Oral contraceptive use and breast cancer in Indonesia

A hospital-based case-control study was conducted in Ujungpandang, Indonesia, to determine the association of breast cancer and current and former oral contraceptive (OC) use. This study included 119 newly diagnosed, histologically-confirmed, breast cancer cases who were admitted to the four largest referral hospitals in Ujungpandang from 1990-1991. Controls were 258 women admitted to these same four hospitals with diagnoses unrelated to breast cancer or OC use. Thirty cases (32%) and 55 (19%) controls reported having ever used OCs. The odds ratio for ever using OCs and breast cancer was 1.8 (95% confidence interval 1.2-3.0) after adjustment for age, age at first pregnancy, and family history of breast cancer. Increasing duration of OC use did not increase risk of breast cancer. No latency trend of increasing years since first OC use among cases was observed; however, a younger age at first OC use was associated with increasing breast cancer risk. A significant recency effect was observed; women last using OCs within five years of study enrollment were at greatest risk of breast cancer (OR = 4.9, 95% CI: 2.1-11.4). This first study of breast cancer and OC use in Indonesia does not provide consistent data to indicate an increased risk of breast cancer associated with OC use. Although breast cancer cases were 80% more likely to have ever used OCs, neither duration nor latency of OC use were associated with cancer risk. The significant recency effect suggests that a detection bias might explain the observed relationship between ever OC use and breast cancer.(ABSTRACT TRUNCATED AT 250 WORDS)