A drug for advanced breast cancer prevents localized tumors from returning after surgery better than the current mainstay drug, according to a broad international study reported in Thursday's edition of the New England Journal of Medicine. Recurrence of such early cancer was reduced by one third in women who started on the gold standard treatment, tamoxifen, then switched after 2.5 years to the newer drug, exemestane, compared with those who took tamoxifen the entire time. The women switching to exemestane, a hormonal drug sold under the brand Aromasin, also suffered fewer serious side effects; they were 56% less likely to get cancer in the other breast and half as likely to develop unrelated cancer in other body areas. The research was partly funded by Pfizer Inc., the maker of Aromasin.
The study, which included 4,742 postmenopausal women in 37 countries, focused on women with breast cancer in which the hormone estrogen fuels tumor growth--the type causing about 70% of the incidences of breast cancer. The results do not apply to premenopausal women or those with hard-to-treat breast cancer not driven by estrogen.
Normally, early-stage breast cancer is treated by surgery to remove the tumor, plus radiation, if part of the breast is conserved. If tumor cells had spread to underarm lymph nodes, cell-killing cancer drugs often are given, particularly in the United States. Then, if the cancer is undetectable and also the type fueled by estrogen, women take daily tamoxifen pills for five years--to prevent any microscopic cancer cells lurking in the body from later triggering cancer in another spot. But cancer cells grow resistant to tamoxifen in many patients, sometimes within 12 months, and prolonged use can cause uterine cancer and dangerous blood clots.
Lead researcher R.C. Coombes, professor of cancer medicine at Imperial College School of Medicine in London, predicted doctors will give exemestane to many women at high risk for recurrence, such as those whose breast cancer spreads to multiple lymph nodes.