Antitumor Activity of Eribulin After Fulvestrant Plus CDK4/6 Inhibitor in Breast Cancer Patient-derived Xenograft Models.

Background/aim: There is no established standard chemotherapy after administration of the combination endocrine plus CDK4/6 inhibitor therapy for luminal-type breast cancer. We used patient-derived xenograft (PDX) models to determine the antitumor activity of eribulin and capecitabine after endocrine therapy plus CDK4/6 inhibitor.

Materials And Methods: We examined the antitumor activity of fulvestrant, palbociclib, eribulin, and capecitabine in 4 luminal-type breast cancer PDX models (OD-BRE-0188, -0438, -0450, -0745). In OD-BRE-0438, we determined the antitumor activity of chemotherapy after fulvestrant-palbociclib treatment. We also performed immunohistochemical analysis to explore the effects of treatment on E-cadherin in tumor tissues.

Results: Fulvestrant, fulvestrant-palbociclib and chemotherapy had antitumor activity in the 4 PDX models. In OD-BRE-0438 (the most resistant to fulvestrant-palbociclib), eribulin had superior antitumor activity to capecitabine after fulvestrant plus palbociclib. Only eribulin tended to increase E-cadherin expression.

Conclusion: Eribulin had superior antitumor activity to capecitabine after fulvestrant-palbociclib in the OD-BRE-0438 model.