Oral contraceptives and risk of breast cancer

Abstract

A national population-based case-control study was conducted in New Zealand to assess the effects of hormonal contraception on breast-cancer risk. A total of 891 women aged 25 to 54 with a first diagnosis of breast cancer, and 1864 control subjects, randomly selected from the electoral rolls, were interviewed. The relative risk of breast cancer for women who had ever used oral contraceptives was 1.0 (95% confidence interval 0.82-1.3). There was no increase in risk with duration of use, even among women who had continued to use oral contraceptives for 14 or more years (relative risk = 1.1, 95% confidence interval 0.78-1.7). The risk of breast cancer was not increased by use of oral contraceptives for long periods before the first pregnancy or by starting use at a young age. Parity, age at menarche, family history of breast cancer, or history of benign breast disease did not modify the effect of oral contraceptives on breast-cancer risk. Relative risk estimates were slightly, although not significantly, increased during the first few years after starting oral contraception and in women under 35 years of age at diagnosis.

PIP: A national population-based case-control study was conducted in New zealand to assess the effects of hormonal contraception of breast cancer risk. A total of 891 women ages 25-54 with a 1st diagnosis of breast cancer and 1864 control subjects, randomly selected from the electoral rolls, were interviewed. The relative risk of breast cancer for women who had ever used oral contraceptives (OCs) was 1.0 (95% confidence interval 0.82-1.3). There was no increase in risk with duration of use, even among women who had continued to use OCs for 14 or more years (relative risk=1.1, 95% confidence interval 0.78-1.7). The risk of breast cancer was not increased by use of OCs for long periods before the 1st pregnancy or by beginning with OCs at a young age. Parity, age at menarche, family history of breast cancer, or history of benign breast disease did not modify the effect of OCs on breast cancer risk. Relative risk estimates were slightly, although not significantly, increased during the 1st few years after initiating use of OCs and in women under age 35 at diagnosis.