• Disease free progression [ Time Frame: 6 months ] [ Designated as safety issue: Yes ]
  

• Measure response rate of each drug combination [ Time Frame: Every 6 weeks cycles 1 - 8; Every 9 weeks Cycles 9 forward ] [ Designated as safety issue: No ]
  
• Asses the side effects of each drug combination. [ Time Frame: Weekly ] [ Designated as safety issue: Yes ]
  

Rationale: Previous studies have demonstrated the anti-tumor efficacy of gemcitabine and trastuzumab against metastatic breast cancer when given alone and in combination. Yet, research indicates that the two drugs given together work more effectively than either alone. Laboratory studies testing the combination of trastuzumab and cisplatin have shown synergistic anti-tumor activity with the two drugs. In addition, clinical studies suggest a high level of anti-tumor activity with the combination of gemcitabine and cisplatin. Researchers are testing the triple drug combination of gemcitabine, trastuzumab, and cisplatin in the current study to evaluate the potential for enhanced responsiveness in patients with Her-2/neu overexpressing breast cancer as well as comparing it to the double drug combination of gemcitabine and trastuzumab.

Purpose: This study will measure patient responses and compare the efficacy of a double drug combination (gemcitabine and trastuzumab) with a triple drug combination (gemcitabine, trastuzumab, and cisplatin) in patients with metastatic breast cancer. Side effects will be carefully assessed in patients.

Treatment: Patients in this study will receive one of two treatment combinations. A computer will randomly assign patients to a treatment group. Group one will be given gemcitabine and trastuzumab. Gemcitabine will be given to patients on days 1 and 8, and trastuzumab on days 1, 8, and 15. Group two will receive gemcitabine, trastuzumab, and cisplatin. Gemcitabine and cisplatin will both be administered on days 1 and 8, and trastuzumab on days 1, 8, and 15. Each treatment cycle (for both groups) will last a total of 21 days. All study drugs will be administered through intravenous infusions. Several tests and exams will be given throughout the study to closely monitor patients. Thorough patient exams will be given at the beginning of each treatment cycle. Imaging tests will be done every two cycles for the first eight cycles and then every three cycles until study completion. Study treatment will be discontinued due to disease growth or unacceptable side effects.