Outcomes of squamous histology in bladder cancer: a population-based study

OBJECTIVES: Squamous cell carcinoma (SCC) of the bladder is an uncommon form of bladder cancer. Using a large population-based sample we sought to describe the outcomes of patients with squamous histology and to define the factors that influence prognosis in these patients.

METHODS: All incident cases of bladder cancer in Ontario undergoing cystectomy from 1994 to 2008 were identified. Electronic treatment records and detailed pathologic information were linked to the study data set. Patients were divided into 3 cohorts: pure SCC, urothelial carcinoma (UC) with squamous differentiation (UCSD), and pure UC. Cox modeling was performed to evaluate factors associated with overall survival (OS) and cancer-specific survival (CSS).

RESULTS: There were identified 178, 325, and 2,884 cases of SCC, UCSD, and UC, respectively. The unadjusted 5-year OS for these groups were 33%, 28%, and 34%, respectively. Patients had higher rates of T3/4 disease with SCC (72%) and UCSD (73%) than those with UC (61%, P<0.001). There was no difference in node positivity among groups (20%, 27%, and 25%, P = 0.519). After adjusting for covariates, SCC did not portend a worse survival, at 5 years. However, SCC did result in a more rapid disease trajectory, with survival curves of SCC and UC crossing at the 5-year mark. Adjusted CSS/OS of UCSD was also not significantly different from UC. Among those patients with SCC, factors associated with CSS included age>70 (hazard ratio [HR] = 1.96, 95% CI: 1.16-3.30), T category≥3 (HR = 2.09, 95% CI: 1.24-3.50), N positive disease (HR = 2.59, 95% CI: 1.55-4.32), lymphovascular invasion (HR = 1.98, 95% CI: 1.13-3.47), and positive surgical margins (HR = 2.95, 95% CI: 1.47-5.93).

CONCLUSIONS: After adjusting for patient and disease characteristics, we have found that SCC leads to a more rapid disease course with survival that is equivalent to UC by 5 years.