Anastrozole provides a significant benefit compared with tamoxifen in preventing recurrence after a lumpectomy and radiation therapy in postmenopausal women ages 60 years or younger who had DCIS (ductal carcinoma in situ), a common diagnosis of non-invasive breast cancer. In women over age 60, it works as well as tamoxifen. These findings were presented today at the 2015 ASCO Annual Meeting in Chicago. The benefit reported in this trial appeared later in follow up of the women in the study.
"This study provides a new option for postmenopausal women undergoing treatment for the frequently diagnosed non-invasive breast cancer," said Kathy Albain, MD, co-investigator on this study, medical oncologist and director of the Breast Cancer Clinical Research Program at Loyola University Chicago Cardinal Bernardin Cancer Center. "These findings will help to better guide treatment decisions for physicians and their patients."
This phase III study evaluated postmenopausal women with estrogen-receptor or progesterone-receptor positive ductal carcinoma in situ and no invasive breast cancer after a lumpectomy and radiation. These women were randomly assigned to receive either 20 mg/day of tamoxifen or 1 mg/day of anastrozole for five years.
The study found that 93.5 percent of women who took anastrozole were free of recurrence of invasive or non-invasive breast cancer at the 10-year follow-up point compared with 89.2 percent in women who took tamoxifen. This study also found that disease-free survival was 77.9 percent for patients who took tamoxifen and 82.7 percent for patients on anastrozole at the 10-year follow-up point. The 10-year follow-up estimates for overall survival were 92.1 percent for the tamoxifen group and 92.5 percent for anastrozole. There were eight deaths due to breast cancer in the tamoxifen group and five in the anastrozole group.
"Overall, we can now offer another drug to women who are either at more risk for or wish to avoid some of the uncommon but real side effects of tamoxifen such as blood clots, embolism, stroke and uterine cancer," Dr. Albain said. "This is a real step forward in the treatment of non-invasive breast cancer."
Loyola University Chicago Cardinal Bernardin Cancer Center