Secular trend analysis for cervical cancer incidence during 1991-2008 in Taiwan

Cervical cancer screening in Taiwan has been implemented since 1995. For evaluation of efficacy, the study aimed to observe the secular incidence trend during 1991-2008 of cervical squamous cell carcinoma(SCC) and adenocarcinoma(ADC), and to build models to found factors influenced the secular change.

The age, education, and residence specific women numbers aged >=30 years were collected from Taiwan demographic fact book. Cancer cases were ascertained from Taiwan Cancer Registry Database. Age-standardized incidences of squamous cell carcinoma and adenocarcinoma were calculated and used joint point regression to find out suitable numbers of joint points. Poisson regressions were used to evaluate the factors associated with the secular changes.

The turning points of SCC and ADC incidence trends were located at 1998 and 2000, incidence before turning point were annually increased 1.04% and 4.38%, and incidence after that were annually decreased 9.05% and 4.52%, respectively. Compared with 30-34 year old women, SCC incidence was increased with age and peaked at aged 65+ (RR=7.5, 95%CI:7.1-8.0), and ADC incidence was peaked at aged 45-49 women (RR=4.7, 95%CI:4.0-5.5). Both SCC and ADC incidence was highest in central Taiwan, and women attended school <6 years possess the highest risk of developing both SCC and ADC.

The secular trend is highly correlated with the ongoing screening program. The decreased incidence was mainly explained by calendar year, and increased age, decreased schooling years and specific residences were correlated with increased incidence. The factors found in Poisson regression may provide improved strategy and hence need to be further evaluated in the future.