Procedure: PET/CT Scan

All subjects will be seen at baseline and then monthly till month 6 of fulvestrant therapy unless clinical or radiological progression or unacceptable toxicity earlier than month 6.

During the study the subject will undergo the following scans:

• A18F-FDG PET/CT scan performed at baseline, prior to starting the fulvestrant treatment, to identify the sites involved by the subject's cancer.
• A 18F-FES PET/CT scan performed at baseline, prior to starting the fulvestrant treatment, to determine the hormone receptor content of the sites involved by the breast cancer.
• A 18F-FES PET/CT scan performed after three (3) monthly injections of fulvestrant to determine whether estrogen uptake is blocked by fulvestrant.

The majority of women diagnosed with breast cancer are post-menopausal, of which up to 75% are estrogen (ER) and/or progesterone receptor (PR) positive. Even in pre-menopausal breast cancer over half of all patients will have expression of these hormone receptors. Thus therapeutic strategies targeting the estrogen receptor or its ligand are the most common treatment offered in breast cancer. Despite substantial benefits now demonstrated with selective estrogen receptor modulators (e.g. tamoxifen) and aromatase inhibitors (e.g. anastrazole, letrozole and exemestane), a significant proportion of patients will still unfortunately have or develop resistance to these hormonal therapies.

Despite approximately two-thirds of patients who are prescribed fulvestrant following prior hormonal agents not benefiting from this therapy, clinicians are still offering this option to all suitable women because of the lack of a better means of identifying the individual responders.

To assess whether the recommended treatment is beneficial to a specific individual, the disease burden is assessed before and following treatment. Conventional imaging techniques such as the bone scan or computerized tomography (CT) can take several months to show a successful response to treatment. Positron emission tomography (PET) can improve the evaluation of women with breast cancer by providing an accurate assessment of the extent of disease and unique information about tumor biology such as metabolic activity.