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 withductal 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 notrequired)

• Patients undergoing primary systemic treatment (hormones or chemotherapy) as initialtreatment with neoadjuvant reducing tumor size

• Previous history of malignant disease does not preclude entry if the expectation ofrelapse-free survival at 10 years or greater

• Any factor included as exclusion criteria in the participating center's treatmentpolicy statement

• Additional exclusion criteria for University of California San Francisco (UCSF) (aslaid 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 inTreatment Policy under "HER2")

• Lymphovascular invasion

• High grade

• Tumors > 3 cm

• Node positive patients

• Prior chemotherapy or hormone therapy