Stage 1-3

The goal of this interventional study is to determine pathological complete response (pCR) after neoadjuvant chemotherapy (NAC) and Efti treatment. This is a prospective single arm interventional trial in patients with early-stage HR+/HER2 -ve breast cancer (Stage I-III) who are eligible for neoadjuvant chemotherapy (NAC). Enrolled patients will be treated with single agent efti for 3 weeks and then start NAC in combination with efti. There are 2 standard NAC usually used and will be determined by treating physician prior to starting on this trial.