Significance of dorsal bladder neck involvement in predicting the progression of non‐muscle‐invasive bladder cancer

OBJECTIVES: Accurately predicting of progression is important for patients with non-muscle-invasive bladder cancer (NMIBC). We previously reported that bladder neck involvement (BNI) was significantly associated with progression of NMIBC. In this study, we evaluated the prognostic significance of the detailed BNI location in NMIBC patients. METHODS: We retrospectively reviewed 651 patients diagnosed with primary NMIBC at a single center between 2000 and 2018. Using the detailed BNI location, patients were divided into the following three groups: dorsal BNI (BNId; 4 to 8 o'clock position), ventral BNI (BNIv; 8 to 4 o'clock but not 4 to 8 o'clock position), and non-BNI group. Both time to progression to muscle-invasive disease and distant metastasis was compared among the three groups. A prognostic model was developed and its discriminative ability was evaluated. RESULTS: Dorsal bladder neck involvement and BNIv were observed in 43 (6.6%) and 36 (5.5%) patients, respectively. During a median follow-up of 61 months, 35 (5.4%) patients progressed. The cumulative incidence at 5 years was 12%, 0%, and 5.0% in BNId, BNIv, and non-BNI groups, respectively. On multivariate analysis, BNId was a significant and independent risk factor for progression, tumor stage pT1, and histologic grade G3. One point was assigned to each factor, and patients were classified into four well-stratified prognostic groups based on the total score. CONCLUSION: Dorsal bladder neck involvement was an independent and significant risk factor for progression in primary NMIBC. Our simple and practical prognostic model including BNId is easy to use and may help selecting the optimal treatment and its timing.