Prognostische waarde van HER2 positieve circulender tumorcellen bij patienten met gemetastaseerde borstkanker die behandeld worden met aromatase inhibitors

Today’s treatment of metastatic breast cancer is guided by characteristics of the primary tumor, while 90% of deaths due to breast cancer occur as a consequence of metastases. Treatment of metastatic breast cancer patients with hormonal agents is often employed in the clinic. A worse outcome to hormonal therapy was observed in patients with primary tumors expressing both ER and HER2 compared to patients with primary tumors positive for ER but negative for HER2. Metastatic breast cancer patients are still treated based on primary tumor characteristics, while it is now increasingly appreciated that important characteristics like ER and HER2 expression may differ between the primary tumor and the metastatic lesion. Circulating tumor cells (CTCs) are cancer cells present in the peripheral blood of patients with metastatic breast cancer and are thought to represent characteristics of the metastases. We hypothesize that HER2 status on CTCs will be stronger associated with outcome to hormonal therapy than HER2 status in primary tumors. If so, this means that patients with primary tumors expressing ER and lacking HER2, but with CTCs expressing HER2, should not be treated with hormonal agents.

We hypothezise that patients with a primary tumor expressing ER and lacking HER2 but with CTCs expressing HER2 have a worse response on hormonal therapy.

- Baseline

- 6 months evaluation

Blood draw for CTC enumeration and characterization (80 mL of blood) at baseline