Intraoperative Radiation Therapy in Treating Patients With Breast Cancer Undergoing Breast-Conserving Surgery

Inclusion Criteria:

Suitable for breast conserving surgery
T1 and T2 (< 3.5 cm), N0, M0

Exclusion Criteria:

Axillary lymph node positive breast cancer
Tumor size > 3.5 cm
Extensive intraductal component (EIC >= 25% of the lumpectomy specimen involved with ductal carcinoma in situ), as assessed on surgical pathologic lumpectomy specimen
Multicentric cancer in the same breast as diagnosed by clinical examination, mammography, ultrasound; magnetic resonance imaging (MRI) or pathologic assessment, not amenable to excision with negative margins with a single lumpectomy
Inability to assess pathologic margin status
Synchronous bilateral breast cancer at the time of diagnosis
Ipsilateral breast had a previous cancer and/or prior in-field radiation
Patients known to have BRCA1/2 gene mutations (testing for gene mutations is not required)
Patients undergoing primary systemic treatment (hormones or chemotherapy) as initial treatment with neoadjuvant reducing tumor size
Previous history of malignant disease does not preclude entry if the expectation of relapse-free survival at 10 years or greater
Any factor included as exclusion criteria in the participating center's treatment policy statement

Additional exclusion criteria for University of California San Francisco (UCSF) (as laid out in the Treatment Policy):

Patients under the age of 50
Estrogen receptor negative (as defined in Treatment Policy under "Pathology")
Human epidermal growth factor receptor 2 (HER2) positive (as defined in Treatment Policy under "HER2")
Lymphovascular invasion
High grade
Tumors > 3 cm
Node positive patients
Prior chemotherapy or hormone therapy