Patients who were resistant to letrozole will be randomized to receive cyclophosphamide alone or letrozole plus cyclophosphamide. Patients in this arm will receive cyclophosphamide 50 mg daily.

Patients who were resistant to letrozole will be randomized to receive cyclophosphamide alone or letrozole plus cyclophosphamide. Patients in the this will receive cyclophosphamide 50 mg daily plus letrozole 2.5 mg daily.

Patients who haven't received letrozole hormonotherapy will be randomized to receive letrozole plus cyclophosphamide or letrozole alone. Patients in this arm will receive cyclophosphamide 50 mg daily plus letrozole 2.5 mg daily.

Patients who haven't received letrozole hormonotherapy will be randomized to receive letrozole plus cyclophosphamide or letrozole alone. Patients in this arm will receive letrozole 2.5 mg daily.

Time from the randomization date to the start of disease progression or subject death from any cause (progression assessed by investigator using Response Evaluation Criteria in Solid Tumors 1.1for elderly metastatic breast cancer subjects).

Assessment based on Adverse Events (AEs) , Serious Adverse Events (SAEs), laboratory abnormalities in subjects .