Cancer drug may not prevent deaths

DALLAS – A new analysis suggests that the high profile, lavishly researched drug tamoxifen, when taken for breast cancer prevention, may in fact keep few women from dying.

A decade and almost $200 million in testing has found that tamoxifen can avert cancer, but little is known about whether that protection actually saves lives. New data, however, conclude that especially among women on the borderline of high risk, the lifesaving benefits “are very small or nonexistent.”

Long known as an effective treatment for cancer, tamoxifen rose to stardom in the 1990s with studies demonstrating that it could also prevent the disease among high-risk women. Most recently, results from a cancer prevention study of 20,000 women released in April compared tamoxifen with a similar drug.

Uncertain is whether fewer cancers would translate into lives saved. Except for women at the highest tiers of risk, the new study concludes that tamoxifen’s influence may be mild at best, and expensive to obtain.

“Overall, the impact is not going to be as large as people had originally hoped,” said Dr. Joy Melnikow of the University of California-Davis. She and her colleagues will publish their report in the Sept. 1 issue of the journal Cancer.

This analysis is one of the few to examine deaths – not just the development of cancer – and to take into account the kind of malignancy avoided. The tumors tamoxifen thwarts are the type less likely to be fatal, and therefore may have a lesser impact on overall mortality.

Melnikow and her colleagues did find that among women with a five-year risk of 3 percent or greater, tamoxifen did make a worthwhile difference. These women, being most in danger of developing breast cancer, stand to gain the most.

In the study, the researchers used a computer program to calculate the survival of a simulated group of 50-year-old women with a 1 to 5 percent risk of breast cancer. The analysis then took into account the known survival of various types of cancers, the influence of tamoxifen, and the natural mortality of the group – that is, how many of them would have died from other causes in addition to breast cancer.