'Pivotal Point' in Breast Cancer Treatment

March 10, 2004 -- A good breast-cancer treatment is getting much better.

After breast-cancer surgery, five years of tamoxifen treatment cuts the risk of recurrent breast cancer in half. It works for the two-thirds of women whose tumors are sensitive to estrogen.

But now it looks as though switching from tamoxifen to a newer estrogen-blocking drug -- Aromasin -- offers an even greater benefit to postmenopausal women.

The finding comes from a huge international study that enrolled more than 4,700 postmenopausal women. After breast cancer surgery, all the women were treated with tamoxifen. But after two to three years, half the women switched to Aromasin.

Results weren't expected so soon. But after only 31 months of treatment, the women who switched to Aromasin were doing a lot better compared with those taking tamoxifen. Researchers found:

• Their risk of recurrent or metastatic breast cancer or death dropped by 32%.
• Their risk of getting cancer in the other breast dropped by almost half.
• Total breast cancer-free survival -- even in this brief period of time -- was about 5% longer.
• Overall, women taking Aromasin did not show a longer survival rate.

It's a revolutionary finding, says Paul E. Goss, MD, PhD, director of breast cancer prevention at Toronto's Princess Margaret Hospital and professor of medicine at the University of Toronto. Goss has chaired a number of pivotal international clinical trials in the hormone treatment of breast cancer.

"The 32% improvement is indeed a dramatically important result which I believe will influence patient care around the world," Goss tells WebMD.

The size and rapidity of the reduction in cancer risk was unexpected, says researcher R. Charles Coombes, MD, PhD. Coombes heads both the cancer medicine department and the cancer cell biology section at Imperial College in London. The study findings are in the March 11 issue of The New England Journal of Medicine.

"The extent of risk reduction surprised us," Coombes tells WebMD. "It indicates a fair number of people become resistant to tamoxifen two to three years after they start taking it."