Temporal Network of Symptoms, Physical Activity and Nutritional Status in Breast Cancer Patients Undergoing Chemotherapy: The Central Role of Fatigue

AIM: To examine longitudinal interrelationships among symptom burden, physical activity and nutritional status in breast cancer patients undergoing chemotherapy. DESIGN: A longitudinal observational study with three repeated measurements. METHODS: A total of 280 breast cancer patients were recruited from two tertiary hospitals in China. Data were collected before chemotherapy (T1), after cycle 3 (T2) and after cycle 6 (T3) using the Memorial Symptom Assessment Scale-Short Form (MSAS-SF), International Physical Activity Questionnaire-Short Form (IPAQ-SF) and Patient-Generated Subjective Global Assessment (PG-SGA). Cross-lagged panel network analysis estimated contemporaneous and temporal networks, with centrality indices identifying influential nodes. RESULTS: Fatigue and appetite loss emerged as consistent central nodes. Higher fatigue severity at T1 predicted decreased physical activity at T2 (β = -0.17, 95% CI: -0.24 to -0.10) and higher physical activity at T2 predicted better nutritional status at T3 (β = -0.18, 95% CI: -0.25 to -0.11). Nutritional status did not predict subsequent symptoms or activity. Fatigue had the highest strength centrality. CONCLUSION: This study reveals a temporally ordered predictive pattern from fatigue to reduced physical activity and subsequent deterioration in nutritional status in breast cancer patients during chemotherapy. Early fatigue management may inform interventions aimed at mitigating this trajectory. IMPLICATIONS FOR THE PROFESSION AND/OR PATIENT CARE: Oncology nurses may consider prioritizing fatigue assessment and management from the start of chemotherapy and promoting physical activity during mid-treatment to help preserve nutritional status. IMPACT: What problem did the study address? The temporal relationships among symptoms, physical activity and nutritional status during chemotherapy were unclear What were the main findings? Fatigue predicted subsequent physical activity decline, which in turn predicted nutritional deterioration; fatigue was the most central node in the network. Where and on whom will the research have an impact? The findings will inform oncology nursing practice for breast cancer patients undergoing chemotherapy in China and internationally. REPORTING METHOD: STROBE guideline for observational studies. PATIENT OR PUBLIC CONTRIBUTION: This study did not include patient or public involvement in its design, conduct, or reporting.