Prevention and treatment of urothelial premalignant and malignant lesions.

Abstract

Bladder cancer is believed to develop through reversible premalignant stages followed by irreversible steps, and ending in invasive cancer giving rise to distant metastases. Because of the variation in the clinical course it has also been suggested that different forms of cancer develop along different molecular pathways leading to tumor presentations of various malignant potential. Today we treat and prognosticate bladder cancer on the basis of clinical and histologic findings that are insufficient to assess all the biologic potential of these tumors. Understanding the pathogenesis of bladder cancer might lead to a more precise identification of particular tumors with regard to clinical aggressiveness, resulting in individualized strategies for treatment and prophylaxis. Bladder cancer is seldom diagnosed in its preclinical stage, it is instead detected at cystoscopy and virtually never recognized as an incidental finding on autopsy. Therefore its "natural history" largely reflects that of "treated" disease. The true incidence of premalignant and malignant epithelial changes is not known. Incidences of hyperplasia and dysplasia of approximately 10% and approximately 5%, respectively and only occasional findings of cancer itself were reported in two autopsy series. Urothelial dysplasia is generally believed to be premalignant and a putative precursor of invasive cancer but unfortunately there has been a lack of standardization in terms of terminology and diagnosis. There is also a need for an agreed definition of the boundary between premalignancy, i.e. urothelial changes that have some but not all the features of carcinoma in situ, and malignancy, especially when considering potentially harmful treatments to prevent this transition. Most new diagnostic tools available and being tested today compare new detection techniques with traditional methods such as cytology or conventional histology of malignant rather than premalignant changes. There is probably also a short preclinical latency, as implied by the incidental findings of bladder cancer at autopsy, which makes it necessary to define how and when to promote early detection and treatment. Future studies therefore have to concentrate on methods for early detection of disease as well as characterization of host susceptibility, evaluation of exposure to carcinogens and potential effects of preventive measures. It is also likely that the improved tools of molecular prognostication will allow us to design trials more precisely in order to tailor therapeutic strategies.