Stage T1 Urinary Bladder Carcinoma : Investigation of A Population-Based Cohort
Abstract: Approximately 2 300 new cases of urinary bladder carcinoma (UBC) are diagnosed every year in Sweden. This type of cancer is characterized as a long-standing disease with a high risk of recurrence and progression from an indolent to a more aggressive course. UBC occurs in a non-muscle-invasive form (stages Ta and T1), which is treated mainly with local resection and BCG instillation, and a muscle-invasive form (stage ≥ T2), for which the treatment of choice is irradiation or cystectomy.The aim of the research underlying this thesis was to explore the factors involved in tumor development and progression, and to find prognostic markers for recurrence and progression in patients with primary stage T1 urothelial carcinoma of the bladder (UCB).Tumor tissue in archived paraffin blocks from patients diagnosed with that type of malignancy was used in the four studies that were conducted. This was a population-based project, because all of the patients had been reported to the cancer center in the Southeast Healthcare Region in Sweden from 1992 to 2001. The follow-up time was comparable long in the cases included and was intended to be at least 10 years.The hospital records were reviewed to gather information on clinical characteristics of the tumors, such as size and multiplicity, as well as treatment modalities, recurrence and/or progression, and eventual death from UBC. The original tumor slides were re-evaluated. These two initial activities yielded a study population comprising 211 well-characterized patients with primary T1 UCB. Some of the originally selected patients were excluded due to missing paraffin blocks or poor quality of the tumor material, the latter being particularly important in the genetic analyses conducted in the fourth study.Ordinary light microscopy was performed to evaluate specific tumor characteristics, such as lymphovascular tumor infiltration, and for T1 sub-staging. Immunohistochemistry was carried out to, among other things, analyze cell cycle regulators. Furthermore, pyrosequencing, single-strand conformation analysis (SSCA), and Sanger sequencing were conducted in the fourth study to assess mutations in the p53 gene and murine double minute 2 SNP309 promoter polymorphism. Statistical analyses to estimate the risk of tumor recurrence and progression were carried out in all four investigations.Conclusions: This population-based cohort of patients with well-characterized T1 tumors of the urinary bladder showed high rates of recurrence (80%) and progression (39%), and the aggressiveness is underlined by the fact that 32% died from the disease. Lymphovascular tumor infiltration and abnormal immunohistochemical staining for p16 were found to be associated with tumor progression, and in the future analysis of these parameters might be used in treatment decisions regarding T1 bladder tumors. No other clinical or pathological variable or cell cycle regulator was associated with progression, and none of the genetic analyses conducted in the current studies were helpful in predicting outcome or explaining the mechanisms of tumor development.
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