Neoadjuvant Lenvatinib Combined With Letrozole in Hormone Receptor Positive Breast Cancer

Inclusion Criteria: * Female, age ≥ 18 years. * Histologic or cytologic diagnosis of breast carcinoma. * Part A: T1-4 breast cancer with measurable primary breast tumor, defined as palpable tumor with both diameters 2.0cm or greater as measured by caliper. Newly diagnosed metastatic patients with measurable primary breast tumor ≥2cm are eligible provided that there are plans for toilet mastectomy after completing 14 weeks of pre-operative drug therapy. Patients must not have received prior chemotherapy or hormonal therapy for the treatment of the current breast cancer. * Part B: Patients with metastatic breast cancer with measurable tumor by RECIST criteria.Patients previously treated with letrozole are eligible if they progressed on letrozole ≥1 year after adjuvant treatment, or ≥ 6 months in the metastatic setting. * ECOG 0-1. * Estimated life expectancy of at least 12 weeks. * Adequate organ function including the following: * Bone marrow: * Absolute neutrophil (segmented and bands) count (ANC) ≥ 1.5 x 109/L * Platelets ≥ 100 x 109/L * Hepatic: * Bilirubin ≤ 1.5 x upper limit of normal (ULN), * ALT or AST ≤ 2.5x ULN, (or ≤5 X with liver metastases) * Renal: Creatinine ≤ 1.5x ULN • Post-menopausal women. Post-menopausal status is defined either by * Age ≥ 60 years and one year or more of amenorrhea * Age \< 60 years and one year or more of amenorrhea (in the absence of ovarian suppression) and with estradiol and FSH levels consistent with menopause, \*Tre…