Aromatase Inhibitors Declared Superior to Tamoxifen in the Adjuvant Treatment of Early Breast Cancer

An international panel of leading breast cancer specialists, in an opinion paper published recently, agreed that aromatase inhibitors (AIs) surpass tamoxifen as the most effective treatment option for postmenopausal women with early, hormone-sensitive breast cancer.

Guideline Clarification

This global opinion, published in Current Medical Research and Opinion, declares the consensus findings of The International Aromatase Inhibitor Expert Panel, composed of 24 breast cancer clinicians from Europe, the United States, Australia, China, and Brazil, who agreed that AIs should be prescribed as the preferred therapy in this patient setting. The panel's findings reaffirm current guidelines regarding the use of aromatase inhibitors, such as anastrozole (Arimidex) is approved for adjuvant treatment of postmenopausal women with hormone receptor-positive early breast cancer.

"Over the last 3 years, there has been an influx of new information about the use of aromatase inhibitors in early breast cancer, and while this is great news, it has created a great deal of confusion," commented panel member Dr. Aman Buzdar, professor of medicine for the department of breast medical oncology at The University of Texas M. D. Anderson Cancer Center in Houston. "This guidance helps to clarify considerations for use of AIs in everyday practice. These data provide the evidence that support using an aromatase inhibitor at the earliest opportunity."

Major Findings

The panel reviewed data from major early breast cancer aromatase treatment trials with the aim of providing a "rational interpretation of the impact of these data on current practice and to highlight areas where further investigation is needed." The conclusions of the paper include several evidence based-recommendations. A summary of a few of the panel's top-line findings include:

• AIs are superior to tamoxifen and should be considered the treatment of choice in postmenopausal women with newly diagnosed hormone-sensitive, early breast cancer.

• Although 5 years of tamoxifen treatment has been the standard of care for 20 years and remains an effective treatment for certain patients, there is no subgroup of patients who do not appear to benefit from initial AI adjuvant therapy.

• Reported gynecologic adverse events are substantially reduced with AIs compared with tamoxifen. The majority of these adverse events with tamoxifen occur during the first 2.5 years of treatment, and may cause a burden to compliance.

• An increased risk of fractures are seen with AIs compared with tamoxifen, but they appear to be predictable and manageable. AI therapy is also associated with an increase in joint symptoms. The mechanisms explaining these conditions are unknown.

• The relationship of coronary heart disease (CHD) to AI use requires further evaluation. Current evidence suggests that AIs have either no or little effect on CHD, and the presence of CHD should not have an impact on the prescribing of AIs for adjuvant use. Further follow-up is required to determine whether differences between the AIs exist.

'Very Strong' Data

"Although tamoxifen has served us well for over 20 years, if we want to give our patients the most effective and well tolerated treatment for their breast cancer, it's time to consider an AI," explained panel member Professor Rowan Chlebowski, of the Harbor-UCLA Medical Center, California. "The data in support of AIs are very strong."

The consensus paper coincides with the publication of mature data from the landmark Arimidex, Tamoxifen, Alone or in Combination (ATAC) trial in the Lancet Oncology. The full consensus paper can be accessed via the Current Medical Research and Opinion website (www.cmrojournal.com). In addition, the publication of the mature data from the ATAC trial is available on the Lancet Oncology website (http://oncology.thelancet.com).