Trends in cancer of the cervix uteri in Sweden following cytological screening

Trends in cervical cancer incidence following the introduction of screening have mostly been studied using cross-sectional data and not analysed separ ately for squamous cell cancer and adenocarcinomas. Using Swedish nationwid e data on incidence and mortality, we analysed trends during more than 3 de cades and fitted Poisson-based age-period-cohort models, and also investiga ted whether screening has reduced the incidence of adenocarcinomas of the c ervix, The incidence of reported cancer in situ increased rapidly during 19 58-1967, Incidence rates of squamous cell cancer, fairly stable before 1968 , decreased thereafter by 4-6% yearly in women aged 40-64, with a much smal ler magnitude in younger and older women. An age-cohort model indicated a s table 70-75% reduction in incidence for women born 1940 and later compared with those born around 1923, The incidence of adenocarcinomas doubled durin g the 35-year study period, The mortality rate increased by 3.6% before 196 8 and decreased by 4.0% yearly thereafter. Although a combination of organi zed and opportunistic screening can reduce the incidence of squamous cell c ancer substantially the incidence of adenocarcinomas appears uninfluenced b y screening.