632 Background: Following the BCIRG 001, PACS 01 and HERA trials, this randomised, multicentre, open-label, Phase III trial was designed to demonstrate the benefit of concomitant docetaxel and epirubicin versus anthracyclines, and evaluate the use of sequential trastuzumab. Methods: Patients (pts) with localised, resectable, unilateral breast cancer who met the following criteria were eligible: age <65 years, ≥1 positive node, M0, adequate heart and organ functions. Pts were randomised to receive either 6 cycles of 5-fluorouracil-epirubicin-cyclophosphamide (FEC100: F and C, 500 mg/m2, E 100 mg/m2) (Arm A) or epirubicin-docetaxel (ET75: E 75 mg/m2, T 75 mg/m2) (Arm B). Primary prophylaxis with G-CSF was not planned. Radiotherapy was mandatory after conservative surgery and tamoxifen was required in pts with hormone receptor-positive tumours. Pts with HER2-positive disease were then further randomised to observation only or to 1 year of trastuzumab monotherapy (6 mg/kg iv every 3 weeks). In HER2-positive pts receiving trastuzumab, left ventricular ejection fraction (LVEF) was determined at Cycles 2, 4, 8, 13, 18 and after 2 years. Otherwise, LVEF was determined at baseline and at 1 year post-surgery. Results: Of the 3010 pts recruited (2622 evaluable for safety to date), 1518 received FEC100 and 1492 received ET75 after the first randomisation. Haematologic toxicity was the most frequent toxicity in both arms. Grade 3–4 toxicities were similar for Arms A and B, except febrile neutropenia (10.3% and 31.4%, respectively) and nausea/vomiting (13.2% and 7.5%, respectively). Grade 2 clinical cardiac toxicity (decreased LVEF) was observed in 4 pts in Arm A and 5 in Arm B, with median LVEF scores of 63% in both arms at the end of chemotherapy. HER2-positive pts (n=500) were then randomised to either receive trastuzumab (n=259) or observation only (n=241). Conclusions: These preliminary safety data indicate that FEC100 and ET75 were both well tolerated, with acceptable cardiac safety values. The trial is ongoing and further analysis regarding the use of trastuzumab in this setting will be presented. [Table: see text]