Weighing the evidence on the pill and breast cancer.

Three new studies have found some connection between oral contraceptive use and breast cancer among women younger than 45. None of the studies find an increased risk of breast cancer among the same subgroups of women, and their results are contradictory. Consequently, a committee advising the U.S. Food and Drug Administration concluded that "the existing data do not support a change in prescribing practices by physicians or in the use of oral contraceptives by women." One of the three studies, a U.S. hospital-based analysis of breast cancer patients, showed ever-users of the pill to have a statistically significant risk of breast cancer of 2.0 compared with never-users. The relative risk was elevated in virtually all duration-of-use categories. A significantly increased relative risk was also found among ever-users aged 30-34 and 35-39, among those who did not experience menarche until age 14 or older and among those who were parous. A new analysis of data from the U.S. population-based Cancer and Steroid Hormone Study found no increased risk among parous women or those who had used the pill for less than eight years. However, nulliparous women who had experienced menarche prior to age 13 and had used the pill for eight or more years did have a significantly increased relative risk. Most of the increased risk was confined to women who had begun pill use as teenagers; they had a relative risk of 5.6 compared with never-users.(ABSTRACT TRUNCATED AT 250 WORDS)