RecruitingBehavioural interventionSDM POSSIBLE: A Breast Cancer Treatment Decision Aid for Women 70+ With Low-Risk Stage I Breast CancersInvestigators aim to conduct a type 1 hybrid effectiveness-implementation surgeon-level cluster randomized clinical trial (RCT) of a multi-level intervention, a shared decision making training for surgeons plus patient decision aid vs. usual care (UC), at 7 large health systems across the U.S. to learn the intervention's effectiveness. Decision aids will be mailed and sent via patient portal and/or via email (when portal/email addresses are available) to patients before their first surgical encounter. The central hypothesis is that the novel intervention will be a key resource to support shared decision making leading to higher quality treatment decisions and as result improved care and outcomes.