Long-term fatigue dimensions in the Multidimensional Fatigue Inventory (MFI) up to five years after radiotherapy and their trajectories in men diagnosed with non-metastatic prostate cancer in the international REQUITE study

Background Fatigue is a common, multidimensional symptom in cancer patients. Little is known about fatigue dimensions and their trajectories in prostate cancer (PCa). Methods Using the Multidimensional Fatigue Inventory (MFI), 1097 men treated with radiotherapy for non-metastatic PCa (2014–2016) prospectively reported fatigue up to five years later. Prevalent fatigue was defined as scores ≥75th percentile in men aged ≥60 years in a German general population sample. Pre-radiotherapy patient characteristics were examined for their associations with general fatigue, physical fatigue, mental fatigue, reduced activity, and reduced motivation two years later using logistic regression models. Fatigue trajectories up to two years post-radiotherapy were explored using latent class growth analysis and multinomial regression. Results About 72% (785/1097) of patients reported being fatigued for at least one dimension in the MFI from before the start of radiotherapy up to five years later, with 45% (367/816) being fatigued two years post-radiotherapy. Pre-radiotherapy fatigue level (OR: 4.7–9.0), depression (OR: 2.5), diabetes (OR: 1.8–2.2), hypertension (OR: 1.6–1.8), and BMI (OR: 1.8–2.2) were statistically significant predictors of long-term fatigue two years post-radiotherapy across dimensions. Depression, BMI, and pelvic radiotherapy were associated with experiencing a high fatigue trajectory. Conclusions Early fatigue assessments, in addition to self-reported comorbidities and BMI, showed additional benefits beyond symptom detection by providing prognostic value for poorer long-term fatigue outcomes. Multidimensional fatigue assessments could guide tailored symptom management strategies, targeting specific dimensions to address associated impairments in quality of life and functioning.