International trends in incidence of cervical cancer: II. Squamous-cell carcinoma.

Time trends in the incidence of squamous-cell carcinomas of the cervix during the period 1973-1991 were examined using data provided by 60 population-based cancer registries from 32 defined populations in 25 countries. Three components of the incidence trend were studied: age, calendar period of diagnosis and birth cohort. Cumulative incidence rates per 1,000 person-years for 2 groups, age ranges 25-49 and 50-74 years, were calculated from the model that best described the incidence data. A significant decline in incidence was noted in the American populations (except for US Hispanic), Australia, the non-Maori women of New Zealand, northern and western Europe (except Italy and Spain, where the rates remain stable) and Asian populations (except Malay women of Singapore, who have stable rates). These trends were of similar magnitude for the whole age range studied (25-74 years). An increasing trend, mainly restricted to younger women, was found for Slovakia, Jewish women born in Israel and the United Kingdom. In Slovenia, the increasing trend was observed for all age groups. The predominant pattern shown by cancer registries in developed countries is of a reduction in the incidence of squamous cervical cancer. This could be, at least partially, attributed to the widespread practice of screening for cervical lesions. The major exception to the pattern is observed in the United Kingdom, though the increasing incidence in young women has changed to a decrease in recent years. There are only a few series covering a long period of time in developing countries, but there is little evidence for a major impact of screening.

International trends in the incidence of cervical cancer: I. Adenocarcinoma and adenosquamous cell carcinomas.

Time trends in the incidence of cervical adenocarcinoma and adenosquamous cell carcinomas during the period 1973-1991 were examined using data provided by 60 population-based cancer registries from 32 defined populations in 25 countries. Three components of the incidence trend were studied: age, calendar period of diagnosis and birth cohort. Cumulative incidence rates per 1,000 for 2 groups with age ranges 25-49 and 50-74 years were calculated from the model that best described the incidence data. There was a significant increase in the cumulative incidence of cervical adenocarcinomas in women born in the mid-1930s and in successive cohorts thereafter in some populations in the United States (whites and Hispanic women), Australia, New Zealand (non-Maori), England, Scotland, Denmark, Slovenia, Slovakia and Japan (Osaka) and among Chinese women in Singapore, with a general decline in the incidence in women born in earlier periods. In Sweden and Slovenia there is a suggestion of an increasing trend in both age groups. A decrease in incidence in both age groups was apparent in Finland, France and Italy. There were no changes in incidence in 24 registries covering other European, Asian and black populations in the United States. Part of the increase may be attributable to an increasing prevalence of human papillomavirus infection, and part to improvements in screening.

Risk factors associated with oesophageal cancer in Bulawayo, Zimbabwe.

This report presents information on risk factors for oesophageal cancer in Bulawayo, Zimbabwe. The data analysed were from the Cancer Registry of Bulawayo for the years 1963-77, when all registered patients were interviewed using a standard questionnaire. The age-standardised incidence rates in the urban population of Bulawayo in the first 10 year period were 58.6 per 100,000 in men and 8.1 in women. The distribution of risk factors was assessed in 881 oesophageal cancer cases (826 male, 55 female) and a control group comprising other non-tobacco- and non-alcohol-related cancer (5238) cases. There was a marked geographical gradient in risk in both sexes, which remained after adjustment for lifestyle variables. In men tobacco smoking was significantly associated with risk of oesophageal cancer, with the relative risk rising to 5.7 among smokers of 15 or more g day-1; this effect is independent of alcohol drinking. Among women who had ever smoked tobacco, the relative risk was 4.0 compared with those who had never smoked. Alcohol intake showed no independent effect on risk. Low socioeconomic status [odds ratio (OR) = 1.5; confidence interval (CI) = 1.0-2.1] and working as a miner (OR = 2.5; CI = 1.5-4.2) conferred increased risks in comparison with men of high socioeconomic status.

Bladder cancer: epidemiology and risk factors in Bulawayo, Zimbabwe.

The incidence of bladder cancer, and the importance of some selected risk 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 high, with age standardized rates of 17.9 per 100,000 in men and 9.5 in women. Risk-factor distribution was compared in 680 bladder cancer cases (494 males, 186 females) and a control group comprising other cases with non-tobacco-related cancers (8,201). Seventy-one percent of bladder cancer cases were squamous cell carcinomas. The presence of schistosomiasis, evaluated from past history of bilharzia or hematuria, was associated with a significantly increased risk of bladder cancer in both genders (odds ratio [OR] = 3.9 for men, 5.7 for women), a result reflected in the differing risk by province of residence, which correlated 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 influenced risk (ORs for literate cf illiterate males = 0.6), but tobacco smoking in men had no effect on the risk of squamous cell tumors. For transitional cell carcinomas or adenocarcinomas, there was a nonsignificant increased risk of 2.0 in the highest smoking categories (15 g of tobacco per day), compared with non smokers.

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 factors in its etiology were estimated from the data collected in the cancer 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 dominant malignant tumor, followed by cancers of the liver, breast, and bladder. Risk factors of cancer cases were estimated by case-control analysis in which other cancers (excluding tobacco-related cancers in men and hormone-related cancers in women) were considered as controls. In men, tobacco smoking was associated with increased risk of lung cancer (odds ratio OR2, 5.2) and esophagus cancer (OR, 5.6) in the highest consumption category (15 g of tobacco per day) compared to nonsmokers. 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 asbestos miners (OR, 0.7). There was no independent effect of alcohol consumption on the risk of esophagus cancer. The presence of schistosomiasis was associated with a significantly increased risk of bladder cancer (OR, 3.9). The risk of invasive cervical cancer increased with number of children--the estimated odds ratio was 1.8 in women with six or more births--but no consistent association was found for first intercourse. In postmenopausal women, the risk of breast cancer increased with age at first pregnancy (but not in the highly fertile) and decreased with high parity, if age at first pregnancy was 19 or more.