A recent meta-analysis demonstrated that CDK4/6i therapy added to endocrine therapy in patients with advanced HR+ HER2-negative BC substantially improved PFS (HR 0.54, p < 0.00001) and OS (HR 0.77, p < 0.00001), irrespective of the endocrine partner, line of therapy, or menopausal status, corroborating individual clinical trial data [34]. This evidence concerns the gene CDK4 and breast cancer.