Study of Stereotactic Radiotherapy for Breast Cancer

This is a single arm phase II study design, evaluating the pathologic response (primary
endpoint) as well as toxicity, cosmetic outcome, quality of life, and translational
correlates (secondary endpoints) to pre-operative stereotactic body radiotherapy (SBRT) to
intact breast tumors in patients with hormone-receptor positive early stage breast cancer.

Inclusion Criteria:

- Female sex

- Age > or = to 50 years of age

- Invasive ductal carcinoma

- Clinically and radiographically T1 tumor

- Clinically node negative

- Clearly demarcated tumor on magnetic resonance imaging (MRI), as determined by
treating physician (MRI may be done after enrollment if not done prior)

- Planning breast conserving surgery including sentinel node biopsy

- ≥10% expression of ER and/or PR

- HER2- using the current College of American Pathologists guidelines

- Post-menopausal

- Willing and able to provide informed consent

Exclusion Criteria:

- Medical conditions that may increase risk for poor cosmetic outcome (i.e. Lupus,
rheumatoid arthritis, scleroderma

- Pure DCIS without invasive cancer

- Patients who have received or will be receiving neoadjuvant systemic therapy,
endocrine therapy, or targeted agents

- Breast implant in the involved breast unless the implant will be removed prior to
initiation of study treatment

- Positive pregnancy test

- Subjects without placement of a biopsy clip at the diagnostic procedure who are
unwilling to undergo clip placement.

- Unable to meet dosimetric constraints due to tumor location and/or patient anatomy

- Planning mastectomy

- Unable to tolerate prone positioning