Low‐risk non‐muscle‐invasive bladder cancer: Further prognostic stratification into the “very‐low‐risk” group based on tumor size

OBJECTIVE: To validate the significance of the entity of "very-low-risk" bladder cancer by analyzing the clinical outcomes of low-risk bladder cancer when further stratified by tumor size. METHODS: We accessed our prospectively maintained, single-institution, electronic bladder cancer registry to extract the clinicopathological data of patients who were diagnosed with primary, solitary, Ta, low-grade tumors that were 1.0 cm). The survival data of the two groups were compared for recurrence, progression and mortality. RESULTS: A total of 165 patients were followed up for a median period of 79 months (interquartile range 47-118 months). A total of 45% (75/165) of the study cohort had tumors that were ≤1.0 cm. Recurrences were found in 40% (66/165) of the study cohort. On Kaplan-Meier analysis, patients with tumor size ≤1.0 cm had significantly longer time to recurrence (P  1.0 cm was significantly associated with shorter time to recurrence (HR 2.54, 95% CI 1.35-4.77, P = 0.004). Tumor size was not significantly associated with any differences in time to overall progression, muscle-invasive progression or overall mortality (P = 0.108, P = 0.362 and P = 0.225, respectively, log-rank test). CONCLUSIONS: Low-risk bladder cancer can be further stratified based on tumor size. Larger tumors (>1.0 cm) are significantly associated with shorter time to recurrence compared with smaller tumors (≤1.0 cm). However, there were no significant differences in the probability of developing disease progression or overall mortality between larger and smaller tumors.