The purpose of this study is to evaluate whether treatment to the axilla (area under the arm) can be safely minimized by omitting axillary surgery and full axillary radiation therapy and replacing it with radiation therapy to the breast and lower axilla.

• Patients will have undergone conservative breast surgery without axillary dissection prior to enrollment in this study.
• Patients will receive radiation therapy to the breast, including the lowest axillary lymph nodes, over a period of 6 1/2 weeks.
• No radiation will be specifically directed toward the upper axilla or supraclavicular lymph nodes.
• Patients will also receive 5 years of tamoxifen or another type of hormone therapy determined by the medical oncologist.
• Follow-up visits will occur every 6 months and mammograms every 12 months.

Inclusion Criteria:

• Patients must have clinical stage I or II breast cancer, clinically uninvolved axillary nodes.
• Patients must be 55 years or older.
• Patients must undergo total excision of the primary invasive tumor
• Final pathologic margin status must be negative
• Only estrogen receptor (ER) or progesterone receptor (PR) positive tumors will be permitted

Exclusion Criteria:

• Prior history of malignancy, except for non-melanoma skin cancers and carcinoma in situ fo the cervix