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.