This is the first Canadian study to describe real-world treatment patterns/sequencing, effectiveness and safety for postmenopausal HR+ HER2- advanced breast cancer patients. This registry incorporates an observational prospective cohort design and will enroll 320 postmenopausal HR+ HER2- advanced breast cancer women that have been previously exposed to non-steroidal aromatase inhibitor (NSAI) therapy being treated with endocrine therapy (ET) or ET in combination with targeted therapy (TT).