followed by multivariate logistic regression to analyze the influencing factors of each trajectory class. ResultsA total of 133 patients were enrolled, including 97 males and 36 females, aged 37-78 (62.54±9.27) years. Five symptom clusters were identified: respiratory symptom cluster, cough-expectoration symptom cluster, chemotherapy-related symptom cluster, gastrointestinal symptom cluster and psychological symptom cluster. All symptom clusters exhibited significant dynamic changes throughout the first chemotherapy cycle (P<0.05). Trajectory analysis revealed 2 to 3 trajectory subtypes for symptom clusters with marked heterogeneity. Most symptom clusters peaked on days 3 to 5 after chemotherapy. Multivariate logistic regression analysis, with the low-level trajectory group as reference, showed that pathological type (P<0.001) and medical insurance type [OR=0.022, 95%CI (0.000, 0.976), P=0.049] were associated with membership of respiratory symptom cluster trajectories; household per capita monthly income [OR=3.102, 95%CI (1.183, 8.129), P=0.021] and chemotherapy regimen [OR=0.306, 95%CI (0.098, 0.959), P=0.042] were associated with membership of cough-expectoration symptom cluster trajectories; smoking amount [OR=1.039, 95%CI (1.003, 1.075), P=0.011] and clinical stage [OR=0.209, 95%CI (0.045, 0.977), P=0.047] were associated with membership of gastrointestinal symptom cluster trajectories; CCI [OR=0.342, 95%CI (0.131, 0.897), P=0.029] was associated with membership of psychological symptom cluster trajectories. ConclusionSymptom clusters in lung cancer patients demonstrate obvious dynamic evolutionary characteristics and individual heterogeneity during the first chemotherapy cycle. Days 3 to 5 post-chemotherapy serve as the critical window for symptom monitoring and intervention. Medical staff should implement individualized stratified management in consideration of patients’ pathological type, economic status, comorbidity burden and treatment regimen to realize precise early warning and timely intervention of symptoms.