Delayed (18)F-FDG PET/CT Appearance of Urachal Adenocarcinomas

BACKGROUND: Urachal carcinoma is a rare urological malignancy. Use of (18)F-FDG PET/CT in urological oncology has developed slowly because of the urinary elimination of (18)F-FDG. We investigated whether delayed postdiuretic (18)F-FDG PET/CT could be used for diagnosing urachal carcinoma. METHODS: This retrospective study included 6 patients who underwent delayed postdiuretic (18)F-FDG PET/CT for the evaluation of urachal carcinoma. The delayed postdiuretic PET/CT parameters and clinical characteristics of urachal carcinoma were investigated. RESULTS: There was no significant difference in the SUVmax between the primary tumors and the urine in the bladder before delayed diuresis (25.4 ± 19.5 vs. 42.9 ± 31.1, P=0.18). However, the SUVmax of the primary tumors was significantly higher than the SUVmax of urine after delayed diuresis (25.4 ± 19.5 vs. 3.5 ± 1.6, P=0.002). Diuretic (18)F-FDG PET/CT was positive in all patients when compared with normal liver tissues or urine after delayed diuresis. The SUVmax, TLR, and TUR of the primary tumors were 25.4 (range: 7.2–58.9), 7.0 (range: 1.8–14.7), and 6.8 (range: 3.8–11.3), respectively. Delayed postdiuretic (18)F-FDG PET/CT had a negative predictive value of 100% (5/5) for predicting lymph node metastasis. One patient received chemotherapy after radical resection of urachal carcinoma because (18)F-FDG PET/CT found lung metastases, and one patient only received chemotherapy because PET/CT found peritoneal and skeletal metastases. CONCLUSIONS: Delayed postdiuretic (18)F-FDG PET/CT is a useful tool for the preoperative evaluation of urachal carcinoma. (18)F-FDG PET/CT may improve clinical decision making and management of urachal carcinomas.