10-Year Follow-up on Anastrozole in Prevention of Breast Cancer
Posted: Friday, March 6, 2020
Patients with an increased risk of breast cancer experienced a significant reduction in estrogen receptor–positive breast cancer occurrence when treated with anastrozole in the post-treatment follow-up period. The results of the IBIS-II trial were presented at the 2019 San Antonio Breast Cancer Symposium by Jack Cuzick, PhD, of the Centre for Cancer Prevention in London, on behalf of his colleagues (Abstract GS4-04).
“Our new results strongly suggest that anastrozole should be the preferred therapy for breast cancer prevention in postmenopausal women at increased risk for the disease, with tamoxifen used for women who experience severe side effects from anastrozole,” said Dr. Cuzick in an American Association for Cancer Reserach press release.
This double-blind study followed 3,864 postmenopausal women at increased risk of developing breast cancer. Women were randomly assigned to receive either anastrozole or matching placebo for 5 years. At a median follow-up of 10.9 years, there were a total of 241 breast cancers reported: 81 in the anastrozole group and 160 in the placebo group (hazard ratio = 0.50). This reduction in breast cancer occurrence was larger in the first 5 years of follow-up, but it remained significant after 5 years.
The number of invasive estrogen receptor–positive breast cancers was reduced by 54% with anastrozole, with a continued benefit in the post-treatment follow-up period. There was a nonsignificant effect seen in estrogen receptor–negative breast cancer. The total number of cases of ductal carcinoma in situ was reduced, with a large reduction in estrogen receptor–positive tumors (hazard ratio = 0.23). There was no significant difference in all-cause mortality or breast cancer mortality between the two arms. Anastrozole also provided a reduction in the development of other cancers such as endometrial, ovarian, lung, and melanomas.
Disclosure: For full disclosures of the study authors, visit abstractsonline.com.
