Single Dose Partial Breast Radiotherapy

This study will assess the safety of partial breast radiosurgery as measured by the incidence
of acute toxicity and wound healing complications in three dose cohorts.

Patients will be enrolled in cohorts of 8 patients starting at dose level 1 (15 Gy). If 2 or
more dose limiting toxicities (DLTs) are observed at dose level 1, the trial will be stopped
for evaluation and consideration of revision. If at most one DLT is observed then escalation
continues to the next dose level. The cohorts will escalate by 3Gy up to 21 Gy of
irradiation.

Inclusion Criteria:

- Women with a biopsy proven diagnosis of low/intermediate grade ductal carcinoma in
situ or invasive ductal (or other favorable histology) carcinoma of the breast

- Breast preservation candidates (no prior breast or nodal radiotherapy, no imaging
evidence of multicentric or multifocal disease, no pregnant women, and no comorbid
conditions precluding surgery)

- Clinical T1N0M0

- 55 years of age or older

- Estrogen receptor (ER) positive,

- No evidence of lymphovascular space invasion on initial biopsy

- Not pregnant. If not post-menopausal must adhere to birth control measures

- White blood cell count > 3000, Hemoglobin > 9, platelets >100000

- Must be eligible for MRI on initial evaluation and GFR at least 60 ml/min

Exclusion Criteria:

- Neoadjuvant chemotherapy

- Breast implants

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

- Patients unable to receive study treatment planning secondary to body habitus or
inability to lie flat on the stomach at length

- HER-2/neu positive

- Positive serum pregnancy test