Radiation Therapy in Treating Post-Menopausal Women With Early Stage Breast Cancer Undergoing Surgery

Inclusion Criteria

• •Core needle biopsy (e.g. Mammotome, core, stereotactic, ultrasound guided) showing invasive mammary cancer (with or without concomitant ductal carcinoma or lobular carcinoma in situ) or ductal carcinoma in situ; acceptable histologic types of invasive mammary cancer include ductal, tubular, mucinous, papillary, cribriform and "NOS" (not otherwise specified); invasive lobular cancer is excluded
• •Age \>= 50 years and postmenopausal with no menses for at least one year prior to study enrollment
• •Age \> 70 years with invasive breast cancer clinical size =\< 3 cm OR Age 50 - 70 years with invasive breast cancer clinical size =\< 1.5 cm OR Age \>= 50 years and postmenopausal with any grade ductal carcinoma in situ (DCIS) clinical extent =\< 1.5 cm (clinical tumor size will be determined by pre-operative breast imaging-mammography, ultrasound and/or magnetic resonance imaging; in cases of multiple measurements, the largest recorded single dimension will be used to determine eligibility)
• •Hormone receptor status
• •* Estrogen or progesterone receptor positive or
• •* Estrogen and progesterone receptor negative and clinical tumor size =\< 1.0 cm
• •Human epidermal growth factor receptor 2 (HER2)/neu negative on the core biopsy analysis defined as 0 or 1+ by immunohistochemistry or not amplified by fluorescent in situ hybridization analysis
• •Tumor \>= 0.5 cm from skin as defined by breast ultrasound
• •Unicentric tumor
• •Axillary lymph nodes negative by pre-operative physical examination in all cases and pathologic examination from surgery for invasive disease
• •Negative surgical margins, defined as no margin-labeling ink on tumor cells from margin evaluation