
This phase 3 trial showed significant prolongation of progression-free survival and higher rates of overall response with the addition of ribociclib to letrozole than with the addition of placebo to letrozole for first-line treatment in postmenopausal women with HR-positive, HER2-negative advanced breast cancer. The improvement in the duration of progression-free survival was associated with a higher rate of myelosuppression among patients in the ribociclib group.

