Risk of Breast Cancer with Oral Contraceptive Use in Women with a Family History of Breast Cancer

Reviewers: Li Liu, MD
Source: JAMA, Volume 284:1791-1798, (October) 2000

Précis: Some oral contraceptives may link to higher risk of developing breast cancer

Introduction

Breast cancer is common and on the increase. Use of hormonal contraceptives is also common and is expected to increase worldwide. Whether hormonal contraceptives (OC) cause breast cancer is an important public health question, as well as one of great importance to women and men choosing their method of family planning. Thus, even a small increase in the risk of breast cancer in women using OCs would be important because of the frequency of the exposure. In this study, the researchers reported risk of developing breast cancer associated with OC use.

Method

A total of 3396 blood relatives of breast cancer patients and 2754 women who married into families with breast cancer were included to determine whether OC use could increase risk of breast cancer in women with family history of breast cancer.

Results

• Among the entire group of women, ever use of OCs was associated with a relative risk (RR) of 1.4 for breast cancer.
• The association was significant only among sisters and daughters of breast cancer patients. They had 3.3 times the risk of sisters and daughters who never used OCs.
• This elevated risk was seen only in those who used OCs for any duration prior to 1975. There was no association between any OC use after 1975 and the risk of breast cancer.

Discussion

In this study, the use of early oral contraceptive formulations was associated with an increased risk of breast cancer in some women with a family history of the disease. This is particularly worrisome since women with an inherited predisposition to breast cancer also face an increased risk of ovarian cancer. OCs are considered to be the most powerful known chemopreventative agents for ovarian cancer (N Engl J Med 1998 Aug 13;339(7):424-8). Recent study demonstrated that low-dose OCs is effective in reducing ovarian cancer risk (Am J Epidemiol 2000 Aug 1;152(3):233-41). It would be interesting to see whether low-dose OCs will reduce the hormonal effect on the development of breast cancer.