Abstract P1-14-02: A phase 2 study of low dose metronomic eribulin in metastatic breast cancer
Authors: Chalasani P , Liu AJ , Khanjian JA , Peha M , Buening BJ , Gadi VK , Specht JM , Salazar L , Linden HM 
Published: May 2019

Background: Eribulin mesylate is a non-taxane microtubule dynamics inhibitor approved by FDA in treatment of metastatic breast cancer (MBC) based on improvements in overall survival in the pivotal EMBRACE trial. Eribulin is approved at 1.4mg/m2 administered D1,8 of q21d cycle. However, this dose and schedule may have significant myelosuppression and peripheral neuropathy requiring dose reductions and treatment delays for some patients. We hypothesized that a low dose metronomic schedule will allow responding patients to remain on treatment, resulting in longer TTP (time to progression) and decreased incidence of toxicities and treatment-related discontinuations.

Methods: A multi-site prospective open-label phase II trial of metronomic dosing of eribulin in patients with MBC has completed accrual of 60 patients, outcomes will be updated at presentation. Patients whose disease had progressed following 1-6 prior regimens with prior exposure to a taxane, ECOG performance status of 0 – 2, measurable disease per RECIST 1.1, with normal marrow and organ function were eligible. Eribulin was administered at 0.9mg/m2 weekly for 3 out of 4 weeks. For patients with HER2 positive disease, concurrent trastuzumab administration was allowed. Concurrent denosumab or bisphosphonates were allowed for patients with bone disease.

Results: 60 patients were enrolled, average age 58 (range 34-83). Majority were postmenopausal Caucasian females, but the study included African American, Hispanic, native American, male patients. The majority of tumors were ER+, infiltrating ductal, but the study included 13 HER2+, and 12 TN tumors, with 5 ILC, and 5 mixed ILC/IDC. Nearly half of the enrolled patients had clinical benefit from the regimen, remaining on therapy for 6 months or longer, with stable disease or response; 50% had progression PD at 3 months 32% had stable disease and 18% had a partial or complete response (1, long term). Overall Survival, OS, for the entire group of heavily pre-treated patients was 1.2 years, with TN and HER2 positive patients faring better than ER+ in this small study. One HER2+ patient remains in long-term remission, off chemotherapy.

The regimen was extremely well tolerated. The majority of the patients experienced grade 0 or 1 toxicity for alopecia (48/60) and peripheral neuropathy (7 with grade 2 neuropathy, 5 pre-existing, 2 with grade 3 neuropathy). There were few dose reductions (n=15), thrombocytopenia (11 grade 1 only), or use of G-CSF (14).

Conclusions: Metronomic weekly low dose eribulin appears to be an active and tolerable regimen with less myelosuppression, alopecia and peripheral neuropathy than is seen with approved dose, allowing longer duration of use and disease control, with similar outcomes compared to the standard dose regimen. Outcomes will be updated at presentation.

Citation Format: Chalasani P, Liu AJ, Khanjian JA, Peha M, Buening BJ, Gadi VK, Specht JM, Salazar L, Linden HM. A phase 2 study of low dose metronomic eribulin in metastatic breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-14-02.