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 syst…