The SERENA-2 trial (61), a randomized, parallel-group, multicenter phase II study, comparing the safety and efficacy of 3 different doses of camizestrant with fulvestrant 500 mg in the treatment of postmenopausal women with ER+/HER2- advanced-stage breast cancer with disease recurrence or progression after at least one line of endocrine therapy (55). Here, ESR1 is linked to breast carcinoma.