Node Negative, Invasive Breast Cancer Single Fraction IOERT

Inclusion Criteria:

Patient agrees to breast conservation therapy (segmental resection, partial mastectomy, and radiation therapy) as the treatment for their breast cancer
Patient agrees to evaluation of the axilla with sentinel lymph node biopsy
Post-menopausal women age > 60, defined as women who have experienced no menstrual period in the past 12 months.
BRCA1 and 2 gene mutation negative, if tested. [genetic testing is NOT required based upon personal or family history]
Unifocal (unicentric), invasive ductal carcinoma or favorable sub-types (mucinous, tubular, colloid) < 2.0 cm in diameter, primary T-stage of T1 (AJCC criteria)
Grade 1, 2 acceptable
Associated LCIS is allowed
Estrogen receptor (ER) status of positive
Negative margins at ink on gross pathologic examination
Patient is node-negative, defined as N0 (i-) or N0 (i+)
Patient must be deemed functionally and mentally competent to understand and sign the informed consent

Exclusion Criteria:

Prior breast malignancy or other malignancy if metastatic, or with expected survival of < 5 years
Immuno-compromised status
Pregnancy
Women with an active connective tissue disorder (i.e. scleroderma, lupus and others)
Breast cancer that involves the skin or chest wall, locally advanced breast cancer
Pure DCIS, all grades
Invasive lobular carcinoma
Evidence of lymphovascular invasion (LVI)
Invasive carcinoma with extensive intraductal component (EIC)
Neoadjuvant chemotherapy indicated
Patients with 1 or more positive lymph node determined during surgery with sentinel node and/or axillary dissection
Not eligible for breast conserving management, i.e., prior whole breast radiation therapy
Estrogen receptor negative
Her2 positive
Grade 3