Cervical cancer risk and use of depot-medroxyprogesterone acetate in Costa Rica

Abstract

The long-term safety of the injectable contraceptive, depot medroxyprogesterone acetate (DMPA), has been the subject of intense debate, chiefly because of reports of breast and endometrial neoplasia in animal studies. Most epidemiological studies of DMPA use and cancer have been hindered by small sample size and short periods of potential latency.1-3 A recent, large case-control study by the World Health Organization (WHO) did not identify any overall increased risk of invasive cervical cancer among DMPA users.4-5 However, women who had used DMPA for five years or more had an elevated risk of invasive cervical cancer, compared to never users (odds ratio = 2.2, 95% confidence interval, 1.2 - 4.2). This increased risk was confined to long-term users who were under 46 years of age at diagnosis or who began using DMPA before 30 years of age. The WHO study did not include cases of carcinoma in situ (CIS). Costa Rica offers an opportunity to examine the relationship between DMPA use and cervical cancer, bfccause of its high incidence of cervical cancer and the popularity of DMPA after its introduction in the early 1970s. In 1983, cervical cancer was the most commonly reported cancer and the second leading cause of cancer mortality among Costa Rican women.6 The reported incidence of invasive cervical cancer in 1983 was 36.2/100 000 women, one of the highest rates in the world.6 DMPA has been a popular contraceptive in Costa Rica; approximately 11 % of currently married women, 15-49 years of age have used an injectable contraceptive, chiefly DMPA.7 However, since 1983, DMPA has not been approved for contraceptive use in Costa Rica. To further address the long-term safety of DMPA, the Costa Rican Demographic Association conducted a population-based, case-control study of cervical and breast cancer in Costa Rica in 1984-85. We report here our analysis of the association between DMPA use and cervical cancer. The breast cancer cases are the subject of a separate report.8