Background
Breast cancer remains one of the most common cancers worldwide. A large proportion of cases, about 70%, are hormone receptor-positive and ERBB2-negative, meaning the cancer cells grow in response to estrogen or progesterone but do not overexpress ERBB2, also known as HER2. For this subtype of advanced breast cancer, endocrine therapy is the foundation of treatment. Aromatase inhibitors such as letrozole and anastrozole are commonly used to reduce estrogen production and slow tumor growth.
In recent years, combining endocrine therapy with a cyclin-dependent kinase 4 and 6 inhibitor has become an important strategy because it can delay disease progression more effectively than endocrine therapy alone. Fovinaciclib is an oral CDK4/6 inhibitor developed to enhance this approach. This phase 3 trial was designed to determine whether adding fovinaciclib to a first-line aromatase inhibitor could improve outcomes for patients with hormone receptor-positive, ERBB2-negative advanced breast cancer.
