Stereotactic Body Radiation Therapy and FES PET/CT Imaging for the Treatment of Oligoprogressive Estrogen Receptor Positive Metastatic Breast Cancer

This phase II trial tests how well stereotactic body radiation therapy (SBRT) works in treating patients with estrogen receptor positive (ER +) breast cancer that has spread from where it first started to other places in the body (metastatic) and has limited disease progression (oligoprogression). Currently, the standard of care for breast cancer patients with oligoprogressive disease is to change systemic therapy when progression occurs. Radiation therapy uses high energy x-rays, particles, or radioactive seeds to kill cancer cells and shrink tumors. SBRT is a type of external radiation therapy that uses special equipment to position a patient and precisely deliver radiation to tumors in the body (except the brain). The total dose of radiation is divided into smaller doses (fractions) given over several days. This type of radiation therapy helps spare normal tissue and has been shown to improve survival. SBRT may kill more tumor cells and allow patients with oligoprogressive ER + metastatic breast cancer to continue taking current systemic treatment. This trial also tests how well ER targeted positron emission tomography (PET)/ computed tomography (CT) imaging, using FES, works in identifying progressive disease in patients with ER + metastatic breast cancer. FES, a radiolabeled substance, binds to estrogen receptors and gives off radiation that can be detected by a PET scan. The PET scan, an established imaging technique that utilizes small amounts of radioactivity attached to very minimal amounts of tracer, FES, forms an image that shows where tumor cells with estrogen receptors can be found in the body. CT images use x-rays to provide an exact outline of organs. FES PET/CT may improve identification of progressive disease in patients with ER + metastatic breast cancer.