Inclusion Criteria: - Histologically confirmed invasive breast cancer meeting the following criteria: - 1-3 node-positive disease (pN1mi, pN1a, pN1b, or pN1c) by sentinel node biopsy or axillary lymph node dissection - Positive estrogen receptor (ER) and/or progesterone receptor (PR) status according to American Society of Clinical Research/College of American Pathologists (ASCO/CAP) guidelines - Considered positive if >= 1% positive tumor nuclei in the sample on testing in the presence of expected reactivity of internal [normal epithelial elements] and external controls - Negative HER-2 as determined by IHC or non-amplified fluorescence in situ hybridization (FISH) for screening - If HER2 is 2+ by IHC, FISH must be performed and must not be positive (must be a ratio of =< 2.2) - If IHC is 0 or 1+ by institutional standards, FISH is not required - Patients with FISH in the indeterminate range (a ratio of 1.8 to 2.2) allowed provided they are not planning to receive treatment with trastuzumab - Recurrence Score (RS) by Oncotype DX =< 25 - Submission of tissue (paraffin block from primary tumor, positive and negative lymph node block) from surgery required - Prior diagnosis of DCIS allowed provided it was treated with mastectomy alone (no therapeutic radiation or endocrine therapy) - No inflammatory breast cancer or metastatic disease - Must have had breast-conserving surgery with planned radiotherapy or total mastectomy (with or without planned post mastectomy radiation) with clear margins within the past 28-84 days - Menopausal status: pre- or post-menopausal - Zubrod performance status 0-2 - Not pregnant or nursing - Fertile patients must use an effective non-hormonal contraception method while on treatment and for ≥ 3 months after completion of protocol treatment - No other prior malignancy except adequately treated basal cell or squamous cell skin cancer; in situ cervical cancer; adequately treated stage 0, I, or II cancer from which the patient is currently in complete remission; or any other cancer from which the patient has been disease-free for the past 5 years - LVEF ≥ 50% if an anthracycline-based regimen is planned - Patients randomized to chemotherapy may also co-enroll in Phase III trials that compare chemotherapies - No prior chemotherapy or endocrine therapy for breast cancer - No prior preventive tamoxifen or raloxifene - No prior therapeutic breast radiotherapy - Not requiring concurrent chronic treatment with systemic steroids or other immunosuppressive agents - Patients randomized to either arm may also co-enroll in Phase III trials that compare local therapies or compare systemic therapies (not including chemotherapy)