MTOR and breast cancer: In recent years, patients with HR-positive advanced breast cancer have been treated with molecular-targeted therapies, including cyclin-dependent kinase 4/6 inhibitors, phosphoinositide-3 kinase (PI3K) inhibitors, and a mechanistic-target-of-rapamycin (mTOR) inhibitor, concurrently with hormonal therapy to augment the effect of the hormonal therapy.