Detectability of residual invasive bladder cancer in delayed 18F-FDG PET imaging with oral hydration using 500 mL of water and voiding-refilling

Objective 2-Fluorine-18-fluoro-2-deoxy- d -glucose positron emission tomography ( 18 F-FDG PET) imaging is not considered useful for assessing bladder cancer due to the physiological uptake of 18 F-FDG in the bladder. Despite reports of the detection of bladder cancer by washing out 18 F-FDG from the bladder, such methods are invasive and impractical in the routine practice. The purpose of this study was to evaluate prospectively the utility of oral hydration with 500 mL of water and voiding-refilling, a minimally invasive method that we introduced to enable detection of residual invasive bladder cancer on delayed 18 F-FDG PET imaging. Methods From January 2015 to December 2017, 267 consecutive patients with bladder cancer underwent 18 F-FDG PET/computed tomography scans. Among these patients, 25 (19 men and 6 women; mean age, 72.0 ± 11.3 years) were newly diagnosed as having muscle-invasive bladder cancer by transurethral resection of bladder tumor and T3b or T4 by magnetic resonance imaging (MRI). All patients were orally hydrated with only 500 mL of water and were then instructed to void frequently for 60 min before early 18 F-FDG PET imaging. After the scans, they were instructed to hold their urine for 60 min. Then, delayed imaging was performed. Two radiologists evaluated the early and delayed 18 F-FDG PET images to determine whether residual invasive bladder cancer could be detected. The maximum standardized uptake values (SUVmax) of the bladder urine and residual tumor site were also measured on early and delayed images. The maximum diameter of the primary bladder tumor was measured on MRI. Results The sensitivity for detecting residual invasive bladder cancer on early and delayed imaging were 24.0 and 92.0%, respectively ( P