FES-PET: setting the stage for breast cancer bone metastases

Written by Caitlin Killen

New research demonstrates a promising role for 18F-Fluoroestradiol (FES)-PET imaging in diagnosis and treatment predictions for metastatic lobular breast cancer.

Research presented at the San Antonio Breast Cancer Symposium (SABCS; TX, USA, 10-14 December 2019) has demonstrated the utility of both FES-PET and 18F-Fluorodeoxyglucose (FDG)- PET imaging in ER+ metastatic lobular breast cancer.

“Last year at SABCS, we demonstrated that FES-PET and FDG-PET can detect lobular breast cancer. The ability to detect bone metastases is an additional advantage of FES-PET that we showed in our current study,” commented study author Poorni Manohar (Seattle Cancer Care Alliance; WA, USA).

FDG-PET measures the metabolic activity of tumors using a glucose tracer; however, inflammation or infection can lead to false positives. FES-PET can simultaneously measure uptake of FES at multiple tumor sites, meaning it can detect lesion location and predict sensitivity to estrogen therapy.

“This has a huge implication on treatment selection. In metastatic breast cancer, there are numerous therapies available and being able to distinguish if a patient will respond to endocrine therapy is essential. Conventionally we biopsy patients to determine estrogen receptor and HER2 status, however, biopsy has limitations including challenging biopsy sites and intra-tumor and inter-tumor heterogeneity,” explained Manohar.

FES and FDG analysis were retrospectively reviewed in 200 lesion samples from 30 individuals with metastatic lobular breast cancer. Diffuse bone marrow uptake was detected in 7 women and was more visible in the FES-PET scans.

There was significant uptake of FDG and FES in all patients, allowing insight into the metastasis of lobular breast cancer. FES and FDG were demonstrated to have similar avidity, meaning that both techniques can be utilized for the detection of bone metastases.

“This type of risk stratification and personalized medicine is very much needed in metastatic breast cancer.”

Other ongoing studies are currently examining the combination of FES-PET with nuclear medicine bone- and CT-scans to improve understanding of how bone metastases evolve. FES-PET could aid the early detection of metastatic bone disease, allowing for the prevention of adverse skeletal events.

“It could help us treat patients with the treatment they need – providing aggressive care to those that require it and protecting against unnecessary treatment in those that would do just fine with endocrine therapy alone. This type of risk stratification and personalized medicine is very much needed in metastatic breast cancer,” concluded Manhar.

While FDG- and FES-PET are both useful in the detection of breast cancer bone metastases, the added utility of FES-PET is its ability to predict estrogen sensitivity. Lobular breast cancer has previously been difficult to detect with conventional imaging techniques, highlighting the exciting step forward that FES-PT presents. Future trials could confirm the use of FES-PET in the staging of bone dominant metastatic lobular breast cancer.