The ORR was 35.5% (11/31) at 8 weeks and 51.7% (15/29) at 16 weeks in patients with evaluable response….This is the first prospective study of neoadjuvant dalpiciclib in patients with HR positive, HER2-negative breast cancer. The findings suggest the promising tumor response to neoadjuvant dalpiciclib plus letrozole in postmenopausal patients with HR-positive, HER2-negative breast cancer, with a manageable safety profile.