Mortality

Rates And Ratios

Age

Trend Last Ten Years

Geographic Distribution

Bladder cancer mortality rates are not widely available for comparison purposes. Bladder cancer is a major cause of deaths due to cancer in Egypt, where it is related to endemic schistosomiasis. Local variation in rates occurs in heavily industrialized countries due to occupational exposures.

Other Features

1. Cancer of the bladder has a number of the hallmarks of a disease which is environmentally induced:

(a) It involves an epithelial surface.

(b) Lesions are frequently multiple.

(c) Tendency to recurrence is marked.

(d) There is a wide male : female discrepancy.

(e) The location of most lesions in the bladder suggests the action of some urine-borne carcinogen.

(f) Known bladder carcinogens have been identified in man and animal.

(g) Regression of lesions has been reported after diversion of the urinary stream in a few instances.

2. Nevertheless, except for the small fraction of cases which will be discussed below, there are no clues to the etiology in the vast majority of cases of cancer of the bladder.

Etiology

Cancer of the bladder represents another of those frustrating instances in which it has been known for about sixty-five years what can cause the disease in a relative handful of cases. What does cause the vast majority of cases is unknown.

The four factors which have been incriminated are: occupation, bilharziasis, tobacco, and tryptophan.

Occupation

The so-called "aniline dye tumors" are a classical example of an occupational cancer. Most of these have been traced to the urinary excretion of one of the metabolic end products of aromatic amines, beta naphthylamine or benzidine.

Strict supervision and the practice of sound preventive measures in the responsible industries have kept this from becoming a major problem. New urinary carcinogens keep turning up, however, and industrial medical men must always be on the alert to recognize them before they have a chance to exert their deadly effects.

Bilharziasis

Infiltration of the bladder by the parasite Schistosoma hematobium, especially as this occurs in Egypt, has been known for over fifty years to be associated with bladder cancer. In Egypt and other countries, this ubiquitous parasitic disease and its malignant late effects are problems of the first magnitude. In the western world, however, cancer of the bladder apparently has its origin from other sources.

Tobacco

The long-term heavy use of tobacco, especially in the form of cigarettes, has been linked with the development of bladder cancer in several studies. The risk of the heavy smoker developing bladder cancer at some time in his life is about 50% greater than that of the nonsmoker.

Tryptophan

Recent studies suggest that abnormalities in tryptophan metabolism may be a factor in the genesis of bladder tumors in some patients. No specific clinical application of this information seems possible at this time.

Pathology. Premalignant Lesions

There are two lesions in the bladder that are usually considered in this category:

1. Leukoplakia

2. Papillomas or bladder polyps

Both of these have a significant propensity for subsequent malignant transformation.

Papillomas are by far the more common clinical problem. A number of institutions attempt to underscore the complexity, malignant potential, and unpredictability of the histologically benign papilloma by calling all such lesions Grade I carcinoma. As long as these are considered separately when reporting end results in the treatment of cancer of the bladder, this approach has it merits.