Long-term oral contraceptive use and the risk of breast cancer. The centers for Disease Control Cancer and Steroid Hormone Study
Using oral contraceptives for long periods or using them when one has other
risk factors has been hypothesized to increase the risk of breast cancer.
To study these issues, we analyzed data from a multicenter, case-control
investigation--the Centers for Disease Control's Cancer and Steroid Hormone
Study. All women 20 to 54 years old with a first diagnosis of breast cancer
ascertained by eight population-based cancer registries are study subjects;
controls are selected at random from the general population of these eight
areas. Analysis of the first 689 cases and 1,077 controls studied showed
that women who had used oral contraceptives at some time in their lives had
a relative risk of 0.9 compared with never-users (95% confidence interval,
0.8 to 1.2). Neither duration of oral contraceptive use nor time since
first use altered a user's risk of breast cancer; women whose first use was
more than 15 years ago and who used oral contraceptives for 11 years or
more had a relative risk of 0.8 (0.5 to 1.4). Oral contraceptive use did
not increase the risk of breast cancer among women with benign breast
disease or a family history of breast cancer. Oral contraceptive use before
a woman's first pregnancy did not increase her risk of breast cancer
significantly more than other methods of delaying first pregnancy. This
study provides no support to the hypothesis that oral contraceptive use
increases a woman's risk of breast cancer.
