Epidemiologic studies of cervical cancer in Costa Rica

A case-control study of cervical cancer was conducted in Costa Rica, Colombia, Mexico and Panama from 1986 to 1987, to determine risk factors operating in these traditionally high-incidence areas. The study included 759 cases and 1,430 hospital and community controls, and accomplished more than 95% participation rates for both types of participants. The major risk factors identified were: detection of human papillomavirus (HPV) types 16 or 18, increasing number of livebirths, decreasing age at first sexual intercourse, increasing number of steady sexual partners, histories of venereal diseases and decreasing reported frequency of ingestion of vitamin C and beta-carotene. In addition, women with the lowest serum levels of beta-carotene and those with a history of not having participated in screening programs were at increased risk of disease. Detection of HPV was performed on cervical cells of cases and controls with filter in situ hybridization (FISH), a technique later demonstrated to have limited sensitivity and specificity. This reduced our ability to estimate the magnitude of the risk associated with HPV infection as well as to properly assess the role of other factors in the multivariate analysis.

From 1993 to 1994, we conducted the enrollment phase of a cohort study of 10,049 randomly selected women in the province of Guanacaste, Costa Rica. Over 90% of eligible women in this mainly rural population participated in the study, which comprised an interview, pelvic examination, several cervical cancer screening tests and complete diagnostic workup of those detected with abnormalities. The enrollment phase will allow the cross-sectional study of prevalence and determinants of cervical cancer and its precursors, in addition to prevalence and risk factors for HPV infection in different age groups. This component of the study will also include the evaluation of several new screening techniques for cervical cancer. Follow-up of the cohort is underway to investigate, prospectively, risk factors for cervical intraepithelial neoplasia (CIN), the main precursors of cervical cancer.