Zoledronate in Preventing Bone Loss in Postmenopausal Women Who Are Receiving Letrozole for Stage I, Stage II, or Stage IIIA Breast Cancer

DISEASE CHARACTERISTICS: * Diagnosis of breast cancer * Stage I, II, or IIIA disease * Completed ≤ 6 years of adjuvant tamoxifen therapy * Total baseline lumbar spine or femoral neck bone mineral density T-score below -2.0 standard deviation (e.g., a patient with a T-score of -2.1 in ineligible; a patient with a T-score of -1.9 is eligible) * No clinical or radiological evidence of recurrent or metastatic disease * Hormone receptor status: * Estrogen receptor- and/or progesterone receptor-positive PATIENT CHARACTERISTICS: Age * Postmenopausal Sex * Female Menopausal status * Postmenopausal, defined by 1 of the following: * Over 55 years of age with cessation of menses * 55 years of age and under with spontaneous cessation of menses for \> 1 year * 55 years of age and under with spontaneous cessation of menses for ≤ 1 year, but amenorrheic (e.g., spontaneous or secondary to hysterectomy) with postmenopausal estradiol levels (\< 5 ng/dL) * Undergone bilateral oophorectomy Performance status * ECOG 0-2 Life expectancy * At least 5 years Hematopoietic * WBC ≥ 3,000/mm\^3 * Platelet count ≥ 100,000/mm\^3 Hepatic * Alkaline phosphatase ≤ 3 times upper limit of normal (ULN) * AST ≤ 3 times ULN Renal * Creatinine \< 2.0 mg/dL * No hypercalcemia (i.e., calcium \> 1 mg/dL above ULN within the past 6 months) * No hypocalcemia (i.e., calcium \> 0.5 mg/dL below lower limit of normal within the past 6 months) Other * No uncontrolled infection * No uncontrolled diabetes mellitus * No uncontrolled thyroid dysfunction * No disease affecting bone metabolism (e.g., hyperparathyroidism, hypercortisolism, Paget's disease, or osteogenesis imperfecta) * No malabsorption syndrome * No uncontrolled seizure disorder associated with falls * No known hypersensitivity to zoledronate or other bisphosphonates, letrozole, calcium, or cholecalciferol (vitamin D) * No mental illness that would preclude giving informed consent * 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 non-malignant systemic disease * No clinical or radiologic evidence of existing fracture in the lumbar spine and/or total hip * No history of fracture with low intensity or not associated with trauma * No contraindication to spinal dual energy x-ray absorptiometry (DEXA) due to any of the following: * History of surgery at the lumbosacral spine, with or without implantable devices * Scoliosis with a Cobb angle \> 15° at the lumbar spine * Immobility, hyperostosis, or sclerotic changes at the lumbar spine * Evidence of sufficient sclerotic abdominal aorta that would interfere with DEXA scan * Any disease of the spine that would preclude proper acquisition of a lumbar spine DEXA * Considered reliable PRIOR CONCURRENT THERAPY: Biologic therapy * Not specified Chemotherapy * No concurrent chemotherapy Endocrine therapy * See Disease Characteristics * Prior parathyroid hormone allowed provided it was not administered for \> 1 week * More than 6 months since prior anabolic steroids or growth hormone * More than 12 months since prior endocrine therapy (including estrogen) except for the following: * Tamoxifen * Insulin * Oral hypoglycemics * Thyroid hormone * Steroid inhalers * More than 12 months since prior systemic corticosteroids except short-term corticosteroids to prevent or treat chemotherapy-induced nausea and vomiting or acute respiratory illness * Concurrent short-term corticosteroids allowed * No other concurrent hormonal therapy * No concurrent parathyroid hormone Radiotherapy * Not specified Surgery * Not specified Other * Prior systemic sodium fluoride allowed provided it was not administered for \> 3 months within the past 2 years * More than 3 weeks since prior oral bisphosphonates * More than 2 weeks since prior and no concurrent drugs known to affect the skeleton (e.g., calcitonin, mithramycin, or gallium nitrate) * More than 30 days since prior systemic investigational drugs and/or devices * More than 7 days since prior topical investigational drugs * No prior IV bisphosphonates * No prior aromatase inhibitor therapy * No concurrent calcitonin, sodium fluoride, or Tibolone * No other concurrent anticancer therapy * No other concurrent bisphosphonates * No other concurrent investigational drugs or devices