Randomized Phase II Study Evaluating Palbociclib in Addition to Letrozole as Neoadjuvant Therapy in Estrogen Receptor–Positive Early Breast Cancer: PALLET Trial

Adding palbociclib to letrozole significantly enhanced the suppression of malignant cell proliferation (Ki-67) in primary ER-positive BC, but did not increase the clinical response rate over 14 weeks, which was possibly related to a concurrent reduction in apoptosis.