Purpose: To evaluate the prognostic significance of the depth of lamina propria invasion in primary T1 transitional cell carcinoma (TCC) of the bladder.
Materials and methods: We retrospectively reviewed the medical records of 183 patients with primary T1 TCC of the bladder who had undergone transurethral resection (TUR) at our institution. Substaging was defined according to the depth of lamina propria invasion as follows: T1a, superficial invasion of lamina propria; T1b, invasion into the muscularis mucosa (MM); T1c, invasion beyond the MM but not to the muscularis propria. The prognostic significance of various clinicopathological variables for recurrence and progression was analyzed.
Results: Of the 183 patients, substaging was T1a in 119, T1b in 57, and T1c in 7 patients. The recurrence rate was 32.8% for T1a and 40.6% for T1b/c, but there was no significant difference between the two groups. The progression rate was significantly different between the two groups: 5.8% in T1a and 21.9% in T1b/c (p=0.003). The cancer-specific mortality rate was also significantly different: 4.2% in T1a and 14.0% in T1b/c (p=0.036). In the univariate analysis, microscopic tumor architecture was the only significant prognostic factor for recurrence. In the univariate and multivariate analysis concerning progression, depth of lamina propria invasion and concomitant carcinoma in situ were significant prognostic factors.
Conclusions: Substaging according to the depth of lamina propria invasion in primary T1 TCC of the bladder was an independent prognostic factor for progression. This suggests that substaging would be helpful for guiding decisions about adjuvant therapies and follow-up strategies.
Keywords: Lamina propria; Muscularis mucosae; Prognosis; Urinary bladder neoplasms.