Inclusion Criteria:

- Written informed consent

- Female patients

- Histologically confirmed invasive breast cancer

- Primary tumor greater than 2cm diameter, measured by sonography

- N0-3 (any N if resectable) and no evidence of distant metastasis (M) (isolated
supraclavicular node involvement allowed)

- ER positive (intermediate and strong positive)

- HER2 positive (IHC3+ or FISH positive in case of IHC 2+)

- No evidence of metastasis (M0)

- No prior hormonal, chemotherapy or radiotherapy is allowed

- No breast operation other than biopsy to make diagnosis is allowed

- Postmenopausal women with ECOG Performance Status of 0 or 1

- Postmenopausal, as defined by any of the following:

- At least 55 years of age

- Under 55 years of age and amenorrheic for at least 12 months OR follicle-stimulating
hormone (FSH) values ≥ 30 IU/L and estradiol levels ≤ 20 IU/L

- Prior bilateral oophorectomy or prior radiation castration with amenorrhea for at
least 6 months

- Adequate hematopoietic, renal, hepatic function:

Exclusion Criteria:

- Patients who received hormonal, chemotherapy or radiotherapy for breast cancer

- Patients who underwent surgery for breast cancer

- Patients with bilateral invasive breast cancer

- Patients with inflammatory breast cancer (T4d)

- Patients without primary tumor (T0) Inability to perform [18F]FES PET imaging due to
physical inability, claustrophobia, or other mental illness.

- ER poor disease as defined locally (e.g: Allred score 1-3, H-score<100)

- Patients who have history of cancer other than in situ uterine cervix cancer or
non-melanotic skin cancer

- Chronic daily treatment with aspirin (>325mg/day) or clopidogrel (>75mg/day)

- Chronic daily treatment with corticosteroids (dose of >10mg /day ethylprednisolone
equivalent)

- Clinically significant cardiovascular disease: CVA/stroke (<6month prior to enroll),
MI (<6month prior to enroll), unstable angina, NYHA Grade II or greater congestive
heart failure, or serious cardiac arrhythmia requiring medication.

- Hormone replacement therapy within 4 weeks of starting treatment

- Known hypersensitivity to any of the study drugs including ditosylate monohydrate
salt

- Pregnant or nursing mother (if applicable)