Validation of the FACIT-Fatigue Scale in Patients With Locally Advanced or Metastatic Breast Cancer

Background Cancer-related fatigue (CRF) is a common symptom in patients with locally advanced or metastatic breast cancer (LA/M BC) receiving taxane-based chemotherapy (CT). CRF is commonly assessed as a subjective experience by patient questionnaires, such as the Functional Assessment of Chronic Illness Therapy (FACIT)-Fatigue. The aim of this study was to extend validity of the FACIT-Fatigue and estimate clinically meaningful group-level differences in this patient population. Materials and Methods This was a prospective, noninterventional, multinational study conducted in the United States and Italy from October 2021 to August 2023 in adult patients with LA/M BC eligible to receive cycle 1 of taxane-based CT. Patients completed a FACIT-Fatigue survey before starting CT and every 3 to 4 weeks for ∼16 weeks; a group of patients participated in a qualitative substudy to explore additional fatigue factors via semistructured, phone-based cognitive interviews. Results Sixty-two female patients with a mean (standard deviation) age of 55.5 (12.2) years were included. Baseline (visit 1) mean (95% confidence interval) FACIT-Fatigue score was 39.0 (36.8, 41.2), and fatigue worsened over time from 36.6 at visit 2 to 31.9 at visit 5. All FACIT-Fatigue items were relevant, with patients frequently reporting physical and psychological fatigue during treatment; the most highly relevant items were “I feel listless” and “I have to limit my social activity because I am tired.” Triangulation of anchor-based, distribution-based, and qualitative-based methods determined a meaningful group-level difference of 2.4 points. Conclusion The FACIT-Fatigue survey includes items relevant to patients with LA/M BC on taxane-based CT.