Breast cancer is the most frequently occurring cancer, assuming that it accounts for 29% of all new cancers in women (European Cancer Information System). The number of long-term survivors is increasing rapidly due to improving accuracy of the detecting methods, the early diagnosis and advances in cancer treatment.

The International Consortium for Health Outcomes Measurement Initiative described upper limb (UL) function as the health outcome that matters most for breast cancer survivors (BCS). 50% of BCS at 6 months post-radiotherapy suffer from of decreased UL function, i.e. difficulties in performing activities of daily living with the upper limb. Patients experiencing UL dysfunctions and other problems are less likely to be physically active. Given that physical inactivity is associated with an increased risk of mortality after breast cancer, taking away the barriers to physical activity (e.g. UL dysfunctions) is very important. Identifying these factors contributing to chronic UL dysfunction is important in terms of identifying targets for prospective evaluation and specific treatment approaches at specific time points during breast cancer treatment.

This study aims to find reliable and valid assessment methods for the prognostic factors and upper limb function itself in a small group of BCS and healthy volunteers.

Inclusion Criteria for breast cancer patients

• Patients scheduled for surgery (mastectomy or breast conserving surgery; in combination with axillary lymph node dissection or sentinel node biopsy) for unilateral primary breast cancer or patients with oligometastatic breast cancer.
• Patients who receive adjuvant radiotherapy .
• Patients with a cognitive and language functioning enabling coherent Dutch communication between the examiner and the participant
• Patients who can comply with the protocol at baseline assessment and willing to provide written informed consent

Inclusion criteria healthy volunteers

• Healthy women and men(quickDASH<15) age- and gender-matched with a breast cancer patient from the main study
• Volunteers who can comply with the protocol at baseline assessment and willing to provide written informed consent

Exclusion Criteria breast cancer patients

• BCS with widespread distance metastases, previous breast surgery, or planned bilateral surgery
• And/or with a diagnosis of a neurological or rheumatological condition, diabetes,
• And/or BCS who are not available the entire duration of the study

Exclusion Criteria healthy volunteers

• History of breast cancer
• Patients with a diagnosis of neurological or rheumatological condition, diabetes