Participants with early breast cancer currently undergoing treatment (either chemotherapy and targeted HER2 therapy OR targeted HER2 therapy alone) will be observed.

Participants with early breast cancer who have completed treatment and are in disease-free survival (i.e. no longer receiving loco-regional treatment, chemotherapy or targeted HER2 therapy; participants may still be receiving hormone therapy) will be observed.

Participants receiving treatment for metastatic breast cancer will be observed.

The WPAI is a patient-reported measure which assesses the effect of general health and symptom severity on work productivity and regular activities. The General Health questionnaire asks participants to estimate the number of hours missed from work due to reasons related and unrelated to their health problems, as well as the total number of hours worked in the preceding 7-day period. The percentage of participants reporting that they were employed (working for pay) was assessed at baseline along with absenteeism (work time missed), presenteeism (impairment at work/reduced on-the-job effectiveness), work productivity loss (overall work impairment/absenteeism plus presenteeism), and activity Impairment. The score range for the scales of the WPAI is between 0 (no effect) to 100% (max effect).

EQ-5D-5L is a standardized, participant-rated instrument for use as a measure of health outcomes. The EQ 5D-5L includes 2 components: the EQ-5D-5L descriptive system and the visual analogue scale (VAS). The EQ-5D-5L descriptive system provides a profile of the participant's health state in 5 dimensions (mobility, self-care, usual activities, pain/discomfort, and anxiety/depression). For each dimension, the participant is instructed to choose one of 5 levels that best describes their health on that day: "no problem" (1), "slight" (2), "moderate" (3), "severe" (4), or "unable/extreme" (5). The VAS is the participant's rating of their health on a scale of 0 "worst health you can imagine" to 100 "best health you can imagine".