Drug lauded for preventing tumors

BARCELONA, Spain -- Recent research indicates a new hormone-blocking drug works better than the standard medicine in preventing women with early-stage breast cancer from developing tumors in the healthy breast.

In the largest breast cancer treatment study to date, women taking Arimidex were less than half as likely as those taking tamoxifen to develop a new cancer in the other breast.

The study, paid for by Arimidex's maker, AstraZeneca, was presented Thursday at the European Breast Cancer Conference in Barcelona, Spain.

International experts were enthusiastic about the findings, and some said it provided a clue that the drug could be a better option than tamoxifen for preventing breast cancer in healthy women.

However, others expressed concern that the women taking Arimidex had more bone fractures than those taking tamoxifen, an indication the new drug accelerates bone loss.

About 700,000 new cases of breast cancer are diagnosed every year worldwide. Estrogen fuels the growth of more than half of all breast cancers, especially those in older women. Tamoxifen, the top hormonal treatment for estrogen-fueled tumors, prevents estrogen from linking up to a receptor on the surface of cancer cells.

Arimidex is among a new class of cancer drugs called aromatase inhibitors, which work differently -- by blocking production of estrogen. They are used mostly when tamoxifen fails in advanced breast cancer.

They do not work so well on cancers that are not driven by estrogen, nor on pre-menopausal women because the drug becomes overwhelmed by the amount of estrogen that women of childbearing age produce.

The study involved 9,366 post-menopausal women with early stage breast cancer followed so far for nearly three years. One-third of them were given tamoxifen after their tumors were removed, another third got Arimidex and the rest got both the drugs.