Phase Iii Study Of Palbociclib In Combination With Exemestane Vs. Capecitabine, In Hormonal Receptor (Hr) Positive/Her2 Negative Metastatic Breast Cancer (Mbc) Patients With Resistance To Non-Steroidal Aromatase Inhibitors (Nsai): Pearl Study (Geicam/2013-02_cecog/Bc.1.3.006)

Background: Endocrine therapy (ET) is the cornerstone treatment for HR–positive, HER2-negative breast cancer (BC) patients. AIs have become the treatment of choice in postmenopausal patients. The high response rates with ET in these patients are partially undermined by the resistance developed by most of them over time. On early disease recurrence/progression to AIs, the treatment options include other AI, estrogen-receptor antagonists or chemotherapy (being capecitabine one of the best options). Preclinical data suggest that ER + /HER2- BC are dependent on cyclin-dependent kinases 4/6 (CDK4/6) function; the inhibition of this target may be effective in delaying/reverting endocrine resistance. Palbociclib is an oral novel CDK4/6 inhibitor that seems to be synergistic with ET in preclinical and clinical studies.