Inclusion Criteria:

Eligibility Criteria

- Breast cancer diagnosis: Patients must have histologically confirmed adenocarcinoma
of the breast requiring comprehensive loco-regional irradiation that includes
treatment to the intact breast/chest wall, supraclavicular (SCV), infraclavicular
nodes (ICV), and internal mammary nodes (IMN).

- Patients must have pathologic T 1, 2, 3 or 4, N 1, 2, or 3 Stage II or III disease as
defined by the AJCC Staging System, 6th edition. Patients who do not undergo axillary
staging but are at risk for nodal involvement may also be treated.

- All patients must have left-sided breast cancer.

- Both men and women are eligible.

- Patients must be adults (18 years of age or older)

- For women of child-bearing age, effective contraception must be used. A written
statement must be obtained that the patient is not pregnant. If there is any question
of pregnancy at time of therapeutic RT or at time of each SPECT-CT scan, a pregnancy
test will be done to confirm the patient is not pregnant.

- Performance status should be 0-2 by ECOG criteria.

- Patients that have received prior RT may be enrolled on the present study if the new
breast lesion can be treated with no overlap of RT fields.

- Patients must be aware of the neoplastic nature of her/his disease.

- Patients must be informed of the investigational nature of this study and must sign
an informed consent in accordance with the Institutional Review Board (IRB) of the
University of Michigan and federal guidelines.

- Patients' blood tests should indicate they are able to tolerate radiotherapy. Tests
must be done within 28 days of registration:

CBC with differential and platelet count (Hemoglobin > 8.0 g/dl; wbc > 2000/mm3; absolute
neutrophil count > 1000/mm3; platelet count > 75,000/mm3.

Exclusion Criteria:

- Patients who are pregnant or are nursing are excluded.

- Pathologically node negative breast cancer unless treated with neo-adjuvant
chemotherapy.

- Performance status > 2 by ECOG criteria

- Patients who are unable to lie on their back and raise their arm above their head in
the treatment planning position for radiotherapy

- Patients with a clinically unstable medical condition

- Patients with a life-threatening disease state

- History or suspicion of serious life-threatening allergic reaction to Tc-99m imaging
agents.

- Patients that have had breast-conservation surgery with positive margins or any
patient with negative margins with a tumor positive for an extensive intraductal
component.

- Patients that are not able to use the ABC device.