Cancer related fatigue (CRF) is the most burdening symptom in breast cancer patients, and prevalence exceeds 75% in patients with metastatic disease. CRF is described as the symptom that has the largest impact on quality of life, with negative effects on work, social activities, and daily activities, and may lead to treatment discontinuation. Currently, there is no gold standard for the treatment of CRF. Drug therapies are not satisfactory. Since physical activity is associated with significant reduction in CRF, patients are encouraged to engage in an at least moderate level of physical activity. However, for many metastatic breast cancer patients this is too burdensome. Finally, there is some evidence that non-pharmacological mind-body techniques may be beneficial in reducing CRF, yet the available data do not allow for final recommendations. Given the high prevalence of CRF and the substantial distress for patients, advancing treatment options for patients with CRF is highly desirable. In the present study, patients with metastatic breast cancer will be randomly assigned to two different non-pharmacological treatments for fatigue: Eurythmy therapy (ERYT), a standardized active mindful movement therapy, or a movement program without mindfulness features (CoordiFit). It will be tested, if ERYT has a superior benefit on fatigue compared to CoordiFit over the period of the intervention (20 weeks). Further, the benefit of ERYT on quality of life, sleep quality, anxiety, depression, pain, mobility of the arm, rate of return to work, compliance with ERYT, and targeted metabolomics will be investigated.

Both groups will have equal frequency and duration of the training sessions. Each patient will receive 13 standardized therapy sessions of 45 min (once a week for 6 weeks and once every second week) during the total period of 20 weeks. The proposed study has been developed in the Breast Cancer Project Group of the Swiss Group for Clinical Cancer Research (SAKK) and is supported by many breast centers, because they realize that the patients value non-pharmacological treatment options and would be keen to participate in such a trial. If ERYT proves to be beneficial, the impact of this trial will be high and will have implications not only for metastatic breast cancer patients but also for other cancer patients, health care personnel, scientists and funding and regulatory bodies.

Inclusion Criteria:

• Female, aged 18 years or older
• Histologically or cytologically confirmed metastatic breast cancer
• FACIT-F subscale score < 34 (considered as cut-off for a diagnosis of relevant fatigue; a score < 30 is considered as severe fatigue [83])
• Eastern Cooperative Oncology Group (ECOG) grade 1 or 2
• Ability to physically and cognitively perform an active movement therapy
• Ability to provide informed consent as documented by signature
• Ability to read, write, and speak German, French, or Italian

Exclusion Criteria:

• Inability or contraindication that would prevent prolonged follow-up, or to undergo the investigated intervention or control intervention, in the opinion of the investigator
• Patients with psychiatric, addictive or any disorder that prevents the patient from adhering to the protocol requirements, in the opinion of the investigator
• Significant uncontrolled cardiac disease (e.g. unstable angina, recent myocardial infarction)
• Haemoglobin < 90 g/L