HealthDay News — Updated guidelines from the American Society of Clinical Oncology (ASCO) urge healthcare providers to discuss chemoprevention as a clinical option with women at increased breast cancer (BC) risk, and add a new drug — the aromatase inhibitor exemestane (Aromasin) — to the armamentarium of available prophylactic options.

Women are considered to be at increased risk if the five-year projected absolute risk of breast cancer is 1.66% or greater based on the National Cancer Institute Breast Cancer Risk Assessment Tool, or if they have been diagnosed with lobular carcinoma in situ. 

The previous version of the guideline recommended discussing raloxifene (Evista) as a prophylactic option in postmenopausal women at increased risk for the disease, and tamoxifen for both pre- and postmenopausal women, but exemestane is not yet approved by the FDA for this use.

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Members of the ASCO guideline panel based the decision to include exemestane in recommendations for breast cancer prevention based on findings from clinical trials that showed the aromatase inhibitor reduced the risk for overall and estrogen receptor-positive invasive breast cancer 70% during a three-year period compared with placebo.

The updated guidelines are the first ASCO has issued since 2009 and are published online in the Journal of Clinical Oncology. Other changes included strengthened recommendations for using tamoxifen and raloxifen, based on new research that has been published since the last update.

Kala Visvanathan, MD, MHS, of the Johns Hopkins Sidney Kimmel Comprehensive Cancer Center, and colleagues on ASCO’s Breast Cancer Risk Reduction Guideline Update Committee, based the new recommendations on data from 19 randomized controlled trials and meta-analyses published from June 2007 through June 2012 with breast cancer incidence as the primary outcome of interest.

“Not every woman should use these preventive agents, but we believe women who are at increased risk for breast cancer should be given the option, because in some cases the magnitude of the risk reduction is large. For some women, these therapies can reduce the risk of breast cancer by up to 50%,” Visvanathan said in a statement. 

Key recommendations include:

  • Tamoxifen (20 mg a day orally for 5 years) “should be discussed as an option” to reduce the risk of invasive, ER-positive breast cancer in premenopausal or postmenopausal women aged 35 years and older at increased risk for breast cancer. The word “should” replaced “may” from the previous guidelines.
  • Raloxifene (60 mg a day orally for 5 years) “should” also be discussed as an option to reduce the risk of invasive, ER-positive breast cancer. Again, the previous guideline used the term “may.”
  • Exemestane (25 mg per day orally for 5 years) should be discussed as an alternative to reduce the risk of invasive, ER-positive breast cancer in postmenopausal women.

“We now have a better understanding of the net health benefits of these interventions. This knowledge will help us identify those women in which the benefit is greater than the risk,” Visvanathan said.


  1. Visvanathan K et al. J Clin Oncol. 2013; doi: 10.1200/JCO.2013.49.3122.