In 2016, the FDA expanded the indication of palbociclib to include combination therapy with fulvestrant for the treatment of advanced ER+HER2- breast cancer that progressed on endocrine therapy following results from the Phase III PALOMA-3 study (NCT01942135), which demonstrated that addition of palbociclib to fulvestrant for the treatment of ER+HER2- metastatic breast cancer that progressed on endocrine therapy extended median progression free survival from 4.6 months to 9.5 months[56,59]. Here, ESR1 is linked to breast carcinoma.