The pill and breast cancer.

The pill and breast cancer

Two years after birth control pills were linked to breast cancer, women who have avoided oral contraceptives will be reassured by a new federal study exonerating the pill--or will they? On one side, results reported in the Nov. 2 LANCET find no relationship between the pill and development of breast cancer in women under 45. On the other side, skeptics, including LANCET editors, fear the report will prematurely settle a serious debate years before all the evidence is available.

In the recent study, researchers at the Bethesda, Md.-based National Institute of Child Health and Human Development (NICHD) and Centers for Disease Control in Atlanta tested the pill-cancer connection in a case-control study of more than 4,000 women aged 20 to 45. The study was prompted by the "pill scare' that followed two 1983 reports suggesting the use of oral contraceptives by young women increased their risk of developing breast cancer before 45 years of age (SN: 10/29/83, p. 279). Statistics underscored the need for such a study. The pill is the leading reversible method of birth control in the United States, with more than 8 million current users (70 to 80 percent of all U.S. women have used it at some time); and 1 out of every 12 women eventually will develop breast cancer.

As part of the NICHD's larger Cancer and Steroid Hormone Study done between Dec. 1, 1980, and Dec. 1, 1982, interviewers had questioned 2,088 women recently diagnosed with breast cancer and 2,065 controls without the disease and living in the same geographic areas. To prompt the subjects' recall of past pill use, interviewers had used a calendar of important events in each subject's life and pictures of different pill types.

Using there previously gathered data, principal investigator Bruce Stadel of NICHD and others analyzed pill-use habits earlier indicted as possible risk factors. One 1983 report from British scientists at Radcliffe Infirmary in Oxford had found that women who use the pill for longer than four years before having their first child appear to be three times more likely to develop breast cancer before age 45 than are those who do not use it before having their first child. The other 1983 report, from a group at the University of Southern California School of Medicine in Los Angeles (USC), had said that women who use pills with high levels of the hormone progestogen for more than four years prior to age 25 have four times the risk of developing breast cancer before age 37.

Stadel, speaking at an NICHD news conference last week, said the large numbers of women interviewed in the latest study lend statistical stability to conclusions that none of the pill-use factors examined in those two studies contributes to early-onset breast cancer. "[The study's relative risk analysis] constitutes strong evidence [that] pill use in the United States over the past 20 years . . . has had no effect on the overall risk of breast cancer,' he said. "We are reasonably confident that those earlier reports do not warrant continued concern.'

Others are not so sure. Although an editorial in the same issue of LANCET calls the Stadel study "a powerful challenge' to earlier conclusions, it says possible biases in survey methods may account for the differences, meaning "firmer conclusions must perforce await more epidemiological investigation.' And Brian Henderson, a coauthor of the 1983 USC study, told SCIENCE NEWS he agrees with the editorial's cautionary statements about geographic differences affecting pill use, as well as with the editors' concern that some cancer cases have not had time to develop since the pill was introduced in 1960.

Henderson, who says he considers the latest study results "less prone to possible error' than his own 1983 conclusions, adds that "[the Stadel study] doesn't necessarily disprove what we found, but shows we need more study.' He and his 1983 coauthors are currently doing two more studies of the pill-breast cancer relationship.