A recent study investigated whether anastrozole treatment could reduce the risk of breast cancer recurrence.
Estrogen hormone promotes the growth and survival of normal and cancerous breast epithelial cells. Some breast cancers are more sensitive to the hormone estrogen, and they are known as estrogen receptor (ER)-positive breast cancers.
Anastrozole is in a class of medications called nonsteroidal aromatase inhibitors. Aromatase inhibitors can slow or stop the growth of many types of breast cancer cells that need estrogen to grow. Anastrozole works by reducing the amount of estrogen made by the fat tissue in the body, but not from ovaries. Therefore, these compounds may be more suitable for postmenopausal women.
A recent study published in the Lancet identified that five years of treatment with anastrozole (Arimidex) safely and effectively prevented breast cancer recurrence in high-risk postmenopausal women at 12 years of follow-up. These results further substantiated the use of anastrozole in breast cancer prevention in high-risk women.
The participants were from a large multicentric trial, that enrolled a total of 3,864 (1920 anastrozole and 1944 placebo) postmenopausal women from 2003 to 2012.
The researchers followed these women for a 12-year period, after the initial treatment. This study indicated that the women’s chance of having their breast cancer recur was reduced by 49%, compared to those who received a placebo.
The reduction was larger in the first five years after anastrozole treatment (61%); however, a significant reduction of 37% was seen in the post-treatment follow-up period, which is still larger than tamoxifen. Also, invasive estrogen receptor (ER)-positive breast cancer was reduced by 54%, with a continued significant effect in the period after treatment. Moreover, a significant reduction in ductal carcinoma in situ was observed, especially in ER-positive patients.
A significant decrease in non-breast cancers was observed with anastrozole treatment, namely in non-melanoma skin cancer. Overall, no effect of anastrozole was observed on cancer-specific mortality. However, the participants were in a younger age group, which highlights the need for a longer-term follow-up.
Written by Purnima Sharma, PhD
Cuzick J, Sestak I, Forbes JF, Dowsett M, Cawthorn S, Mansel RE, Loibl S, Bonanni B, Evans DG, Howell A. Use of anastrozole for breast cancer prevention (IBIS-II): long-term results of a randomized controlled trial. Lancet. 2020; 395: 117-122.
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