Moleculaire beeldvorming van de oestrogeenreceptor dichtheid om de hormonale behandelingsmogelijkheden voor patiënten met borstkanker te verbeteren.

Patients with different types of acquired anti-hormonal resistance are likely to respond differently to a particular kind of treatment. The ER+ subtype would most likely initially respond to a second or third line of anti-hormonal therapy, but ultimately these tumors will again become resistant. At that stage, chemotherapy is the only treatment available. Chemotherapy is currently also the only treatment option for tumors of the ER- phenotype. In contrast, treatment with estrogen is highly effective for the hypersensitive ER++ phenotype and could therefore be an attractive alternative for chemotherapy in this selected group of patients. Currently, this treatment option is not utilized due to the absence of proper stratification methods.
FES-PET may allow identification of patients without ER expression (ER-), patients with preserved ER expression (ER+) and patients with ER overexpression (ER++). This project therefore aims to investigate in a pilot clinical study whether the acquired anti-hormonal resistant phenotypes in breast cancer patients can be discriminated on basis of ER expression levels as measured by FES-PET. The discrimination of phenotypes could allow selection of patients eligible to estrogen treatment.

Measuring ER-density with FES-PET can be used as a predictive test to select patients sensitive for estrogen therapy.

At the start of study ER densitity will be determined by FES-PET, the patient will be staged with CT-scan, and baseline clinical information will be collected (laboratory results, VAS-score, ECOG performance, ECG).

Follow-up will take place monthly during the first 3 months, and thereafter every 3 months.

In patients with acquired antihormonal resistance, eligible for estrogen therapy, a FES-PET scan will be made to determine FES-PET tumor uptake (which corresponds to estrogen receptor expression levels). Immediately after the FES-PET scan, all patients will start with a standard accepted dose of 2mg estradiol TID. Therapy response will be monitored by regular follow-up. RECIST criteria and clinical benifit will be used as criteria. In case of disease progression before end of the study period, estradiol treatment will be stopped.