18F-FES and 18F-FDG PET for Differential Diagnosis and Quantitative Evaluation of Mesenchymal Uterine Tumors: Correlation with Immunohistochemical Analysis

The aim of this study was to investigate the relationship between the tumor uptake of 16 alpha-F-18-fluoro-17 beta-estradiol (F-18-FES) and F-18-FDG using PET and expressions of sex hormone receptors, such as estrogen receptor (ER), as well as glucose transporter 1 (GLUT-1) and Ki-67 analyzed by the immunohistochemistry method in mesenchymal uterine tumors. Methods: Forty-seven patients with mesenchymal uterine tumors were studied with F-18-FES and F-18-FDG PET. Postoperative pathologic diagnosis revealed 33 uterine leiomyomas and 14 uterine sarcomas. Tissue samples were assayed for expression of ER alpha, ER beta, progesterone receptor (PR), PR-B, GLUT-1, and Ki-67 by an immunohistochemistry method. Standardized uptake values (SUVs) for F-18-FES and F-18-FDG were compared with the semiquantitative immunoreactive score (0-12) and quantitative labeling index (LI) for Ki-67 in immunohistochemistry. Results: F-18-FES uptake was significantly lower (P < 0.001) and the F-18-FDG uptake and SUV ratio of F-18-FDG to F-18-FES (F-18-FDG/F-18-FES ratio) (P < 0.005 and P < 0.001, respectively) were significantly higher in uterine sarcomas than in leiomyomas. Immunohistochemistry analysis showed significantly higher expressions of ER alpha, PR, and PR-B in uterine leiomyomas than in sarcomas. The Ki-67 LI was significantly greater in uterine sarcomas than in leiomyomas. Correlation analysis for all tumors showed positive correlations between F-18-FES SUV and immunohistochemistry scores of ER alpha, PR (P < 0.001), and PR-B (P < 0.005) as well as between F-18-FDG SUV and GLUT-1 and Ki-67 (P < 0.001). However, the F-18-FDG/F-18-FES ratio showed significantly negative correlations with ER alpha, PR (P < 0.001), and PR-B (P < 0.005) and a positive correlation with Ki-67 LI (P < 0.001). In uterine sarcomas, ER alpha and F-18-FES SUV showed a positive correlation (P < 0.001) in a low SUV range, and the F-18-FDG/F-18-FES ratio showed positive correlations with ERb and GLUT-1 expression (P < 0.005). Conclusion: F-18-FES and F-18-FDG PET showed correlations between tracer uptake and expressions of sex hormone receptors, GLUT-1, and Ki-67 in mesenchymal uterine tumors. The F-18-FDG/F-18-FES ratio was correlated with Ki-67, GLUT-1, and ER beta in uterine sarcoma. Functional PET imaging and PET parameters would be useful noninvasive biomarkers for the assessment of tumor hormone receptor expression, glucose metabolism, and proliferation and for differential diagnosis of uterine leiomyoma and sarcoma.