Characteristics of HER2 3+ metastatic breast cancer patients with long-term benefit of trastuzumab.

e12523 Background: Because there is no cumulative dose, trastuzumab could be given until disease progression. However, characteristics of patients with long term benefit of trastuzumab treatment are seldom reported. Methods: Trastuzumab become available for HER2 3+ MBC at November 2005 at the Institute for Oncology and Radiology of Serbia. Since then, we have registered 42 patients with HER2 3+ MBC and/or inoperable loco-regional recurrent BC treated with first line trastuzumab for at least 24 months (range 24-123+). Results: Median age was 53 years (range 35-76). 30/42 patients (71%) had ER/PR positive BC. MBC was initial presentation in 14 patients (33%), and as relapse in 28 (67%) patients. Only 7/28 (25%) patients received neoadjuvant/adjuvant trastuzumab, therefore majority have been trastuzumab naive (83.3%). Metastases were present in the liver (9), lungs (9), bones (16), soft tissue (6), CNS (1), while 20 (48%) patients had multiple metastatic sites. After antracyclines based chemotherapy, patients have been treated with first line weekly taxane concurrently with three weekly trastuzumab. After taxanes (up to 24 doses), trastuzumab was continued +/-hormonal therapy. Objective response was achieved in 29 (69%) patients with 17 patients (40%) achieving complete response. Median duration of response was 32+ months; 11 patients are still in remission 5 years after trastuzumab initiation. The longest complete remission duration is 123+ months, in patient with initially inoperable BC and solitary cerebellar metastasis. During observational period 10 patients stopped trastuzumab predominantly because of disease progression (8/42 19%) and 2 (4.8%) because of decreased ejection fraction (EF≤ 50%) that occurred as a rather late effect, after 34 and 49 months of continuous trastuzumab treatment. Three patients are lost from follow-up (7%); 39 (93%) patients included in this analysis are alive, still receiving trastuzumab for median 37 cycles (range 29-172+). Conclusions: A subgroup of patient with HER2 3+ MBC has a long-term benefit of trastuzumab treatment. In this analysis majority (71%) had also ER/PR positive MBC and majority have not been treated with neoadjuvant/adjuvant trastuzumab (83.3%).