Tumor Bed Dose Delivery Using A Breast Specific Radiosurgery Device, The Gammapod: (A Clinical Feasibility Study)

Inclusion Criteria:

* The patient must sign consent for study participation.
* The patient must be female and have a diagnosis of an invasive breast cancer that was treated surgically by a partial mastectomy.
* The surgical cavity is clearly visible on CT images and delineated by surgical clips
* We have at least one of the following clinico-pathological factors:

  * Age ≥18 and ≤ 50 years
  * Lymphovascular space invasion positive
  * Grade III histology
  * More than 2 close resection margins ( \> 0 mm to ≤ 2 mm)
  * 1 close resection margin and extensive in-situ component (EIC)
  * Non-hormone sensitive breast cancer (ER and PR negative)
* Surgical margins are negative for invasive or non-invasive breast cancer.
* The volume of the TB PTV is less than 25% of the whole breast volume which is a criteria used for partial breast alone trials (NSABP B-39). The absolute value of the boost PTV is ≤ 100 cc
* Multifocal disease is allowed if it was removed by a single lumpectomy resection and the patient remained a candidate for breast conservation.
* Women of childbearing potential must use an effective contraceptive method such as condom/diaphragm and spermicidal foam, intrauterine device (IUD), or prescription birth control pills. For these women of childbearing potential, a negative pregnancy test must be obtained prior to study enrollment or waiver signed.
* The patient must weigh less than 150Kg (330lb), which is the limit of the imaging couch.
* The patient must be less than 6'6" in height.
* The patient must feel comfortable in the prone position.

Exclusion Criteria:

* Patients with proven multi-centric carcinoma (tumors in different quadrants of the breast or tumor separated by at least 4 cm).
* Prior radiation therapy above the umbilicus
* Unable to fit into the immobilization breast cup with an adequate seal
* Male gender.
* Patient cannot comfortably be set up in the prone position (i.e. physical disability)
* Unable to fit into the breast immobilization device due to breast size or other anatomical reason.
* Mastectomy is the surgery performed.
* Patient has received prior radiotherapy to the involved breast.
* Regional nodal irradiation is part of the treatment plan.
* Tumor bed is less than 5 mm from the skin surface.
* Patients with skin involvement, regardless of tumor size.
* Patients with connective tissue disorders specifically systemic lupus erythematosis, scleroderma, or dermatomyositis.
* Patients with psychiatric or addictive disorders as indicated in their medical histories that would preclude obtaining informed consent.
* Patients who are pregnant or lactating due to potential exposure of the fetus to RT and unknown effects of RT to lactating females.