THURSDAY, Aug. 4, 2005 (HealthDay News) -- A new Austrian study offers more evidence for a move away from tamoxifen as the standard drug for postmenopausal women with early breast cancer whose tumor is fueled by estrogen.
Data from two trials including more than 3,000 women found a 40 percent reduction in "events" -- such as a new breast cancer or a spread of the tumor to another part of the body -- for those who switched to a drug called an aromatase inhibitor after two years of tamoxifen therapy, compared to women who continued taking tamoxifen.
The study, reported in the Aug. 6 issue of The Lancet, provides additional support for a treatment "which is not only a standard in Europe but also in the United States," said study author Dr. Raimund Jakesz, a professor of surgery at Vienna Medical University.
But whether tamoxifen should be replaced entirely by aromatase inhibitors such as anastrazole, the one used in the European trials, "is an unsolved problem," Jakesz said.
Both tamoxifen and anastrazole prevent estrogen from spurring cancer growth -- tamoxifen by blocking it from reaching the cancer cells, anastrazole by stopping estrogen's production by body tissues other than the ovaries. The treatment is limited to postmenopausal women because their ovaries have stopped producing estrogen.
Several studies, the largest of which included more than 6,000 women, have shown that switching from tamoxifen to an aromatase inhibitor after two years of tamoxifen therapy has a positive effect like that seen in the Austrian study, said Dr. Timothy Hobday. He is a professor of oncology and director of the breast program at the Mayo Clinic College of Medicine, in Rochester, Minn.
"Making the switch is supported by the evidence, but it doesn't tell us what is the optimum thing to do with a patient starting from zero," he said. "The unanswerable question now is whether to go with an aromatase inhibitor at once or after a period of time."
A panel of experts convened by the American Society of Clinical Oncology said that aromatase inhibitor treatment "should be strongly considered," Hobday said. "But their assessment does not come down on when to use them."
A number of factors must be considered before prescribing an aromatase inhibitor, he said. One is cost. "An aromatase inhibitor is expensive -- $250 a month versus $70 to 80 for tamoxifen," Hobday noted.
And a major medical issue is that aromatase inhibitors "have a negative effect on bone density," he said. There has been a significant increase in fractures in women who took the drugs in studies, Hobday said.
"So what it comes down to is a case-by-case discussion -- of the cost, of side effects, of an individual's breast cancer risk, of her bone density and the characteristics of her bone cancer," he said. An aromatase inhibitor "makes more of a difference in higher-risk patients, those with bigger tumors or cancers that have spread to the lymph nodes."
To learn more about aromatase inhibitors, visit the National Cancer Institute.