Study of 18F-FFNP Breast PET/MRI

Inclusion Criteria:

• Postmenopausal status defined by either

• prior bilateral oophorectomy

• age greater than or equal to 60 years of age

• age less than 60 years of age and amenorrheic for 12 or more months in theabsence of prior chemotherapy, tamoxifen, toremifene or ovarian suppression andFSH and estradiol in the postmenopausal range per local normal range (Group 2only)

• Diagnosis of biopsy-proven invasive breast cancer measuring at least 1.0 cm indiameter by any imaging modality

• Biopsy-proven PR-positive invasive breast cancer

• Breast MRI planned or performed before surgery

• Definitive surgical excision of the primary tumor planned without neoadjuvanttherapy; defined as therapy (chemotherapy, targeted therapy, radiation therapy orendocrine therapy) given to decrease the size of the tumor prior to planned surgery.

Exclusion Criteria:

• Inability or unwillingness to provide informed consent to the study

• HER2-positive breast cancer, as defined by immunohistochemical staining 3+ ORpositive by in situ hybridization (Group 2 only)

• PR and Ki67 IHC slides or FFPE tissue blocks from clinical breast biopsy notavailable

• Patients who have completed neoadjuvant chemotherapy, endocrine therapy, targetedtherapy, surgical resection, or radiation for the current biopsy-proven malignancy

• Patients who are planning to undergo anastrozole as standard of care neoadjuvanttherapy

• Patients who are currently taking aromatase inhibitors or ER antagonists (tamoxifen,raloxifene)

• Patients with breast expanders

• Patients who are pregnant or lactating

• Patients with a contraindication to gadolinium-based contrast agents, includingallergy or impaired renal function (per UW Health Guidelines)

• Patients with a history of allergic reaction attributable to compounds of similarchemical or biologic composition to 18F-FFNP

• Patients with history of allergic reaction to anastrozole (Group 2 only)

• Patients in liver failure as judged by the patient's physician

• Patients with standard contraindications to MRI (per UW Health Guidelines)

• Patients requiring conscious sedation for imaging are not eligible; patientsrequiring mild, oral anxiolytics for the clinical MRI scan will be allowed toparticipate as long as the following criteria are met:

• The patient has their own prescription for the medication

• The informed consent process is conducted prior to the self-administration ofthe medication.

• The patient comes to the research visit with a driver.

• Patients unable to lie prone for 45 minutes for imaging

• Patients taking hormone replacement therapy or over-the-counterproducts/supplements/herbal preparation with potential estrogenic effects who areunwilling to discontinue these agents during the timeframe of the study untilsurgery.