Progestin fails to cut breast cancer risk.

Taking estrogen for 5 or more years may raise postmenopausal women's risk of developing breast cancer and of dying from the disease, a controversial new study shows. What's more, taking progestin does not reduce those odds, the researchers report.

Earlier studies produced conflicting results on whether estrogen, a hormone that helps lower postmenopausal women's likelihood of getting heart disease and other disorders, raises their chance of developing breast cancer (SN: 2/4/95, p.74). Taking progestin counteracts estrogen's effect of increasing women's susceptibility to uterine cancer, but few studies examined whether progestin also protects against breast cancer.

In the new study, women who had taken hormones for 5 or more years and who

were still taking them showed a 30 to 40 percent higher incidence of breast cancer than nonusers, report Graham A. Colditz of Harvard Medical School in Boston and his colleagues in the June 15 New England Journal of Medicine.

A woman who continually takes hormones from age 55 onward would have approximately 3 chances in 100 of developing breast cancer between age 60 and

65, Colditz explains. Without the treatments, she would have less than 2 chances in 100.

However, stopping hormone treatment for 2 or more years brings a woman's likelihood of developing breast cancer down to that of nonusers, they report.

The study had several confusing findings, notably that risk drops quickly once women stop taking hormones, says William C. Andrews of Eastern Virginia Medical School in Norfolk. However, the large size of the study demands that researchers take its findings--which differ from many other investigators' results--seriously, he says.

To do the nationwide study, Colditz and his colleagues sent questionnaires

to nurses age 30 to 55 asking about their health and health practices, including use of hormones. In 1976, when the study began, almost 24,000 of the nurses had entered menopause. By 1992, that number had increased to almost 70,000, and 1,935 of the women had developed breast cancer. Over one-third of the participants took hormones; about one-third of that group also used progestin.

The researchers failed to take into account certain behaviors that may increase a woman's chance of getting breast cancer, including drinking alcohol, argues R. Don Gambrell Jr. of the Medical College of Georgia in Augusta. Also, using a questionnaire prevented the researchers from finding out important details, such as what sort of treatments breast cancer patients

received, notes Paul G. Stumpf of the Robert Wood Johnson Medical School in New Brunswick, N.J.

Indeed, the benefits of hormone therpy for postmenopausal women outweigh the risks, some researchers assert. Colditz, however, recommends that each woman weigh carefully the pros and cons of hormone therapy and consider whether heart disease or breast cancer poses a greater risk to her.