Validation of the risk stratification newly defined in the Japanese Urological Association guidelines 2019 for non‐muscle invasive bladder cancer: A multi‐institutional collaborative study

OBJECTIVES: To validate the risk stratification newly defined in the Japanese Urological Association guidelines 2019 for non-muscle invasive bladder cancer and provide a more accurate stratification model for a heterogeneous intermediate-risk group. METHODS: A total of 1610 patients, who underwent transurethral resection, diagnosed with non-muscle invasive bladder cancer in nine collaborating hospitals were retrospectively reviewed. They were classified into low-risk, intermediate-risk, high-risk, and highest-risk groups, and recurrence-free survival, progression-free survival, cancer-specific survival, and overall survival were compared among the groups. The intermediate-risk group was subdivided into two groups based on the multivariable Cox regression model of recurrence and progression risk factors, and a revised risk model was created. RESULTS: The progression-free survival, cancer-specific survival, and overall survival were well stratified, while the recurrence-free survival of the intermediate-risk group was the shortest among the four groups (p < 0.001). The independent risk factors for recurrence and progression-free survival in the intermediate-risk group were as follows: age ≥ 70 years, sex, multiple tumors, tumor size ≥3 cm, and recurrent cases. The intermediate-risk group was subdivided into two groups: favorable intermediate-risk group and unfavorable intermediate-risk group. The revised risk model showed significant differences. CONCLUSION: We validated the Japanese Urological Association guidelines 2019 stratification model. The revised risk model provided a more accurate treatment selection for this disease subset.