AR and ER Imaging in Metastatic Breast Cancer

Androgen Receptor and Estrogen Receptor Imaging in Metastatic Breast Cancer Patients

Knowledge of breast cancer estrogen receptor (ER) expression is of major importance in treatment-decision making. Patients with ER-positive tumors can be treated with anti-oestrogen therapy, which has relatively few side effects compared to chemotherapy. Whole-body tumor ER-expression can be visualized by 18F-fluoroestradiol PET imaging (FES-PET). In addition to ER, the androgen receptor (AR) is a potential new target in breast cancer. PET imaging with 18F-fluorodihydrotestosterone (18F-FDHT) may allow visualization of tumor AR-expression. In the current study we will perform FES-PET and FDHT-PET in metastatic breast cancer patients and evaluate the concordance with concurrent biopsies. Molecular imaging of tumor AR- and ER-expression may well be of value for future treatment decision-making.

Inclusion Criteria:

1. Metastatic breast cancer, with at least one known metastasis outside of the liver

2. Presence of a lesion that is safely accessible for tumor biopsy (may be liver lesion)

3. Postmenopausal status defined as one of the following:

   • age ≥60 years
   • previous bilateral oophorectomy
   • age <60 years and amenorrhea for >12 months in the absence of interfering hormonal therapies (such as LH-RH agonists and ER-antagonists)
   • patients age <60 years using an ER-antagonist should have amenorrhea for > 12 months and FSH >24 U/L and LH >14 U/L e. patient age <60 years using LH-RH agonists should continue LH-RH-agonists until after the PET procedures

4. Initially ER-positive tumor histology.

5. ECOG performance status 0-2.

6. Signed written informed consent

7. Able to comply with the protocol

Exclusion Criteria:

1. Use of estrogen receptor ligands, including tamoxifen, fulvestrant or estrogens, or androgen receptor ligands, during the 6 weeks before entry into the study
2. Life-expectancy ≤ 3 months