BLADDER-CANCER - EPIDEMIOLOGY AND RISK-FACTORS IN BULAWAYO, ZIMBABWE

The incidence of bladder cancer, and the importance of some selected r isk factors in its etiology, were estimated from the data collected in the cancer registry of Bulawayo, Zimbabwe, during the period 1963-77. Cancer cases were interviewed with a standard questionnaire, and more than 70 percent of these were complete. Incidence rates in the urban population of Bulawayo in the first 10-year period were relatively hig h, with age standardized rates of 17.9 per 100,000 in men and 9.5 in w omen. Risk-factor distribution was compared in 680 bladder cancer case s (494 males, 186 females) and a control group comprising other cases with non-tobacco-related cancers (8,201). Seventy-one percent of bladd er cancer cases were squamous cell carcinomas. The presence of schisto somiasis, evaluated from past history of bilharzia or hematuria, was a ssociated with a significantly increased risk of bladder cancer in bot h genders (odds ratio [OR] = 3.9 for men, 5.7 for women), a result ref lected in the differing risk by province of residence, which correlate d with the prevalence of infection among cancer cases. The proportion of bladder cancer attributable to schistosomiasis was estimated to be 28 percent. Social status, as reflected by education level, also influ enced risk (ORs for literate cf illiterate males = 0.6), but tobacco s moking in men had no effect on the risk of squamous cell tumors. For t ransitional cell carcinomas or adenocarcinomas, there was a nonsignifi cant increased risk of 2.0 in the highest smoking categories (15g of t obacco per day), compared with non smokers.