The Paris System for reporting urinary cytology in the follow-up of non-muscle-invasive bladder cancer

INTRODUCTION: This study aimed to investigate the correlation between the Paris System for Reporting Urinary Cytology (TPS) and cystoscopic findings in histologically confirmed bladder cancer recurrences. We also assessed patient-specific variability in urinary cytology findings during the bladder cancer follow-up. MATERIALS AND METHODS: This retrospective, single-center study included 180 patients with non-muscle-invasive bladder cancer (NMIBC) who were treated at Kuopio University Hospital between January 2014 and December 2021. A total of 968 follow-up urinary specimens were correlated with cystoscopy results. Of the 336 histological samples obtained during follow-up, 271 were paired with the cytology results. RESULTS: Patients with high-grade urothelial carcinoma (HGUC) cytology showed a high cumulative risk of progression to muscle-invasive disease. Recurrence risk increased with higher cytological class, whereas negative for high-grade urothelial carcinoma (NHGUC) and atypical urothelial cells (AUC) showed consistently low and comparable recurrence rates. When stratified by the highest cytological category during follow-up, biopsies of red patches at cancer recurrence revealed neoplasia rates of 3.6%, 4.8%, 40.0%, and 100% for NHGUC, AUC, suspicious for high-grade urothelial carcinoma (SHGUC), and HGUC, respectively. CONCLUSION: This study suggests that urinary cytology using TPS is useful for assessing the risk of malignancy when no exophytic tumor is observed on cystoscopy. The risk of high-grade recurrence or progression was low when cytology was classified as NHGUC or AUC. In the absence of visible tumors, surveillance without biopsy may be a safe option if cytology is NHGUC or AUC. MICRO-ABSTRACT: The role of urinary cytology in guiding the biopsy of non-exophytic bladder lesions remains unclear. We retrospectively analyzed 968 follow-up cytology specimens from 180 patients with NMIBC using the Paris System. NHGUC and AUC were associated with low recurrence and progression risk, supporting the conservative management of non-exophytic lesions in selected patients.