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 Exclusion Criteria: * Initial core biopsy showing invasive lobular cancer * Estrogen receptor and progesterone receptor negative tumor with clinical size \> 1 cm * Any Her 2+ breast cancer (immunohistochemistry 3+; or amplified by fluorescence in situ hybridization \[FISH\]) * Cancer in a patient with a known inherited susceptibility mutation in breast cancer (BRCA)1 or BRCA2 * Multicentric breast cancer (two foci of known cancer in the breast separated by greater than 5 cm, or in separate quadrants * Clinically or pathologically positive axillary lymph nodes * Any prior breast cancer * Prior breast radiation therapy