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Substaging and Stratified Treatment of T1 Bladder Cancer - a Nationwide Register-Based Study
Ninna K Nielsen1,2,3, Peter B Hjort1,2, Erik B Hansen2
1Department of Clinical Medicine, Aarhus University, Aarhus, Denmark.
Background And Objective:
Substaging of T1 bladder cancer (BC) was implemented in Denmark in 2010 based on depth of lamina propria invasion-pT1a (superficial) and pT1b (deep)-with bladder-sparing therapy recommended for pT1a and early cystectomy for pT1b. This study evaluated outcomes of this substage-guided approach in a nationwide cohort.
Methods:
In this nationwide register-based study (2012-2018), all patients diagnosed with T1 BC were identified from the Danish Bladder Cancer Database. Patients were stratified by substage (pT1a, pT1b, unspecified pT1). Overall survival was estimated using Kaplan-Meier analysis; intravesical recurrence and progression were analysed using the Aalen-Johansen estimator, treating death as a competing risk; hazard ratios (HRs) were calculated using Cox models adjusted for sex, age, and comorbidities.
Key Findings And Limitations:
Among 3086 patients (pT1a: 1,542; pT1b: 1,195; unspecified pT1: 349), the 5-yr overall survival (OS) was 67% for pT1a, 53% for pT1b, and 53% for unspecified pT1 (p < 0.001). The 5-yr cumulative incidence of intravesical recurrence was 19% (95% CI: 17-22), 28% (95% CI: 24-32), and 29% (95% CI: 24-35), respectively (p < 0.001). Cause-specific HRs for recurrence and progression were significantly higher for pT1b and unspecified pT1 versus pT1a. As treatment was stratified by substage, outcomes reflect both tumour biology and management. Main limitations relate to the register-based design.
Conclusions And Clinical Implications:
Nationwide T1 substaging was feasible and retained prognostic value. pT1b disease was associated with worse outcomes, and one in five patients with pT1b who underwent cystectomy had muscle-invasive disease. These findings support substage-based management while warranting prospective evaluation accounting for treatment selection.
