Objectives: To evaluate microstaging by means of quantifying the depth of invasion of the subepithelial connective tissue in pT1 transitional cell carcinoma (TCC) of the bladder for its additional prognostic value with respect to disease recurrence and progression.
Methods: We reviewed the pathologic findings of a consecutive series of 124 patients with pT1 tumors entered in a prospective randomized multicenter trial comparing mitomycin C and bacillus Calmette-Guérin treatment, with at least 3 years of follow-up and clinical outcome hidden from reviewers. The depth of invasion was established by identifying submucosal tumor invasion up to, in, or beyond the muscularis mucosae or vascular plexus and classified as pT1a, pT1b, or pT1c, respectively. In addition to tumor grade, the presence of carcinoma in situ (CIS) near the primary tumor or in biopsy specimens taken from abnormal looking mucosa was taken into account. The risks of recurrence and progression were calculated using Kaplan-Meier curves and modeled with proportional hazard models.
Results: pT1 subclassification was possible in more than 90% of the specimens. The 3-year risk of recurrence was not different in any of the subgroups. By contrast, the Kaplan-Meier 3-year risk for progression was 6%, 33%, and 55% for pT1a, pT1b (hazard ratio [HR] 5.51), and pT1c (HR 12.35) tumors, respectively (log-rank test P < 0.001). The Kaplan-Meier 3-year risk of progression was 9% versus 39% (HR 5.62) for the absence or presence of CIS in the tumor (P=0.001) and 8% versus 49% (HR 6.72) for CIS in biopsy specimens (P < 0.001). Tumor grade had no statistically significant prognostic value with respect to progression, nor had tumor volume or multifocality. The combination of the parameters (pT1c and CIS) increased the risk of progression by a factor of 27 (P < 0.0001) compared with the absence of pT1c and CIS.
Conclusions: These data show that the extent of lamina propria invasion (pT1a, pT1b, pT1c) is a clinically relevant prognostic factor for progression of pT1 TCC of the bladder. With the combination of this pT1 subclassification and the presence of CIS subgroups, distinct risks of progression can be identified that may give additional information for follow-up and treatment policies.