MAYWOOD, Ill. -- Changing the order in which two drugs are taken significantly extended the lives of women with metastatic breast cancer, a study has found.
Women who took the drugs anastrozole and fulvestrant in combination lived more than six months longer than women who took the drugs in sequence, researchers reported Dec. 7 at the 2011 CTRC-AACR San Antonio Breast Cancer Symposium.
"This most likely will change the standard of care for how we treat these patients," said Kathy Albain, MD, of Loyola University Medical Center, a co-author of the study. First author is Rita Mehta, MD, of the University of California at Irvine.
Anastrozole (brand name, Arimidex®) is a pill that is taken daily. It is in a class of medications called aromatase inhibitors. It works by decreasing the amount of estrogen the body makes. (Estrogen fuels breast cancer.) Fulvestrant (brand name Faslodex®) is given by injection. It binds to estrogen receptors, thereby blocking the effect estrogen has on cancer cells.
The study included 707 postmenopausal women who had metastatic breast cancer that was hormone-receptor-positive. About half the women were randomly assigned to receive the standard regimen: treat first with anastrozole, and after the disease progresses, switch to fulvestrant. The other half were randomly assigned to receive anastrozole and fulvestrant in combination.
Women who received the standard regimen survived a median of 41.3 months. Women who received the two drugs in combination survived a median of 47.7 months.
Among women who received the standard regimen, it took a median of 13.5 months for the disease to progress. Among those who received the drugs in combination, it took 15 months before the disease progressed.
The combination treatment produced even greater benefits among women who had not previously taken tamoxifen.
Side effects generally were similar in both treatment groups, although only the combination group experienced the most severe side effects (one stroke and two pulmonary embolisms).
Albain is a professor in the Department of Medicine, division of Hematology/Oncology at Loyola University Chicago Stritch School of Medicine.
The study was conducted by the SWOG clinical trials network and supported by grants from the National Cancer Institute and AstraZeneca.