Zoledronate in Treating Osteopenia or Osteoporosis in Postmenopausal Women Receiving Letrozole for Stage I, Stage II, or Stage IIIA Primary Breast Cancer

DISEASE CHARACTERISTICS: * Diagnosis of localized breast cancer * Stage I-IIIA disease * Adequately treated breast cancer * No clinical or radiological evidence of recurrent or metastatic disease * Baseline total lumbar spine or femoral neck bone mineral density T-score \< -2.0 standard deviation (e.g., a patient with a T score of -2.1 is eligible) * Hormone-receptor status: * Estrogen receptor and/or progesterone receptor-positive breast cancer PATIENT CHARACTERISTICS: * Female * Postmenopausal, defined by 1 of the following criteria: * Age \> 55 years with cessation of menses * Age ≤ 55 years with spontaneous cessation of menses for \> 1 year * Age ≤ 55 years with spontaneous cessation of menses for ≤ 1 year, but amenorrheic (e.g., spontaneous or secondary to hysterectomy), AND has postmenopausal estradiol levels * Bilateral oophorectomy * ECOG performance status 0-2 * Life expectancy ≥ 5 years * WBC ≥ 3,000/mm³ OR granulocyte count ≥ 1,500/mm³ * Platelet count ≥ 100,000/mm³ * Alkaline phosphatase ≤ 3 times upper limit of normal (ULN) * AST ≤ 3 times ULN * Creatinine \< 2.0 mg/dL * Creatinine clearance ≥ 45 mL/min * No hypercalcemia (i.e., calcium level \> 1 mg/dL above ULN) OR hypocalcemia (i.e., calcium level \> 0.5 mg/dL below lower limit of normal) within the past 6 months * No other malignancy within the past 5 years except adequately treated basal cell or squamous cell skin cancer or carcinoma in situ of the cervix * No other nonmalignant systemic diseases, including any of the following: * Uncontrolled infection * Uncontrolled diabetes mellitus * Uncontrolled thyroid dysfunction * Disease affecting bone metabolism (hyperparathyroidism, hypercortisolism, Paget's disease, osteogenesis imperfecta) * Malabsorption syndrome * No uncontrolled seizure disorders associated with falls * No known hypersensitivity to zoledronate or other bisphosphonates, letrozole, calcium, or vitamin D * No concurrent active dental problems, including any of the following: * Infection of the teeth or jawbone (maxillary or mandibular) * Dental or fixture trauma * Prior or current diagnosis of osteonecrosis of the jaw * Exposed bone in the mouth * Slow healing after dental procedures * No contraindication to spine dual energy x-ray absorptiometry (DXA) as defined by any of the following: * History of surgery at the lumbosacral spine, with or without implantable devices * Scoliosis with a Cobb angle \> 15 degrees at the lumbar spine * Immobility, hyperostosis, or sclerotic changes at the lumbar spine, or evidence of sclerotic abdominal aorta sufficient to interfere with DXA scan * Disease of the spine that would preclude the proper acquisition of a lumbar spine DXA * No condition that would preclude study follow-up or compliance * No psychiatric illness that would preclude giving informed consent PRIOR CONCURRENT THERAPY: * More than 3 weeks since prior and no other concurrent oral bisphosphonates * No prior intravenous bisphosphonates * No prior aromatase inhibitor therapy * More than 6 months since prior anabolic steroids or growth hormone * More than 2 weeks since prior and no concurrent inhibitor of osteoclastic bone resorption (e.g., calcitonin, mithramycin, or gallium nitrate) * More than 30 days since prior systemic investigational drug and/or device * More than 7 days since prior topical investigational drug * More than 6 weeks since prior and no concurrent dental or jaw surgery (e.g., extraction, implants) * Concurrent short-term corticosteroid therapy allowed * No concurrent sodium fluoride, parathyroid hormone, or tibolone * No other concurrent investigational drug or device