Premenopausal Patients With Clinically Aggressive Metastatic Breast Cancer Successfully Treated With a First‐Line Palbociclib‐Containing Regimen: Two Cases and Literature Review

In the two cases we reported, first-line palbociclib therapy shows adequate and timely responses for premenopausal HR+/HER2- metastatic breast cancer patients. Although not widely utilized, frontline therapy with palbociclib combined with endocrine treatments may be a choice for HR+/HER2- metastatic breast cancer patients experiencing severe visceral metastasis.