831 Background: Preclinical data indicate that H and N have synergistic activity. This observation has prompted a number of clinical studies of this combination in women with HER2-positive MBC. H plus N has been shown to be active, producing response rates of up to 84% when used first line, and well tolerated. We are conducting a phase II study to further evaluate this combination. Methods: Women with histologically confirmed, HER2-positive (IHC 3+, or 2+ and FISH positive) MBC who had not received prior N or anti-HER2 therapy were eligible. Patients with active heart disease or with clinical manifest CNS metastases were excluded. Women received N 25mg/m2 weekly and H 4mg/kg loading dose followed by 2mg/kg weekly for at least 8 weeks and thereafter until progression. Results: 26 of a target enrolment of 32 patients have been enrolled: median age 58 (range 3175) years; median Karnofsky performance status 90% (70100). Median duration of therapy is currently 15.6 (0.129.3+) weeks; 11 patients remain on therapy. The overall response rate is 50% (2 CR, 11 PR), with 5 of 26 patients not evaluable (RR in evaluable patients, 61.9%); 2 patients had stable disease and 6 progressive disease as their best response. Treatment was well tolerated, with adverse events being mainly mild to moderate in severity and as expected based on the known side effects of these agents: fatigue 50%; nausea 34.6%; diarrhoea 23.1%; vomiting 19.2%. The majority of patients experienced neutropenia (53.8%), anaemia (76.9%) or leucopenia (73.1%); 6 patients had grade 3 or 4 neutropenia. 6 patients experienced 10 serious adverse events, including 2 infusion-related reactions and 2 cases of dyspnoea with the initial trastuzumab infusion, and one decrease in LVEF to below 50%. Conclusions: This interim analysis of a phase II study of H and N supports previous trials demonstrating that this combination is an effective and well-tolerated regimen for the treatment of women with HER2-positive metastatic breast cancer. Enrolment continues and updated data will be presented. Author Disclosure Employment or Leadership Consultant or Advisory Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Roche
