A Cochrane review of randomized trials shows no difference in overall survival between surgery and primary endocrine therapy (PET) in older women with operable primary breast cancer. Most of these trials were small and unselected for estrogen receptor (ER) status. Evidence exists showing a significant correlation between the degree of ER-positivity and response and outcome in patients receiving PET. Although surgery remains the treatment of choice, patients with ER-rich tumors tend to do equally well on PET. When deciding optimal therapies, co-morbidities and frailty (which impact on the likelihood of death due to competing causes), patient choice, agent of choice (notably the third-generation aromatase inhibitors) and biology (more than just being ER-positive) should all be taken into account.