Imaging agent could improve breast cancer treatment by measuring changes in PR levels

PET imaging with 18F-fluorofuranylnorprogesterone (18F-FFNP) could help specialists treat patients with estrogen-receptor (ER)-positive breast cancer, according to a new study published in The Journal of Nuclear Medicine. The imaging agent can measure changes in progesterone receptor (PR) levels that occur following short-course estrogen treatments.

The authors studied T47D human breast cancer cells and mice bearing T47D tumor xenografts, treating them with estrogen to increase PR expression. The cells, and the mice, were imaged with 18F-FFNP.

The imaging results revealed that, after 48 hours, the T47D cells showed an increase in 18F-FFNP. After 48 hours and 72 hours, the mice bearing T47D tumor xenografts showed a similar increase.

“There was no significant preferential 18F-FFNP binding or uptake by PR-A versus PR-B in the PR isoform–specific cell lines and tumor xenografts,” the study’s authors noted.

Co-author Amy M. Fowler, MD, PhD, department of radiology at the University of Wisconsin-Madison, explained in a prepared statement from the Society of Nuclear Medicine & Molecular Imaging that this was noteworthy “given the variability of PR isoform expression observed in breast cancer patients.”

“Validation of PR imaging as a biomarker of endocrine sensitivity in patients before and after estradiol challenge could provide new opportunities in the field of molecular imaging and nuclear medicine for breast cancer imaging,” Fowler said in the statement. “Improved methods for testing endocrine sensitivity in patients could better inform decisions for optimal individualized ER-positive breast cancer therapy, potentially reducing morbidity and mortality.”