Low-dose Oral Cyclophosphamide and Methotrexate Maintenance for Hormone Receptor-negative Early Breast Cancer

DISEASE CHARACTERISTICS: * Histologically confirmed stage I, II, or III breast cancer * T1-3, N0-2, M0 * Patients with sentinel node biopsy positive disease must have undergone axillary dissection * Tumor must be confined to the breast without detected metastases elsewhere * T4 disease with minimal dermal invasion allowed * No T4 disease with ulceration of skin, infiltration of skin (except pathologically minimal dermal involvement), peau d'orange, or inflammatory breast cancer * No bilateral breast cancer (except in situ carcinoma) or suspicious mass in opposite breast that has not been proven benign * No distant metastases * No skeletal pain of unknown cause, elevated alkaline phosphatase, or bone scan showing hot spots that cannot be ruled out as metastases by x-ray, MRI, and/or CT * Must have undergone prior total mastectomy OR breast-conserving procedure (e.g., lumpectomy, quadrantectomy, or partial mastectomy with negative margins) with radiotherapy planned * Patients must begin or have begun an approved induction chemotherapy regimen within 8 weeks after definitive surgery * Negative surgical margins * Axillary clearance with at least 6 lymph nodes examined OR negative sentinel node biopsy * Known HER2 status by immunohistochemistry or fluorescence in situ hybridization * Hormone receptor status: * Estrogen and progesterone receptor negative * Less than 10% positive tumor cells by immunohistochemistry PATIENT CHARACTERISTICS: Age: * No…