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Aromatase Inhibitors Demonstrate Long-Term Benefit Versus Tamoxifen in Preventing Breast-Cancer Recurrence: Presented at SABCS

By Ed Susman

SAN ANTONIO, Tex -- December 13, 2008 -- Aromatase inhibitors demonstrate greater long-term benefits than tamoxifen in preventing the recurrence of breast cancer, according to doctors who analysed two types of clinical trials and presented the findings at the 31st Annual San Antonio Breast Cancer Symposium (SABCS).

In the dual-barrel meta-analysis, researchers reported a statistically significant improvement with aromatase inhibitors in the risk of recurrence -- a difference that increased over time -- when the aromatase inhibitors were compared in a head-to-head trial with tamoxifen.

The analysis also demonstrated that switching to an aromatase inhibitor after 2 to 3 years of tamoxifen use resulted in a significant benefit in overall survival -- a difference that increased over time as well.

"The importance of these findings can be seen from the fact that 80,000 to 90,000 women in the United States alone are using endocrine therapy this year," said James Ingle, MD, Mayo Clinic, Rochester, Minnesota, speaking here on December 11 on behalf of the Aromatase Inhibitors Overview Group. "While a 3% difference in cancer recurrence may not seem like much, it can mean that several thousand women could be spared from a breast-cancer recurrence."

In the monotherapy trials, Dr. Ingle and colleagues reviewed the records of 9,856 women, determining that about 15.3% experienced recurrence on aromatase inhibitors (anastrozole, exemestane, and letrozole) compared with 19.2% of those on tamoxifen (P < .00001). There were no statistically significant survival gains between the two groups, Dr. Ingle noted. "We need to follow these patients longer, for 10 to 15 years, to be sure of the effect on survival," he said.

In the switch trials, the researchers retrospectively scrutinised records of 9,015 women, finding that the risk of death after 8 years was 10.8% if they were taking aromatase inhibitors compared with 13% of women who remained on tamoxifen (P = .004).

"Tamoxifen is a good drug, but it looks like aromatase inhibitors may be somewhat better," said Dr. Ingle.

"The meta-analysis process provides the potential for learning more about cancer treatments than can be learned from individual clinical trials. The more we know, the better doctors can treat their patients," Dr. Ingle added.

The Aromatase Inhibitors Overview Group represented leaders of the major clinical trials that tested aromatase inhibitors against tamoxifen.

Funding for this meta-analysis was provided by Cancer Research UK and the Medical Research Council, United Kingdom.

[Presentation title: Aromatase Inhibitors Versus Tamoxifen as Adjuvant Therapy for Postmenopausal Women With Estrogen Receptor-Positive Breast Cancer: Meta-Analyses of Randomized Trials of Monotherapy and Switching Strategies. Abstract 12]

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