Phase II study of eribulin mesylate for treatment of CNS metastases (mets) in metastatic breast cancer (mBC).

Abstract

e12571 Background: There is no approved drug therapy for CNS mets from mBC. Eribulin mesylate (eribulin) is a microtubule inhibitor approved for treatment of mBC patients (pts) who have received at least 2 prior chemotherapy regimens. Previously reported cases have demonstrated significant CNS responses in mBC pts treated with eribulin. This study evaluates the CNS response in pts with mBC treated with eribulin. Methods: CASE7113 was a prospective phase II single-arm study to evaluate the 12-week CNS progression free survival (12-wk CNS-PFS) of pts with mBC and CNS mets treated with eribulin. 20 pts were to be enrolled to demonstrate a 40% 12-wk CNS-PFS (95% CI, 8.5% - 61.5%). All pts had radiologically confirmed mBC CNS lesions with at least one lesion that did not receive prior radiation or surgical resection. Eribulin was administered at standard dose of 1.4mg/m2 IV on days 1 and 8 of a 21 day-cycle. Pts underwent baseline and 12-week brain MRI. The study was closed due to slow accrual; an analysis of enrolled pts was performed. Results: 9 female pts were enrolled; median age was 56 (32-82) years. 55% and 67% had ER+ and/or PR+ and Her2+ mBC respectfully. 1 pt had triple negative breast cancer (TNBC). Median number of prior therapies was 3 (0-12). The 12-wk CNS-PFS (95% CI) was 88.9% (51.8% - 99.7%), the median PFS (95% CI) was 22.6 (4.3 - 31.9) weeks, the median OS (95% CI) was 15.7 (4.0 - 27.3) months. 4 pts achieved stable disease and 1 pt had a partial response. There were no unexpected toxicities. Conclusions: For mBCa pts with CNS mets, this estimate of 12-wk CNS-PFS suggests activity of eribulin and merits further investigation in this population in the context of clinical trials. Clinical trial information: NCT02581839.