INTERNATIONAL INCIDENCE RATES OF INVASIVE CERVICAL-CANCER BEFORE CYTOLOGICAL SCREENING

Huge differences in incidence rates of invasive cervical cancer occur among populations, These differences reflect the influences of both et iological environmental factors and removal of precursor lesions detec ted upon screening, The purposes of this article are (i) to describe s imilarities and differences in the shapes and magnitudes of age-specif ic incidence rates of invasive cervical cancer before screening had an effect, (ii) to provide baseline data for further global study of scr eening effects, and (iii) to provide baseline incidence data for the d esign of optimal screening programs, To eliminate the impact of screen ing effects, we have selected age-specific incidence rates from times when and from populations in which screening was insignificant, The se lected rates were suitably scaled and compared regarding age at onset of increase in incidence, age at peak incidence, and rate of subsequen t decline, Despite a 16-fold difference in incidence rates, all curves had the same basic structure, with an increase to a peak followed by a decline or a plateau, Although all populations but one had an onset around age 25, 7 European countries showed an earlier peak age (mean = 46 vs. 59) and a more rapid decline after the peak than most other po pulations, The common basic shape of the age-specific incidence curve, overall, suggests a relatively similar development of invasive cervic al cancer in different populations, These results illustrate the under lying similarities in the markedly different age-specific incidence ra tes of invasive cervical cancer, They also provide a basis for studyin g screening effects and for optimizing screening programs in specific geographic areas. (C) 1997 Wiley-Liss, Inc.