BACKGROUND: Cancer-related fatigue (CRF) is the most prevalent, distressing, and quality of life disturbing symptom during and after cancer treatment for many cancer types including breast cancer. The experience and burden of this symptom can induce a cognitive bias towards fatigue or a fatigue-related self-image, which can further increase the fatigue symptoms and related behaviour. For this, a Cognitive Bias Modification (CBM) eHealth app (IVY) has been developed. The app aims to counter …