IBIS-II long-term results confirm preventive benefits for ER+ breast cancer

In an updated data analysis of the IBIS-II trial, researchers confirmed the long-term preventive benefits of anastrozole in postmenopausal women with estrogen-receptor (ER)-positive breast cancer, according to lead author Jack Cuzik, CBE, FRS, Queen Mary University of London, London, UK.

Anastrozole is a nonsteroidal aromatase inhibitor that works by decreasing the amount of estrogen produced by the body. This action can slow or even stop the growth of many types of breast cancer cells dependent on estrogen for growth.

Dr. Cuzik and colleagues enrolled 3,864 postmenopausal women at increased risk of developing breast cancer in their 5-year double-blind trial of anastrozole vs placebo. After a median follow-up of 10.9 years, reductions in the number of patients who developed breast cancer was greater during the first 5 years, but were still significant after 5 years. Anastrozole also significantly reduced the incidence of invasive ER-positive breast cancer and ductal carcinoma in situ, particularly in ER-positive women.

Dr. Cuzik and colleagues concluded that, when given in the post-treatment follow-up period, anastrozole significantly reduces the incidence of breast cancer.

These results were shared at SABCS 2019.