The conventional treatment for hormone receptor positive, HER2 receptor negative breast cancer is hormone therapy. However, some patients acquired resistance after hormone therapy and lead to treatment failure. Alternate treatment options, cyclin-dependent kinases 4/6 (CDK4/6) inhibitors, which are new target therapies for cell cycle inhibition, have shown efficacy in HR (+) and HER2 (-) metastatic breast cancer. FDA have approved two CDK4/6 inhibitors accompanied with hormone therapy for this cancer subtype. Additionally, the researchers conducted a phase III, double-blind MONARCH2 trial recruiting 669 patients to assess the efficacy of a third CDK4/6 inhibitor, abemaciclib, combined with fulvestrant in HR (+) and HER2 (-) metastatic breast cancer. The results showed that progression free survival (PFS) extended 7.1 months in the abemaciclib and fulvestrant combination group (PFSs were 16.4 months and 9.3 months in the combination group compared with fulvestrant-alone group). The objective response rate (ORR) was 48.1% in the combination group and 21.3% in fulvestrant-alone group. These findings indicate that adding abemaciclib to fulvestrant have exhibited excellent response in HR (+) and HER2 (-) metastatic breast cancer.
2. 2017 ASCO: http://abstracts.asco.org/199/AbstView_199_180696.html