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

(A) Qualitative maximum-intensity-projection whole-body assessment of effect of pharmacologic interventions to slow progression of radioactive intestinal bolus. Without use of any intervention (left panel), ¹⁸F-4FMFES PET typically produces intense abdominal uptake caused by progression of radiometabolites excreted by gallbladder in intestines. Ingestion of 4 mg of loperamide 15 min before injection of radiotracer yielded mitigated results (center panel). Repeated intravenous injection of 20 mg of hyoscine N-butylbromide at 0, 20, and 40 min after ¹⁸F-4FMFES injection apparently reduced lower-abdomen background and slowed transit of radioactive intestinal bolus (right panel). (B) Measured volume extracted from application of SUV threshold of >4 on abdominal ROI. Both use of loperamide and use of hyoscine N-butylbromide significantly reduced intestinal background volume. **P < 0.01. ****P < 0.001.

Representative case of endometrial carcinoma (arrows) imaged with ¹⁸F-FDG PET/CT (top row) and ¹⁸F-4FMFES PET/CT (bottom row), displayed in frontal maximum-intensity projection (MIP) and in sagittal views.

A 69-y-old endometroid adenocarcinoma patient with ¹⁸F-FDG–negative, ¹⁸F-4FMFES–positive primary tumor. ¹⁸F-FDG PET did not yield any abnormal uptake in uterus, whereas ¹⁸F-4FMFES PET revealed intense signal (SUV_max, 9.6; arrows) over 44 × 32 × 25 mm region. Postsurgery pathology report measured size of tumor to be 20 mm in its long axis, meaning ¹⁸F-4FMFES overestimated size of tumor in this case.

A 75-y-old endometroid adenocarcinoma patient with ¹⁸F-FDG false-positive inguinal node. (A) Endometroid adenocarcinoma primary tumor, with SUV_max uptake of 12.3 for ¹⁸F-FDG and 8.9 for ¹⁸F-4FMFES (black arrows). The ¹⁸F-FDG PET also revealed a suspected right inguinal node metastasis (red arrow), which yielded SUV_max of 5.2 (T/B, 7.2). (B) Transaxial slices of the suspected inguinal node metastasis (red arrows). The ¹⁸F-FDG–positive node was ¹⁸F-4FMFES–negative and of normal appearance in CT image. Pathology examination considered inguinal node as normal, meaning ¹⁸F-FDG signal was false-positive.

A 67-y-old endometrial carcinoma patient with ¹⁸F-4FMFES false-positive iliac node. (A) Endometrial carcinoma primary tumor, with SUV_max uptake of 12.9 for ¹⁸F-FDG and 12.7 for ¹⁸F-4FMFES (arrows). (B) Coronal (top) and transaxial (bottom) views centered on suspected left iliac sentinel node metastasis with ¹⁸F-4FMFES (arrows), which was of normal aspect in CT images. Pathology examination after surgery considered iliac node normal, confirming false-positive result for ¹⁸F-4FMFES.