THOR Study: A Study of Continued Herceptin (Trastuzumab) in Combination With Second Line Chemotherapy in Patients With HER2 Positive Metastatic Breast Cancer.

A Randomized, Open-label Study to Compare Progression-free Survival in Patients With HER2 Positive Metastatic Breast Cancer Who Continue or Discontinue Herceptin in Combination With 2nd Line Chemotherapy, Having Progressed on 1st Line Chemotherapy in Combination With Herceptin

This 2 arm study will compare the efficacy and safety of continuation or discontinuation of Herceptin treatment in combination with 2nd line chemotherapy, in patients with HER2 positive metastatic breast cancer whose condition has progressed on 1st line chemotherapy plus Herceptin. Patients will be randomized either to continue or discontinue Herceptin treatment (2mg/kg iv infusion weekly, or 6mg/kg iv infusion every 3 weeks) while receiving 2nd line chemotherapy of the investigator's choice. The anticipated time on study treatment is until disease progression, and the target sample size is 100-500 individuals.

Inclusion Criteria:

• female patients, >=18 years of age;
• metastatic breast cancer;
• HER2 overexpression (IHC 3+ and/or FISH positive);
• disease progression during or after previous 1st line chemotherapy plus Herceptin;
• scheduled to receive 2nd line chemotherapy.

Exclusion Criteria:

• incompatibility with previous Herceptin therapy;
• pregnancy.