Intensity Modulated Radiation Therapy or 3-Dimensional Conformal Radiation Therapy in Treating Patients With Lymph-Node Positive Breast Cancer

Inclusion Criteria: * Pathologically proven diagnosis of breast cancer * Patients that receive neoadjuvant systemic therapy (chemotherapy, anti-HER2 therapy, or endocrine therapy) are eligible * History/physical examination within 60 days prior to study entry * Patients who have undergone either a lumpectomy or mastectomy are eligible * Patients that have undergone any type of breast reconstruction are eligible * The interval between the date of last surgery or chemotherapy and registration must be =\< 84 days * Women of childbearing potential must have a negative urine or serum pregnancy test within 14 days of start of radiation therapy * Women of childbearing potential must be non-pregnant and non-lactating and willing to use medically acceptable form of contraception during radiation therapy * Patients must provide study specific informed consent prior to study entry Exclusion Criteria: * Clinical or radiologic evidence of distant metastases * Patients with known unresected disease in the axillary apex or supraclavicular fossa * Prior invasive or in-situ carcinoma of the breast (prior lobular breast carcinoma in situ \[LCIS\] is eligible) * Prior surgery to the ipsilateral shoulder for any condition * Baseline impaired mobility of the ipsilateral shoulder from a condition not related to the breast cancer surgery as determined by the treating physician * Non-epithelial breast malignancies such as sarcoma/lymphoma * Prior radiotherapy to the breast or prior radiation to t…