Stereotactic Body Radiation Therapy (SBRT) for Invasive Breast Cancer Patients Not Undergoing Definitive Surgery

Inclusion Criteria: * Age \>/= 18 * Biopsy proven invasive carcinoma of the breast * Clinical T1-T4 invasive carcinoma * Cancer is deemed unresectable with no possibility of future resection or the patient is a poor surgical candidate as determined following evaluation by a surgeon. * Women who are not post-menopausal should have a negative urine or serum pregnancy test. Women of childbearing potential must agree to adequate contraception for the duration of study participation. * Ability to understand and willingness to sign a written informed consent document * Life expectancy \> 6 months * Patient is to be treated at Stony Brook University Hospital Exclusion Criteria: * Women with a known pregnancy, positive serum pregnancy test, or currently breastfeeding as well as women of childbearing potential unwilling or unable to use an acceptable method of birth control (including abstinence or barrier method of birth control) to avoid pregnancy for the duration of the study. Should a woman become pregnant or suspect she is pregnant while participating in this study, she should inform her treating physician immediately. * Breast implant in the breast to be treated with SBRT * Insufficient breast imaging to judge clinical stage * Inability to receive study treatment planning and treatment secondary to body habitus * Inability to understand or unwillingness to sign a written consent document * Life expectancy \< 6 months * Children (\< 18 years of age) * Uncontrolled intercurrent illness including, but not limited to, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness or social situation that would limit compliance with study requirements