The relative risk of breast cancer in women using oral contraceptive pills (OCPs) has been debated on a fairly regular basis during the past few decades. Newer OCPs differ substantially from those used in older studies, and most women have not been followed long enough to reach the sixth or seventh decade of life, when breast cancer rates greatly increase. Marchbanks and colleagues report on a population-based retrospective study of OCP usage and subsequent breast cancer.

The investigators interviewed 4,575 women with breast cancer who resided in five metropolitan areas of the United States. Their usage of OCPs was compared with that of 4,682 control subjects. The women interviewed ranged from 35 to 64 years of age, and the average age was 50 years. More than 35 percent were from minority ethnic groups. In contrast to previous large studies, most of these women (77 to 79 percent) had used OCPs at some point in life.

There was no significant difference in the risk of breast cancer between women who had used OCPs and those who had not. Duration of use did not increase the risk for breast cancer, even in the subgroup that had used OCPs for at least 15 years. Age at first use, time since last use, high-estrogen–dose pill, and type of progestin did not significantly affect the risk of breast cancer. The investigators further analyzed subgroups of women according to family history of breast cancer, body-mass index, and menopausal status and again found no association between OCP use and risk of breast cancer.

The authors concluded that their retrospective analysis showed no association between OCP use and breast cancer, regardless of duration of use, age at first use, type of pill used, or family history of breast cancer.