Switching to an aromatase inhibitor provides mortality benefit in early breast carcinoma

For breast cancer patients taking tamoxifen, switching to an aromatase inhibitor within three years significantly improves survival rates, according to a new study.

Published in the March 15, 2007 issue of CANCER, a peer-reviewed journal of the American Cancer Society, the study reveals that the clear survival benefit was also achieved without an increased risk of death from other causes ? a significant risk associated with tamoxifen.

Hormone modulating therapies have made a significant impact on the survival rates of women with estrogen-sensitive breast cancer over the last two decades. The drugs are used as adjuvant to primary surgical treatment for a period of five years.

Tamoxifen was the first estrogen modulator shown to increase survival and reduce the risk of breast cancer recurrence. However, tamoxifen is associated with increased risk of death from other causes, such as strokes and endometrial cancer. Despite this risk, tamoxifen and another drug in this class, raloxifene, remain an extensively used and popular treatment.

Aromatase inhibitors, such as aminoglutethimide and anastrozole, work in a different way to lower estrogen levels. Recent evidence shows aromatase inhibitors used alone or in follow-up after two years of tamoxifen therapy demonstrates clear and, in some cases, improved reduction of recurrence risk. However, there is conflicting evidence about mortality benefits.

Led by Professor Francesco Boccardo, M.D. of the National Cancer Research Institute and the University of Genoa in Italy, researchers pooled data from two studies (828 women) comparing five year treatment with tamoxifen alone (415 women) or tamoxifen for two to three years followed by an aromatase inhibitor for the remaining treatment period (413 women).

Dr. Boccardo and his colleagues found that compared to treatment with tamoxifen alone, all cause mortality risk and breast cancer-related mortality risk both fell significantly for women switching to an aromatase inhibitor. In addition, there was no increased risk of death from other causes in women who were prescribed the aromatase inhibitor.

"This pooled analysis provides solid evidence that switching to an aromatase inhibitor following a few years of tamoxifen treatment, implies a mortality benefit over continued tamoxifen and that the benefit on breast cancer-related mortality is mainly due to the effect of switching," conclude the authors.