Results of the Belgian expanded access program of eribulin in the treatment of metastatic breast cancer closely mirror those of the pivotal phase III trial

Background: Eribulin is a non-taxane microtubule dynamics inhibitor that showed a survival benefit versus treatment of physician's choice in a phase III trial enrolling patients with metastatic breast cancer (MBC).

Methods: The E7389-G000-398 trial was designed to provide eribulin to MBC patients pre-treated with anthracylines, taxanes and capecitabine. Patient characteristics, efficacy and safety data were collected prospectively. Efficacy and survival analyses were performed using retrospectively collected data of patients treated at a single institution.

Results: One hundred fifty-four patients were enrolled and the median number of previous lines of chemotherapy was 4. The most frequent adverse events were fatigue/asthenia (74%), alopecia (55%), peripheral neuropathy (46%) and neutropenia (43%). Objective response rate (ORR) was 24% in the evaluable population and 14% in patients pre-treated with both taxanes and vinorelbine. In patients with oestrogen receptor (ER)+/human epidermal growth factor receptor 2 (HER2)- MBC, response rate was 29% and 21% with triple-negative disease. Activity was minimal in HER2+ MBC treated with eribulin monotherapy (14% ORR). Median progression-free survival was 3.2 months. Median overall survival was 11.3 months; 77% of patients were alive at 6 months and 43% at 12 months.

Conclusion: Eribulin was active in MBC patients with a high tumour burden and predominant visceral disease. Safety profile was similar to what was reported in the phase III trials. Prophylactic granulocyte colony-stimulating factor administration allowed optimal dose intensity and could have contributed to the recorded response rate. Activity is sustained after treatment with taxanes and vinorelbine. The recently investigated combination of eribulin and trastuzumab should lead to higher activity in HER2-positive MBC.