POEMs

Anastrozole Decreases Rate of Breast Cancer in High-Risk Postmenopasusal Women

 


FREE PREVIEW. AAFP members and paid subscribers: Log in to get free access. All others: Purchase online access.


FREE PREVIEW. Purchase online access to read the full version of this article.

Am Fam Physician. 2014 Aug 15;90(4):online.

Clinical Question

Does anastrozole (Arimidex) decrease the rate of breast cancer in high-risk postmenopausal women?

Bottom Line

Postmenopausal women at high risk of developing breast cancer who take anastrozole for five years have a lower rate of developing invasive breast cancer during that time frame. (Level of Evidence = 1b)

Synopsis

These authors report outcomes from the second International Breast Cancer Intervention Study (IBIS-II), in which postmenopausal women in 18 countries who were at high risk of breast cancer were randomly assigned to receive anastrozole (1 mg daily for five years; n = 1,920) or placebo (n = 1,944). The authors used a complex series of definitions to identify high-risk women: 40 to 44 years of age with an estimated fourfold increased risk compared with the general population; 45 to 60 years of age with double the estimated risk; and 60 to 70 years of age with 1.5-fold increased risk. The authors also used the Tyrer-Cuzick model and included any additional women with an estimated 10-year risk greater than 5%. They excluded women who were premenopausal, had a previous breast cancer diagnosis, or had previously received chemoprophylaxis.

The researchers and support staff were masked to treatment allocation. The researchers evaluated the women at baseline, six months, 12 months, and then annually for five years. The researchers used intention-to-treat to analyze the rate of incident breast cancers. By the end of the study, 2% of women receiving anastrozole had invasive breast cancer compared with 3% of women who received placebo (number needed to treat = 62 for five years; 95% confidence interval, 38 to 155). Approximately one-third of the women in the anastrozole group and one-fourth in the placebo group stopped taking their medication, mainly because of side effects. There was no difference in the overall death rate (1%) in each group.

Study design: Randomized controlled trial (double-blinded)

Funding source: Industry plus government

Allocation: Uncertain

Setting: Population-based

Reference: Cuzick J, Sestak I, Forbes JF, et al. IBIS-II investigators. Anastrozole for prevention of breast cancer in high-risk postmenopausal women (IBIS-II): an international, double-blind, randomised placebo-controlled trial [published correction appears in Lancet. 2014;383(9922):1040]. Lancet.. 2014; 383 ( 9922): 1041– 1048.

POEMs (patient-oriented evidence that matters) are provided by EssentialEvidence Plus, a point-of-care clinical decision support system published by Wiley-Blackwell. For more information, please see http://www.essentialevidenceplus.com. Copyright Wiley-Blackwell. Used with permission.

For definitions of levels of evidence used in POEMs, see http://www.essentialevidenceplus.com/product/ebm_loe.cfm?show=oxford.

To subscribe to a free podcast of these and other POEMs that appear in AFP,search in iTunes for “POEM of the Week” or go to http://goo.gl/3niWXb.

A collection of POEMs published in AFP is available at http://www.aafp.org/afp/poems.



 

Want to use this article elsewhere? Get Permissions


More in AFP


Editor's Collections


Related Content


More in Pubmed

MOST RECENT ISSUE


Sep 15, 2016

Access the latest issue of American Family Physician

Read the Issue


Email Alerts

Don't miss a single issue. Sign up for the free AFP email table of contents.

Sign Up Now

Navigate this Article