FES PET/CT in Predicting Response in Patients With Newly Diagnosed Metastatic Breast Cancer Receiving Endocrine Therapy

PRIMARY OBJECTIVES: I. To determine the negative predictive value (NPV) of \[18F\]fluoroestradiol (FES) uptake for response (clinical benefit) at 6 months in patients with estrogen-receptor positive (ER+) metastatic breast cancer treated with first-line endocrine therapy. SECONDARY OBJECTIVES: I. To determine the test-retest reproducibility of quantitative assessment of tumor FES uptake by standardized uptake values (SUVs). II. To evaluate the accuracy of FES-PET/CT for predicting response in patients treated with first line endocrine therapy for metastatic breast cancer. III. To evaluate the accuracy of FES-PET/CT for predicting progression-free survival (PFS) in patients treated with first line endocrine therapy for metastatic breast cancer. IV. To examine the role of FES-PET/CT in predicting progressive disease (PD) or clinical benefit (CB), in concert with semi-quantitative interpretation of ER, progesterone receptor (PgR), and marker of proliferation Ki-67 (Ki-67). V. To evaluate the relationships among FES uptake, as measured by maximum SUV (SUVmax) and semi-quantitative ER from immunohistochemistry (IHC). VI. To evaluate FES SUVmax \< 1.5 as the optimal cutpoint for predicting progression-free survival (PFS) to first line endocrine therapy for metastatic breast cancer. VII. To determine the percent of eligible patients for whom biopsy is not feasible, i.e., determine the clinical utility of indirect assay of ER expression by FES-PET/CT. VIII. To evaluate the heterogeneity of tumor FES uptake in individual patients defined as variability in lesion's FES uptake. OUTLINE: Between 0 to 30 days before start of endocrine therapy, patients receive F-18 16 alpha-fluoroestradiol intravenously (IV) over 2 minutes and undergo PET/CT. Patients may undergo a second FES-PET/CT study at least 24 hours after the first study and no later than 10 days after the initial study. After completion of study, patients are followed up for 6 months and then periodically for up to 2 years.