This 2 arm study will assess the efficacy and safety of intravenous Herceptin with or without a taxane for the first line treatment of metastatic breast cancer in women who have relapsed at least 12 months after a minimum of 10 months of (neo)adjuvant treatment with Herceptin for HER2-positive early breast cancer.Patients will receive either Herceptin monotherapy (loading dose of 4mg/kg iv, followed by weekly doses of 2mg/kg iv, or 8mg/kg loading dose followed by 3-weekly doses of 6mg/kg)or Herceptin + a taxane (docetaxel 100mg/m2 iv every 3 weeks, or paclitaxel 175mg/m2 iv every 3 weeks or 75mg/m2 every week). The anticipated time on study treatment is until disease progression, and the target sample size is <100 individuals.

• Drug: trastuzumab [Herceptin]
  4mg/kg iv loading dose followed by 2mg/kg iv weekly, or 8mg/kg iv loading dose followed by 6mg/kg iv 3-weekly
• Drug: Taxane (docetaxel or paclitaxel)
  As prescribed

• 1: Experimental
  Interventions:

  • Drug: trastuzumab [Herceptin]
  • Drug: Taxane (docetaxel or paclitaxel)
• 2: Active Comparator
  Intervention: Drug: trastuzumab [Herceptin]

Inclusion Criteria:

• at least 10 months of Herceptin treatment for HER2-positive early breast cancer;
• metastatic breast cancer >=12 months after discontinuation of Herceptin;
• measurable disease.

Exclusion Criteria:

• previous chemotherapy for metastatic breast cancer;
• brain metastases;
• invasive malignancy other than metastatic breast cancer.