18F-FES PET/CT in the Treatment Planning, and Response Assessment of ER-Positive Breast Cancer

This study uses FES PET/CT imaging to evaluate estrogen receptor-positive breast cancer. FES PET/CT is a type of imaging that can show whether breast cancer cells have estrogen receptors. The purpose of this study is to see how well FES PET/CT can help doctors: (1) diagnose ER-positive breast cancer, (2) plan the best treatment, and (3) check how well treatment is working. Participants will undergo FES PET/CT scans as part of their regular cancer care or study procedures. The results may help improve how doctors use imaging to guide treatment decisions for patients with ER-positive breast cancer.