Inclusion Criteria:

1. Informed Consent. Each eligible patient must willingly give written consent after
being informed of the procedures to be followed, the experimental nature of the
therapy, alternatives, potential benefits, side effects, risks, and discomforts.

2. Histology. Patients must have biopsy-proven invasive ductal or lobular carcinoma of
the breast.

3. Female, age ≥ 48 years.

4. Clinically and/or histologically negative axillary lymph nodes.

5. No imaging or clinical findings that indicate metastatic disease.

6. Procedure deemed appropriate based upon factors such as breast size by the treating
surgeon and radiation oncologist.

Exclusion Criteria:

1. Male sex

2. Age < 48

3. Non-epithelial breast malignancies such as sarcoma, lymphoma, or metastatic breast
cancer

4. Pregnancy or lactation

5. Serious psychiatric or addictive disorders

6. More than one obvious cancer in the same breast as diagnosed by clinical examination,
mammography, ultrasonography, and/or CE-MRI.

7. Bilateral breast cancer at the time of diagnosis, unless agreed upon by the surgeon
and radiation oncologist.

8. Ipsilateral breast with a previous cancer and/or irradiation.

9. Extensive Intraductal Component (DCIS ≥ 25% of the tumor).

10. Patients presenting with gross nodal disease considered to be clinically malignant by
scanning or proven cytologically or by sentinel node biopsy will be cancelled.

11. Previous history of malignant disease does not preclude entry if the expectation of
relapse-free survival at 10 years is 90% or greater.

12. Lymphovascular invasion on needle biopsy.

13. Patients undergoing primary medical treatment (hormones or chemotherapy) as initial
treatment with intent to reduce tumor size.