The overall objective of the REBECCA studies at Stavanger University Hospital (SUH) is to improve the QoL of patients affected by cancer-related fatigue during and after end of treatment, by collecting multi-source real world data (RWD) and intervening based on the collected RWD.

In the intervention study, REBECCA-2, the investigators will use the collected real world data to provide a personalised follow-up to the breast cancer patients in order to improve their quality of life. The patients in this study are randomised into 2 groups after end of primary treatment:

• The control group (n=55): Patients will receive standard follow-up according to national guidelines plus 3 generic lifestyle consultation sessions via telephone.
• The experimental REBECCA group (n=55): Patients will, in addition to receiving standard follow-up also receive REBECCA-assisted follow-up. Data will be collected from a REBECCA smartwatch, plug-in and PROMs.

If the REBECCA system detects signs of deterioration in patients' QoL during the study period, the intervention will include changes in medication given, dietary advice, referral to a psychologist/psychiatrist and/or personal training with a physiotherapist at 'Pusterommet' (SUH)

After 12 months of RWD collection participants will be offered the option to continue in the study for another 6 months. For patients in the experimental Rebecca group this includes the use of the REBECCA system for another 6 months. In the clinical REBECCA-2 study, patients' visits are planned every 6 months and include collection of both PROMs and biological samples.