New research published in the February issue of The Journal of Nuclear Medicine shows that using an imaging agent called 18F-fluoroestradiol in PET scans can help predict responsiveness to less invasive treatments for patients with ER-positive, HER2-negative metastatic breast cancer.
Nearly two-thirds of invasive breast cancers are ER-positive, meaning that the cancer cells grow in response to estrogen, as opposed to other hormones such as progesterone (PR-positive). The first course of action for these cancers is typically endocrine therapy which targets the hormones responsible for cancer growth. Should the cancer progress in these patients, more aggressive treatments are recommended including chemotherapy.
“In some ER-positive breast cancer patients, cancer progression can be a result of a gradual resistance to endocrine therapy,” noted senior author Hannah M Linden, MD, FACP, Athena Distinguished Professor and breast medical oncologist at the University of Washington Fred Hutchison Cancer Research Center and Seattle Cancer Care Alliance in Seattle, Washington.
The study included patients with ER-positive, HER2-negative metastatic breast cancer who were already on a course of endocrine therapy, and were also being treated with Histone daecetylase inhibitors (HDACIs) to reverse endocrine resistance.
Patients were then given periodic PET scans with F-fluoroestradiol, an imaging agent to help detect ER-positive breast cancer lesions.
The results showed a correlation between increased uptake of F-fluoroestradiol at patient’s baseline scan and responsiveness to their course of therapy, indicated by longer cancer progression-free survival.
“We test ER expression in a metastatic biopsy once at the beginning of the patient’s journey,” explained Linden, “and we make decisions all along—when to give chemotherapy, when to use endocrine therapy, whether or not to use targeted agents—based on that one measurement.”
“Since we know that ER expression can fluctuate, imaging with 18F-fluoroestradiol at various time points could help clinicians predict response to endocrine therapy and select optimal treatment in the future.”
Linden and team’s earlier research contributed to F-fluoroestradiol’s FDA approval for use in imaging for breast cancer patients in May of 2020.
