Prediction of Response to 2nd-line Hormone Therapy by FES CT/PET in Patients With Metastatic Breast Cancer

Approximately 70% of breast cancer patients have estrogen-receptor-expressing tumors, making hormone therapy an attractive option for adjuvant and metastatic treatment. The expression of estrogen receptors is modified during the course of treatment. Tumor development, there is a discrepancy between primary tumors and metastases from 14.5% to 40% of cases. Biopsies are useful for reassessing a patient's "estrogen receptor" status, but it is not always feasible especially at the stage of multiple metastases and the gesture remains invasive. The sensitivity and specificity of PET FES has been studied in patients with "estrogen-positive receptor" breast cancer lesions. Sensitivity was good except for liver metastases due to physiological binding of this tracer to the liver. Quantification of FES binding was correlated with expression of estrogen receptors visualized in IHC. Metastases could be seen with FES in the bone, lung and lymph nodes and more difficult in the liver. Clinicians are currently proposing second-line hormonal treatment to a metastatic patient who is progressing after first-line hormonal therapy if the initial disease was RH + with an increase in survival without recurrence more or less long. The biopsy of the metastatic site or sites is rarely performed because of the heaviness of the gesture. Clinicians are waiting for imaging, which can replace biopsy before the second-line metastatic hormone treatment in breast cancer, which will reveal the metastatic lesion heterogeneity allowing to establish if hormone therapy is the best therapeutic option for these patients and therefore lead to a personalized medicine driven by PET FES. This imaging approach seems all the more interesting as ER expression appears to evolve over time under the pressure of treatment or the natural evolution of carcinomas. Currently, no studies in breast cancer, in an ER + population on the initial tumor and Her2 negative, are listed for the study of ER expression by PET FES before a second metastatic hormone treatment line.