Estrogen receptor PET imaging detects early stage breast cancer, with limitations

Early-stage breast cancer lesions can be detected with F-18 FES PET, but success depends on tumor size and level of disease, according to a study published online Aug. 22 in the Journal of Nuclear Medicine.

A team of researchers, including Mary L. Gemignani, MD, of Memorial Sloan-Kettering Cancer Center in New York City, and others evaluated the feasibility of using F-18 FES (16 alpha-F-18 fluoro-17 beta-estradiol) to ferret out new cases of breast cancer by searching for estrogen receptor expression as an indicator of disease. Previous studies have already laid a foundation for the radiotracer in cases of advanced-stage breast cancer. Results of this study indicated that while F-18 FES was sensitive to cancer in disparate areas, it did not catch all tumors present.     

“Our study supported the existing data on the role of F-18 FES PET in characterizing ER expression,” wrote Gemignani et al. “In the perioperative setting, F-18 FES PET reliably identified additional sites of disease. However, our study highlighted the effects of tumor size and disease burden in imaging with F-18 FES PET and possible limitations on its role in the primary operative, early breast cancer setting.”

For this prospective study, 48 patients, a majority having either stage I or II breast cancer, underwent F-18 FES PET for perioperative tumor detection based on estrogen and progesterone receptor expression. Researchers took note of both clinical and tumor characteristics, outcomes following treatment and an immunohistochemical analysis for the expression of both estrogen and progesterone. Standardized uptake values of lesions were correlated with percentages of expression.

Findings indicated that F-18 FES spotted axillary nodal uptake in five patients with more than four estrogen-receptor positive tumors. The tracer was discovered to have 85 percent overall sensitivity for detecting perioperative early-stage breast cancer.

“We found a correlation with immunohistochemistry estrogen receptor expression but not with gene expression,” wrote the authors. “There was a significant association with F-18 FES uptake and size of primary tumor, likely accounting for the lower sensitivity we saw in our study group as compared with prior published work.”

Not only was FES PET able to find axillary involvement, but also distant bone metastases. However, small volume tumors were not identified. The issue of estrogen receptor immunohistochemistry versus genetic expression indicated high heterogeneity between tumors. Given this study’s indications, F-18 FES PET may have limitations for perioperative detection, but the researchers noted that it could have significant potential for evaluating response to endocrine therapy.