Monitoring the Early Response of Fulvestrant Plus Tanshinone IIA Combination Therapy to Estrogen Receptor-Positive Breast Cancer by Longitudinal 18F-FES PET/CT

Endocrine monotherapy of breast cancers is generally hampered by the primary/acquired resistance and adverse sides in clinical settings. Herein, advantaging the multitargeting antitumor effects and normal organ-protecting roles of Chinese herbal medicine, the aim of this study was to investigate the enhanced synergistic efcacy of fulvestrant plus Tan IIA combination therapy in ERpositive breast cancers and to monitor the early response by longitudinal 18F-FES PET/CT imaging. The experimental results showed FUL + Tan IIA combination therapy significantly inhibited tumor growth of ER-positive ZR-75-1 tumor xenografts and exhibited distinct antitumor effects at an earlier time point after treatment than did the monotherapy of FUL or Tan IIA. Moreover, 18F-FES PET/CT imaging competently monitored the early response of FUL + Tan IIA combination therapy. The quantitative 18F-FES %ID/gmax in vivo was further confirmed by and correlated well with ERα expression ex vivo. In conclusion, the synergic effect of FUL + Tan IIA combination therapy to ER-positive breast cancers was verified in the preclinical tumor models and the early treatment response could be monitored by 18F-FES PET/CT.