Real-world progression-free survival and overall survival of palbociclib plus endocrine therapy (ET) in Japanese patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative advanced breast cancer in the first-line or second-line setting: an observational study.

Background: A recent large real-world study conducted in the United States reported the effectiveness of palbociclib plus aromatase inhibitor in HR+/HER2- advanced breast cancer (ABC). However, local clinical practice and available medical treatment can vary between Japan and Western countries. Thus, it is important to investigate Japanese real-world data.