Functional oestrogen receptor α imaging in endometrial carcinoma using 16α-[¹⁸F]fluoro-17β-oestradiol PET

To investigate the correlation between uptake of 16α-[(18)F]fluoro-17β-oestradiol (FES) and expression of oestrogen receptors as well as other related immunohistochemistry markers, positron emission tomography (PET) was performed in patients with endometrial carcinoma before surgery.

Nineteen patients with endometrioid adenocarcinoma underwent preoperative PET studies with FES and 2-[(18)F]fluoro-2-deoxy-D: -glucose (FDG). Standardized uptake values (SUVs) for each tracer and the regional FDG to FES SUV ratio were calculated using images after coregistration. PET values were compared with postoperative stage, differentiation grade and immunohistochemical scores including oestrogen receptor subtypes (ERα, ERβ), progesterone receptor B (PR-B), Ki-67 and glucose transporter 1 (GLUT1).

FES uptake showed a significantly positive correlation with expression of ERα. The FDG to FES ratio showed a significantly negative correlation with expression of ERα and PR-B. The FES uptake and FDG to FES ratio did not correlate with expression of ERβ, Ki-67 or GLUT1. FDG uptake was not correlated with any of the immunohistochemical scores. The PR-B score was strongly correlated with the ERα score. Well-differentiated carcinoma (grade 1) showed a significantly higher FES uptake and significantly lower FDG to FES ratio than moderately or poorly differentiated carcinoma (grade 2-3). None of the PET parameters were significantly different between advanced-stage carcinoma (≥ stage IB) and early-stage carcinoma (IA) based on the Féderation International de Gynécologie et d'Obstétrique (FIGO) staging classification. Differentiation grade was the most closely correlated parameter to FES uptake and FDG to FES ratio by multivariate analyses.

FES PET combined with FDG would be useful for non-invasive evaluation of ERα distribution, as well as ERα function, which reflects differentiation grade in endometrial carcinoma.