Hormone Therapy Increases Survival for Some Breast Cancer Patients
A drug commonly used for prostate cancer, buserelin, helped premenopausal women with advanced breast cancer live longer, according to a report in the June 7, 2000, issue of the Journal of the National Cancer Institute (see the journal abstract). When combined with tamoxifen, buserelin increased the average survival time of patients by almost a year. This combined therapy yielded an average survival time of 3.7 years, versus 2.9 years with tamoxifen alone or 2.5 years with buserelin alone.
Many premenopausal breast cancer patients have their ovaries removed to eliminate estrogen from their system. Estrogen is thought to cause some types of breast cancer to grow more quickly. But treating these same patients who have tumors classified as estrogen-receptor positive with tamoxifen is an accepted alternative to ovarian removal.
However, women treated with tamoxifen often develop high levels of estradiol, a sex hormone. Estradiol is thought by some researchers to inhibit the action of tamoxifen or even cause breast cancer to regrow. Buserelin suppresses ovarian production of estradiol, just as it blocks testosterone in prostate cancer patients.
The European Organization for the Research and Treatment of Cancer (EORTC) tested the drug combination in a phase III clinical trial that enrolled 161 patients in nine countries. All of the patients had locally advanced (spread to many lymph nodes) or metastatic (spread to other organs) breast cancer, and all had estrogen receptor positive tumors.
Women taking buserelin alone had 6.6 milligrams implanted under their skin at 6-week intervals for the first 12 weeks, and then at 8-week intervals. Women on tamoxifen took 40 milligrams of the drug daily. Women in the combined-treatment group took both drugs at these same dosages.
After following the women for an average of 7.3 years, the researchers found the combined treatment superior in overall survival and progression-free survival. In another measure, the combined therapy group had an overall five-year survival rate of 34 percent, compared with 15 to 18 percent for the single-agent groups. Blood levels of estradiol were suppressed equally in the combined treatment group and the buserelin-only group; in the tamoxifen-only group, levels of the hormone jumped threefold or higher.
These results open the door to more widespread use of hormone treatment for breast cancer, writes Nancy Davidson, M.D., of the Johns Hopkins Oncology Center in Baltimore, in an editorial. However, she cautions that the study was fairly small (due to problems accruing enough participants), and that newer hormone treatments under study may be more effective than buserelin.
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