This study will evaluate the safety/efficacy of zoledronic acid when given by intravenous infusion every 4 weeks in addition to letrozole as endocrine therapy in postmenopausal patients with hormone responsive breast cancer

Open-label, multicenter, randomized phase II trial over approx 6.5 months of neoadjuvant treatment with letrozole with or without zoledronic acid in postmenopausal patients with primary breast cancer. A total of approximately 850 patients were originally planned to be enrolled; primary study endpoint was the objective response rate (according to modified RECIST criteria) after 6 months of treatment. After the core study, patients willing to participate were followed-up for further 5 years.

Inclusion criteria:

• Postmenopausal women with primary invasive breast cancer, histologically confirmed by core needle biopsy, whose tumors are estrogen (ER) and / or progesterone (PgR) positive
• Clinical Stage T1c (Size ≥ 1.5 cm), T2, T3, T4a, b, c, N0 or N1, M0 (TNM Classification). According to the modified RECIST criteria, tumors of size ≥ 1.5 cm are considered measurable by mammography and can be determined as target lesions).
• Tumor measurable by mammography, sonography and clinical examination.
• Adequate bone marrow, renal and hepatic function
• Good health status (ECOG Performance status of 0, 1 or 2)

Exclusion criteria:

• Prior treatment with letrozole or bisphosphonates. Prior and concomitant anti-breast-cancer treatments such as chemotherapy, immunotherapy / biological response modifiers (BRM's), endocrine therapy other than letrozole (including steroids), and radiotherapy. Patients who have received hormone replacement therapy (HRT) will NOT be excluded, provided that HRT is discontinued at least 2 weeks prior to entry into the study.
• Patients with unstable angina, or uncontrolled cardiac disease (e.g. Class III and IV New York Heart Association's Functional Classification, see Appendix 9) or uncontrolled endocrine disorders.
• Evidence of inflammatory breast cancer or distant metastasis.
• Current active dental problems including infection of the teeth or jawbone (maxilla or mandibular); dental or fixture trauma, or a current or prior diagnosis of osteonecrosis of the jaw (ONJ), of exposed bone in the mouth, or of slow healing after dental procedures. Recent (within 6 weeks) or planned dental or jaw surgery (e.g. extraction, implants).
• History of diseases with influence on bone metabolism, such as Paget's disease, Osteogenesis Imperfecta, and primary or secondary hyperthyroidism within the 12 months prior to study entry

Other protocol-defined inclusion/exclusion criteria may apply

Open-label, multicenter, randomized

Principal Investigators are NOT employed by the organization sponsoring the study. Other disclosure agreement that restricts the right of the PI to discuss or publish trial results after the trial is completed. The terms and conditions of Novartis' agreements with its investigators may vary. However, Novartis does not prohibit any investigator from publishing. Any publications from a single-site are postponed until publication of the pooled data (i.e.,data from all sites)in the clinical trial.