Newly diagnosed post-menopausal women with clinical stage II-III, HR+HER2- breast cancer are eligible for this randomized trial that will be concurrently open at five US academic institutions. Patients receiving 4 months of standard neoadjuvant hormonal therapy with letrozole are randomly assigned to one of 4 arms of the trial testing focal hypo-fractionated RT alone or with immunotherapy combinations. 

Patients will be on the study for a total of 5 months. This includes 4 months on active study intervention with breast surgery at week 16, and a one month follow-up period after surgery.