This may be especially important, given the findings of the RIGHT Choice trial (Study to Compare the Combination of Ribociclib Plus Goserelin Acetate With Hormonal Therapy Versus Combination Chemotherapy in Premenopausal or Perimenopausal Patients With Advanced or Metastatic Breast Cancer) comparing 1st-line ET + CDK4/6i versus chemotherapy for pre- or peri-menopausal patients with HR+, HER2 negative “aggressive” MBC [44]. This evidence concerns the gene CDK4 and breast cancer.