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.