10720 Background: Trastuzumab provides significant clinical benefit in HER2 positive metastatic breast cancer. Gemcitabine and cisplatin (GC) combination is attractive treatment options for anthracyclines-taxanes-pretreated metastatic breast cancer. These agents demonstrated synergistic activity and minimal overlapping toxicity. On the other hand, additional synergistic activity was observed with trastuzumab and GC. Methods: Histologically confirmed metastatic breast cancer patients with FISH positive tumors (HER2/choromosome 17 ≥2) were eligible if they were at least one measurable disease; ≥18 and ≤70 years; life expectancy >3 month; ECOG 0–2; prior anthracyclines and taxanes treatment but no prior trastuzumab therapy; adequate marrow, renal and hepatic function. Treatment schedule was as follows: Gemcitabine 1000 mg/m2 and cisplatin 30 mg/m2 d1, 8 every 3 weeks conjunction with trastuzumab 4 mg/kg d1 and 2 mg/kg for weekly. Chemotherapy was scheduled for up to eight cycles. Treatment was discontinued in case of progression or prohibitive toxicity. After progression additional regimen was administered with trastuzumab. Results: Eleven women were enrolled. All patients were eligible for toxicity and efficacy evaluations. Median age was 48 (range 28–64) years and median ECOG performance status was 0. Ten patients (90.9%) had visceral metastases, most commonly located in the liver (8 pts) and lung (4 pts). Estrogen receptor positivity was 63.6% (7 pts). A total of 80 cycles were delivered with a median of 8 cycles. Objective response rate was 54.5% (6 pts) with 27.2% (3 pts) complete response and 27.2% (3 pts) partial response. Stabile disease was achieved 36.3% (4 pts). Median time to progression and overall survival were 8 (95% CI: 3.97–12.02) and 18 months (95% CI: 15.89–20.10) respectively. Grade 3–4 toxicity was observed in 18.1% (2 pts). Treatment of one patient was discontinued due to grade 4 thrombocytopenia. Dose reductions due to myelotoxicity were performed in 1 (9.0%) patients. Conclusions: Our preliminary data shows that gemcitabine and cisplatin and trastuzumab combination regimen is effective and has manageable toxicity profile. No significant financial relationships to disclose.