AGE-PERIOD-COHORT ANALYSIS OF CERVICAL-CANCER INCIDENCE IN TAIWAN - DIFFERENCES BETWEEN SQUAMOUS-CELL CARCINOMA AND ADENOCARCINOMA

To examine the etiologic distinction between squamous cell carcinoma a nd adenocarcinoma of the cervix, the relationship between the incidenc e of both histotypes of cancer and age at diagnosis, time period at di agnosis and birth cohort was analyzed using data from the Taiwan Cance r Registry. Included in the study were all cases of both histotypes oc curring during the period 1979-90 within a population of Taiwanese wom en aged 25 to 75 years. A log-linear model modified from the method of Osmond and Gardner was used for the analyses. Age-period-cohort analy ses of age effect indicated that, prior to the age group of 49-51, the re is an almost identical incidence of both histotypes with an approxi mate linear trend of age effect but that, after this time, there is a divergence, with the age effect of increase slightly declining with ag e for squamous cell carcinoma and clearly declining for adenocarcinoma . In regard to period and cohort effects, a substantial moderation of squamous cell carcinoma risk was exhibited with both advancing recent calendar periods and birth cohorts, while adenocarcinoma risk also has a moderation but to a lesser extent. The model also identified the ch anges in female sex hormones after the menopause as a determinant of t he differing age effects, the efficiency of Pap smear screening practi ces as a determinant of the differing period effects, and changes in r eproductive patterns as a determinant of the differing cohort effects. These findings may provide clues with which to develop etiologic hypo theses and support the contention of etiologic distinctions between bo th histologic types.