Inclusion Criteria

Inclusion Criteria

1. Histologic Documentation:

- Patients will have histologically confirmed Unicentric Stage I (T1 N0 M0)
invasive ductal breast cancer.

- Histologically negative tumor margin 2 mm or more from any inked edges, or no
tumor in a re-excision specimen or final shaved specimen.

- Tubular, mucinous and medullary variant histologies of infiltrating ductal
carcinoma are permitted.

- Low-grade DCIS (I and II) of 2 cm or less with histologically negative margins
of at least 2 mm margins (or a negative re-excision) are permitted.

- Women age 70 years or older with T1 invasive ductal carcinoma which are
estrogen-receptor positive (ER+) with clinically negative axillary nodes who do
not undergo surgical lymph node evaluation are also eligible if patient will
take hormonal therapy.

- Patients with T1N0 (i+) tumors on sentinel lymph node mapping or dissection
(i.e. is tumor deposit is 0.2mm or less, regardless of whether the deposit is
detected by IHC or H&E staining) will also be eligible, provided that completion
axillary dissection has been performed to confirm N0 status.

- In the case where invasive cancer is present, the invasive cancer's pathology
will be used regardless if DCIS is also present.

2. Prior Treatment: Patient may have been treated with adjuvant chemotherapy. Patients
may be on adjuvant hormonal therapy or begin hormonal therapy following XRT at the
discretion of the medical oncologist.

Radiation therapy should begin within:

- 4-12 weeks from definitive surgical procedure

- 2-6 weeks after chemotherapy, if chemotherapy given first

- Radiation cannot be delivered concurrently with chemotherapy.

3. Age >= 18 years of age

4. ECOG Performance Status 0-2.

5. Signed Informed Consent

Exclusion Criteria

The following guidelines are to assist physicians in selecting patients for whom protocol
therapy is safe and appropriate. Physicians should recognize that the following may
seriously increase the risk to the patient entering this protocol. Patients who meet the
following criteria should not be entered in this study:

1a Multicentric IDC of the breast defined as discontiguous tumors separated by at least 5
cm of uninvolved tissue; alternatively, discontiguous tumors that are clinically or
mammographically within separate breast quadrants or subareolar central region.

1. b Multifocal IDC of the breast, defined as discontiguous discrete foci of invasive
carcinoma, separated by uninvolved intervening tissue, but within an overall span of
5cm, or within the same breast quadrant or subareolar central region.

2. Tumor > 2.0 cm, nodal involvement on H&E staining, or metastatic involvement

3. Histological evidence of:

1. Lymphovascular invasion: as defined by a tumor embolus present in an
endothelial-lined space; cases with tumor emboli present in a space not lined by
endothelial cells but otherwise very suspicious for an angiolymphatic space were
also considered ineligible.

2. EIC (Extensive Intraductal Component): defined as the presence of intraductal
carcinoma both within the primary infiltrating ductal tumor (comprising at least
25% of the tumor area) and intraductal carcinoma present clearly beyond the
edges of the invasive tumor, or as a predominantly intraductal tumor with one or
more areas of focal invasion 7, 55.

3. Invasive Lobular Carcinoma

4. Infiltrating carcinoma with mixed ductal and lobular features: cases with
ambiguous or mixed histologic features that showed positive E-cadherin staining
throughout the tumor by immunohistochemistry were classified as ductal type and
considered eligible 56, 57.

5. Infiltrating papillary carcinoma

6. Margins: In-situ or invasive carcinoma present less than 2 mm from the inked
resection margin.

4. History of cosmetic or reconstructive breast surgery

5. Psychiatric illness which would prevent the patient from giving informed consent.
Medical condition such as uncontrolled infection (including HIV), uncontrolled
diabetes mellitus or connective tissue diseases (lupus, systemic sclerosis or other
collagen vascular diseases) which, in the opinion of the treating physician, would
make this protocol unreasonably hazardous for the patient.

6. Patients with a "currently active" second malignancy other than non-melanoma skin
cancers. Patients are not considered to have a "currently active" malignancy if they
have completed therapy and considered by their physician to be at less than 5% risk
of relapse within three years.

7. Patients with diffuse (> 1 quadrant or > 5cm) suspicious microcalcifications

8. Women who are pregnant.