Comparison between the diagnostic accuracies of 18F-fluorodeoxyglucose positron emission tomography/computed tomography and conventional imaging in recurrent urothelial carcinomas: a retrospective, multicenter study

Purpose: To determine the performance accuracy of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) after primary tumor treatment for both bladder cancer (BC) and upper tract urothelial cancer (UTUC). To compare the accuracy of FDG PET/CT with that of contrast-enhanced-ceCT and magnetic resonance imaging (MRI). Methods: Data of patients with recurrent urothelial carcinomas (UC) after primary treatment were collected in a retrospective, international multicenter study. Inclusion criteria were (1) patients with a known history of UC in the BC and/or in the UTUC; (2) PET/CT images after curative intent treatment of the primary tumor; (3) conventional imaging modalities (abdominal ceCT or MRI, or total body ceCT, and chest X-ray: called C.I.) performed no more than 3 months from PET/CT; (4) available standard of reference (e.g., histological data or follow-up imaging modalities) for the validation of PET/CT findings. Exclusion criteria were other abdominal tumors, chemotherapy administration prior to and/or concomitant to imaging, and non-urothelial histologic variants. Sensitivities, specificities, positive, and negative predictive values were evaluated for all patients and separately for bladder and UTUC. Results: Overall, 287 patients were enrolled. Two-hundred thirteen patients underwent cystectomy (74.2%), 35 nephroureterectomy (12.2%), 31 both cystectomy + nephroureterectomy (10.8%), 5 both cystectomy + conservative treatment for UTUC (1.4%), and 3 (1%) other types of nephron-sparing treatments for UTUC. Neoadjuvant and adjuvant treatments were performed in 36 (12.5%) and 111 (38.7%) patients, respectively. Sensitivity and specificity (95% confidence intervals) of PET/CT for the detection of recurrent UC were 94% (91% to 96%) and 79% (68% to 88%), respectively. However, sensitivity was higher for BC than UTUC (95% vs. 85%) while specificity was lower in BC (78% vs. 85% for BC and UTUC, respectively). PET/CT and C.I. findings were available in 198 patients. The results were positively concordant in 137 patients, negatively concordant in 23 patients, and discordant in 38 patients (20 negative at C.I. vs. positive at PET/CT and 18 positives at ceCT/MRI vs. negative at PET/CT) (K Cohen = 0.426; p < 0.001). Sensitivities, specificities, and accuracies (95% confidence intervals) of PET/CT vs. C.I. for the detection of recurrent BC and UTUC were 94% (90% to 97%) vs. 86% (81% to 92%), 79% (67% to 92%) vs. 59% (44% to 74%), and 91% (87% to 95%) vs. 81% (75% to 86%), respectively. Conclusions: FDG PET/CT has a high diagnostic accuracy for the identification of recurrent UC, particularly in patients with BC. Moreover, its accuracy outperforms C.I. for both BC and UTUC.