Abstract
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Objectives: 18F-FDG PET/CT has been limited used in the diagnosis of urogenital cancers, because of the physiological urinary excretion of 18F-FDG. Diuretic 18F-FDG PET/CT can overcome this limitation and improve detection efficacies of urogenital cancers. However, the dose and administration of diuretics have not reached a consensus yet. Previous studies conduct diuretic PET/CT by injection of 40mg furosemide intravenously, which is invasive and increases radiation risk of nurses. In this study, we investigated the clinical value of diuretic delayed 18F-FDG PET/CT via taking small dose of diuretics orally in diagnosing urogential cancers. To our knowledge, it is the first report which has successfully used the oral intake of small dose of furosemide in diuretic 18F-FDG PET/CT.
Methods: Forty-seven patients suspected of urogenital cancers from 2015 to 2017 were divided into small dosage group (26 males and 9 females, aged 33-82 years, 20mg furosemide) and routine dosage group (9 males and 3 females, aged 50-80 years, 40mg furosemide). All patients underwent whole body PET/CT scan (Discovery, GE Healthcare, Waukesha, WI, USA) from the mid-thighs to the skull 60min after intravenous injection of 3.7 MBq/kg of 18F-FDG. Diuretic delayed PET/CT images were acquired after oral intake of 40 mg or 20 mg furosemide. The urine SUVmax and L/U (the ratio of lesion and urine SUVmax) before and after diuresis were compared respectively. The imaging findings were confirmed by cystoscopy, pathology or radiological follow-up. Diagnostic efficacies for urogenital cancers were calculated. Informed consents were obtained. Results In small dosage group, forced diuresis eliminated significant 18F-FDG activity from urinary tract in 32 patients (91.43%) (Figure 1). The urine SUVmax of routine and delayed scans were 27.87±18.28 and 3.35±1.40, with statistical difference (P<0.001). The L/U of routine and delayed scans were 0.49±0.44 and 4.12±2.95 (P<0.001). The urine SUVmax of routine and delayed scans had no statistical differences between the two groups (p =0.57, 0.07). So did L/U (p=0.28, 0.38). In small dosage group, there were 31 malignancies (6 renal clear cell carcinoma, 2 renal pelvis transitional cell carcinoma, 2 ureter transitional cell carcinoma, 7 bladder urothelial carcinoma, 9 prostate cancer, 4 renal lymphoma, 1 bladder lymphoma ), 1 renal tuberculosis and 3 negative outcome after prostate cancer cystectomy. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of delayed imaging were 96.77% (30/31), 75.00% (3/4), 96.77% (30/31), 75.00% (3/4) and 94.29% (33/35), respectively. In routine dosage group, there were 10 malignancies (5 renal clear cell carcinoma, 2 bladder urothelial carcinoma, 3 prostate cancer), 1 ureter tuberculosis and 1 negative outcome. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of delayed imaging were 90.00% (9/10), 50.00% (1/2), 90.00% (9/10), 50.00% (1/2), 83.33% (10/12), respectively. Conclusion Diuretic delayed 18F-FDG PET/CT imaging post oral intake of small dose of furosemide has implications in the diagnosis of urogenital cancers. Key words Urogenital neoplasms; Diuresis; Positron-emission tomography; Tomography, spiral computed Research Support Guangdong Natural Science Foundation (2015A030313106, 2016A030313241)Figure 1. 18F-FDG PET/CT images of a 57-year-old man with uroepithelial bladder cancer. 1A-1D PET/CT images. CT image shows a soft tissue mass of left wall of bladder (1B, arrow). PET image shows high radioactivity in bladder (1C). The metabolic character of the lesion can’t be identified (1D). 2A-2D Diuretic PET/CT images. A soft tissue mass (2B, arrow) of left wall of bladder can be detected by CT, with a size of 16mm×11 mm. PET image shows excellent tracer washout of bladder (2C). Diuretic PET/CT image reveals intense tracer uptake (SUVmax=16.2) of bladder lesion (2D, arrow).