CYP19A1 and breast cancer: The MONALEESA-7 trial, a phase III randomized double-blind study, enrolled 672 pre-/perimenopausal women with HR+/HER2- advanced breast cancer to evaluate ribociclib + endocrine therapy (tamoxifen or non-steroidal aromatase inhibitors [NSAI] + goserelin) versus placebo + endocrine therapy.