A Retrospective Study to Characterize Patients With HER2-positive Metastatic or Locally Advanced Breast Cancer, Treated by Herceptin® as 1st Line-therapy and Without Progression for at Least 3 Years Followed by a 1-year Prospective Study for Patients Stil

Primary objective: This observational study will characterize retrospectively patients with HER2-positive metastatic or locally advanced breast cancer who had received treatment with Herceptin (trastuzumab) in 1st line and who were without progression for at least three years. Secondary objectives: The secondary objectives of this study were to describe: - The progression-free survival, time to progression and patients overall survival; - Modalities of use of trastuzumab, the duration of treatment and the reasons leading to treatment discontinuation; - Antineoplastic treatments in combination with trastuzumab and after discontinuation of trastuzumab treatment; - Relevant biological tumor markers; - The safety of trastuzumab treatment.