¹⁸F-4FMFES and ¹⁸F-FDG PET/CT in Estrogen Receptor-Positive Endometrial Carcinomas: Preliminary Report.

Abstract

This article reports the preliminary results of a phase II clinical trial investigating the use of the estrogen receptor (ER)-targeting PET tracer 4-fluoro-11β-methoxy-16α-¹⁸F-fluoroestradiol (¹⁸F-4FMFES) and ¹⁸F-FDG PET in endometrial cancers. In parallel, noninvasive interventions were attempted to slow progression of ¹⁸F-4FMFES metabolites in the intestines to reduce abdominal background uptake. <b>Methods:</b> In an ongoing study, 25 patients who received prior pathologic confirmation of an ER-positive endometrial cancer or endometrial intraepithelial neoplasia agreed to participate in the ongoing clinical trial. Patients were scheduled for ¹⁸F-FDG and ¹⁸F-4FMFES PET/CT imaging in random order and within 2 wk. Patients were administered either 4 mg of loperamide orally before ¹⁸F-4FMFES tracer injection or repeated intravenous injection of 20 mg of hyoscine <i>N</i>-butylbromide during ¹⁸F-4FMFES PET/CT. Regions of interest covering the whole abdomen and excluding the liver, bladder, and uterus were drawn for the ¹⁸F-4FMFES PET images, and an SUV threshold of more than 4 was applied. The volume of the resulting region was compared between the different interventions to estimate the extent of the intestinal background uptake. <b>Results:</b> Repeated injection of hyoscine <i>N</i>-butylbromide substantially reduced the intestinal background volume, whereas loperamide had a significant but moderate effect. ¹⁸F-4FMFES tumor SUV_max ranged from 3.0 to 14.4 (9.4 ± 3.2), whereas ¹⁸F-FDG SUV_max ranged from 0 to 22.0 (7.5 ± 5.1). Tumor-to-background ratio was significantly higher for ¹⁸F-4FMFES (16.4 ± 5.4) than for ¹⁸F-FDG (7.4 ± 4.6). Significant differences were observed between grade 1 and higher-grade tumors concerning ¹⁸F-4FMFES uptake and contrast, ¹⁸F-FDG uptake, and the ¹⁸F-FDG/¹⁸F-4FMFES uptake ratio. <b>Conclusion:</b> It is possible to improve ¹⁸F-4FMFES abdominal background using hyoscine <i>N</i>-butylbromide. Both ¹⁸F-FDG and ¹⁸F-4FMFES PET are suitable for detection of ER-positive endometrial cancers, although ¹⁸F-4FMFES yielded a better tumor contrast than did ¹⁸F-FDG.