CANCER PATTERNS AND RISK-FACTORS IN THE AFRICAN POPULATION OF SOUTHWESTERN ZIMBABWE, 1963-1977

The incidence of cancer and the importance of some selected risk facto rs in its etiology were estimated from the data collected in the cance r registry of Bulawayo, Zimbabwe, during the period 1963-1977. Cancer cases were interviewed with a standard questionnaire, and more than 71 % of these were complete. In men, the most frequent cancer sites were liver, esophagus, and lung, while in women, cervical cancer was the do minant malignant tumor, followed by cancers of the liver, breast, and bladder. Risk factors of cancer cases were estimated by case-control a nalysis in which other cancers (excluding tobacco-related cancers in m en and hormone-related cancers in women) were considered as controls. In men, tobacco smoking was associated with increased risk of rung can cer (odds ratio OR(2), 5.2) and esophagus cancer (OR, 5.6) in the high est consumption category (15 g of tobacco per day) compared to nonsmok ers. Copper (OR, 1.5), gold (OR, 1.5), and nickel (OR, 2.6) miners had an increased risk of lung cancer, but no increase was found among asb estos miners (OR, 0.7). There was no independent effect of alcohol con sumption on the risk of esophagus cancer. The presence of schistosomia sis was associated with a significantly increased risk of bladder canc er (OR, 3.9). The risk of invasive cervical cancer increased with numb er of children-the estimated odds ratio was 1.8 in women with six or m ore births-but no consistent association was found for first intercour se. In postmenopausal women, the risk of breast cancer increased with age at first pregnancy (but not in the highly fertile) and decreased w ith high parity, if age at first pregnancy was 19 or more.