A multicenter phase II trial of neoadjuvant letrozole plus low-dose cyclophosphamide in postmenopausal patients with estrogen receptor-positive breast cancer (JBCRG07): The efficacy and its correlation with circulating endothelial cells.

618 Background: Neoadjuvant endocrine therapy has been increasingly employed in clinical practice to improve surgical outcomes in postmenopausal women with ER-positive breast cancer. Addition of metronomic cyclophosphamide (CPA) to letrozole (LET) has been suggested to be more active than LET alone in elderly pts. We conducted a phase II study to assess the efficacy and safety of the combination of LET and metronomic CPA and to examine the association between its efficacy and changes in circulating endothelial cell (CEC) and its progenitor cell (CEP) counts. Methods: Postmenopausal pts aged ≥60 yrs with ER-positive (≥10%) breast cancer (T2-4N0-1M0) were eligible. Pts received LET (2.5mg daily) and CPA (50mg p.o. daily) for 24 wks before surgery. Treatment responses were assessed every 8 wks by palpation and ultrasound. The primary endpoint was objective response rate (ORR). Secondary endpoints included breast conserving rate (BCR), safety, disease free survival and overall survival. CECs and CEPs were mea...