Tamoxifen's Risks

By Christine Gorman

Sometimes I think we all need to take a course in statistics before ever setting foot in a doctor's office. Case in point: the Food and Drug Administration's decision last week to approve the use of a breast-cancer drug called tamoxifen for women who don't have the disease but are at high risk of developing it. The FDA was swayed by the results of a study, made public by the National Cancer Institute last April, that showed that tamoxifen reduces by 45% these women's risk of developing breast cancer.

The catch: it also doubles their risk of uterine cancer and triples their risk of potentially fatal blood clots, at least if they're over 50. Whew! How do you sort out all those numbers and decide whether to take the drug?

With a computer, of course. The NCI has developed a program that enables a woman, in conjunction with her health-care provider, to calculate her own risk of developing breast cancer by answering a series of questions about her medical and family history. You can order the program, which is formatted on a regular 3 1/2-in. floppy disc (available for Windows or Mac), free at cancertrials.nci.nih.gov or by calling 800-4-CANCER. You'll probably have to wait a few weeks to receive it, since the NCI has already mailed out most of the copies it had on hand. Zeneca Pharmaceuticals, which manufactures tamoxifen under the brand name Nolvadex, also plans to distribute the disc.

Once you get the program, you'll be happy to learn, as I did last week, that you don't have to be a computer whiz to use it. I recommend taking the tutorial on the disc before calculating your own risk; it will help you make better sense of your results. And you'll get more out of the program if you talk it over with your physician.

There are five major pieces of information you have to supply. The first is your age, which turns out to be one of the most important risk factors. (In the U.S., the annual incidence of breast cancer in women 80 to 85 years old is 15 times as high as that in women 30 to 34 years old.) That is followed by your age at first menstruation, age when you delivered your first child, number of breast biopsies and family history of breast cancer. The program does not work for women who have already had breast cancer; doctors for years have given them tamoxifen to help prevent recurrence.

In essence, the risk disc determines whether or not you would have been eligible to take part in the NCI trial. Participants had to demonstrate at least a 1.7% risk of developing breast cancer over the next five years. On average, theirs was twice that. An important fact to note: this percentage is not the same as a woman's lifetime risk of developing breast cancer, which is naturally higher.

What the disc won't do is calculate your risk of developing uterine cancer or a blood clot. (Researchers hope to add that feature in coming months, so be sure to get on the mailing list for upgrades.) Nor can it tell you when to start taking tamoxifen. Some researchers believe that taking the drug for five years will lower your risk for the rest of your life, but that hasn't been proved. "The disc can't give you all the information you need to make a decision," says Dr. Barnett Kramer, deputy director of cancer prevention at the NCI. "But it can help you begin the process."

For more information on tamoxifen, see time.com/personal You can e-mail Christine about this article at [email protected]