Abstract
IMPORTANCE: Fatigue is a common symptom reported by patients with cancer, yet its role as a predictor of treatment-related toxic effects has not been well characterized. Understanding whether fatigue measured at treatment initiation may be associated with subsequent toxic effects could help guide individualized treatment planning and symptom monitoring. OBJECTIVE: To evaluate the association between baseline patient-reported fatigue and the risk of adverse events (AEs) in cancer treatment trials. DESIGN, SETTING, AND PARTICIPANTS: This cohort study and pooled analysis assessed baseline fatigue data from 17 SWOG phase 2 and 3 trials conducted from 1990 to 2022. Patients were enrolled across multiple cancer types and treatment settings. Data analysis was performed from March 1, 2023, to October 17, 2025. EXPOSURES: Baseline fatigue, classified on a 5-point Likert scale, analyzed as binary thresholds (eg,