We evaluated the feasibility of non-invasive imaging of estrogen receptors (ER) in primary breast cancer with iodine-123-labeled ER specific ligand (17α,20E)-21-[¹²³I] iodo-19-nonpregna-1,3,5-(10), 20-tetraene-3, 17-diol using conventional nuclear medicine technique.

Before they underwent surgical management, planar scintigraphy and single-photon emission computed tomography (SPECT) were performed in 18 patients with proven primary breast cancer, after single IV injection of 5~10 mCi I-123-estradiol. The results were compared with those of immunohistochemical staining against ER of the surgical specimens.

Planar and SPECT imaging showed hot uptake in nine of eighteen (50%) breast cancer patients. The results of ER immunohistochemistry were all positive in these patients. In the 9 cases of negative scintigraphy, 8 showed negative staining results but one showed positive staining results. Therefore, the overall concordance rate of ER scintigraphy and ER immunohistochemistry was 94.4% (17/18).

ER scintigraphy using I-123-estradiol is a highly predictable in vivo technique to detect ER-positive breast cancer preoperatively. It has potential application as a reliable diagnostic modality and indicator of hormone therapy for breast cancer patients.