A randomized feasibility study of 18F-fluoroestradiol positron emission tomography to predict response after neoadjuvant chemotherapy and endocrine therapy in postmenopausal patients with estrogen receptor-rich breast cancer: A sub-study of NEOCENT trial

566 Objectives 18F-fluoroestradiol (FES) positron emission tomography (PET) may predict response to neoadjuvant chemotherapy (NC) and neoadjuvant endocrine therapy (NET) for breast cancer. Methods This is a randomized, prospective, single-center feasibility study conducted as a sub-study of NEOCENT trial. Twenty-six postmenopausal women with biopsy proven intermediate to strong estrogen receptor (ER) positive invasive breast cancer were included. Patients were randomized to NC (6 cycles of 5-FU, epirubicin and cyclophosphamide [FEC] or 3 cycles of FEC followed by 3 cycles of docetaxel) (n=13) or NET (letrozole, 2.5mg daily for 21-23 weeks) (n=13). Baseline FES PET was performed prior to NC or NET. After surgery, the pathologic response was assessed on the basis of the Miller-Payne system as nonresponse (grades 1 and 2) and response (grades 3-5). Results Pathologic responders were 8 with NC and 4 with NET. Maximal standardized uptake (SUVmax) of FES PET was not significantly different between two groups (P > 0.05). The mean SUVmax of NET pathologic responder group (17.3±14.5) was significantly higher than that of NC pathologic responder group (5.5±3.4, P=0.028) but there was no difference between nonresponder groups (NET: 9.6±5.2 and NC: 9.2±4.7, P=0.710). The SUVmax values of NET group were positively correlated with reduction rates in tumor cellularity (r=0.619, P=0.024), while those of NC group showed negative correlation (r=-0.627, P=0.029). Five out of 7 NC patients with a baseline SUVmax less than 7.3 achieved a pathologic response, but none of 5 NET patients with SUVmax Conclusions FES PET has a potential to assess response to neoadjuvant therapy in postmenopausal women with ER-rich breast cancer. FES PET may help guide treatment selection.