Inclusion Criteria:

- Signed informed consent

- Female, 18 years or older

- Histologically confirmed invasive breast cancer

- Bone metastases

- ECOG Performance Status of 0 to 2

- Life expectancy of more than 3 months

- Subject must have adequate organ function:

- Cr ≤ 3 mg/dL (265 µmol/L)，

- CrCl (Cockcroft & Gault) ≥ 30 mL/min，

- Ca2+ > 8.0 mg/dL (2.0 mmol/L) and ≤ 12 mg/dL (3.0 mmol/L)

- Negative serum pregnancy test for women with childbearing potential

- Good conditions for infusion and willing to undergo phlebotomy during the whole study

- Have ceased anti-tumor treatment including chemotherapy, endocrinotherapy and
bio-targeted therapy for over 28 days

Exclusion Criteria:

- Pregnant or lactating females

- History of other malignancy. However, subjects who have been disease-free for 5
years, or subjects with a history of completely resected non-melanoma skin cancer or
successfully treated in situ carcinoma are eligible.

- Concurrent disease or condition that would make the subject inappropriate for study
participation, or any serious medical disorder that would interfere with the
subject's safety

- Active or uncontrolled infection

- Current active dental problems including infection of the teeth or jawbone (maxilla
or mandible); dental or fixture trauma; or a current or prior diagnosis of
osteonecrosis of the jaw (ONJ); or exposed bone in the mouth; or slow healing after
dental procedures

- Recent (within 6 weeks of Randomization) or planned dental or jaw surgery (e.g.
extraction, implants)

- Known history of uncontrolled or symptomatic angina, arrhythmias, or congestive heart
failure

- Concomitant with liver, brain or symptomatic lung metastases (symptoms such as
hemoptysis, severe cough and shortness of breath)

- Accepted radiotherapy for solitary bone disease within 30 days before study

- Previous treatment with other bisphosphonates or radionuclides within one month
before study

- Known hypersensitivity to bisphosphonates

- History of treatment with calcitonin, gallium nitrate or mithracin within 14 days
before study.